A great alternative to resistors are peltier devices. I run 2 in series or parallel depending on the cell count i am discharging. I have them attached to a big server CPU heatsink and it works amazingly. I can discharge a 1300 4s pack in about 4 mins. What I REALLY want to do is automate it...
Joshua, this video was awsome, this high tecnical stuff was one of the reasons I subbed to your channel in the first place. I personally think you should do more of this, becouse you are really good at explaining this stuff. And as a viewer I can feel the passion you have about it, wich is what makes really interesting content. Your enthusiasm reflects in your teatching becouse you like what your nerding ;-) Keep up the hard work, and thanks for the great content BTW: 11:30min... hillarious I am personally getting more into electronics, and electronic components, and found that alot of the stuff we do with drone and flight controllers, apply with alot of other things, such as robots, arduinos and so on. Oh and welcome to Europe, I am in the neighbouring country Denmark, salutes from here.
Great educational video Joshua. I think the green one is a wire wound ceramic and the other one is silicon which is why the green one doesn't need a heatsink..
I’m A First Time Viewer, I Have To Agree Already. It’s A Natural Thing To Resist Currents. “All Currents” Governing Currents IS A Must. Everyone Stay Grounded. Dependent On That Governor. Harvest It All While I Can. Free Flowing Thought IS Currently Being Gathered But No Output. I Like To Believe We ARE All Free Floating Ions, Waiting To Be Grounded And Leached Off Of. All Energy IS Free. Those Who Govern. Shame On You. 😂 😉
Perfect timing! I’ve just been looking into this and had been wishing you’d done a how to video. Had found a good RCG link on converting a hairdryer to be a 1 ohm load Bank and about to have a go at that. Thanks again!
I don't think this is a good value though. It's about $7 for 2x 25 watt bulbs. That's only 50 watts for $7. Well, they are 2-element bulbs so they're actually more like 30 watts, or 60 watts in total. I can get a 10-pack of 50 watt halogen bulbs for $12. Way better value if you want to go that direction.
It reminds me my first discharge attempt. After crashing my first quad, the (faulty) esc burnt, my battery was full and my charger couldn't discharge... So I quickly built an electric circuit to discharge the battery by using a big stepper motor. It took 3 hours...
This is quite useful, when I break all my quads and have a bunch of fully charged lipos the situation really sucks. Then I know when I get home I'll have to dishonourably discharge all my packs on chargers that fail horribly at discharging AND then repair the quads. It would be nice not to have to be too concerned about the batteries, it's bad enough breaking all your quads :P
Or buy a bunch of 1 USD Ceramic Cartridge Heater for Arduino 3D Printer ( 24V, 40W) - Basically they are power resistor, but works at full potential as a bulb. and $ per Watt is the lowest, and comes with nice wires too. win/win ? I do use one of this heater to discharge my batteries when needed. I'd like to hear your thoughts JB
Assuming you're working at 24 volts, you'd need 25 of those to get to 1000 watts. Or maybe less than double that at 4S voltage. Still only about $50. But geez it's a lot of wiring! I wonder what the downside might be...
nice idea I was thinking of ceramic heaters too but only knew about the room heating bars and solder iron rods. lol these are cheap too I might get some for a pocket heat project. thanks
Downside would be messy, but with a nice cover, the topside would look nice, like some Chinese products - Ok, in practical terms, I am not discharging a nuclear power supply, but my simples 1300 mA 4S occasionally - One simple ceramic heater in a XT 60 is doing the trick in couple minutes. But for serious guys out there with many batteries and serious needs, a more robust anti-power-bank is a must. As always, great class.
I watched it all lol. This video was very helpful for me trying to make a home made heater. (To discharge batteries and make heat as a bonus lol) Im going to use different inputs to have different settings. I can use series to control temperature and parallel to control heat/power consumption Ill figure it out lol
Hmm. I wonder whether getting really cold or really hot is better? What is the efficiency of TEC anyway? Hey! Maybe the ideal would be to pair a TEC with a load resistor, then their temperature would cancel out!
woah, that slideshow template. You got my attention. Lets go :) edit: You have shown me that I am a very lazy engineer. 1. How much current will flow through a 0.5 ohm resistor across a 4s lipo? answer: too much. go get your friends first so they can watch. 2. how much resistance is needed to get 3c out of a battery? answer: lets start with 1k and see what happens. 3. how much resistance is needed to get 60 amps from a 4s lipo? answer: 60 is a lot, lets just short the output through this big roll of house electrical wire. That should do it. 4. how many watts through a 0.25 ohm resistor across a 4s lipo? answer: very little because I wont use the right resistor and it will blow up before dissipating much power. math avoided :)
I am an airsoft player and I think this is exactly what I need to discharge my 7.4v and 11.1v batteries for long term storage. I am also electrically inclined but I am just terrible with math and formulas.
Okay so not crazy 😂😂😂😂😂 it’s okay. It would be great if you did make it. I’m actually working on plans for a lithium powered portable electric heater/ dump load style with a fan. I’d be using left over solar power in a separate battery than the pack powering my small RV.
