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Help with 352AH Li-Po battery case

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RyanAK

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Built this battery box with a friends help, I think he exaggerated his knowledge a little and we ended up with this setup. I am aware of some issues that need to be fixed when I go through and re-wire it all, but if you see anything I missed feel free to chime in.

The major issue I am looking for an answer on, is these Li-Po pouch cells each have their own onboard BMS. On the first initial use, the voltage was brought too low and some of the cells shut down and now will not accept a charge, and when I plug in the BMS it just shows low voltage on two of them.

Can I just switch the charger to a Ni-MH charge setting and force charge them the way its hooked up, until the voltage gets high enough to be recognized then switch to Li-Po charging? Or do I need to charge the cells individually?

Current issues I noticed:

The setup needs to be a 3S configuration, currently wired as a 4S. The power inverter only accepts up to 15 volts for the top end, so most of the 352AH is unusable in the current 4S configuration

Needs a beefier charger. Took several days to fully charge.

I need a better BMS (I think)

Thanks,
Ryan
 

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Welcome to the forum.

RyanAK said:
Built this battery box with a friends help, I think he exaggerated his knowledge a little and we ended up with this setup. I am aware of some issues that need to be fixed when I go through and re-wire it all, but if you see anything I missed feel free to chime in.

The major issue I am looking for an answer on, is these Li-Po pouch cells each have their own onboard BMS. On the first initial use, the voltage was brought too low and some of the cells shut down and now will not accept a charge, and when I plug in the BMS it just shows low voltage on two of them.

Can I just switch the charger to a Ni-MH charge setting and force charge them the way its hooked up, until the voltage gets high enough to be recognized then switch to Li-Po charging? Or do I need to charge the cells individually?
Click to expand...

You can try the NiMH charging profile, but you should do it on individual cells. Use the lowest current you possibly can. 0.05-0.1A. Once cells will HOLD 3.0V for 60 seconds, switch to LiPo.

RyanAK said:
Current issues I noticed:

The setup needs to be a 3S configuration, currently wired as a 4S. The power inverter only accepts up to 15 volts for the top end, so most of the 352AH is unusable in the current 4S configuration
Click to expand...

15V/4 = 3.75V = nominal voltage - likely right around 50% SoC.

Need to know inverter cut-off. You may find that you are just flipping it the other way... top 50% available, but bottom 50% not.

Unfortunately, 3.6-3.8V Lithium chemistries makes for crap 12V. You want 7S for 24V and 14S for 48V.
 
Thanks for the reply!

Do I need to un-solder each cell to charge them individually? it's 80 cells, obviously took a long time to solder so hoping to get away with just removing one of the packs of 20 cells and turning it into a 3S (just moving over a bus bar) then just charging the cells individually while all still connected.

The range for the inverter is 11-15v. I looked up a charge percentage chart for Li-Po and it looks like from 30% charge capacity to 90% is 11.3V to 12.3V for 3S. Does that sound right? I attached a pic of the chart I found on google.

Lipoly Voltage vs. State of Charge 2S - 6S Packs.JPG
 
RyanAK said:
Thanks for the reply!

Do I need to un-solder each cell to charge them individually? it's 80 cells, obviously took a long time to solder so hoping to get away with just removing one of the packs of 20 cells and turning it into a 3S (just moving over a bus bar) then just charging the cells individually while all still connected.
Click to expand...

No. You should be able to charge any parallel cell group, i.e., 20 cells at once.

RyanAK said:
The range for the inverter is 11-15v. I looked up a charge percentage chart for Li-Po and it looks like from 30% charge capacity to 90% is 11.3V to 12.3V for 3S. Does that sound right? I attached a pic of the chart I found on google.

View attachment 42573
Click to expand...

The numbers I gave are off-the-top of my head based on Lithium LMO/NMC. They tend to be similar, but cells vary. It really just depends on their chemistry. If you can find manufacturers data, that's the best way to go.

If the above chart is true for your cells, then yes, 3S would be fine.
 
snoobler said:
Ugh. Kill that Imax B6 clone with fire!
Click to expand...
Ok, I can and will post a video haha. What should i replace it with? It would be nice to use the same case but I do have a slightly larger one I can use. Would be nice to add a solar input.20210325_181045.jpg20210325_181101.jpg
 
That pack frightens me on many levels. I think it is all of the LiPo Pouch Cells in one place. :)
 
Update to the project and a question. I am hoping these new issues are due to my crappy charger, but looking for confirmation.

