This USB power bank has 28 lithium ion cells all connected in parallel. Total capacity is 36,400 mAh or 131 Watt hours. I'm using the Vruzend 1.6 system of end caps and link strips.
I spent £20 on a spot welder and some strips of nickel. Far faster and cheaper to assemble and takes up a lot less space. Also welded joints are more reliable that spring terminals, especially if you have a lot of them. I built my mother a new battery for her mobility scooter using 60 18650 cells and now it goes for 3 days use before needing a recharge. Old battery didn't last a full day if she went for a day out anywhere.
It's great that you can spot weld them, but some of us have no desire to spend that money (I only want to make 1 powerbank, so the money would be wasted), so spring terminals are desirable.
did the same thing. got a load of old laptop batteries.made two "power" banks and 4 5W lights. i used a small grinding tool to smooth down those weld bits
I've had major reliability issues with those spring caps. A bunch of them split and lost grip and even the ones that didn't lose split weren't reliable. I even used clamp bolts that came with the kit and still wound up losing connection to 3 out of 4 in parallel in a 14s4p pack within a couple of weeks. I tore the whole thing apart and built a new pack using holders soldered to a PCB style system.
I use my DeWalt Battery. Going on 2 years and only charged it once. The day in the start. It was a bit of pain but got the voltage regulator in order. I added a set of 12 USB ports.
Just keep an eye on the warm cell, if it doesn't cool down and the voltage of your pack continues to drop even without a load you have what HPPowerwall refers to as a burner cell. This is a bad cell that has such high resistance that it will burn off the energy it is storing as heat and then start to pull power from the other cells as well. If you leave it for long enough you can have a thermal runaway event and fireworks, just replace the bad cell and dispose of it safely.
A li-ion battery at 4.0V is almost fully charged. A battery at 3.6V can be at 80% or 20% charge because li-ion cells typically stay at that voltage during most of their discharge cycle. If these cell can discharge at 15A they will do just that given the opportunity. The capacity of the cells is 1350mAh. A cell at 3.6V might be at 30% charge = 950mAh. When connected to 3 cells that are charged at 4.2V that one cell at 3.6V might get a 15A charge for 3.8 minutes. I wouldn’t take the risk and certainly not with those old cells. Just my thoughts. (I might be wrong. If so, please let me know where)
Refreshing to see the relaxed attitude about the voltage differences, that much is probably not ideal, but also not that big of a deal. Some people panic over a few millivolts difference but thinks it's ok to discharge at a rate that makes the pack really hot, and to way below nominal voltage range.
A li-ion battery at 4.0V is almost fully charged. A battery at 3.6V can be at 80% or 20% charge because li-ion cells typically stay at that voltage during most of their discharge cycle. If these cell can discharge at 15A they will do just that given the opportunity. The capacity of the cells is 1350mAh. A cell at 3.6V might be at 30% charge = 950mAh. When connected to 3 cells that are charged at 4.2V that one cell at 3.6V might get a 15A charge for 3.8 minutes. I wouldn’t take the risk and certainly not with those old cells. Just my thoughts. (I might be wrong. If so, please let me know where)
@@Conservator. SOC, State Of Charge, is measured primarily by measuring the voltage. Li-ion typically have almost flat voltage curve, but not entirely flat. At the nominal voltage they're typically considered at 50% SOC, so, if the nominal voltage is 3.6 volt, the cell is considered 50% charged at 3.6 volt, unloaded. If the nominal range is 3.2 to 4.2 they're considered 80% charged at 4.0 volt. There are variations, and these are simplifications, there's no practical/easy way to actually measure the amount of energy in the cells that I know of, without discharging them and measure the amount of energy you get out, but that defeats the purpose if you just want to know how much charge you have. Also, charge or discharge affects the voltage over the cells, that makes it more difficult to accurately tell the SOC if the battery is in use, especially if you don't know how much the voltage is affected by that rate of charge or discharge. That may be the reason why some people thinks voltage doesn't say anything about SOC, but it does. Well yes, unprotected cells will discharge at the rate they can, given the opportunity. The rate they can discharge and what you should let them is typically not the same. If discharge amps are stated, it's usually the rate you can let them discharge, without causing to much damage. If 3 cells are at 4.2V and one is at 3.6V, and they get connected in parallell, the higher voltage cells will charge the lower voltage cell at a high rate initially, but the rate is limited by the voltage difference, or lack of, and internal resistance. If each cell can put out 15A to a drain at very low voltage, or even short circuited, they will only produce a small fraction of that in this scenario. The voltage difference will decrease quite fast, and because of that also the transfer rate. I'm not saying you should connect any mismatched cells in parallell, but Julian knows what he's doing, and those cells are probably fairly rugged.