Best use case for a load bank: keep a good relationship with the neighborhood while designing an hi-fi amplifier - but that is quite similar to your generator example
Joshua,First, thank you for such a great, detailed video. I am a teacher in the largest public school system in Ohio and your presentation was top-notch. Second, although I understand the formula's and math, I am confused on:1) what stops a 2S lipo battery from dumping all of its juice. While racing, we have to use the ESC to determine how much and where. (I.E. 6v or 7.4v to the servo)2) Why not just buy a 200w, 10k Ohm resistor and plug it in? Does the resister determine how much the battery can dump?Also, could you please make a quick video for a 2S lipo, 7,000Mah battery. I see many people using six 100 watt, 1ohm resisters in parallel but based on the math, they should blow. Thank you for your time. I just found your channel but will share it will all of the racing community. Tony
Since you're a teacher, to answer your question, I'll throw one back at you. 1. Based on Ohm's Law, how many amps will flow through a 10 kOhm resistor when a 7.4 volt potential is applied across it? 2. Using the formula given in the video, how many watts will the resistor dissipate? Assume constant 7.4 volts although in reality, the volts will drop as the battery discharges. 3. How long will it take to completely discharge a 7000 mAh battery at this rate? (At a rate of 7 amps, a 7000 mAh pack will completely discharge in 1 hour. At a rate of 14 amps, it will discharge in 0.5 hour. And so forth.) Assume constant discharge rate, although in reality discharge rate will go down as the battery voltage drops and actual time will be longer. The real-world situation is that you are balancing all of these factors: amps, watts, and time to discharge. The ultimate answer to why those guys use 6x 100W 1 ohm resistors is that produces the right balance of those factors for their needs. The rest is just math.
Q1: .00074 amps (I) will flow (I'm assuming 10 Kohm Resistor is 10,000 ohm.) I used the formula I=V/RQ2: .005476 watts will be dissipated by a 10k ohm resistor on a 7.4v battery using P= V squared/RAnswering your questions using a 100watt, 1ohm resistor, my answers are:1) 7.4 amps (I) will flow2) P= 54.76 for a 1 ohm resistor from a 7.4 battery. If I am correct, I can see why they are using a 1ohm resistor now. I would like to know you opinion on "can a battery try to discharge 100% of it's charge if plugged into a group of parallel resistors or does can the battery only discharge so much at once"? Why not buy resistors that a larger so they are not as close to they max load?I know this is a lot of questions and I thank you for your time. You will be compensated for it.
automobile headlight bulb is the cheapest load for drones batteries. i'm using H4 60W halogen with simplest lipo-beeper, works well with 4S. even with parallel board and multiple packs, discharge rate is ok for me.
Let's see if that's true... I looked yesterday, and a 25W+5W dual-element bulb was $7 for two, or $0.11 per watt. In my experience this bulb will pass about 3 amps at 4S voltage, which gives it an effective resistance of about 5 ohms. Can we do better? Here's a 200W 2 Ohm resistor for $20. amzn.to/2zIqEVs So that's $0.1 per watt. But actually the picture is not that rosy because I would never run that at full 200 watts in reality. I chose 2 ohms because that produces about 140 watts. So actually we are at about $0.14 per watt. So maybe that's right... Especially when you consider you have to buy heat sinks for the wirewound resistors. But at the same time, it's best to buy receptacles for the automotive bulbs unless you want to desolder them when they burn out. But it's at least worth considering.
I still think halogen bulbs win though. amzn.to/2yZ1LI2 That's 5x 50 watt 24v halogen bulbs for $12. So you get 250 watts at 24 volts, or only about $0.05 / watt. And if you buy 12v bulbs (amzn.to/2yBLrc9) you get 10x 50 W for $10, or oly $0.02 per watt. So I think halogen bulbs beat automotive bulbs, but all of them beat the pants off resistors.
+Joshua Bardwell here in local store we have it around $1, and if you own a car, you may use old one for free (if near light is broken) anyway, it depends on either you want to heavily test different electronics or just discharge few packs after flights.
So If I make a resistor bank for a 4s battery (10x 100w 3ohm resistors) for an icharger 406. Can I use it to discharge a 2s battery also? Or should I make one just for 2s batteries. (5x 100w 1ohm resistor)?
Why not electronic switching and power adjustment with MOSFETs, 100A should be no problem? Or do you want to use the knife switsch just as additional emergency disconnect?
Excited to see where this goes and what you come up with! I actually built a resistor bank using the copper looking ones you have in the video. I ended up wanting more power and plan to double it in parallel just as you mentioned.
Thanks for this! I have been wondering if the idst fd-100 will be fine or DIY. So far it looks like the fd-100 would be good for plug and play piece of mind and the DIY gives the ability for much higher discharge which will be faster and "fun" since we can do our own battery tests. Next we need to play around with just using old motors and ESCs we all have laying around. Lots of issues though, enclosing props, directing airflow etc...
i think you can use this not only to discharge packs. i am sure the law can be used to charge multiple packs with diffrent voltage (same cell amount for sure). remember me? ;) anyways where you at in germany. greetings from near wiesbaden
I thought about building my own Load Bank: I wanted to use an arduino, a load and a few lines of code. Should have all functionalities you want, even balancing for only a few bucks.
No need to make a video. The claim that they are sub-1-ms latency is not supported by any evidence. Every test I have seen claiming to demonstrate 1 ms latency uses the "point the camera at a stopwatch" method. Here is a video I made about why that method is inadequate: ruclips.net/video/SfbPaRTiB1g/видео.html In short: the NTSC or PAL signal output by the camera has a 30 fps or 25 fps framerate. That means the "point a camera at a stopwatch" method cannot have greater precision than 1/30th or 1/25th of a second. So it is impossible to measure sub-1ms latency with this method. No matter what. Anybody who claims to measure camera latency by pointing a camera at a stopwatch immediately loses all credibility since that method is totally flawed. The right way to measure camera latency is how Oscar Liang and RCSChim do it. You put a photodiode on the screen and shine an LED at the camera. You measure with an Arduino or an oscilloscope how long it took between triggering the LED and the photodiode registering the light on the screen.
