I would challenge the assumption that EV on-board chargers use Diode-based AC to DC conversion (rectification), along with the associated losses. Modern electronics (such as in EVs) use "Synchronous Rectification", which uses extremely efficient MOSFET transistors as the AC to DC rectifier switches. This reduces the "rectifier losses" of a typical 0.5v voltage drop of a Schottky diode - down to 0.1v drop... reducing the rectification losses by 80%. These manufacturers have marketing departments whose job is to come up with the best sales pitch, and drastically over-estimates the power losses in modern EV onboard chargers. Also, the trend today is to use micro-inverters on home solar installs, which makes them far more resistant to the effects of residential shading. However, this eliminates the possibility of using the solar array for DC-DC charging, because the solar array does not output DC... only AC. Even if the solar array is series DC connected, the external charge controller still has to perform DC Current Regulation (to prevent damage to the solar array and equipment), which is a high speed switching circuit, which has losses... just as in the onboard EV charger. Just have a think... marketing is always about stretching the truth... hoping someone who knows better doesn't burst their bubble. (yes, I am a EE, and have been designing electronic circuits since 1980, and also drive an EV... an i3 BEV)
there is a reason they are not around yet, and only hot talk. yes and it still needs a voltage regulator. then there will be a device needed to separate the solar panels to either EV or house. or else another regulator to separate or split. and like mentioned most EV charging is at night. unless you are retired. i suspect it will be a costly exercise for not that much benefit.
100% agree... and with the microinverters why on earth do they output AC not DC? I can easily see a micro-MPPT being very useful to the point of being integrated into panels, but there is no intrinsic need I know of to then convert the normalized DC output of the MPPT into AC?
@@rivimey What you are asking is what Solar Optimizer are. They are a "per panel" device (some can handle 2 panels), and do MPPT per panel, then have DC output. They're pretty cool... though they are connected in series with each other, a shaded panel will never allow a voltage drop across that optimizer... and this the entire array. Instead, it will maintain the String Current, and add as much Voltage to the string as the panel illumination allows... maximizing output Power (Volts x Amps). Of course, if the intent is also to provide solar energy to the house, a String Solar Inverter would also be required. But regardless, there will never (essentially) be a perfect match in the total HV DC from the string and the DC Volts required by the EV battery - since it changes during charging. The DCFC interface includes a signal from the car back to the EVSE to control its output... so a DC to DC conversion/regulation is always needed. This would most liky be what's called a "Buck-Boost regulator" that can either lower or raise the Solar array DC voltage as needed... a high power circuit which obviously has its own losses... even if only 5-7%. The solar optimizer are also slightly lossy... another 3-5%.
This could apply to home appliances. Most electrical devices in the home are 24 Volt DC or thereabouts. Only a few devices use 220 Volt AC. A home could be wired with two systems: a DC system for low-powered devices including lights; and an AC system for big appliances, making it more efficient to power smaller devices directly from DC solar panels, and meaning that smaller devices don’t need to be supplied with AC adapters.
I like the concept but the downside of low voltage DC is the reality of voltage drop from cable attenuation. You'd need super-thick cables to wire a house and even then they would still have voltage drop. Still, having a dedicated DC circuit is great, you just want the AC to DC conversion done close to where the DC appliances are
The wait was caused by lack of demand, mostly. It's not a simple problem; you have to convert low voltage DC to high voltage DC, somehow avoiding the inefficiencies of transformers. I think the sort of solid state power electronics to do this hasn't been around for all that long.
Also the new alternator car to ev solar battery... ecoflow makes it for any car and it charges in 1 hour of driving. You then can move it to home and have electric all night
@@vitaliybaban6568 charging lithium-ion batteries is quite complex, though. You can't just attach a DC power source and let 'er rip. The charger needs to follow specific voltage and current curves specific to the type of battery.
Thanks Dave. With the new GaNfets efficiencies are getting so good that it really isn't a big deal, we're seeing efficiencies of over 95% on DC to pure AC inverters now. I thought about this myself and what I did was install an Emporia EVSE. It only charges my batteries when the sun is out through my paid off PV system. Works like a charm. In fact, last month, charging my car, cooling my house, hot water and all appliances we only used 40 kWh from the grid - that's about $4.00!
Well I've lived off grid in the mountains of Santa Barbara for a super long time and the vast majority of my house is DC and we have been doing DC solar to DC batteries to DC loads since the late 90s. This newer stuff is a bit tricky however as there are much higher DC voltages.
My first job post-college was in an off-grid solar community working for the solar installer that built the community. All 4 buildings were wired for both AC and DC and we sold a lot of DC light bulbs, refrigerators etc. As inverters got a lot better and cheaper, most people skipped the DC wiring, but it really does make things more efficient, and would be a better choice for developing nations that are going to build out micro-grids rather than national utility grids.
Nice thought, but solar panels deliver DC power very seldom in a condition you can use without adaptation for home devices. This goes with the help of dc/dc converters. Depending of the application, the converter needs an internal ac circuit to achieve the necessary step up or down voltage. Things short: the ac circuit in your house is not the devil you must get rid of, but you should think carefully about your special application.
@@rainerpick5491 Most residential solar is 600V DC and most commercial solar is 1,000V DC. Back in the day the panels themselves were 12v, 24v, 48v, obviously designed for specific battery bank voltages.
@@patrickcorcoran4828 yes but we have specialty charge controllers now so we can go from 300 to 500 V DC in and output whatever DC voltage we want to, to a battery bank. So my input voltage is 350 V DC and my output voltage to battery is 48 V DC and then I have DC to DC converters that feed 12 VDC circuits in the house. Very simple stuff.
A good micro inverter conversion efficiency is about 97.5%. This was a relevant piece of data for your video and it was better to mention that but putting the rest of the video in context
Actually more like 98%-99% these days @ 240VAC. For a multitude of reasons and assuming the electrician didn't do something stupid like highi-ball the trunk gauge.
Oh, *everyone* has thought of it. It's just not an easy problem to solve. Some requirements: a) Implement CCS Type 1, a protocol notorious for interoperability issues between different charge vendors and different vehicle models; b) Convert between the variable voltage of a solar array, to the specific voltage negotiated in each CCS session, which could range from 400 to 900 volts; c) Regulate the amperage as well (dynamically, through feedback from the EV's battery management system); d) Handle that massive voltage and power in such a way that, if millions of idiot DIY homeowners deploy your thing, most of them won't electrocute themselves at some point. Easy, right? Yeah, if you're willing to spend the money. Commercial DC fast chargers cost 6 figures. This thing had better be waaaaaaay below that, since its entire value prop is to avoid "losses of up to 13%." As such, it only makes sense if it is cheaper than, you know, just installing 13% more solar panels.* *Yes, I know, the reciprocal of 87% is not 113% but 115%. But I don't buy the "losses of up to 13%," nor that this device would have losses of 0%.
@@ps.2 thank you for all the points but everything you have listed minus the solar and css, is considered on all products design to protect consumers and networks and there is set guidence which is required to be followed to meet the required standards. The electric stability would be the hardest thing when charging from solar and most people will only have arrays of 5-6kw and in peak conditions will easily reach the voltage requirements on a sunny day. People with larger arrays would be better suited for these chargers for business who have a warehouse roof full of panels. I know its a bit more complicated then what I have listed but I don't have the time lol
@@Sean_S1000 Huge difference in safety engineering between a 120 or 240VAC EVSE - which is little more than a specialized extension cord - and a 400-900V DC fast charger. (Also a huge difference in the power electronics - the DC fast charger has to implement a full CCS Type 1 endpoint, while the EVSE does not - but let's just talk about safety for now.) _There are good reasons_ residential electricity is limited to 240 volts. If it were easy to design lights, plugs, cords, and appliances to operate at 400 volts or higher, we would. It'd mean thinner, cheaper wires, right? But it's _not_ so easy. You need better insulation and isolation (live wires have to be further apart). You need faster, higher-end switches - the ones on walls, in lamps and appliances, in circuit breakers. And it's super dangerous to human touch in a way 120V or even 240V is not.
@@ps.2 is this not already something which has been designed in to the DC 22kwh charger which are already available for the 3 phase market are already readily available in the market. I am aware of the dangers of higher voltages and current amps and DC over Ac and higher safety requirements. The only difference I can see is this new charger as the ability to utilize DC input, without the need to of an inbuilt inverter. I could be missing reading the sales and spec info but, I do appreciate the level of detail you are going in as it will highlight the engineering considerations for others and filling in gaps I may have in my knowledge
@@Sean_S1000 I'm not familiar with a 22 kW DC charger with 3-phase input. But I wonder if you are thinking of a *3-phase A/C charger* instead? I ask because CCS Type 2, used in Europe, directly supports 3-phase A/C charging. Though for some reason I had the impression it was limited to 11 kW. (CCS Type 1, used in North America, does not. This is because European residential electrical service often provides 3-phase, while North American residential service usually does not. And now you know why the CCS Type 2 pinout has 3 pins for A/C power, while the CCS Type 1 pinout has only 2.) I don't live in Europe, but I presume 3-phase residential power is 208V RMS phase-to-phase. If that's the case, 22 kW would require each pin to carry 35A. That's a lot, but still practical.
One of the earliest ways of converting AC to DC, as rotary converter (AC motor attached to DC generator). London underground originally used this method.
Thanks Dave once again for positively encouraging reports that continue to exercise that part of my intellectual capacity I haven’t used since I studied physics and engineering! 🤔🤷♀️💫😊
Here in the Netherlands some energy providers are already switching their peak and off peak hours around to be off peak when the sun is out and abundand during the day
I've started seeing electricity prices go negative here in northern Europe in the middle of summer days now, that only used to happen during very windy nights before. Solar installations have really taken off.