@@fishyerik Thank you for your response. I agree with almost everything you’ve written. I think the cells were rated at 15A. That would indicate that they could go significantly higher. Maybe 0.6V difference isn’t enough for a thermal runaway but I wouldn’t take any risks. I noticed that Julian was only measuring the temperature on the ends of the cells. I got the impression that he hadn’t measured the voltages and that would not be correct imo. I agree that you don’t have to balance them at the mV level but I wouldn’t feel comfortable with more than 0.1 or 0.2V difference. Maybe I’m too cautious 🤷♂️
I think it would be a better deal to sell those 10.8V powertool batteries for more money than new cells cost. Power tool specific have more value. And new cells usually have 2900-3500mAh, where those power tool cells come in 2000-2500mAh.
7:06 - I find that the easiest way to remove the welding spots are by using the little angle cutter you used for cutting the wires. Gentle nip the welding spot with the pliers, and rotate. Do no cut or pull, only nip/hold the spot with the pliers and then rotate sideways, with the pliers tip not pointing towards the cell.
@@JulianIlett It's a method for getting rid of welding points that remains after removing the plates. There isn't really much you can do about the plates other than rolling/pealing them off.
The only danger is that if one cell shorts all the other cells dump their energy into it, however most cells have built in protection in case of high current failure a sort of built in fuse that disconnects.
Fun project. It's not the charged cells that don't like rapid discharge, as they are designed for high discharge currents, especially as there's lots to share the discharge current. However the discharged cells aren't designed to charge rapidly, so when connecting partially charged or discharged cells into a charged pack, large currents can flow into the discharged cells. I've measured currents of over 10C for short periods after connecting discharged cells to charged cells, which is well over the maximum allowed by the manufacturer for charging. However as you pointed out, the current flow stabilises very quickly, but in that time considerable heating can take place initially. I must admit that on expensive cells, I join the discharged cells to the charged cells with a resistance, simply to limit current flow to within the manufacturer's specifications.
So a good strategy for adding a few more cells to a big pack would be: Discharge the large pack to a lower voltage (below the typical voltage of newly purchased cells). Then add the new cells (so they discharge at a high current rather than charge at a high current).
@@JulianIlett If you take the main pack and use it till its dead and take the powerbank board and connect it to the new set and make sure that they are also dead and then connect them together. That way they would be at that low voltage cutoff and the voltages should be matched relative to the powerbank board.
@@JulianIlett I normally try to get all my cells to within a few millivolts of each other before connecting them. 4 tenths difference could damage your cells.
if you drop two nuts in your nut-spinner the 3rd one will stick out a bit and allow you to run the 3rd nut onto the uneven studs with just enough force and guidance to not spin them off while tightning
Those low capacity cells are probably optimized for much higher current draw (and charge rate) than they'll ever see in power bank usage. But ya use what ya got!
Hi, I've been watching these Vruzend for years. With regards to your nuts spinning off any not stick a small magnet on your spinner and then you can just drop a bit in the spinner and nothing would fly away, just a thought!
Very interesting. Any reason for using four metal links instead of three, when constructing the four-cell modules? It seems like the fourth link is a bit redundant since they're all in parallel.