I have a discharge bank trying to discharge 6s lipo... the resistors are wired in parallel. I'm using a icharger 4010 dou and on the discharge side it's only showing 7 volts / 40 amps. Why is it only going up to 7 volts?
looking to build a racer, but i wanted to use magnum. heard bad things about it, and kinda want asgard. so, would you say asgard or magnum? Im using a floss
These have been used for many years in the Off Road Stock Buggy rc world. You can buy them premade on ebay. The seller is saltyperformance . I believe a guy name Raymond McCoy out of Arizona came up with this style bank for the icharger. check them out not much more then the actual resistors and fans cost
Probably a stupid question, but if XT60 connectors are only good up to 60 amps, why are they the de facto standard for lipo batteries with a discharge rate well above that?
Kurt is right. An XT60 can handle burst discharges much higher than 60 amps without melting. If your mini quad is pulling 100 amps, how long is your flight going to last? You see bigger connectors on aircraft that pull higher amps for longer times.
Love your video....I would like to discharge lower level LIPO's. Such as 1S to 3S batteries. I have some 50Watt 6 Ohm resisters laying round (used for automobile hyper-flash). I found 6 of them. Would there be any way i could connect these in parallel or serial and use this to discharge smaller LIPO's? These resisters are gold colored and say "50W6ΩJ" right on the top of them. Subscribed !
the ampacity and temp of your wires when your talking 12awg at 60 amps, its more so based on the length. take the same 1 ft wire and make it 10 ft long and it will most likely melt. Just be smart about it. for instance a 1ft 12awg wire will have about .19v of voltage drop, at 10ft it will drop 1.91v.
No, its not. Sure you get a higher voltage drop with longer wires (and therefore lose more energy total), but there is also more area to dissipate the heat. With constant current and wire diameter, the energy/length is constant. That is why these current rating tables dont contain a length specification.
Hippo I don't have a lab to setup a test like this. But my thought is with more voltage drop comes higher current. More current would be more heat and could lead to failure? Maybe I'm wrong.
So if I have a charger where I can control the amperage/power for the discharge into the bank, do I still have to calculate exactly for the current, or can I just build a resistorbank as beefy as possible, or will that not work if I just want to dicharge with low current?
or buy a 12-24v to 5v car usb charger and mod the charger, hook the xt60 male to 12-24v input and plugin the lipo battery and use it to charge your cellphones. what I use to charge my cellphones and to discharge my lipo batteries
The wirewound resistors are actualli wery good (i have never used china versions) I dont like the ceramic resistors, they gets really red hot. I would not use any of them beyond half the rated wattage. A heat sink for 1000W is quite big and expensive.
Good stuff, this is the home-made load bank I've used for the last 3 years: s20.postimg.org/v99oj2ksd/Load_resistor_1.jpg It's 6 x 10 ohm 100W resistors in parallel - per the spec. sheet you can run them at up to 35W without cooling. On 4S it pulls 10A, so around 160W (i.e. 27W per resistor). The temperature stabilises at 160C and the resistors are rated for 220C, so everything is within spec. The input is switched by a relay triggered via a CellLog 8M LiPo monitor hooked up to the balance lead. The bulb on the bank is so you can see when discharge is taking place.
Hi, I want to make a lipo discharge unit but I have an idea about the calculation of the resistance. 4S 5200mAh lipo battery pulling 10 amps to 50% storage level you want to download? What resistance should I use for this?
The right way to do it would be with a current-control supply. But I don't have that. So the battery will sag and I will measure the result. Frankly, I think this may be a bit more realistic since that's also what happens in real life.
There’s a solid math error at 19:02 You squared 16.8 to get 282 but left the ^2 on the equation in the next 2 lines. This implies that it is 282 squared and that would be 79,524 volts. But I’m sure most of us who understand this shit know what you meant here and can ignore this error.
No, I disagree. When you multiply 16.2 volts * 16.2 volts, the result is 282 volts^2. The unit is volts-squared. Like when you measure the area of a square, if it is a 10 foot by 10 foot square, the resulting unit is 100 square feet, which is 100 ft^2. It's the unit that is being squared, not the number. Tracking units like this is something that is often overlooked (even by me) but I was going out of my way to be precise in this video.
Could you build this with a current sensor and volt meter attached? I'm assuming so since you did something similar in the battery trials. However, what would be super cool is if you used a really beefy relay in the circuit and attached the volt and current sensor outputs to an Arduino (I'm a fan of those). Then with some simple coding you could have the Arduino trip the relay when it senses the volts drop to a set value. I'm thinking for storage charging. You could also store the values for current that goes through the battery to figure out if the capacity has been lost or retained over use of the battery (by fully charging the battery and then discharging while sensing the current passing).
in practice no the devices would have to be enormous as well as expensive if such a device existed. what you want is a voltage comparator which controls a mosfet or heavy duty relay.
while this is a sound application of ohms law and the current limiting properties of light bulbs there is no reason to go trough all of this unless you like a science project. If you just want it to work, get a proper charger ; the cellpro 8 for example that can use regenerative discharge into a lead battery up to 40 amp or 10 if you just want a small fan heater without the lead battery connected.
Will this work, and are the calculations the same, for using with an iCharger 308 Duo in Regenerative Discharge, To Channel mode? I assume I wouldn’t need the knife blade switch as the charger circuits act as the switch?
You're right about the knife switch. About regenerative discharge, I don't know for sure. Because the charger is not going to simply treat the load as a resistance, but will current control the output.
Joshua Bardwell Thanks for replying! Things get sooo complicated! I assume as long as you limit the current within the resistors limit, all should be ok :/ I’m getting a bit lost now! I’ll wait for your next instalment and hope for enlightenment.
*crying* Would have loved to meet you but I also live in Berlin... :D Next time you come to Germany you _have_ to come here, too! ... please?! ;) kind regards
Yoooo Mr J duuuuude! Where in Germany are you? I'm currently in hamburg. If your near and have some time it would be awesome to hang out and fly maybe. We have an awesome little fpv community here. Watchya say BuDi :D
Now we just need the plans for a circuit that cuts off the flow at storage (or a configurable) voltage. Come home from flying, pop our batteries on this load, and discharge to storage in 5 minutes (instead of an hour). I love the idea of a discharger that runs like a quad.