I removed one of the parallel cell groups (20 cells) to charge it, the charger almost instantly showed it was at 4.2v, although the it was still accepting milliamps. I knew it couldn't be at 4.2 because I completely drained it prior to this.

So I disconnected a 4 pack to do the same test, similar issue.

So I un-soldered one individual cell to test and it showed 3.31V on the meter, shown in the picture. But when I hooked it up to the charger it showed it at 4.07v.

Am I using too crappy of a multi meter, charger, both? I am ordering the one linked20210403_184038.jpg above, just have this one to use for now and trying to make some kind of progress.

Thanks :)
Ryan20210403_184246.jpg
 
snoobler said:
Are you using alligator clips?
Click to expand...
The charger was hooked up with alligator clips. For the meter i used prongs that i held on the leads pinched with my fingers until it was stable.

I just finished un-soldering and testing 12 individual packs on the first PCG and 11 of them were 3.05v - 3.06v with one outlier being at 3.64v.

I am assuming there must be at least one pack in the 20 cell group thats at 4.2V which is why I got that reading when all 20 were connected in parallel.

Here's a pic cuz pics are fun.
20210403_204825.jpg
 
Tested the last 8 individual cells. 7 out of 8 were at 3.05v - 3.06v. Again, one of them was at 3.67.

So the charger showing 4.2 must just be off and my multimeter seems consistent.

I plan to discharge the 2 cells to 3.06 volts. I am really not wanting to disconnect all the other 60 cells and re-solder them but i think that is what must be done.

Could the uneven cell voltage be from improper wiring/soldering?

Thank you for all the input!

Ryan
 
Alligator clips have HORRIBLE resistance. The 4mm banana plugs aren't great either. You've demonstrated a 0.7V drop between the meter and the charger.

That charger is notoriously untrustworthy on any readout. I had one version report current and capacity 30% higher than actual.

If you use the same leads with the other charger, you'll have bad results as well.

Try charging again comparing meter and charger voltages. Once noted pinch the alligator clips hard onto the wires and see how it changes. Current should go up and/or voltage should go down.
 
Normally, parallel cells stay in balance as they share and distribute the current. But having the separate BMS on each cell is actually causing a lot of your trouble here. Once the voltage went either too high or too low and they started disconnecting, the cells became unbalanced. When they try to reconnect, the current flowing between a 3.06 volt cell and a 3.65 volt cell is likely high enough that it is tripping off the BMS current protection over and over.

I would just bypass all those separate BMS units. Parallel all the cells in a group but with say 10 ohm resistors at first. That 0.6 volt difference would just pull 60 milliamps between the cells and bring them all to a voltage in the middle. Let it sit like that for a day and then try to charge the single 1S 20P group at 5 amps or so and see how that goes. Since you are splitting this all apart, break the forth group into 3 more groups of 6, and 2 spares. And add them on, so now you have 3S 26P total. At 4,400 mah each, that get's you up to 114.4 AMP hours at 9 to 12.6 volts. Going down to just 11 volts, you get close to 60 amp hours of useable power. Not to bad. If the cells are good for 1C rate, that is also 114.4 amps, or over 1,000 watts out of the inverter. Not a bad little backup power box. Get a good charger for it, and a solid 3S BMS like a 200 amp rated Daly. Here is the cheaper 100 amp one. This has no monitoring or adjustments, but it says it will take a surge to 300 amps.

Amazon.com: DALY BMS 3S 12V 100A Li-ion Battery Protection Board with Balance Leads Wires for Ebike Battery Pack 12V : Electronics

Buy DALY BMS 3S 12V 100A Li-ion Battery Protection Board with Balance Leads Wires for Ebike Battery Pack 12V: Battery Chargers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com
The smart ones and 200 amp rated get a bit more expensive.
And here is a 150W charger that will work from AC line input or from a 12 volt car battery source.
150 watts (actually a 10 amp limit at 3S) is still going to take a full day to top this beast up from a full discharge. If you used 60 amp hours, that is over 6 hours to charge it back up. Most higher power chargers won't have the balance charge feature. That is okay as long as the BMS can keep the cells in balance, but for something like this, the balance charger is a good idea.
 