@@zapfanzapfan over the last 4 years we've gone from occasional negative prises to half of the days having atleast 1 hour of 0 or negative. Thats why they are now changing to feed in tarifs aswswell
As solar and wind get ever cheaper, I suspect that eventually it'll be worthwhile to overproduce to the extent that there's enough power on cloudy, calm days. Then the storage needed is just for 24 hours...much like nuclear (which tends to be used to produce the same power 24 hours a day, and uses storage to save power from the lowest demand hours to return during peak use hours).
In Australia, 20 million BV parked 23hrs all day long and all night long. TRICKLE currents all day long. Like the home robotic vacuum cleaner's selfplug-in feature. Every building parking space with a $60 wall outlet.
This is great news! Always wondered why our solar panels generate DC power that has to get converted to AC power for home appliances and then has to be converted back to DC to power our electric vehicle. And we're off-grid so this news will be a game changer.
Thanks Dave, this is a reason to celebrate. In Australia, the wholesale cost of electricity is negative between 10am and 2pm in most States, except for summer. We have lots of rooftop Solar PV here (43% of residences where I live), so it makes good sense to divert as much of that generation during the Solar peak period to EV and other battery storage. Most residences are connected by single phase AC mains which limits EV charging to 7.2 kW rate. A hybrid AC + DC input / DC output charger could typically double that rate, based on most residences having 6kW ~ 10kW of Solar PV output when there’s little domestic load. There are two major issues though : 1. many vehicles are used to commute during the day, and won’t be at home during the Solar peak, 2. While efficiency is important, a DC/ DC charger needs to be economic. AC from my Solar inverter costs ~ AUD $0.06 kWh. Losing 13% charging efficiency still doesn’t increase the cost of charging an EV from Solar PV by much. The only bidirectional DC/ DC charger currently approved for V2X in Australia cost around AUD $11,000 - hopefully that will change.
Solar Edge has been making a charger built in to its inverters for a while now. It isn't DC, but it puts the AC from the inverter to the charger before it hits the production meter, so it saves customers money in cases where net metering gives home owners less-than-retail value for the kWh they produce. A friend of mine has one and avoids a 3 cent penalty from the utility, just on his EV charging.
Since I work from home 4 days a week, this paired with a solar car port would be fantastic. (I have a slate roof, so going solar on the house would have to be a whole roof replacement/ solar tiles). I could put a car port on my driveway turnaround (two car parking area) and charge my car under the car port during the day. I still have my 48A charger in the garage for faster charging. I need to do the math on possible charge speed of a set of panels covering approx two parking spaces getting decent sun all day. Though as others point out, $2500 for the charger is steep!
I also have slate and have installed PV on my roof. If you get the right installer you can install PV on a slate roof. Don't get one that wants to drill through the tiles though.
I think the best possible solution would be to charge a stationary battery in your home via PV DC. Then charge the car from that as and when. That way you get to collect sunshine watts all day regardless of where your car is and then top it up at night when you’re in the land of nod. This would also feed into options of trickle charging to reduce dendrite build up (presumably). Any excess could be converted to AC and used by the home or fed back into the grid for credit.
DC wiring creates a lot of resistance in the wires - that is why AC is used worldwide - AC can travel much further on samller wires than DC without voltage drops that affect the equipment.
Strictly speaking, higher voltage leads to less current for the same power and hence power loss in wires AC or DC. When you want to transmit high power over long distances we use HVDC (High Voltage DC) lines. AC has a bunch of advantages for a distributed grid. When you have your power source and loads very close especially when your sources (solar, battery) and loads are DC (computers, lights, TVs etc.) DC does make more sense except for the fact that we have economies of scale and experience because we have used AC for a century. See the RV (recreational vehicle) and off grid communities for dwellings wired for DC.
@@synthwave7 Simply not true. The resistance of any conductor does not change (well, usually it rises as the temperature rises, but conductor cross sectional areas are controlled to avoid this affecting the system) High Voltage Direct Current (HVDC) is used for all inter-connectors from one distant region to another because the AC grid system loses more energy doing the same thing. AC current goes through zero 100 or 120 times every second (50 or 60 Hz) so the peak current has to be much larger. The only good things about AC are that AC is safer at the domestic level (240V DC is far more lethal and as AC current passes through zero 100 or 120 times each second (50 or 60 Hz) disconnection does not cause a continuous arc - which would need to be avoided with much more robust switching, to avoid contact damage if even only 240V DC). Different countries/regions grids may well be out of phase, so converting DC to grid frequency in phase with that country/region is no more difficult than keeping the whole world at the exact same phase relationship.
As you say, what we have now in cheap overnight rates, will change over time. This is a really interesting idea, cutting out conversion of our solar and feeding straight into the EV, makes total sense and gives more miles per kWh. Great news.
Years ago I knew an old timer who had a bank of those old Edison batteries and an old d.c. generator to change them. His house had d.c. wiring for lighting and few other things, and regular a.c. incoming power also, for the rest.
Good thoughts there, with a couple of caveats. The modern and more efficient micro-inverter array systems deliver AC from each panel, optimising the array efficiency. So this uses sub optimised arrays. Current 'smart' chargers and tariffs can demand shift any plugged in car to balance any grid needs, while achieving the required charge for a customer.
Looked at SolarEdge marketing materials for this and the main benefit seems to be the ability to simultaneously use grid AC and solar DC for faster charging. No particular efficiency gains (other than the benefit of solar itself). FYI, AC->DC conversion has a power loss as mentioned. DC->DC conversion also has a power loss. MPPT solar charge controllers are converting higher panel voltages (20-100Vish) to previously lower battery voltages (12,24V etc.). Now, with direct to EV charging you need to take solar panel voltages to higher battery voltages (at highest 400-800V). Every conversion comes with a penalty. It's not so much that AC->DC efficiency is worse than DC->DC efficiency, but the combination of DC->AC->DC is extra losses, shorter transmission (hundreds of km/miles to a power station vs 10s of m/yards to your panels) and the fundamentally greater efficiency/cost of distributed solar over centralized thermal combustion (full system costs).
In some cases a step up in DC voltage isn’t required as the home solar setup already strings panels together in series to increase the voltage and house solar inverters can normally handle up to 1000VDC input.
Just wish they would release it. I looked a month ago and it was still marketing. Solaredge Marketing seem to always bee about 1 year infront of the ability to provide the product. There was meant to be an update to software for the solaredge battery to import power from grid. Still waiting
@@peteinwisconsin2496 Fair enough but 600VDC strings probably gets you to where you want to be for direct DC charging of your EV. The OP makes out like you have to convert 24VDC to around 400-800VDC when that’s not the case for most installations. Interestingly here in Australia you can use 1000VDC strings in a residential installation provided the system isn’t grid connected.
But just using a grid-tie inverter lets you use both at once! Edit: Had paused the video just before Dave said that their device is supposed to be more efficient than the on-board charger.
Great round-up, have been looking for a DC to DC, two way charger (solar to car and car to 30kwh of LFP battery) for our 8KW solar system. Will watch these suppliers. Thanks Dave.
Thanks for the new video! I don't have a car, electric or otherwise, so this one isn't really for me. But from the comments it sounds like a lot of people could really use one of these chargers.
Most people just don't understand product lifecycles. They always start off crap, have problems, slowly get better, then finally work really well and are quite efficient. I think we're up to the 'have problems/slowly get better' point in EV's. I don't think it will be long until we reach the next step.
EVs already work well and are far more efficient then continuously blowing up fossil fuel to produce a lot of heat and little forward motion. We're already there. If you have access to a plug at home or work yet you buy a new combustion car, you're doing it wrong.
I'd like to see more modular solar/hydro systems for rural communities. I live off the paved road and be nice to have a way to power my well, and other things but in a Lego approach where each year I could add more panels, batteries, etc. A charger that work with solar would be a step towards that.
@@faustinpippin9208but are your DC-DC conversion losses any less than converting solar to generally useful AC and then having a standard battery charger?
DC slow chargers makes perfect sense for parking lots. The cars will be parked for hours so no need for fast charging. 10 cars can get slow charged at 20kWh chargers instead of 1 car fast charging at 200kWh, and it will be cheaper too. Fast charging should only be used for long trips, not for daily charging.
500 solar panels are needed to output 200kw in good conditions. 500 solar panels rated at 430w (SunPower Maxeon 3) calculated at 400w, outputting 200kw over 8 hours = 1,600kw. 1,600kw/h / 60 = 26.67. (Battery packs are around 48kw/h to about 80kw/h) 500 solar panels can not even provide reliable power for one fast charger at 200kw; About 25-30 cars could be fully charged over a good day.
A Solar PV DC-DC EV charger with V2H/G capability & mains charging option is fantastic. 1) enables me to install more solar.* 2) don’t have to buy a home battery to use own generation at night. 3) EV gets charged (for ‘free’) without cannibalising own home PV consumption. 4) option to earn $$ selling power back to the grid. 5) back-up mains charging when needed. 6) lower system losses. This doesn’t need thinking about as it’s a win, win, win, win, win & win! * at time of installation local electricity authority limited solar PV system size to 5KW to avoid overloading local grid. Though now systems with 5KW peak export limits with over provisioned panels can be installed.