Troy Nahrwold I do this they my icharger. One channel has my discharge amplifier on it and the other channel has the batteries. I just tell the charger to discharge at a certain amperage and where to stop discharge at certain voltage (3.8v per cell) works great
What stops you from using a bunch of high power handling NPN's like uk.farnell.com/semelab/mag6332/trans-audio-npn-230v-30a-to-264/dp/1856783 (in series?) Heatsinked with a fan, connecting the pack(s) to controlled by an arduino and interfaced by a cheap LCD display and clicky button input. Set the number of packs, or pick a discharge rate and and let it PWM the transistors to the load (array of bulbs etc)
That would be a smart way of doing it but I'm looking for a dumb way because I don't want to spend time programming an Arduino. Actually, I already have a device graciously built for me by Cheng Lin that will control the relays to run a discharge program and log the results. I just need to build the load right now.
Hey How long do you stay in Germany and where in Germany? Let me know if you have a bit of sparetime. Maybe its possible to catch up :). Have a save trip. Cheers Matt
if you feel like dorking out to use mosfets under control: ruclips.net/video/8xX2SVcItOA/видео.html with an arduino or rasberry pi - pc logging would be possible for 'battery testing' - this might be one hell of a project
youtube is trying to be family friendly but I got an ad of a (basically) nude woman? and they demonetize basically all videos in which someone cusses in?
Yes but show me a battery that can happily be charged at 100+ amps. Or even 60 amps really? I would be happy to use it as a load but I think it is going to be pretty difficult.
Sure. Don't get me wrong. The topic was waaay to nerdy for me. But keep it up. Someday I'll consume this stuff like chokolate. I love your deep tec knowhow and how nerdy content and learnings you put on YT. That's why I support you on Patreon. I learned mor from your videos than I learned in school in this topics.
I actually built a "load bank" out of 12 old stove heating elements. I use it to quickly discharge my 12S ebike batteries at about 1000w. Works great.
A great alternative to resistors are peltier devices. I run 2 in series or parallel depending on the cell count i am discharging. I have them attached to a big server CPU heatsink and it works amazingly. I can discharge a 1300 4s pack in about 4 mins. What I REALLY want to do is automate it...
Joshua, this video was awsome, this high tecnical stuff was one of the reasons I subbed to your channel in the first place. I personally think you should do more of this, becouse you are really good at explaining this stuff. And as a viewer I can feel the passion you have about it, wich is what makes really interesting content. Your enthusiasm reflects in your teatching becouse you like what your nerding ;-) Keep up the hard work, and thanks for the great content
BTW: 11:30min... hillarious
I am personally getting more into electronics, and electronic components, and found that alot of the stuff we do with drone and flight controllers, apply with alot of other things, such as robots, arduinos and so on.
Oh and welcome to Europe, I am in the neighbouring country Denmark, salutes from here.
men I am from Puerto Rico I follow you because you are very technical
Great educational video Joshua. I think the green one is a wire wound ceramic and the other one is silicon which is why the green one doesn't need a heatsink..
Yes, that's what I'm being told.
I just realized I hit like on your vids before I finish watching almost every time. Great work!
I’m A First Time Viewer, I Have To Agree Already. It’s A Natural Thing To Resist Currents. “All Currents” Governing Currents IS A Must.
Everyone Stay Grounded. Dependent On That Governor. Harvest It All While I Can. Free Flowing Thought IS Currently Being Gathered But No Output.
I Like To Believe We ARE All Free Floating Ions, Waiting To Be Grounded And Leached Off Of.
All Energy IS Free. Those Who Govern.
Shame On You.
😂 😉
Thank You ☺️
Loved it. I like getting real deep into how stuff works. Great watch!
Perfect timing! I’ve just been looking into this and had been wishing you’d done a how to video. Had found a good RCG link on converting a hairdryer to be a 1 ohm load Bank and about to have a go at that.
Thanks again!
Good old automotive bulbs work well too. Been using them for years. Then you get light for the shop too :)
I don't think this is a good value though. It's about $7 for 2x 25 watt bulbs. That's only 50 watts for $7. Well, they are 2-element bulbs so they're actually more like 30 watts, or 60 watts in total.
I can get a 10-pack of 50 watt halogen bulbs for $12. Way better value if you want to go that direction.
It reminds me my first discharge attempt. After crashing my first quad, the (faulty) esc burnt, my battery was full and my charger couldn't discharge... So I quickly built an electric circuit to discharge the battery by using a big stepper motor. It took 3 hours...
lol I like when you bust out the slides good stuff Teach this is a good experiment for a class to do learning ohms law. very nice presentation
This is quite useful, when I break all my quads and have a bunch of fully charged lipos the situation really sucks. Then I know when I get home I'll have to dishonourably discharge all my packs on chargers that fail horribly at discharging AND then repair the quads. It would be nice not to have to be too concerned about the batteries, it's bad enough breaking all your quads :P
Even if you were to get a couple of automotive bulbs, you can discharge relatively quickly. The full Load Bank approach is for faster discharge.
Joshua Bardwell I like the load bank idea, think I might build one. Hit the nail with a sledgehammer 🙂
Josh!! Come fly with us in the Netherlands! You’re so close now! 😎👍
Or buy a bunch of 1 USD Ceramic Cartridge Heater for Arduino 3D Printer ( 24V, 40W) - Basically they are power resistor, but works at full potential as a bulb. and $ per Watt is the lowest, and comes with nice wires too. win/win ? I do use one of this heater to discharge my batteries when needed. I'd like to hear your thoughts JB
Assuming you're working at 24 volts, you'd need 25 of those to get to 1000 watts. Or maybe less than double that at 4S voltage. Still only about $50. But geez it's a lot of wiring!