GXMnow said:
Normally, parallel cells stay in balance as they share and distribute the current. But having the separate BMS on each cell is actually causing a lot of your trouble here. Once the voltage went either too high or too low and they started disconnecting, the cells became unbalanced. When they try to reconnect, the current flowing between a 3.06 volt cell and a 3.65 volt cell is likely high enough that it is tripping off the BMS current protection over and over.

I would just bypass all those separate BMS units. Parallel all the cells in a group but with say 10 ohm resistors at first. That 0.6 volt difference would just pull 60 milliamps between the cells and bring them all to a voltage in the middle. Let it sit like that for a day and then try to charge the single 1S 20P group at 5 amps or so and see how that goes. Since you are splitting this all apart, break the forth group into 3 more groups of 6, and 2 spares. And add them on, so now you have 3S 26P total. At 4,400 mah each, that get's you up to 114.4 AMP hours at 9 to 12.6 volts. Going down to just 11 volts, you get close to 60 amp hours of useable power. Not to bad. If the cells are good for 1C rate, that is also 114.4 amps, or over 1,000 watts out of the inverter. Not a bad little backup power box. Get a good charger for it, and a solid 3S BMS like a 200 amp rated Daly. Here is the cheaper 100 amp one. This has no monitoring or adjustments, but it says it will take a surge to 300 amps.

Amazon.com: DALY BMS 3S 12V 100A Li-ion Battery Protection Board with Balance Leads Wires for Ebike Battery Pack 12V : Electronics

Buy DALY BMS 3S 12V 100A Li-ion Battery Protection Board with Balance Leads Wires for Ebike Battery Pack 12V: Battery Chargers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com
The smart ones and 200 amp rated get a bit more expensive.
And here is a 150W charger that will work from AC line input or from a 12 volt car battery source.
150 watts (actually a 10 amp limit at 3S) is still going to take a full day to top this beast up from a full discharge. If you used 60 amp hours, that is over 6 hours to charge it back up. Most higher power chargers won't have the balance charge feature. That is okay as long as the BMS can keep the cells in balance, but for something like this, the balance charger is a good idea.
Click to expand...
Thanks for all this information!

I didnt see this reply until now and have been busy soldering most of the day. Took a few pics in between I posted below.

I think I must have read your mind because I did exactly that and ended up with a 3S 26P configuration. Came out to 10"×7" and I have 10.5"x7.5" opening in the box. I had already ordered the balanced charger that snoobler listed above. Although Im not opposed to ordering a 2nd charger for another build! The one you listed is about half the price.

I realized I was mistaken with the 3.65v cell vs the 3.06. I disconnected all 80 cells and had to apply charge to each one as NiMH and each one was at 3.06. I have already soldered them all back together so leaving individual bms's on for now.

I previously had the 1000w inverter connected directly to the battery, with no bms in between, causing the low voltage to trigger one bms then I am guessing the rest followed.

Some follow up questions if you please:)
1. I would like to add a BMS that i can set a low voltate cut off to the inverter at 11.2volts. If you know of any bms that does this and will handle the 1kw inverter load. I am going to look at the daly. I wish overkill had their BT bms in stock as it looks like it takes up less real estate inside my already cramped case. Plus of course its Will recommended.

2. Do you know of a charger that would also accept solar and have mppt/bms and fit inside my case, or am I living in a dream world?

Below, cells all disconnected. Removing the liquid electrical tape, old chunks of solder and wire. Charging each pack to turn back on bms. Re-soldering 4packs in parallel.

20210406_140036.jpg

Below, all the batteries removed. Need to remove the crappy B6 charger and power supply still. Make room for the new charsoon antimatter 300w 20a balance charger.

20210406_141450.jpg

Below, 3S26P battery pack hot glued and electrical taped back together. Series connections done. Trying to get solder to stick onto bus bar is my current step. Then adding connections for bms.
20210406_202101.jpg
 
Last edited:
!,000 watts at about 12 volts is going to pull close to 100 amps. There are a few BMS units that will take that for a reasonable time. The Daly I linked should work. That cheap version though is not adjustable for a higher cut off voltage. This one is a Blue Tooth "Smart" BMS that might fit the bill.