You might want To nibble The bolts Down a little So you can find a Metal box (Genuine Army Ammo Box) and Add A Hand Crank Generator + XT 60 ~ XT 90 (Panel Mounting Kit) Socket (Solar ~ AC > DC Mains Faster charging ) Plus a Super caps array (just for that Extra fast charging with the hand Crank Generator )
My only concern while wiring all the modules together would be to make sure that the distribution of resistances across the links are balanced, otherwise you might get some parts of the pack charging faster or slower than the rest. Unlikely to really matter, esp at low current and an all parallel pack, just something I'd try to avoid if I was doing it. Then again personally I'd be more inclined towards building a 4S pack with a buck boost (or just buck) on the output. Admittedly more complicated and probably marginal efficiency difference in practice.
I did come up With a An Idea of "Tasty Electronics " basically buy Bulks Sweets/biscuits in (Reusable) Containers then (wash and Home Self Recycle Re use them containers for Hobby Electronics Enclosures )
New York City will be introducing legislation dealing with lipo batteries due to over 200 fires and 6 deaths last year from lipo fires. They have a huge amount of delivery cyclists and its becoming a growing concern. We'll see how the EU & UK reacts.
Does anybody else store unused cells in the Fridge? Low temperature slows chemical reaction. I also keep Bread (sealed, no drying) and Eggs in the Fridge!
Bread in the fridge will go stale much faster than frozen, and also faster than just in the cupboard. This is because starch crystalizes faster as temperatures drop but remain above above freezing and this change in the starch is what makes bread stale (as opposed to just dry).
@@Sylvan_dB Your analysis is super interesting. I keep my bread in the fridge to slow mold growth. I should have said, I keep it sealed in the same bag it was supplied in. Purely to keep the same moisture. From ambient; about 23°C to the 6°C in the fridge. Any starch crystals taste great.
Looks like a great set up. Rather than spot welding, it would be easy to change or add to it. Oh man, car will not start, make it a 12 volt or whatever. If voltage isn't to far off, I think you could just lay the bus bars on and leave them loose for awhile so they wouldn't have a real solid contact until they've redistributed there loads some, then tighten down.
Given failure probability of each induvidual cell, massive parralleling of cells rapidly magnifies probabilty of catastrophic failure. As any cell developing a potentially fire mode failure, in this parraleled mode will also increase severity as the non failed cells feed directly their energy into the "failed " cell without sny limits on current dumped. You are constructing a massive fire bomb. Second hand batteries only make the failure probability higher. Suggest extreme caution to anyone trying to duplicate the construction. While all cells are driven to same voltage state, the charging wise there is NO provision to ensure charge current balance over all those cells, so overcharging some cells and under charging others depending on cell aging and chemical state properties. Forming thermal/heating imbalances. There are real reasons that high energy power storages adopt series battery thus higher voltage systems not massive parallel construction.
i can remember when the best way to have a battery was one very large capacity cell and a DC-DC converter to give the required output. No issues with any thing, downside you just need a very large cell 🙂 but very reliable.
Because the cells are forced to be at the same voltage, they will charge at different currents. The lower capacity cell will charge (and discharge) at a lower current than the high capacity cell.
@@JulianIlett cell impedance determines charge current when supplied with an unregulated voltage (like when many unbalanced cells are put in parallel) not necessarily capacity. If I had to guess though there is probably a roughly proportional relationship between impedance and capacity.
You couldn't have made this look anymore like a boom device. That stereotypical 8 segment display is the chefs kiss on top hahaha
Yeah, it's not very practical - you wouldn't want to take it to public events or on public transport.
Oh couse, then you would want it in a backpack and don't forget to wear you hoody.
@@putteslaintxtbks5166 and throw in some extra un-needed wires just handing out of the backpack?
That's a 7 segment display.
@Okurka Decimal point is the eighth segment... 😊 (but yes, the generic term is seven-segment)
I built some small packs with Vruzend. Was fun watching you build with them. You gave a lot of good tips.