I wonder what the downside might be...
nice idea I was thinking of ceramic heaters too but only knew about the room heating bars and solder iron rods. lol these are cheap too I might get some for a pocket heat project. thanks
Downside would be messy, but with a nice cover, the topside would look nice, like some Chinese products - Ok, in practical terms, I am not discharging a nuclear power supply, but my simples 1300 mA 4S occasionally - One simple ceramic heater in a XT 60 is doing the trick in couple minutes. But for serious guys out there with many batteries and serious needs, a more robust anti-power-bank is a must. As always, great class.
I️ have built one of these for a decent discharge rate, but it gets HOTTT, gotta add more resistors and fans
Welcome to Germany!
Joshua, come here to my country. We got a lot of great places to fly in North Korea.
I'm in Switzerland!! come fly with us!!
LegendärerPirmin nomol e schwiizer 😉
I watched it all lol. This video was very helpful for me trying to make a home made heater. (To discharge batteries and make heat as a bonus lol)
Im going to use different inputs to have different settings.
I can use series to control temperature and parallel to control heat/power consumption
Ill figure it out lol
@15:40 good visual explanation...I take it this is why adding more lipos when parallel charging lowers the IR reported on a charger?
Yes that's exactly right.
Joshua, You never looked better!!!
Oh, you.
LOL! Thanks for the videos!
The mk2b 3d printer heatbed has windings for 1 and 3ohm, should handle ~10a with a small fan blowing across it, and costs under $15.
Joshua you can easily use TEC (thermoelectric cooler) and stick old CPU fan on it and solder XT60. It will work good for discharging lipos
Hmm. I wonder whether getting really cold or really hot is better? What is the efficiency of TEC anyway?
Hey! Maybe the ideal would be to pair a TEC with a load resistor, then their temperature would cancel out!
Joshua Bardwell yeah :D I like really cold, I use them when discharging my lipos. And I can play with it :D
woah, that slideshow template. You got my attention. Lets go :)
edit: You have shown me that I am a very lazy engineer.
1. How much current will flow through a 0.5 ohm resistor across a 4s lipo?
answer: too much. go get your friends first so they can watch.
2. how much resistance is needed to get 3c out of a battery?
answer: lets start with 1k and see what happens.
3. how much resistance is needed to get 60 amps from a 4s lipo?
answer: 60 is a lot, lets just short the output through this big roll of house electrical wire. That should do it.
4. how many watts through a 0.25 ohm resistor across a 4s lipo?
answer: very little because I wont use the right resistor and it will blow up before dissipating much power.
math avoided :)
Excellent content Josh, this is exactly why I subbed years ago, keep it up!
I am an airsoft player and I think this is exactly what I need to discharge my 7.4v and 11.1v batteries for long term storage. I am also electrically inclined but I am just terrible with math and formulas.
Perhaps I missed it but I can’t find a PART 2 or this video, can you link me please? I did find this helpful.
Sorry but I haven't made it :-(
Okay so not crazy 😂😂😂😂😂 it’s okay. It would be great if you did make it. I’m actually working on plans for a lithium powered portable electric heater/ dump load style with a fan. I’d be using left over solar power in a separate battery than the pack powering my small RV.
Best use case for a load bank: keep a good relationship with the neighborhood while designing an hi-fi amplifier - but that is quite similar to your generator example
Yes, that's definitely a common use.
If I want to discharge a 6000mah 100C 2S Lipo battery @ 40 Amps, what size (& how many) resistors do I need? Thank you!!!! :)
WOW. I FINALLY get it. Thanks so much!
Joshua,First, thank you for such a great, detailed video. I am a teacher in the largest public school system in Ohio and your presentation was top-notch. Second, although I understand the formula's and math, I am confused on:1) what stops a 2S lipo battery from dumping all of its juice. While racing, we have to use the ESC to determine how much and where. (I.E. 6v or 7.4v to the servo)2) Why not just buy a 200w, 10k Ohm resistor and plug it in? Does the resister determine how much the battery can dump?Also, could you please make a quick video for a 2S lipo, 7,000Mah battery. I see many people using six 100 watt, 1ohm resisters in parallel but based on the math, they should blow. Thank you for your time. I just found your channel but will share it will all of the racing community. Tony
Since you're a teacher, to answer your question, I'll throw one back at you.
1. Based on Ohm's Law, how many amps will flow through a 10 kOhm resistor when a 7.4 volt potential is applied across it?
2. Using the formula given in the video, how many watts will the resistor dissipate? Assume constant 7.4 volts although in reality, the volts will drop as the battery discharges.
3. How long will it take to completely discharge a 7000 mAh battery at this rate? (At a rate of 7 amps, a 7000 mAh pack will completely discharge in 1 hour. At a rate of 14 amps, it will discharge in 0.5 hour. And so forth.) Assume constant discharge rate, although in reality discharge rate will go down as the battery voltage drops and actual time will be longer.
The real-world situation is that you are balancing all of these factors: amps, watts, and time to discharge. The ultimate answer to why those guys use 6x 100W 1 ohm resistors is that produces the right balance of those factors for their needs. The rest is just math.
Q1: .00074 amps (I) will flow (I'm assuming 10 Kohm Resistor is 10,000 ohm.) I used the formula I=V/RQ2: .005476 watts will be dissipated by a 10k ohm resistor on a 7.4v battery using P= V squared/RAnswering your questions using a 100watt, 1ohm resistor, my answers are:1) 7.4 amps (I) will flow2) P= 54.76 for a 1 ohm resistor from a 7.4 battery. If I am correct, I can see why they are using a 1ohm resistor now. I would like to know you opinion on "can a battery try to discharge 100% of it's charge if plugged into a group of parallel resistors or does can the battery only discharge so much at once"? Why not buy resistors that a larger so they are not as close to they max load?I know this is a lot of questions and I thank you for your time. You will be compensated for it.