On neat, that's awesome! And thanks for the explanation of how inverters and rectifiers work, every other source just seems to assume that's a known and understood thing, and I've just let it be a black box component in my head. (I'm sure I'd have looked it up if I ever actually needed to know, it's just never come up)
Totally agree with your arguments. The local airport in Illinois has been moving to cover the entire parking lot with panels to power the airport and an increasing number of EV vehicles, both private and airport support commercial units. As a side benefit, personal vehicles are shaded from the sun and snow not to mention thevoccasionsl hail. The latter opens different issues. Your example of covering Walmart and other commercial business parking lots depends on the desire to invest in the business and the general n public. The future is here and simply the mommentem is increasing.
We installed 13.2 kW Solar PV system in 2012 and two Tesla Powerwall batteries in 2018 to our all electric home with Heat pump and heat pump water heater and have been net positive in producing more energy than we use for past 12+ years, operating effectively as a microgrid for 8+ months of the year. We also charge our two EVs off our roof utilizing our solar panels to charge our cars 95% of the time and charge predominately during the peak solar period (11a.m.- 3 p.m.).
@@LilyWasHereMB Our early adoption Solar system costs us $83k in 2012, but solar costs have come down dramatically and a comparable system today would cost ~$20-25k. With incentives in place in Washington State where we live, and were able to pay off our pricey system within 7 years through net metering, and our electric provider issued us an annual check for our excess solar amounting to $5k/year for 7 years. Our Powerwall batteries cost us $15k, and have enable us to operate as a microgrid for 8 months of the year and also weather multiple power outages.
We did similar in 2019 but in our case an 11.4kw solar PV system (the max number of panels our roof could fit), a single Powerwall, a heat pump water heater and A Tesla Model 3. We are retired so mainly charge the car on sunshine. The cost of the solar, battery and heat pump combined was around $30,000AUD and it has saved us at least $5,000AUD a year so the investment has now been fully repaid. It would have paid for itself within 3 years if not for the Powerwall but still pleased to have it and be totally self sufficient and essentially off grid on most days of the year. We still export more than we import.
Here’s a thought. When building shopping malls, put a subterranean battery storage facility in so surplus from the DC canopies can be stored and used to either DC charge EVs when there’s no sun or exported to the grid as and when permits have been obtained and the grid requires.
Dave is right about cheap overnight electricity going away one day. The cheapest electricity is during the day in advanced nations such as Chile and Spain. DC direct charging of EVs is a fantastic solution for the fifteen states in the USA that do not allow net metering. All 50 of the US states can also implement PV-->domestic hot water with no grid connection needed. Heating water and one's space is a DC task that we perform with AC. Edison was not completely wrong, at least not for small grids like one's home.
As someone who grew up in the days of wringer washing machines I think my idea for a roller rectifier will finally bring electrification to the Flintstones. 😉
It's interesting that you mention Australia as a place that has solar energy geographically for longer periods of time, but we actually don't have any grid connections between the Eastern and Western states. The USA, Europe or China are probably better examples of good utilisation of peak solar.
A bit off topic…but I am still shocked that it only costs me $1.60 USD to charge my Model Y from 0 to 100% here in Burlington, Ontario, Canada - every night from 11pm to 7pm the rate is 2.8 cents (CDN) per kwhr - this along with the fact I am paying zero for maintenance is amazing
I am currently charging my EV at home from a DIY solar power system. My system has to convert to AC and then back to DC and in the process loses that 13% you are talking about. It works pretty good and provides free car charging but a DC version would be nice if it manages through the ups and downs of cloud cover. I would want it to be pretty steady so I would think a battery would need to be involved in the design somehow??? Great video, Thanks!
Seems like I heard that there are places working on capacitors for storing that energy for such purposes which would be nice. Much cheaper and longer lasting technology. Also would allow round the clock charging as it would not matter what time of day you used it as long as it charged while the sun was shining.
@@Humungojerry Round-trip through a low-voltage (48V) battery system would be a bit worse than a standard EVSE, yes. Round-trip through a high-voltage (typically 300V-500V) battery system would be significantly better. But maintaining such a long multi-stage high voltage DC path that exposes the HVDC battery bus to a third party charger is mostly a non-starter. Its extremely dangerous compared to pushing power with AC. Definitely not worth the 5-7% improvement one could achieve. -Matt
We are currently building a off-grid home in regional Victoria, Australia. When the home is completed, we will be purchasing an EV with a bidirectional battery - this DC-DC charging is one of the innovations I have been waiting for! Nonetheless, I am still eagerly anticipating the advent of technology that would enable an EV to directly power home storage batteries during extended periods of ‘dunkelflaute’. To me, this is the missing link which would allow people to go off-grid using the EV as the backup generator (avoiding the use of a fossil-fuel generator). PS - I am not referring to V2L/H as this is too selective and restricted.
But the car battery wants a specific voltage, and it would be a rare coincidence if the PV panels happened to produce that particular voltage. So you need a DC- DC converter. And while they are getting better, they are not lossless. So the net benefit of direct pv- to vehicle is less than the 13% cited. And there is a definite advantage to being able to have the pv panels and the vehicle in different locations, with the ac grid as the intermediate.
In fact there are additional losses in DC coupled systems that are minimal with AC coupled systems but these losses are simply ignored by the proponents of DC coupled systems. The losses I am referring to are related from the legislative required fault protection devices - I.E., fuses and circuit breakers. With AC coupled systems you simply use existing AC rated electrical fuses and circuit breakers which work great. However these AC fuses and circuit breakers can't be used for DC - they require circuit protection equipment that can interupt DC current. One commonly used way to get a DC rated circuit breaker is to string 8 or so AC circuit breakers together and have them mechanically linked together - this allows them to be able to break the DC current. It is clearly obvious that the losses associated with having 8 circuit breakers connected in series on a DC coupled system will be 8 times higher than an equivalent AC coupled system. The proponents for DC coupled systems ignore this detail on the basis that this is the consequence of safety legislation that can't be avoided. It's true that you can't just ignore safety requirements, but you can be smart as to how you meet these requirements and by using an AC coupled system then you can minimize the system losses associated with the safety protection equipment.
I don't really know anything about electric cars, except that they run on DC batteries. I know a bit about solar panels, namely, they produce DC not AC. If the two industries could decide on a specific Direct Current voltage, then it would be rather simple to charge your car battery with your solar panels with no loss except from the wires. The only real problem is that everybody wants to do things differently. The battery powered tool industry seems to have come to some sort of agreement, but they do keep upping the voltage on the batteries, 7 to 12 to 18 to 24 to 48. I think I would like a 48-volt battery for my hand drill so I can break my wrist the first time I use it.
It doesn't quite make sense, because you still have to adjust the panel voltage to match what the battery wants - and that involves something like a buck boost converter - which involves conversion to AC, and then back again.
The only thing though, for me, when the sun is shining, my EV is normally not at home. So I'll have to spend more to add a battery at home. Here in Switzerland, the payback time of such an installation is pretty bad, more than 20 years. For me.
If you are designing are system from scratch one should consider the cost of the wire for transmitting DC power. In general for high power transmission in DC the guage of cable required is very big and thus very expensive. Thus if the main use of your solar cells is to supply A/C to your house, you will have a less expensive and more efficient install using micro inverters on each panel and moving A/C on less expensive house wire. other advantages of micro inverters: -Easier to add and remove panels - lower voltage coming off roof with less danger - not having to convert to AC for most common applications. I dream of being able to take a panel with me on road trips and get AC when the sun shines.
Known as a Wheatstone bridge. Anyway. Dave, keep your eye open for a kit that would allow someone with solar panels to buy, say, a used Leaf with at least 10kWh of storage left and to connect it as a home battery. The price of degraded leafs is becoming quite attractive for such an application.
The DC-DC Charger is just a bolt on or extension of your solar inverter and linked management of the power storage. 100% right we have miles of roads and parking areas where we can better manage the collection of solar for electricity and heat and also add water management. When are we going to give up trying patch up the legacy AC grid and see a move to a parallel DC and HVDC grid, Big Solar Energy projects and Mega Batteries linked to it.
Thanks. I'm hoping to get a 'system' in the next few years, but (and it isn't what's delaying me.) tech is advancing so fast, every time I think I know what I need, something better comes along.
Solar pannels in series can reach as much as 1000v dc, surely wouldnt it be a case of taking few panels off to calculate the right voltage and the amps would vary threw out the day, bit jack the laid, but it only takes one person to do it or a big fail and a right off a elictric car. more in parallel for more watts
I love the idea of saving 10-13% of my single biggest use of energy, i.e., EV charging. But I am even more excited by the idea of commercial charging stations composed of PV, batteries and DC-to-DC chargers. That would need no or minimal grid connection -- another step towards decentralization. Computing has been distributed for decades but energy distribution is still on the mainframe model.