I spent £20 on a spot welder and some strips of nickel. Far faster and cheaper to assemble and takes up a lot less space. Also welded joints are more reliable that spring terminals, especially if you have a lot of them. I built my mother a new battery for her mobility scooter using 60 18650 cells and now it goes for 3 days use before needing a recharge. Old battery didn't last a full day if she went for a day out anywhere.
It's just a bit harder to replace a cell if they're welded.
@@JulianIlett Couple of mins once you find the faulty cell.
@@fuzzybobbles Everyone is aware of the spot welding option; go away
It's great that you can spot weld them, but some of us have no desire to spend that money (I only want to make 1 powerbank, so the money would be wasted), so spring terminals are desirable.
@@mattsadventureswithart5764 No no no you have to spot weld them the whole world falls apart if you dont
a dremel or equivalent with a little grinding stone bit removes the remnants of torn-off 18650 tabs nicely
did the same thing. got a load of old laptop batteries.made two "power" banks and 4 5W lights. i used a small grinding tool to smooth down those weld bits
I've had major reliability issues with those spring caps. A bunch of them split and lost grip and even the ones that didn't lose split weren't reliable. I even used clamp bolts that came with the kit and still wound up losing connection to 3 out of 4 in parallel in a 14s4p pack within a couple of weeks. I tore the whole thing apart and built a new pack using holders soldered to a PCB style system.
Some of mine have split too. They were in the shed all winter subject to large temperature variations.
I use my DeWalt Battery. Going on 2 years and only charged it once. The day in the start. It was a bit of pain but got the voltage regulator in order. I added a set of 12 USB ports.
There's slightly more clueless comments than I expected. But only slightly. Great video!
Just keep an eye on the warm cell, if it doesn't cool down and the voltage of your pack continues to drop even without a load you have what HPPowerwall refers to as a burner cell. This is a bad cell that has such high resistance that it will burn off the energy it is storing as heat and then start to pull power from the other cells as well. If you leave it for long enough you can have a thermal runaway event and fireworks, just replace the bad cell and dispose of it safely.
Shit Julian, I just jumped a mile when you dropped the nut adapter!
That looks awesome.
Thanks
I tend to dremel the spot weld off..Then the Nickel strips come off with no effort... and...With no damage and danger of shorting someting at all..
7:06 super solution ❤
A li-ion battery at 4.0V is almost fully charged.
A battery at 3.6V can be at 80% or 20% charge because li-ion cells typically stay at that voltage during most of their discharge cycle.
If these cell can discharge at 15A they will do just that given the opportunity.
The capacity of the cells is 1350mAh. A cell at 3.6V might be at 30% charge = 950mAh.
When connected to 3 cells that are charged at 4.2V that one cell at 3.6V might get a 15A charge for 3.8 minutes.
I wouldn’t take the risk and certainly not with those old cells.
Just my thoughts.
(I might be wrong. If so, please let me know where)
I would have kept long leads on the still useable 3s board.
Refreshing to see the relaxed attitude about the voltage differences, that much is probably not ideal, but also not that big of a deal. Some people panic over a few millivolts difference but thinks it's ok to discharge at a rate that makes the pack really hot, and to way below nominal voltage range.
A li-ion battery at 4.0V is almost fully charged.
A battery at 3.6V can be at 80% or 20% charge because li-ion cells typically stay at that voltage during most of their discharge cycle.
If these cell can discharge at 15A they will do just that given the opportunity.
The capacity of the cells is 1350mAh. A cell at 3.6V might be at 30% charge = 950mAh.
When connected to 3 cells that are charged at 4.2V that one cell at 3.6V might get a 15A charge for 3.8 minutes.
I wouldn’t take the risk and certainly not with those old cells.
Just my thoughts.
(I might be wrong. If so, please let me know where)
@@Conservator. SOC, State Of Charge, is measured primarily by measuring the voltage. Li-ion typically have almost flat voltage curve, but not entirely flat. At the nominal voltage they're typically considered at 50% SOC, so, if the nominal voltage is 3.6 volt, the cell is considered 50% charged at 3.6 volt, unloaded. If the nominal range is 3.2 to 4.2 they're considered 80% charged at 4.0 volt.