My answer can't be correct due to how large the amp draw is. It would never be that large.
@@TD-zx7kf Bueller ?
I use stove heating elements and string 12 of them in parallel. I get them from my scrapyard for $1 a pound so they are extremely cheap
automobile headlight bulb is the cheapest load for drones batteries. i'm using H4 60W halogen with simplest lipo-beeper, works well with 4S. even with parallel board and multiple packs, discharge rate is ok for me.
Let's see if that's true...
I looked yesterday, and a 25W+5W dual-element bulb was $7 for two, or $0.11 per watt. In my experience this bulb will pass about 3 amps at 4S voltage, which gives it an effective resistance of about 5 ohms.
Can we do better? Here's a 200W 2 Ohm resistor for $20. amzn.to/2zIqEVs So that's $0.1 per watt. But actually the picture is not that rosy because I would never run that at full 200 watts in reality. I chose 2 ohms because that produces about 140 watts. So actually we are at about $0.14 per watt.
So maybe that's right... Especially when you consider you have to buy heat sinks for the wirewound resistors. But at the same time, it's best to buy receptacles for the automotive bulbs unless you want to desolder them when they burn out. But it's at least worth considering.
I still think halogen bulbs win though.
amzn.to/2yZ1LI2
That's 5x 50 watt 24v halogen bulbs for $12. So you get 250 watts at 24 volts, or only about $0.05 / watt. And if you buy 12v bulbs (amzn.to/2yBLrc9) you get 10x 50 W for $10, or oly $0.02 per watt.
So I think halogen bulbs beat automotive bulbs, but all of them beat the pants off resistors.
+Joshua Bardwell here in local store we have it around $1, and if you own a car, you may use old one for free (if near light is broken) anyway, it depends on either you want to heavily test different electronics or just discharge few packs after flights.
Yes, for sure. If you just want to discharge a pack, you should use the SMOKE STOPPER that you already own!
A Fix load bank is ok, but perhaps a Mosfet load back with controllable current control is more versatile
So If I make a resistor bank for a 4s battery (10x 100w 3ohm resistors) for an icharger 406. Can I use it to discharge a 2s battery also? Or should I make one just for 2s batteries. (5x 100w 1ohm resistor)?
Nice video with great in depth explanation.
Hi Joshua, why want to discharge battery in high amps, what will happen to the battery 😮 i m new
I found some 250w 24v G6.35 base halogen bulb
The wire ga depends on the voltage. Higher voltage requires less thickness
Why not electronic switching and power adjustment with MOSFETs, 100A should be no problem? Or do you want to use the knife switsch just as additional emergency disconnect?
I am trying to keep this simple and not have to design electric circuits and write Arduino code.
Excited to see where this goes and what you come up with! I actually built a resistor bank using the copper looking ones you have in the video. I ended up wanting more power and plan to double it in parallel just as you mentioned.
Next time we go fly or drink a beer here in Stuttgart. No video making in the hotel!
Thanks for this! I have been wondering if the idst fd-100 will be fine or DIY. So far it looks like the fd-100 would be good for plug and play piece of mind and the DIY gives the ability for much higher discharge which will be faster and "fun" since we can do our own battery tests.
Next we need to play around with just using old motors and ESCs we all have laying around. Lots of issues though, enclosing props, directing airflow etc...
Well organized information! Great video.
Josh....gave me a brain ache today....but smarter me is now;)
Willkommen in Deutschland!
is there a part 2 as i cant find it
was there any further update to this video like the build video you said was coming? i dont see anything on your channel
No. There was no update. But the math in this one is still super useful so I leave it up.
i think you can use this not only to discharge packs. i am sure the law can be used to charge multiple packs with diffrent voltage (same cell amount for sure). remember me? ;) anyways where you at in germany. greetings from near wiesbaden
If you connect multiple packs with different voltages in parallel, they will exchange current and damage each other.
I'm in Stuttgart.
Too bad no video, but still, excellent "video" :) Thanks!
I thought about building my own Load Bank:
I wanted to use an arduino, a load and a few lines of code.
Should have all functionalities you want, even balancing for only a few bucks.
PLease make a video on the tbs zero zero v2 1ms latency fpv camera
No need to make a video. The claim that they are sub-1-ms latency is not supported by any evidence. Every test I have seen claiming to demonstrate 1 ms latency uses the "point the camera at a stopwatch" method. Here is a video I made about why that method is inadequate: ruclips.net/video/SfbPaRTiB1g/видео.html
In short: the NTSC or PAL signal output by the camera has a 30 fps or 25 fps framerate. That means the "point a camera at a stopwatch" method cannot have greater precision than 1/30th or 1/25th of a second. So it is impossible to measure sub-1ms latency with this method. No matter what.
Anybody who claims to measure camera latency by pointing a camera at a stopwatch immediately loses all credibility since that method is totally flawed.
The right way to measure camera latency is how Oscar Liang and RCSChim do it. You put a photodiode on the screen and shine an LED at the camera. You measure with an Arduino or an oscilloscope how long it took between triggering the LED and the photodiode registering the light on the screen.
I have a discharge bank trying to discharge 6s lipo... the resistors are wired in parallel. I'm using a icharger 4010 dou and on the discharge side it's only showing 7 volts / 40 amps. Why is it only going up to 7 volts?
Because the charger is limiting output to 40 amps to try to avoid frying something.