Not really true. Before the internet, computers were mostly standalone, but now practically every one of them is entirely dependent on the internet. If the 'grid' goes down, nothing will work.
there are also battery less inverters, that one could plug standard "chargers" into.... probably a lower up front cost, plus you can use the AC for other things....efficiency amy or may not matter whem adding more panels is so cheap these days... if one is a DIYer
DB raises a good point, that most people don't seem to be aware of, that when everybody can use off peak electricity, off peak will no longer exist, especially not as a fixed number of hours overnight. With high levels of wind and solar in the electricity mix, peak and off-peak periods are likely to move around from day to day, which is why we need a properly intelligent grid and genuinely smart smart meters that allow you to control equipment automatically in real time based on real time electricity pricing data. As far as I am aware, this is not something that current (UK) smart meters allow you to do, which is why I would suggest they are a very limited value. With regard to dcdc charging systems these are probably going to make an insignificant difference to electricity demand or cost savings. I'm not quite sure where Entelligent get their 13% higher efficiency claim from (I saw it claimed on their site but then couldn't find the screenshot again) because knowing the efficiency that you can get from chargers (which are basically switch mode DC power supplies) and inverters, even when combining them you should get well over 90% combined efficiency and when you take into account that Entelligent's chargers have a maximum efficiency of 98%, then I suspect the real world efficiency gain is probably closer to around 5%, and then only if you're charging from your PV panels or batteries. However, that wouldn't be a very good marketing ploy for a 12.5KW charger which, at $2,499, probably costs about 3 or 4 times more than it should. You can get 11KW mains chargers for well under £400 (although you can pay much more) so I don't understand why anyone would pay an extra £1,500+ to save themselves 5 to 10% on their electricity (but only when the sun shining closed bracket) and you are probably looking at about 100,000KWh (300,000+ miles) of charging before you get your money back. I would say Entelligent's marketing is basically green hype to justify an over inflated price tag, and their claim that with it being DC to DC is some great advantage, because you don't have to have AC to DC, is part of the hype. A PV system will not be producing a DC voltage at the right level for charging your EV so this charger is basically a dc dc converter, and internally a dc dc converter is basically a DC to AC to DC converter, albeit quite high efficiency one. Okay, you get rid of the AC to DC rectifier bit on the input, but at mains voltages that will probably only save about 0.5%, and the rest of the gobbins inside will be very similar. If you're charging from your PV system or batteries you also save another 5% by eliminating the mains inverter, a useful saving if you're not paying a huge price premium for it. Also, you could probably replace the basic rectifier with a synchronous switching rectifier to save a fraction of a percent, but it's probably not worth it.
The big question I was hoping to see an answer to, but didn't, is how much this DC-DC charger actually costs. Nor only does the inverter/rectifier equipment add to the cost, but there's also the fact that it's new technology with a rather limited market of people who have both the right kind of home solar setup and an EV. This is a problem because, if the DC->DC charger costs thousands more to buy or install than a conventional level 2 AC charger, the additional up-front cost will completely overwhelm the value of whatever energy it saves. Even for a person that is living entirely off-grid, I can easily see DC->DC charging being mor expensive than simply dealing with the energy loss of a conventional charger and buying more solar panels to compensate. That said, this does seem like the type of thing where, even if it's initially too expensive to make sense right now, it will likely get cheaper in the future.
This has existed for many years and is currently built into some new houses in Scotland. 8 years ago I built a house for a client in Scotland and he engineered vehicle charging using solar panels, a wind turbine and batteries.
Surely your house had a solar inverter converting to AC and then a conventional EV charger plugged in to a circuit. Otherwise what do you do with all the solar and battery power when you're not charging? Until you're off grid and everything is DC to DC, it doesn't make sense. For decades off-grid people in campers and trailers ran small appliances from 12-volt cigarette lighters, but the grid and most things you plug into the wall run on AC.
Lots of talk on this thread about DC systems being more efficient. What's not been made clear is that DC systems often require dc to dc conversion which is just a lossy as dc to ac. Also ac to dc, if it's using a simple bridge rectifier, is very efficient. BTW I run an off grid system with 48v battery, various 12 and 24v dc loads plus 230v ac for mains appliances including charging an EV.
It would be interesting to see the real world efficiency of the devices being compared. The 13% loss they claim for an AC system is probably a worst-case scenario. The charger featured here is quite expensive. It might be better to invest in a more efficient AC system.
Dc - DC conversions definitely do have losses but not remotely as much as DC-AC and then AC-DC conversions currently been utilised. Also most EV batteries run at about 400V DC, which is very close to the mppt voltage of most string and hybrid inverters. Similarly, most high voltage home energy storage batteries (e.g. from SMA, Fronius, Huawei etc) operate between 160-600V DC so not much stepping up/down will be required.
@@adon8672 DC to DC converters generally work by converting the input DC into high frequency AC, changing the voltage using a magnetic component and then rectifying it back to DC so it's the same. There are some differences as DC to mains voltage AC is generating low frequency AC. How much difference depends how it's done.
@@petewright4640they don't go full AC usually - just pulse the current on and off, it behaves the same in the magnetic element. Then "rectification" is just smoothing caps.
Those 13% losses must be the absolute worst scenario, not a typical one. There's absolutely no way that they've chosen such poor electronics. And DC-to-DC transformations (which are needed, as your PV system won't run on 400 V) also have losses. I can't imagine the gains being all that huge. If this technology can reduce costs by providing a simpler solution, then great, but I don't think shaving off a few percent of losses is going to be a game changer
PV systems (e.g. mine) can easily run on voltages as high as 400V... mine happens to be about 350V but the difference is only the number of panels in a string. Consumer panels tend to have nominal output voltage of around 48V, and a string is often wired in series (adding voltages). My GivEnergy inverter requires 125V to start, and has a max solar PV input of 550V IIRC. 13% is probably comparing their unit to a bog-standard solar inverter + EV diode rectifier setup, and the latter is I agree unlikely to be the case in the longer term even if it might be true for some cars now. However, it is true that inverting the power to AC then rectifying it back to DC will definitely lose non-trivial amounts of power, so avoiding doing it is always going to be a win.
A diode drop relative to 240VAC is insignificant, by the way. The IGBT drop (roughly 1.5V) is more significant but still clocks in at only 0.6%. Other losses dominate. But yes, 13% would definitely be worst case. Grid-to-vehicle losses are typically less than 10%. The real problem is that the DC-DC would have to be a buck-boost and the input would have to be at string voltages. And because it has to be a buck-boost and not just a buck, the efficiency is likely going to clock-in at 95%-97% or so. And it would only be valid while the sun is actually shining. So the "improvement" is only going to be 5-7% at best, and only under certain conditions. And it will require some rather expensive circuitry and safety features. I've done a ton of solar over the last two decades and can say with some authority that It is generally going to be far better to spend the money on simply adding more solar instead of spending it on a DC-DC EVSE. -Matt
Yes. Look at the efficiency rating of your computers power supply (easiest to find for a desktop system). This is AC to DC, but in Europe anything as inefficient as 13% losses at 80% full rated power is not on sale new (though if you like subsidising your utility you can pick up very inefficient pre-used ones)
I agree. What I would say though, is that there are advantages on a commercial scale, as Dave said. Using car parks with solar canopies and DC connection is a great way of avoiding using grid power and would stop all the wasted time in getting a permit to connect to the grid.
I'm off-grid. My house is single-phase and the cost of converting it to 3-phase is uneconomical. This leaves me with a maximum charge rate of 7.36kWh for my EV. Even if I had 3-phase, the AC charger in the vehicle is limited to 11kWh, but there is no such limitation on DC charging. I can't wait for it to hit the market here in Oz. Something like this DC-DC charging would enable me to get upwards of 13.5kWh.
I've been looking for DC-DC chargers forever! so happy to hear this.
Same, it's such obvious solution I was surprised that I've only managed to find one tiny startup, when I was looking for it about 6 months ago
Worthless. Steel needs conversion. The DC voltage has to match. DC to DC converters aren't that efficient.
@@tarstarkusz so you saying that converting dc to dc would be less efficient than converting dc to ac and then back to dc? Makes sense ;)
@@AtaSeddighMohammadi My point is only that DC-DC conversion is not very efficient.
@@tarstarkusz But DC to DC is more efficient,which is what this video is all about !😂
At last! This is such a glaringly obvious need; I’m glad someone is working on it.
I would challenge the assumption that EV on-board chargers use Diode-based AC to DC conversion (rectification), along with the associated losses.
Modern electronics (such as in EVs) use "Synchronous Rectification", which uses extremely efficient MOSFET transistors as the AC to DC rectifier switches. This reduces the "rectifier losses" of a typical 0.5v voltage drop of a Schottky diode - down to 0.1v drop... reducing the rectification losses by 80%.
These manufacturers have marketing departments whose job is to come up with the best sales pitch, and drastically over-estimates the power losses in modern EV onboard chargers.
Also, the trend today is to use micro-inverters on home solar installs, which makes them far more resistant to the effects of residential shading. However, this eliminates the possibility of using the solar array for DC-DC charging, because the solar array does not output DC... only AC.
Even if the solar array is series DC connected, the external charge controller still has to perform DC Current Regulation (to prevent damage to the solar array and equipment), which is a high speed switching circuit, which has losses... just as in the onboard EV charger.
Just have a think... marketing is always about stretching the truth... hoping someone who knows better doesn't burst their bubble.
(yes, I am a EE, and have been designing electronic circuits since 1980, and also drive an EV... an i3 BEV)
there is a reason they are not around yet, and only hot talk. yes and it still needs a voltage regulator. then there will be a device needed to separate the solar panels to either EV or house. or else another regulator to separate or split. and like mentioned most EV charging is at night. unless you are retired. i suspect it will be a costly exercise for not that much benefit.
@@HayesHaugen Only when you have the space for the panels. Many people don't.
100% agree... and with the microinverters why on earth do they output AC not DC? I can easily see a micro-MPPT being very useful to the point of being integrated into panels, but there is no intrinsic need I know of to then convert the normalized DC output of the MPPT into AC?
@@rivimey What you are asking is what Solar Optimizer are. They are a "per panel" device (some can handle 2 panels), and do MPPT per panel, then have DC output. They're pretty cool... though they are connected in series with each other, a shaded panel will never allow a voltage drop across that optimizer... and this the entire array. Instead, it will maintain the String Current, and add as much Voltage to the string as the panel illumination allows... maximizing output Power (Volts x Amps). Of course, if the intent is also to provide solar energy to the house, a String Solar Inverter would also be required.