There are variations, and these are simplifications, there's no practical/easy way to actually measure the amount of energy in the cells that I know of, without discharging them and measure the amount of energy you get out, but that defeats the purpose if you just want to know how much charge you have.
Also, charge or discharge affects the voltage over the cells, that makes it more difficult to accurately tell the SOC if the battery is in use, especially if you don't know how much the voltage is affected by that rate of charge or discharge. That may be the reason why some people thinks voltage doesn't say anything about SOC, but it does.
Well yes, unprotected cells will discharge at the rate they can, given the opportunity. The rate they can discharge and what you should let them is typically not the same. If discharge amps are stated, it's usually the rate you can let them discharge, without causing to much damage.
If 3 cells are at 4.2V and one is at 3.6V, and they get connected in parallell, the higher voltage cells will charge the lower voltage cell at a high rate initially, but the rate is limited by the voltage difference, or lack of, and internal resistance. If each cell can put out 15A to a drain at very low voltage, or even short circuited, they will only produce a small fraction of that in this scenario. The voltage difference will decrease quite fast, and because of that also the transfer rate.
I'm not saying you should connect any mismatched cells in parallell, but Julian knows what he's doing, and those cells are probably fairly rugged.
@@fishyerik Thank you for your response. I agree with almost everything you’ve written.
I think the cells were rated at 15A. That would indicate that they could go significantly higher.
Maybe 0.6V difference isn’t enough for a thermal runaway but I wouldn’t take any risks. I noticed that Julian was only measuring the temperature on the ends of the cells.
I got the impression that he hadn’t measured the voltages and that would not be correct imo.
I agree that you don’t have to balance them at the mV level but I wouldn’t feel comfortable with more than 0.1 or 0.2V difference.
Maybe I’m too cautious 🤷♂️
I'm not sure I can watch a video that doesn't start "Good morning all!". :)
Yes, sorry - the 'time of day' greeting is gone :)
@@JulianIlett Haha, I’ll keep watching but if the “Cheerio” goes away, I might not know what to do with myself! Haha!
Hi Julian, not as pedantic as myself, I would have to have all the cells writing the same way 🤣
Nice little build, Thanks
Nice project 👍 I liked it
If a cell was shorted you could have had some fireworks. ;)
Glad I'm not the only one that aligns my burrs.
I think it would be a better deal to sell those 10.8V powertool batteries for more money than new cells cost. Power tool specific have more value. And new cells usually have 2900-3500mAh, where those power tool cells come in 2000-2500mAh.
7:06 - I find that the easiest way to remove the welding spots are by using the little angle cutter you used for cutting the wires. Gentle nip the welding spot with the pliers, and rotate. Do no cut or pull, only nip/hold the spot with the pliers and then rotate sideways, with the pliers tip not pointing towards the cell.
Yes, that does result in the cleanest break. You do have to cut the strip first though, to individualise each of the welds.
@@JulianIlett It's a method for getting rid of welding points that remains after removing the plates. There isn't really much you can do about the plates other than rolling/pealing them off.
The only danger is that if one cell shorts all the other cells dump their energy into it, however most cells have built in protection in case of high current failure a sort of built in fuse that disconnects.
When you were younger you must have played with Lego and Meccano ~ nice project indeed 👍🏻
Yes, both :)
Fun project.
It's not the charged cells that don't like rapid discharge, as they are designed for high discharge currents, especially as there's lots to share the discharge current.
However the discharged cells aren't designed to charge rapidly, so when connecting partially charged or discharged cells into a charged pack, large currents can flow into the discharged cells.
I've measured currents of over 10C for short periods after connecting discharged cells to charged cells, which is well over the maximum allowed by the manufacturer for charging. However as you pointed out, the current flow stabilises very quickly, but in that time considerable heating can take place initially.