There is also the choice of a series/parallel setup. Two sets of parallel 5- 1ohm 100watt resistors in series??? Is my math off?
Awesome video thanks!
That was excellent, Thank you!
looking to build a racer, but i wanted to use magnum. heard bad things about it, and kinda want asgard. so, would you say asgard or magnum? Im using a floss
These have been used for many years in the Off Road Stock Buggy rc world. You can buy them premade on ebay. The seller is saltyperformance . I believe a guy name Raymond McCoy out of Arizona came up with this style bank for the icharger. check them out not much more then the actual resistors and fans cost
The formula symbol for the potential is U not V. Might want to correct your Slide.
I left that in there just for you to find ;-)
could i use this for testing 18650 li-ion batteries?
Probably a stupid question, but if XT60 connectors are only good up to 60 amps, why are they the de facto standard for lipo batteries with a discharge rate well above that?
Kurt is right. An XT60 can handle burst discharges much higher than 60 amps without melting. If your mini quad is pulling 100 amps, how long is your flight going to last? You see bigger connectors on aircraft that pull higher amps for longer times.
Thanks guys; makes sense. Interesting video!
There are XT90s but they aren’t particularly small or light.
Love your video....I would like to discharge lower level LIPO's. Such as 1S to 3S batteries. I have some 50Watt 6 Ohm resisters laying round (used for automobile hyper-flash). I found 6 of them. Would there be any way i could connect these in parallel or serial and use this to discharge smaller LIPO's? These resisters are gold colored and say "50W6ΩJ" right on the top of them. Subscribed !
the ampacity and temp of your wires when your talking 12awg at 60 amps, its more so based on the length. take the same 1 ft wire and make it 10 ft long and it will most likely melt. Just be smart about it. for instance a 1ft 12awg wire will have about .19v of voltage drop, at 10ft it will drop 1.91v.
Yup. Keep the wires short and you'll be okay.
No, its not. Sure you get a higher voltage drop with longer wires (and therefore lose more energy total), but there is also more area to dissipate the heat.
With constant current and wire diameter, the energy/length is constant. That is why these current rating tables dont contain a length specification.
Hippo I don't have a lab to setup a test like this. But my thought is with more voltage drop comes higher current. More current would be more heat and could lead to failure? Maybe I'm wrong.
So if I have a charger where I can control the amperage/power for the discharge into the bank, do I still have to calculate exactly for the current, or can I just build a resistorbank as beefy as possible, or will that not work if I just want to dicharge with low current?
The charger manual will give recommended resistance for the external load.
or buy a 12-24v to 5v car usb charger and mod the charger, hook the xt60 male to 12-24v input and plugin the lipo battery and use it to charge your cellphones. what I use to charge my cellphones and to discharge my lipo batteries
+Jara FPV not very fast...
The wirewound resistors are actualli wery good (i have never used china versions) I dont like the ceramic resistors, they gets really red hot. I would not use any of them beyond half the rated wattage. A heat sink for 1000W is quite big and expensive.
You mean the green one in my video, right? That's the wirewound? Or is the aluminum one also wirewound?
The small one is wirewound, the big one is ceramic.
Good stuff, this is the home-made load bank I've used for the last 3 years:
s20.postimg.org/v99oj2ksd/Load_resistor_1.jpg
It's 6 x 10 ohm 100W resistors in parallel - per the spec. sheet you can run them at up to 35W without cooling. On 4S it pulls 10A, so around 160W (i.e. 27W per resistor). The temperature stabilises at 160C and the resistors are rated for 220C, so everything is within spec. The input is switched by a relay triggered via a CellLog 8M LiPo monitor hooked up to the balance lead. The bulb on the bank is so you can see when discharge is taking place.
J.B. do you have a video on adding 4 more channels to the FlySky i6 transmitter? Thanks
No, I haven't done that mod.
Good info . thanks
Hi,
I want to make a lipo discharge unit but I have an idea about the calculation of the resistance. 4S 5200mAh lipo battery pulling 10 amps to 50% storage level you want to download? What resistance should I use for this?
A simple resistive load will not stop at 50%. It will always fully discharge the battery.
When you do this do you have a plan for how you are going to correct for voltage sag?
The right way to do it would be with a current-control supply. But I don't have that. So the battery will sag and I will measure the result. Frankly, I think this may be a bit more realistic since that's also what happens in real life.
There’s a solid math error at 19:02
You squared 16.8 to get 282 but left the ^2 on the equation in the next 2 lines. This implies that it is 282 squared and that would be 79,524 volts.
But I’m sure most of us who understand this shit know what you meant here and can ignore this error.
No, I disagree. When you multiply 16.2 volts * 16.2 volts, the result is 282 volts^2. The unit is volts-squared. Like when you measure the area of a square, if it is a 10 foot by 10 foot square, the resulting unit is 100 square feet, which is 100 ft^2. It's the unit that is being squared, not the number. Tracking units like this is something that is often overlooked (even by me) but I was going out of my way to be precise in this video.
Could you build this with a current sensor and volt meter attached? I'm assuming so since you did something similar in the battery trials. However, what would be super cool is if you used a really beefy relay in the circuit and attached the volt and current sensor outputs to an Arduino (I'm a fan of those). Then with some simple coding you could have the Arduino trip the relay when it senses the volts drop to a set value. I'm thinking for storage charging. You could also store the values for current that goes through the battery to figure out if the capacity has been lost or retained over use of the battery (by fully charging the battery and then discharging while sensing the current passing).
Yes, that's a good approach. Use a SSR (solid state relay).
I was going to try zener diodes to cut off at storage voltage. That would work right?
in practice no the devices would have to be enormous as well as expensive if such a device existed. what you want is a voltage comparator which controls a mosfet or heavy duty relay.