But regardless, there will never (essentially) be a perfect match in the total HV DC from the string and the DC Volts required by the EV battery - since it changes during charging. The DCFC interface includes a signal from the car back to the EVSE to control its output... so a DC to DC conversion/regulation is always needed. This would most liky be what's called a "Buck-Boost regulator" that can either lower or raise the Solar array DC voltage as needed... a high power circuit which obviously has its own losses... even if only 5-7%. The solar optimizer are also slightly lossy... another 3-5%.
@@rivimeyexcept for car park owners
Great visuals! The demonstration of the motion of the current through the diagram helped me understand what you were describing.
This could apply to home appliances. Most electrical devices in the home are 24 Volt DC or thereabouts. Only a few devices use 220 Volt AC. A home could be wired with two systems: a DC system for low-powered devices including lights; and an AC system for big appliances, making it more efficient to power smaller devices directly from DC solar panels, and meaning that smaller devices don’t need to be supplied with AC adapters.
More and more devices can be PoE powered, which is DC.
I like the concept but the downside of low voltage DC is the reality of voltage drop from cable attenuation. You'd need super-thick cables to wire a house and even then they would still have voltage drop. Still, having a dedicated DC circuit is great, you just want the AC to DC conversion done close to where the DC appliances are
I've been waiting for this tech for 6 years now. I can't believe it's taken this long for what seems like a common sense solution.
The wait was caused by lack of demand, mostly. It's not a simple problem; you have to convert low voltage DC to high voltage DC, somehow avoiding the inefficiencies of transformers. I think the sort of solid state power electronics to do this hasn't been around for all that long.
Also the new alternator car to ev solar battery... ecoflow makes it for any car and it charges in 1 hour of driving. You then can move it to home and have electric all night
@@incognitotorpedo42 modern solar systems operates on voltages up to 300+VDC, which is also the case
@@vitaliybaban6568 charging lithium-ion batteries is quite complex, though. You can't just attach a DC power source and let 'er rip. The charger needs to follow specific voltage and current curves specific to the type of battery.
@@incognitotorpedo42 I am electrical noob, but i think that transformers only work for AC, not DC. Somebody please correct me if I am wrong.
Thanks
Thanks for your support. Much appreciated
A parking lot covered with a solar panel canopy, then we would get shade while we walk in from the parking lot, I call that a win-win!
And what if the drivers could choose net metering for the charging. So, the EV batteries could be used to balance the grid.
Thanks Dave.
With the new GaNfets efficiencies are getting so good that it really isn't a big deal, we're seeing efficiencies of over 95% on DC to pure AC inverters now.
I thought about this myself and what I did was install an Emporia EVSE. It only charges my batteries when the sun is out through my paid off PV system. Works like a charm. In fact, last month, charging my car, cooling my house, hot water and all appliances we only used 40 kWh from the grid - that's about $4.00!
Well I've lived off grid in the mountains of Santa Barbara for a super long time and the vast majority of my house is DC and we have been doing DC solar to DC batteries to DC loads since the late 90s. This newer stuff is a bit tricky however as there are much higher DC voltages.
My first job post-college was in an off-grid solar community working for the solar installer that built the community. All 4 buildings were wired for both AC and DC and we sold a lot of DC light bulbs, refrigerators etc. As inverters got a lot better and cheaper, most people skipped the DC wiring, but it really does make things more efficient, and would be a better choice for developing nations that are going to build out micro-grids rather than national utility grids.
Nice thought, but solar panels deliver DC power very seldom in a condition you can use without adaptation for home devices. This goes with the help of dc/dc converters. Depending of the application, the converter needs an internal ac circuit to achieve the necessary step up or down voltage. Things short: the ac circuit in your house is not the devil you must get rid of, but you should think carefully about your special application.
@@rainerpick5491 Most residential solar is 600V DC and most commercial solar is 1,000V DC. Back in the day the panels themselves were 12v, 24v, 48v, obviously designed for specific battery bank voltages.
@@rainerpick5491 you are patently wrong! DC DC converters do not need an AC circuit! 🙄 i've only been using them for about 25 years now!
@@patrickcorcoran4828 yes but we have specialty charge controllers now so we can go from 300 to 500 V DC in and output whatever DC voltage we want to, to a battery bank. So my input voltage is 350 V DC and my output voltage to battery is 48 V DC and then I have DC to DC converters that feed 12 VDC circuits in the house. Very simple stuff.
Brilliant explanation of complex ideas … well done
A good micro inverter conversion efficiency is about 97.5%. This was a relevant piece of data for your video and it was better to mention that but putting the rest of the video in context
Actually more like 98%-99% these days @ 240VAC. For a multitude of reasons and assuming the electrician didn't do something stupid like highi-ball the trunk gauge.
Im just amazed people have not thought of this before, its so simple to reduce losses due to the conversion process
Oh, *everyone* has thought of it. It's just not an easy problem to solve. Some requirements:
a) Implement CCS Type 1, a protocol notorious for interoperability issues between different charge vendors and different vehicle models;
b) Convert between the variable voltage of a solar array, to the specific voltage negotiated in each CCS session, which could range from 400 to 900 volts;
c) Regulate the amperage as well (dynamically, through feedback from the EV's battery management system);
d) Handle that massive voltage and power in such a way that, if millions of idiot DIY homeowners deploy your thing, most of them won't electrocute themselves at some point.
Easy, right? Yeah, if you're willing to spend the money. Commercial DC fast chargers cost 6 figures. This thing had better be waaaaaaay below that, since its entire value prop is to avoid "losses of up to 13%." As such, it only makes sense if it is cheaper than, you know, just installing 13% more solar panels.*
*Yes, I know, the reciprocal of 87% is not 113% but 115%. But I don't buy the "losses of up to 13%," nor that this device would have losses of 0%.
@@ps.2 thank you for all the points but everything you have listed minus the solar and css, is considered on all products design to protect consumers and networks and there is set guidence which is required to be followed to meet the required standards.
The electric stability would be the hardest thing when charging from solar and most people will only have arrays of 5-6kw and in peak conditions will easily reach the voltage requirements on a sunny day. People with larger arrays would be better suited for these chargers for business who have a warehouse roof full of panels. I know its a bit more complicated then what I have listed but I don't have the time lol
@@Sean_S1000 Huge difference in safety engineering between a 120 or 240VAC EVSE - which is little more than a specialized extension cord - and a 400-900V DC fast charger. (Also a huge difference in the power electronics - the DC fast charger has to implement a full CCS Type 1 endpoint, while the EVSE does not - but let's just talk about safety for now.) _There are good reasons_ residential electricity is limited to 240 volts. If it were easy to design lights, plugs, cords, and appliances to operate at 400 volts or higher, we would. It'd mean thinner, cheaper wires, right? But it's _not_ so easy. You need better insulation and isolation (live wires have to be further apart). You need faster, higher-end switches - the ones on walls, in lamps and appliances, in circuit breakers. And it's super dangerous to human touch in a way 120V or even 240V is not.
@@ps.2 is this not already something which has been designed in to the DC 22kwh charger which are already available for the 3 phase market are already readily available in the market.
I am aware of the dangers of higher voltages and current amps and DC over Ac and higher safety requirements.
The only difference I can see is this new charger as the ability to utilize DC input, without the need to of an inbuilt inverter.
I could be missing reading the sales and spec info but, I do appreciate the level of detail you are going in as it will highlight the engineering considerations for others and filling in gaps I may have in my knowledge
@@Sean_S1000 I'm not familiar with a 22 kW DC charger with 3-phase input. But I wonder if you are thinking of a *3-phase A/C charger* instead? I ask because CCS Type 2, used in Europe, directly supports 3-phase A/C charging. Though for some reason I had the impression it was limited to 11 kW.
(CCS Type 1, used in North America, does not. This is because European residential electrical service often provides 3-phase, while North American residential service usually does not. And now you know why the CCS Type 2 pinout has 3 pins for A/C power, while the CCS Type 1 pinout has only 2.)
I don't live in Europe, but I presume 3-phase residential power is 208V RMS phase-to-phase. If that's the case, 22 kW would require each pin to carry 35A. That's a lot, but still practical.
I love your ability to express complex things simply. Thank you
Nice explainer of a rectifier circuit. It's key to remind ourselves that we could manufacture these circuits for ourselves.
Can’t wait to get my hands on one of these.
One of the earliest ways of converting AC to DC, as rotary converter (AC motor attached to DC generator). London underground originally used this method.
Love that blue jumper...😊
Logic is nicely falling into place with EV's.
Thanks Dave once again for positively encouraging reports that continue to exercise that part of my intellectual capacity I haven’t used since I studied physics and engineering! 🤔🤷♀️💫😊
Here in the Netherlands some energy providers are already switching their peak and off peak hours around to be off peak when the sun is out and abundand during the day
I've started seeing electricity prices go negative here in northern Europe in the middle of summer days now, that only used to happen during very windy nights before. Solar installations have really taken off.
@@zapfanzapfan over the last 4 years we've gone from occasional negative prises to half of the days having atleast 1 hour of 0 or negative. Thats why they are now changing to feed in tarifs aswswell
As solar and wind get ever cheaper, I suspect that eventually it'll be worthwhile to overproduce to the extent that there's enough power on cloudy, calm days. Then the storage needed is just for 24 hours...much like nuclear (which tends to be used to produce the same power 24 hours a day, and uses storage to save power from the lowest demand hours to return during peak use hours).