I must admit that on expensive cells, I join the discharged cells to the charged cells with a resistance, simply to limit current flow to within the manufacturer's specifications.
So a good strategy for adding a few more cells to a big pack would be:
Discharge the large pack to a lower voltage (below the typical voltage of newly purchased cells).
Then add the new cells (so they discharge at a high current rather than charge at a high current).
@@JulianIlett If you take the main pack and use it till its dead and take the powerbank board and connect it to the new set and make sure that they are also dead and then connect them together. That way they would be at that low voltage cutoff and the voltages should be matched relative to the powerbank board.
@@JulianIlett I normally try to get all my cells to within a few millivolts of each other before connecting them. 4 tenths difference could damage your cells.
I'd like to see you try to take that on a plane 😄
Putting that on a plane wouldn't be a problem. A plane is just a woodworking tool after all. Taking it on an aeroplane would be a problem. 😁😁
@@SpeccyMan A plane is a vehicle designed for air travel, with wings and one or more engines.
if you drop two nuts in your nut-spinner the 3rd one will stick out a bit and allow you to run the 3rd nut onto the uneven studs with just enough force and guidance to not spin them off while tightning
I use a Dremel tool to easily sand down the "pips".
Those low capacity cells are probably optimized for much higher current draw (and charge rate) than they'll ever see in power bank usage. But ya use what ya got!
Yes, this was mentioned at 29:33.
No fuse(s)? No temperature monitoring? No thermal fuse? No cell balancing?
- Rather you than me.
you dont need balancing on a 1s battery...
When charging LiPo or Li-Ion packs in the fpv hobby, we need to be sure to have a maximum cell drift of
Yeah, it got a bit warm :)
Can you go over lining up the dovetails and slots again? :)
Yeah, I just dont get it lol
Hi, I've been watching these Vruzend for years. With regards to your nuts spinning off any not stick a small magnet on your spinner and then you can just drop a bit in the spinner and nothing would fly away, just a thought!
How many times do you need to say "module" "dovetail" and "recess"?! 😂
Very interesting. Any reason for using four metal links instead of three, when constructing the four-cell modules? It seems like the fourth link is a bit redundant since they're all in parallel.
Just symmetry really :)
How about a “12” volt pack for inverter use ?
I have an older version of these. I don't know if they are made by the same people or not? Mine are white instead of red and blue.
You might want To nibble The bolts Down a little So you can find a Metal box (Genuine Army Ammo Box) and Add A Hand Crank Generator + XT 60 ~ XT 90 (Panel Mounting Kit) Socket (Solar ~ AC > DC Mains Faster charging ) Plus a Super caps array (just for that Extra fast charging with the hand Crank Generator )
With the increase in domestic fires, self build shouldn't be encouraged.
My only concern while wiring all the modules together would be to make sure that the distribution of resistances across the links are balanced, otherwise you might get some parts of the pack charging faster or slower than the rest. Unlikely to really matter, esp at low current and an all parallel pack, just something I'd try to avoid if I was doing it. Then again personally I'd be more inclined towards building a 4S pack with a buck boost (or just buck) on the output. Admittedly more complicated and probably marginal efficiency difference in practice.
No
Looks like a bomb in those movies. Round cylinders with cables and a display co7nting down…😅
Great video, would you mind sharing details of thermo imaging camera you used? Thanks
It's the Topdon TC004. I did a review video of it recently.
I did come up With a An Idea of "Tasty Electronics " basically buy Bulks Sweets/biscuits in (Reusable) Containers then (wash and Home Self Recycle Re use them containers for Hobby Electronics Enclosures )
👍👍
Hi love ya vids...do you charger this 40v at 5v?
And Will you do a vida how to make them,I need a 90v 20amp .I have a soocter thanks
With such a large capacity in parallel, how do you plan on charging the pack and how long will it take to fully charge?