I'm not sure about htat...
while this is a sound application of ohms law and the current limiting properties of light bulbs there is no reason to go trough all of this unless you like a science project.
If you just want it to work, get a proper charger ; the cellpro 8 for example that can use regenerative discharge into a lead battery up to 40 amp or 10 if you just want a small fan heater without the lead battery connected.
+cmulder002 a lot of my viewers like a science project.
Will this work, and are the calculations the same, for using with an iCharger 308 Duo in Regenerative Discharge, To Channel mode? I assume I wouldn’t need the knife blade switch as the charger circuits act as the switch?
You're right about the knife switch. About regenerative discharge, I don't know for sure. Because the charger is not going to simply treat the load as a resistance, but will current control the output.
Joshua Bardwell Thanks for replying! Things get sooo complicated! I assume as long as you limit the current within the resistors limit, all should be ok :/ I’m getting a bit lost now! I’ll wait for your next instalment and hope for enlightenment.
Could you add a link to the hefty knife switch you used in your battery tests?
I did. It's in the video description. The exact one :-)
Part 2?? :)
One day in Germany an this is what you have turned to??? ;-)
Question: how long does it takes to unload the battery?
Maybe Part 2 can happen now in 2022, to see this thing be build up!!!1
Guten Tag Herr Bardwell,
Also planning to visit the German neighbors on the west? (the Netherlands) If not than you must visit Berlin!
For this trip, it's only Stuttgart, unfortunately.
*crying*
Would have loved to meet you but I also live in Berlin... :D
Next time you come to Germany you _have_ to come here, too! ... please?! ;)
kind regards
Early post. ;) Back to school.. LOL... Its been a long time,
Yoooo Mr J duuuuude!
Where in Germany are you?
I'm currently in hamburg. If your near and have some time it would be awesome to hang out and fly maybe. We have an awesome little fpv community here.
Watchya say BuDi :D
What are you doing in Germany? Do you have any Quads with you?
Working for my day job. No, I didn't bring any quads, and I won't have time to fly regardless.
Where are you/have you been?
I definitely learned something today.
Hey how long are you staying in Germany? Will you do another meet&greet?
I will be working long days straight up until I leave, so unfortunately there won't be time for another meet and greet.
Just out of curiosity, where in Germany are you? ;)
Stuttgart.
thanks, hope you will be in Hamburg one day! cheers and keep on the good stuff
Now we just need the plans for a circuit that cuts off the flow at storage (or a configurable) voltage. Come home from flying, pop our batteries on this load, and discharge to storage in 5 minutes (instead of an hour). I love the idea of a discharger that runs like a quad.
Troy Nahrwold I do this they my icharger. One channel has my discharge amplifier on it and the other channel has the batteries. I just tell the charger to discharge at a certain amperage and where to stop discharge at certain voltage (3.8v per cell) works great
What stops you from using a bunch of high power handling NPN's like uk.farnell.com/semelab/mag6332/trans-audio-npn-230v-30a-to-264/dp/1856783 (in series?) Heatsinked with a fan, connecting the pack(s) to controlled by an arduino and interfaced by a cheap LCD display and clicky button input. Set the number of packs, or pick a discharge rate and and let it PWM the transistors to the load (array of bulbs etc)
That would be a smart way of doing it but I'm looking for a dumb way because I don't want to spend time programming an Arduino. Actually, I already have a device graciously built for me by Cheng Lin that will control the relays to run a discharge program and log the results. I just need to build the load right now.
Hey How long do you stay in Germany and where in Germany? Let me know if you have a bit of sparetime. Maybe its possible to catch up :). Have a save trip. Cheers Matt
I'm in Stuttgart, but working long days with no spare time I'm afraid.
Whatever happened to part 2?
I did this instead ;-/
www.gofundme.com/best-droneracing-lipo-testing-evar
if you feel like dorking out to use mosfets under control: ruclips.net/video/8xX2SVcItOA/видео.html
with an arduino or rasberry pi - pc logging would be possible for 'battery testing' - this might be one hell of a project
Part two in 2021?
Where are you in Germany? Would love to meet you :)
Welcome Joshua! :) What city if I may ask
Stuttgart.
Business with Porsche or Mercedes? :D If you are near Munich, let me know so I can invite you to a couple of beer. cheers
Just working a show at the conference center. Nothing too exciting, unless you are into CAD design.
CAD design? Is that Computer Aided Design Design? :)
Yes, like an ATM Machine.
Welcome to Germany Joshua.
What are you doing here?
+RCfreak1 - working.
Anderson Power Pole connectors: www.andersonpower.com/us/en/products/powerpole/index.aspx
First! Can't wait to see what this vids all about
youtube is trying to be family friendly but I got an ad of a (basically) nude woman? and they demonetize basically all videos in which someone cusses in?
what a waste of energy.
Not if it's winter ;-)
Regenerative charging anyone? ;)
Yes but show me a battery that can happily be charged at 100+ amps. Or even 60 amps really? I would be happy to use it as a load but I think it is going to be pretty difficult.
just idea for you next video ;) anyways, 100a only if you are in a rush. ;) Usually its when you charge ;)
Discharge through Roomba would be nice 😁
Hm, couldn’t watch the whole vid. It was too boring to watch the slides and listening.
If you are not excited by the topic, then it will be hard to listen. It's okay. This type of content is not for everybody.
Sure. Don't get me wrong. The topic was waaay to nerdy for me. But keep it up. Someday I'll consume this stuff like chokolate. I love your deep tec knowhow and how nerdy content and learnings you put on YT. That's why I support you on Patreon. I learned mor from your videos than I learned in school in this topics.
you cant survive university :P this is like 100x more interesting than most lecturers :/
What have you expected? FPV is not a f%$king entertainment! :)
n00b_fpv :-) I just wanted to give feedback.