In Australia, 20 million BV parked 23hrs all day long and all night long.
TRICKLE currents all day long.
Like the home robotic vacuum cleaner's selfplug-in feature.
Every building parking space with a $60 wall outlet.
Yes this is the thinking and stuff we need to make a better world. Thanks for great videos.
This is great news! Always wondered why our solar panels generate DC power that has to get converted to AC power for home appliances and then has to be converted back to DC to power our electric vehicle. And we're off-grid so this news will be a game changer.
I've been designing a home solar/battery system, and this would make a great addition to my setup.
Thanks Dave, this is a reason to celebrate. In Australia, the wholesale cost of electricity is negative between 10am and 2pm in most States, except for summer. We have lots of rooftop Solar PV here (43% of residences where I live), so it makes good sense to divert as much of that generation during the Solar peak period to EV and other battery storage. Most residences are connected by single phase AC mains which limits EV charging to 7.2 kW rate. A hybrid AC + DC input / DC output charger could typically double that rate, based on most residences having 6kW ~ 10kW of Solar PV output when there’s little domestic load.
There are two major issues though : 1. many vehicles are used to commute during the day, and won’t be at home during the Solar peak, 2. While efficiency is important, a DC/ DC charger needs to be economic. AC from my Solar inverter costs ~ AUD $0.06 kWh. Losing 13% charging efficiency still doesn’t increase the cost of charging an EV from Solar PV by much. The only bidirectional DC/ DC charger currently approved for V2X in Australia cost around AUD $11,000 - hopefully that will change.
Solar Edge has been making a charger built in to its inverters for a while now. It isn't DC, but it puts the AC from the inverter to the charger before it hits the production meter, so it saves customers money in cases where net metering gives home owners less-than-retail value for the kWh they produce. A friend of mine has one and avoids a 3 cent penalty from the utility, just on his EV charging.
Since I work from home 4 days a week, this paired with a solar car port would be fantastic. (I have a slate roof, so going solar on the house would have to be a whole roof replacement/ solar tiles). I could put a car port on my driveway turnaround (two car parking area) and charge my car under the car port during the day. I still have my 48A charger in the garage for faster charging. I need to do the math on possible charge speed of a set of panels covering approx two parking spaces getting decent sun all day. Though as others point out, $2500 for the charger is steep!
I also have slate and have installed PV on my roof. If you get the right installer you can install PV on a slate roof. Don't get one that wants to drill through the tiles though.
Best episode yet. Thoroughly enjoyed it
Excellent as always thanks Dave
Thank you again. Well presented.
I think the best possible solution would be to charge a stationary battery in your home via PV DC. Then charge the car from that as and when.
That way you get to collect sunshine watts all day regardless of where your car is and then top it up at night when you’re in the land of nod. This would also feed into options of trickle charging to reduce dendrite build up (presumably).
Any excess could be converted to AC and used by the home or fed back into the grid for credit.
While attractive, the losses of charge/discharge battery are (currently) even higher than DC->AC->DC conversion.
Nice find. Ive often wondered why we don't have a DC system wired into each home for lighting, TVs computers etc 💚
Primarily because AC systems are way easier to make safe.
DC wiring creates a lot of resistance in the wires - that is why AC is used worldwide - AC can travel much further on samller wires than DC without voltage drops that affect the equipment.
DC loses more power over longer distances AC is good for power lines to transfer energy across cities. DC is good for easier circuit diagrams
Strictly speaking, higher voltage leads to less current for the same power and hence power loss in wires AC or DC. When you want to transmit high power over long distances we use HVDC (High Voltage DC) lines. AC has a bunch of advantages for a distributed grid. When you have your power source and loads very close especially when your sources (solar, battery) and loads are DC (computers, lights, TVs etc.) DC does make more sense except for the fact that we have economies of scale and experience because we have used AC for a century. See the RV (recreational vehicle) and off grid communities for dwellings wired for DC.
@@synthwave7 Simply not true. The resistance of any conductor does not change (well, usually it rises as the temperature rises, but conductor cross sectional areas are controlled to avoid this affecting the system)
High Voltage Direct Current (HVDC) is used for all inter-connectors from one distant region to another because the AC grid system loses more energy doing the same thing. AC current goes through zero 100 or 120 times every second (50 or 60 Hz) so the peak current has to be much larger.
The only good things about AC are that AC is safer at the domestic level (240V DC is far more lethal and as AC current passes through zero 100 or 120 times each second (50 or 60 Hz) disconnection does not cause a continuous arc - which would need to be avoided with much more robust switching, to avoid contact damage if even only 240V DC).
Different countries/regions grids may well be out of phase, so converting DC to grid frequency in phase with that country/region is no more difficult than keeping the whole world at the exact same phase relationship.
As you say, what we have now in cheap overnight rates, will change over time. This is a really interesting idea, cutting out conversion of our solar and feeding straight into the EV, makes total sense and gives more miles per kWh. Great news.
Years ago I knew an old timer who had a bank of those old Edison batteries and an old d.c. generator to change them. His house had d.c. wiring for lighting and few other things, and regular a.c. incoming power also, for the rest.
Amazing. Hopefully people will get engaged with this new tech.
Good thoughts there, with a couple of caveats.
The modern and more efficient micro-inverter array systems deliver AC from each panel, optimising the array efficiency. So this uses sub optimised arrays.
Current 'smart' chargers and tariffs can demand shift any plugged in car to balance any grid needs, while achieving the required charge for a customer.
Looked at SolarEdge marketing materials for this and the main benefit seems to be the ability to simultaneously use grid AC and solar DC for faster charging. No particular efficiency gains (other than the benefit of solar itself).
FYI, AC->DC conversion has a power loss as mentioned. DC->DC conversion also has a power loss. MPPT solar charge controllers are converting higher panel voltages (20-100Vish) to previously lower battery voltages (12,24V etc.). Now, with direct to EV charging you need to take solar panel voltages to higher battery voltages (at highest 400-800V).
Every conversion comes with a penalty. It's not so much that AC->DC efficiency is worse than DC->DC efficiency, but the combination of DC->AC->DC is extra losses, shorter transmission (hundreds of km/miles to a power station vs 10s of m/yards to your panels) and the fundamentally greater efficiency/cost of distributed solar over centralized thermal combustion (full system costs).
In some cases a step up in DC voltage isn’t required as the home solar setup already strings panels together in series to increase the voltage and house solar inverters can normally handle up to 1000VDC input.
Just wish they would release it. I looked a month ago and it was still marketing. Solaredge Marketing seem to always bee about 1 year infront of the ability to provide the product. There was meant to be an update to software for the solaredge battery to import power from grid. Still waiting
@@David-lr2vi 1,000 VDC strings are Not legal on homes but up to 600 VDC is.
DC-DC conversion is now almost as easy as AC-AC conversion.
@@peteinwisconsin2496 Fair enough but 600VDC strings probably gets you to where you want to be for direct DC charging of your EV. The OP makes out like you have to convert 24VDC to around 400-800VDC when that’s not the case for most installations. Interestingly here in Australia you can use 1000VDC strings in a residential installation provided the system isn’t grid connected.
But just using a grid-tie inverter lets you use both at once!
Edit:
Had paused the video just before Dave said that their device is supposed to be more efficient than the on-board charger.
Doah, i just upgraded my solar edge. Well I welcome the new tech, thanks Dave.
Sounds like a good idea.
Great round-up, have been looking for a DC to DC, two way charger (solar to car and car to 30kwh of LFP battery) for our 8KW solar system. Will watch these suppliers. Thanks Dave.
Thanks for the new video! I don't have a car, electric or otherwise, so this one isn't really for me. But from the comments it sounds like a lot of people could really use one of these chargers.
Thank you, Dave, for another very interesting video!
Most people just don't understand product lifecycles. They always start off crap, have problems, slowly get better, then finally work really well and are quite efficient. I think we're up to the 'have problems/slowly get better' point in EV's. I don't think it will be long until we reach the next step.
EVs already work well and are far more efficient then continuously blowing up fossil fuel to produce a lot of heat and little forward motion. We're already there. If you have access to a plug at home or work yet you buy a new combustion car, you're doing it wrong.
Thanks for another informative video, we definitely need this in Australia.
Brilliant 🎉 thanks for that
I'd like to see more modular solar/hydro systems for rural communities. I live off the paved road and be nice to have a way to power my well, and other things but in a Lego approach where each year I could add more panels, batteries, etc. A charger that work with solar would be a step towards that.
I made this like 2 year ago,
Diy homemade car and directly hooking up the battery to my of grid solar inverter
ah yes, what is the voltage of your home made EV?
192volts, before pluging it into the inverter the pack switches to 48volts
@@faustinpippin9208but are your DC-DC conversion losses any less than converting solar to generally useful AC and then having a standard battery charger?
Thanks for sharing this resource.
DC slow chargers makes perfect sense for parking lots. The cars will be parked for hours so no need for fast charging. 10 cars can get slow charged at 20kWh chargers instead of 1 car fast charging at 200kWh, and it will be cheaper too. Fast charging should only be used for long trips, not for daily charging.
500 solar panels are needed to output 200kw in good conditions. 500 solar panels rated at 430w (SunPower Maxeon 3) calculated at 400w, outputting 200kw over 8 hours = 1,600kw.
1,600kw/h / 60 = 26.67. (Battery packs are around 48kw/h to about 80kw/h)
500 solar panels can not even provide reliable power for one fast charger at 200kw; About 25-30 cars could be fully charged over a good day.
Great info! Thank you… will have to look into the cost, hopefully it is reasonable.