With mobile charger and 2A current it'll take 10-16 hrs, probably not more than 10 since we never discharge cells fully
New York City will be introducing legislation dealing with lipo batteries due to over 200 fires and 6 deaths last year from lipo fires. They have a huge amount of delivery cyclists and its becoming a growing concern. We'll see how the EU & UK reacts.
Think I'll take a "car" 12v phone changer and put it on a makita 18v battery.
Would it work?
Measure the output voltage before you destroy your phone, some "car charger" say 12-24 volts but not all of them, some may be just for 12 volts.
No fuse links on each cell and a lot of unprotected cells in parallel? RIP.
Does anybody else store unused cells in the Fridge?
Low temperature slows chemical reaction.
I also keep Bread (sealed, no drying) and Eggs in the Fridge!
Bread in the fridge will go stale much faster than frozen, and also faster than just in the cupboard. This is because starch crystalizes faster as temperatures drop but remain above above freezing and this change in the starch is what makes bread stale (as opposed to just dry).
@@Sylvan_dB Your analysis is super interesting.
I keep my bread in the fridge to slow mold growth. I should have said, I keep it sealed in the same bag it was supplied in. Purely to keep the same moisture. From ambient; about 23°C to the 6°C in the fridge. Any starch crystals taste great.
Looks like a great set up. Rather than spot welding, it would be easy to change or add to it. Oh man, car will not start, make it a 12 volt or whatever. If voltage isn't to far off, I think you could just lay the bus bars on and leave them loose for awhile so they wouldn't have a real solid contact until they've redistributed there loads some, then tighten down.
Given failure probability of each induvidual cell, massive parralleling of cells rapidly magnifies probabilty of catastrophic failure. As any cell developing a potentially fire mode failure, in this parraleled mode will also increase severity as the non failed cells feed directly their energy into the "failed " cell without sny limits on current dumped.
You are constructing a massive fire bomb. Second hand batteries only make the failure probability higher.
Suggest extreme caution to anyone trying to duplicate the construction.
While all cells are driven to same voltage state, the charging wise there is NO provision to ensure charge current balance over all those cells, so overcharging some cells and under charging others depending on cell aging and chemical state properties. Forming thermal/heating imbalances.
There are real reasons that high energy power storages adopt series battery thus higher voltage systems not massive parallel construction.
i can remember when the best way to have a battery was one very large capacity cell and a DC-DC converter to give the required output. No issues with any thing, downside you just need a very large cell 🙂 but very reliable.
A fire bomb! Don't ever assemble li-ion batteries in parallel like this! This is RUclips.
❤WOW❤
WHY not and DROP A NUT...darned autocorrect and my fault for not spell checking too....
Does you house insurance cover home made battery fires?
All that stuff lives in the shed :)
@@JulianIlett Best place for it. :) so at least you could have a self-heating shed with built in firework display. when is the next shed update?
@@JulianIlett The shed? You have 4.
Hmm, yes fine if you have a lot of 18650 all the same, but not if you have a lot of different capacities 😞
As long as they're all in parallel and the same chemistry, different capacities isn't a problem.
@@JulianIlett will they not try and back charge the lower value ones when they get low voltage ???
Because the cells are forced to be at the same voltage, they will charge at different currents. The lower capacity cell will charge (and discharge) at a lower current than the high capacity cell.
@@JulianIlett cell impedance determines charge current when supplied with an unregulated voltage (like when many unbalanced cells are put in parallel) not necessarily capacity. If I had to guess though there is probably a roughly proportional relationship between impedance and capacity.
My guess is you might have mixed up your charged pack with one of the fresh packs when reassembling. That would explain the .4V difference.
YESSSSSS! hahahahah
"Say 'dovetail' again... Say 'dovetail' again, I dare you, I double dare you, motherf*cker, say 'dovetail' one more G*ddamn time!" - Joules Wattfield
Dovetail.
@@SpeccyMan 🔫
@@SpeccyMan 😉
Very bad combination of build , can’t blance voltage amounts of these cell.... use 3S or 4S combination with BMS for charging and balance cells .
This pack has the ultimate cell voltage balancing - they're all the same :)