A Solar PV DC-DC EV charger with V2H/G capability & mains charging option is fantastic. 1) enables me to install more solar.* 2) don’t have to buy a home battery to use own generation at night. 3) EV gets charged (for ‘free’) without cannibalising own home PV consumption. 4) option to earn $$ selling power back to the grid. 5) back-up mains charging when needed. 6) lower system losses. This doesn’t need thinking about as it’s a win, win, win, win, win & win!
* at time of installation local electricity authority limited solar PV system size to 5KW to avoid overloading local grid. Though now systems with 5KW peak export limits with over provisioned panels can be installed.
3) Because you're *_stealing power-service._*
4) Because you're *_stealing power-service._*
5) Because you're *_stealing power-service._*
Can we chat about this. I’m guessing you’re in WA, as am I and I want charge our ev directly from some surplus off grid panels.
You're doing a great job Dave, certainly a bit more optimism about renewables in the UK this week; let's hold them to their promises
On neat, that's awesome!
And thanks for the explanation of how inverters and rectifiers work, every other source just seems to assume that's a known and understood thing, and I've just let it be a black box component in my head. (I'm sure I'd have looked it up if I ever actually needed to know, it's just never come up)
A brilliant move towards cheap energy, keep them coming.
Totally agree with your arguments. The local airport in Illinois has been moving to cover the entire parking lot with panels to power the airport and an increasing number of EV vehicles, both private and airport support commercial units. As a side benefit, personal vehicles are shaded from the sun and snow not to mention thevoccasionsl hail. The latter opens different issues. Your example of covering Walmart and other commercial business parking lots depends on the desire to invest in the business and the general n public. The future is here and simply the mommentem is increasing.
Thanks Dave
We installed 13.2 kW Solar PV system in 2012 and two Tesla Powerwall batteries in 2018 to our all electric home with Heat pump and heat pump water heater and have been net positive in producing more energy than we use for past 12+ years, operating effectively as a microgrid for 8+ months of the year. We also charge our two EVs off our roof utilizing our solar panels to charge our cars 95% of the time and charge predominately during the peak solar period (11a.m.- 3 p.m.).
How much did your independence cost?
@@LilyWasHereMB costs a lot up front, but there comes a point when it's paid itself off and saves you money.
@@LilyWasHereMB Our early adoption Solar system costs us $83k in 2012, but solar costs have come down dramatically and a comparable system today would cost ~$20-25k. With incentives in place in Washington State where we live, and were able to pay off our pricey system within 7 years through net metering, and our electric provider issued us an annual check for our excess solar amounting to $5k/year for 7 years. Our Powerwall batteries cost us $15k, and have enable us to operate as a microgrid for 8 months of the year and also weather multiple power outages.
We did similar in 2019 but in our case an 11.4kw solar PV system (the max number of panels our roof could fit), a single Powerwall, a heat pump water heater and A Tesla Model 3. We are retired so mainly charge the car on sunshine.
The cost of the solar, battery and heat pump combined was around $30,000AUD and it has saved us at least $5,000AUD a year so the investment has now been fully repaid. It would have paid for itself within 3 years if not for the Powerwall but still pleased to have it and be totally self sufficient and essentially off grid on most days of the year.
We still export more than we import.
@@LilyWasHereMB My thought exactly - its great if you have the cash...
Here’s a thought. When building shopping malls, put a subterranean battery storage facility in so surplus from the DC canopies can be stored and used to either DC charge EVs when there’s no sun or exported to the grid as and when permits have been obtained and the grid requires.
Dave is right about cheap overnight electricity going away one day. The cheapest electricity is during the day in advanced nations such as Chile and Spain. DC direct charging of EVs is a fantastic solution for the fifteen states in the USA that do not allow net metering. All 50 of the US states can also implement PV-->domestic hot water with no grid connection needed. Heating water and one's space is a DC task that we perform with AC. Edison was not completely wrong, at least not for small grids like one's home.
Thanks for the info on direct to direct
As someone who grew up in the days of wringer washing machines I think my idea for a roller rectifier will finally bring electrification to the Flintstones. 😉
As NEM3.0 kicks into California solar, this makes more sense
Cant wait to get my hands on one
Very good!! It is unstoppable progress.
It's interesting that you mention Australia as a place that has solar energy geographically for longer periods of time, but we actually don't have any grid connections between the Eastern and Western states. The USA, Europe or China are probably better examples of good utilisation of peak solar.
A bit off topic…but I am still shocked that it only costs me $1.60 USD to charge my Model Y from 0 to 100% here in Burlington, Ontario, Canada - every night from 11pm to 7pm the rate is 2.8 cents (CDN) per kwhr - this along with the fact I am paying zero for maintenance is amazing
I am currently charging my EV at home from a DIY solar power system. My system has to convert to AC and then back to DC and in the process loses that 13% you are talking about. It works pretty good and provides free car charging but a DC version would be nice if it manages through the ups and downs of cloud cover. I would want it to be pretty steady so I would think a battery would need to be involved in the design somehow??? Great video, Thanks!
Seems like I heard that there are places working on capacitors for storing that energy for such purposes which would be nice. Much cheaper and longer lasting technology. Also would allow round the clock charging as it would not matter what time of day you used it as long as it charged while the sun was shining.
I was just going to add that thought regarding capacitor banks instead of batteries. They could be built and added at a cheaper cost.
yeah capacitors. i’d imagine the round trip losses from using a battery would be more than conversion
you guys, capacitors are very expensive, particular in high voltage. and they are not meant for storage just short term. good luck with that idea.
@@Humungojerry Round-trip through a low-voltage (48V) battery system would be a bit worse than a standard EVSE, yes.
Round-trip through a high-voltage (typically 300V-500V) battery system would be significantly better. But maintaining such a long multi-stage high voltage DC path that exposes the HVDC battery bus to a third party charger is mostly a non-starter. Its extremely dangerous compared to pushing power with AC. Definitely not worth the 5-7% improvement one could achieve.
-Matt
Great educational content!
We are currently building a off-grid home in regional Victoria, Australia. When the home is completed, we will be purchasing an EV with a bidirectional battery - this DC-DC charging is one of the innovations I have been waiting for!
Nonetheless, I am still eagerly anticipating the advent of technology that would enable an EV to directly power home storage batteries during extended periods of ‘dunkelflaute’.
To me, this is the missing link which would allow people to go off-grid using the EV as the backup generator (avoiding the use of a fossil-fuel generator).
PS - I am not referring to V2L/H as this is too selective and restricted.
But the car battery wants a specific voltage, and it would be a rare coincidence if the PV panels happened to produce that particular voltage. So you need a DC- DC converter. And while they are getting better, they are not lossless. So the net benefit of direct pv- to vehicle is less than the 13% cited. And there is a definite advantage to being able to have the pv panels and the vehicle in different locations, with the ac grid as the intermediate.
besides other drawbacks
In fact there are additional losses in DC coupled systems that are minimal with AC coupled systems but these losses are simply ignored by the proponents of DC coupled systems. The losses I am referring to are related from the legislative required fault protection devices - I.E., fuses and circuit breakers. With AC coupled systems you simply use existing AC rated electrical fuses and circuit breakers which work great. However these AC fuses and circuit breakers can't be used for DC - they require circuit protection equipment that can interupt DC current. One commonly used way to get a DC rated circuit breaker is to string 8 or so AC circuit breakers together and have them mechanically linked together - this allows them to be able to break the DC current. It is clearly obvious that the losses associated with having 8 circuit breakers connected in series on a DC coupled system will be 8 times higher than an equivalent AC coupled system.
The proponents for DC coupled systems ignore this detail on the basis that this is the consequence of safety legislation that can't be avoided.
It's true that you can't just ignore safety requirements, but you can be smart as to how you meet these requirements and by using an AC coupled system then you can minimize the system losses associated with the safety protection equipment.
Thanks Dave. I am off grid and have just purchased an ev.
Amazing Video!
I don't really know anything about electric cars, except that they run on DC batteries. I know a bit about solar panels, namely, they produce DC not AC. If the two industries could decide on a specific Direct Current voltage, then it would be rather simple to charge your car battery with your solar panels with no loss except from the wires. The only real problem is that everybody wants to do things differently. The battery powered tool industry seems to have come to some sort of agreement, but they do keep upping the voltage on the batteries, 7 to 12 to 18 to 24 to 48. I think I would like a 48-volt battery for my hand drill so I can break my wrist the first time I use it.
Great info, as always.
Great vid, thanks for sharing. 👏⚡️👍
It doesn't quite make sense, because you still have to adjust the panel voltage to match what the battery wants - and that involves something like a buck boost converter - which involves conversion to AC, and then back again.
About time. An answer to make charging EVs more available. Charging network in Australia is woeful.
I've been wondering about DC houses for the same reason for some time. I suspect that's where we'll end up
Cheers Dave
Great video thanks
That is good news
The only thing though, for me, when the sun is shining, my EV is normally not at home. So I'll have to spend more to add a battery at home. Here in Switzerland, the payback time of such an installation is pretty bad, more than 20 years. For me.
If you are designing are system from scratch one should consider the cost of the wire for transmitting DC power. In general for high power transmission in DC the guage of cable required is very big and thus very expensive. Thus if the main use of your solar cells is to supply A/C to your house, you will have a less expensive and more efficient install using micro inverters on each panel and moving A/C on less expensive house wire. other advantages of micro inverters:
-Easier to add and remove panels
- lower voltage coming off roof with less danger
- not having to convert to AC for most common applications.
I dream of being able to take a panel with me on road trips and get AC when the sun shines.
Known as a Wheatstone bridge. Anyway. Dave, keep your eye open for a kit that would allow someone with solar panels to buy, say, a used Leaf with at least 10kWh of storage left and to connect it as a home battery. The price of degraded leafs is becoming quite attractive for such an application.
The DC-DC Charger is just a bolt on or extension of your solar inverter and linked management of the power storage. 100% right we have miles of roads and parking areas where we can better manage the collection of solar for electricity and heat and also add water management. When are we going to give up trying patch up the legacy AC grid and see a move to a parallel DC and HVDC grid, Big Solar Energy projects and Mega Batteries linked to it.
Great video as usual 👌
I feel like celebrating too 😊
Thanks. I'm hoping to get a 'system' in the next few years, but (and it isn't what's delaying me.) tech is advancing so fast, every time I think I know what I need, something better comes along.
Solar pannels in series can reach as much as 1000v dc, surely wouldnt it be a case of taking few panels off to calculate the right voltage and the amps would vary threw out the day, bit jack the laid, but it only takes one person to do it or a big fail and a right off a elictric car. more in parallel for more watts
I love the idea of saving 10-13% of my single biggest use of energy, i.e., EV charging. But I am even more excited by the idea of commercial charging stations composed of PV, batteries and DC-to-DC chargers. That would need no or minimal grid connection -- another step towards decentralization. Computing has been distributed for decades but energy distribution is still on the mainframe model.
Not really true. Before the internet, computers were mostly standalone, but now practically every one of them is entirely dependent on the internet. If the 'grid' goes down, nothing will work.
there are also battery less inverters, that one could plug standard "chargers" into.... probably a lower up front cost, plus you can use the AC for other things....efficiency amy or may not matter whem adding more panels is so cheap these days... if one is a DIYer
DB raises a good point, that most people don't seem to be aware of, that when everybody can use off peak electricity, off peak will no longer exist, especially not as a fixed number of hours overnight. With high levels of wind and solar in the electricity mix, peak and off-peak periods are likely to move around from day to day, which is why we need a properly intelligent grid and genuinely smart smart meters that allow you to control equipment automatically in real time based on real time electricity pricing data. As far as I am aware, this is not something that current (UK) smart meters allow you to do, which is why I would suggest they are a very limited value.
With regard to dcdc charging systems these are probably going to make an insignificant difference to electricity demand or cost savings. I'm not quite sure where Entelligent get their 13% higher efficiency claim from (I saw it claimed on their site but then couldn't find the screenshot again) because knowing the efficiency that you can get from chargers (which are basically switch mode DC power supplies) and inverters, even when combining them you should get well over 90% combined efficiency and when you take into account that Entelligent's chargers have a maximum efficiency of 98%, then I suspect the real world efficiency gain is probably closer to around 5%, and then only if you're charging from your PV panels or batteries. However, that wouldn't be a very good marketing ploy for a 12.5KW charger which, at $2,499, probably costs about 3 or 4 times more than it should. You can get 11KW mains chargers for well under £400 (although you can pay much more) so I don't understand why anyone would pay an extra £1,500+ to save themselves 5 to 10% on their electricity (but only when the sun shining closed bracket) and you are probably looking at about 100,000KWh (300,000+ miles) of charging before you get your money back.
I would say Entelligent's marketing is basically green hype to justify an over inflated price tag, and their claim that with it being DC to DC is some great advantage, because you don't have to have AC to DC, is part of the hype.
A PV system will not be producing a DC voltage at the right level for charging your EV so this charger is basically a dc dc converter, and internally a dc dc converter is basically a DC to AC to DC converter, albeit quite high efficiency one. Okay, you get rid of the AC to DC rectifier bit on the input, but at mains voltages that will probably only save about 0.5%, and the rest of the gobbins inside will be very similar. If you're charging from your PV system or batteries you also save another 5% by eliminating the mains inverter, a useful saving if you're not paying a huge price premium for it. Also, you could probably replace the basic rectifier with a synchronous switching rectifier to save a fraction of a percent, but it's probably not worth it.
The big question I was hoping to see an answer to, but didn't, is how much this DC-DC charger actually costs. Nor only does the inverter/rectifier equipment add to the cost, but there's also the fact that it's new technology with a rather limited market of people who have both the right kind of home solar setup and an EV. This is a problem because, if the DC->DC charger costs thousands more to buy or install than a conventional level 2 AC charger, the additional up-front cost will completely overwhelm the value of whatever energy it saves.
Even for a person that is living entirely off-grid, I can easily see DC->DC charging being mor expensive than simply dealing with the energy loss of a conventional charger and buying more solar panels to compensate.
That said, this does seem like the type of thing where, even if it's initially too expensive to make sense right now, it will likely get cheaper in the future.
The problem is most people (and their cars) are at work during the daytime. My battery system is there to time-shift that energy.
This has existed for many years and is currently built into some new houses in Scotland. 8 years ago I built a house for a client in Scotland and he engineered vehicle charging using solar panels, a wind turbine and batteries.
Surely your house had a solar inverter converting to AC and then a conventional EV charger plugged in to a circuit. Otherwise what do you do with all the solar and battery power when you're not charging? Until you're off grid and everything is DC to DC, it doesn't make sense. For decades off-grid people in campers and trailers ran small appliances from 12-volt cigarette lighters, but the grid and most things you plug into the wall run on AC.
Lots of talk on this thread about DC systems being more efficient. What's not been made clear is that DC systems often require dc to dc conversion which is just a lossy as dc to ac. Also ac to dc, if it's using a simple bridge rectifier, is very efficient. BTW I run an off grid system with 48v battery, various 12 and 24v dc loads plus 230v ac for mains appliances including charging an EV.
It would be interesting to see the real world efficiency of the devices being compared. The 13% loss they claim for an AC system is probably a worst-case scenario. The charger featured here is quite expensive. It might be better to invest in a more efficient AC system.
@@incognitotorpedo42 Anything and everything is better than using polluting fossil fuels. At every opportunity.
Dc - DC conversions definitely do have losses but not remotely as much as DC-AC and then AC-DC conversions currently been utilised. Also most EV batteries run at about 400V DC, which is very close to the mppt voltage of most string and hybrid inverters. Similarly, most high voltage home energy storage batteries (e.g. from SMA, Fronius, Huawei etc) operate between 160-600V DC so not much stepping up/down will be required.
@@adon8672 DC to DC converters generally work by converting the input DC into high frequency AC, changing the voltage using a magnetic component and then rectifying it back to DC so it's the same. There are some differences as DC to mains voltage AC is generating low frequency AC. How much difference depends how it's done.
@@petewright4640they don't go full AC usually - just pulse the current on and off, it behaves the same in the magnetic element. Then "rectification" is just smoothing caps.
YEA!!! SOLUTIONS! 😊❤😃👍
Those 13% losses must be the absolute worst scenario, not a typical one. There's absolutely no way that they've chosen such poor electronics. And DC-to-DC transformations (which are needed, as your PV system won't run on 400 V) also have losses. I can't imagine the gains being all that huge.
If this technology can reduce costs by providing a simpler solution, then great, but I don't think shaving off a few percent of losses is going to be a game changer
PV systems (e.g. mine) can easily run on voltages as high as 400V... mine happens to be about 350V but the difference is only the number of panels in a string. Consumer panels tend to have nominal output voltage of around 48V, and a string is often wired in series (adding voltages). My GivEnergy inverter requires 125V to start, and has a max solar PV input of 550V IIRC.
13% is probably comparing their unit to a bog-standard solar inverter + EV diode rectifier setup, and the latter is I agree unlikely to be the case in the longer term even if it might be true for some cars now. However, it is true that inverting the power to AC then rectifying it back to DC will definitely lose non-trivial amounts of power, so avoiding doing it is always going to be a win.
Exactly, makes no sense to make such a poor performing converter as it costs money to build heat sinks to dissipate it all.
A diode drop relative to 240VAC is insignificant, by the way. The IGBT drop (roughly 1.5V) is more significant but still clocks in at only 0.6%. Other losses dominate. But yes, 13% would definitely be worst case. Grid-to-vehicle losses are typically less than 10%.
The real problem is that the DC-DC would have to be a buck-boost and the input would have to be at string voltages. And because it has to be a buck-boost and not just a buck, the efficiency is likely going to clock-in at 95%-97% or so. And it would only be valid while the sun is actually shining.
So the "improvement" is only going to be 5-7% at best, and only under certain conditions. And it will require some rather expensive circuitry and safety features.
I've done a ton of solar over the last two decades and can say with some authority that It is generally going to be far better to spend the money on simply adding more solar instead of spending it on a DC-DC EVSE.
-Matt
Yes. Look at the efficiency rating of your computers power supply (easiest to find for a desktop system). This is AC to DC, but in Europe anything as inefficient as 13% losses at 80% full rated power is not on sale new (though if you like subsidising your utility you can pick up very inefficient pre-used ones)
I agree. What I would say though, is that there are advantages on a commercial scale, as Dave said. Using car parks with solar canopies and DC connection is a great way of avoiding using grid power and would stop all the wasted time in getting a permit to connect to the grid.
I'm off-grid. My house is single-phase and the cost of converting it to 3-phase is uneconomical. This leaves me with a maximum charge rate of 7.36kWh for my EV. Even if I had 3-phase, the AC charger in the vehicle is limited to 11kWh, but there is no such limitation on DC charging. I can't wait for it to hit the market here in Oz. Something like this DC-DC charging would enable me to get upwards of 13.5kWh.