Amazon.com: DALY Smart BMS with Bluetooth Wireless Control SOC UART 3S 12V 100A 3.7V Li-ion Battery Protection Board with Balance Leads Wires BMS for 18650 Battery Pack : Electronics

Buy DALY Smart BMS with Bluetooth Wireless Control SOC UART 3S 12V 100A 3.7V Li-ion Battery Protection Board with Balance Leads Wires BMS for 18650 Battery Pack: Electronics - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com
I can't find a listing for what parameters are adjustable though. The add only lists the basic values that the non smart ones use. My JK BMS allows full adjustments, but it requires 40 volts as it will take up to 24 cells and it costs $200. I did run it at 4S with a 48 volt converter to power it, so it would work, but that is a bit of an over kill for your use. Here is a thread on a Daly smart BMS that might have the info you need.
diysolarforum.com

Daly BMS settings for protection parameters

Hello, I have a 12v 4S 250a Daly BMS and I'm wanting recommendations for the "Protection Parameters" page in the Daly BMS BT app, my cells are 500ah
diysolarforum.com diysolarforum.com
The screen shot of the app does look like you can change your voltage cut off per cell and for total pack.

You will likely need to have the MPPT controller external. I can't think of one small enough to stuff inside there. How much solar panel are you thinking of using? There are cheap PWM controllers that would fit, if you don't mind the poor efficiency. The cheapest PWM controllers basically just connect and disconnect the solar panel from the battery to limit the max voltage. So you need to run a solar panel that works well at your pack voltage. MPPT works better with higher voltage solar panels and they optimize the charge current continuously to get more energy out of the solar panel. If you are just going to leave a panel out to top it up, efficiency is not a big deal and the PWM should be fine. But to use it as a reliable energy source, then the MPPT is worth the cost. Most of the cheaper units that say lithium compatible are pre set for a 4S LFP battery. You will need one that can be adjusted down for your 3S cobalt LiPo cells. I just found this one that has a 3S Li Ion 3.7 per cell setting.
I have never used it, no idea if it is any good. This 10 amp version could take up to a 250-300 watt solar panel, but you will only get about 130 watts of charge power out of it. They also list a 20 amp version. But the single panel would still only charge at about 130 watts, you would need parallel panels to get the current up to 20 amps. This thing can't step voltage, so anything above 15 volts or so is wasted under full sun, but a 30 volt 300 watt panel will make that 130 watts under less sun, so it is not all bad. The unit actually has some pretty good reviews.
 
GXMnow said:
!,000 watts at about 12 volts is going to pull close to 100 amps. There are a few BMS units that will take that for a reasonable time. The Daly I linked should work. That cheap version though is not adjustable for a higher cut off voltage. This one is a Blue Tooth "Smart" BMS that might fit the bill.

Amazon.com: DALY Smart BMS with Bluetooth Wireless Control SOC UART 3S 12V 100A 3.7V Li-ion Battery Protection Board with Balance Leads Wires BMS for 18650 Battery Pack : Electronics

Buy DALY Smart BMS with Bluetooth Wireless Control SOC UART 3S 12V 100A 3.7V Li-ion Battery Protection Board with Balance Leads Wires BMS for 18650 Battery Pack: Electronics - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com
I can't find a listing for what parameters are adjustable though. The add only lists the basic values that the non smart ones use. My JK BMS allows full adjustments, but it requires 40 volts as it will take up to 24 cells and it costs $200. I did run it at 4S with a 48 volt converter to power it, so it would work, but that is a bit of an over kill for your use. Here is a thread on a Daly smart BMS that might have the info you need.
diysolarforum.com

Daly BMS settings for protection parameters

Hello, I have a 12v 4S 250a Daly BMS and I'm wanting recommendations for the "Protection Parameters" page in the Daly BMS BT app, my cells are 500ah
diysolarforum.com diysolarforum.com
The screen shot of the app does look like you can change your voltage cut off per cell and for total pack.

You will likely need to have the MPPT controller external. I can't think of one small enough to stuff inside there. How much solar panel are you thinking of using? There are cheap PWM controllers that would fit, if you don't mind the poor efficiency. The cheapest PWM controllers basically just connect and disconnect the solar panel from the battery to limit the max voltage. So you need to run a solar panel that works well at your pack voltage. MPPT works better with higher voltage solar panels and they optimize the charge current continuously to get more energy out of the solar panel. If you are just going to leave a panel out to top it up, efficiency is not a big deal and the PWM should be fine. But to use it as a reliable energy source, then the MPPT is worth the cost. Most of the cheaper units that say lithium compatible are pre set for a 4S LFP battery. You will need one that can be adjusted down for your 3S cobalt LiPo cells. I just found this one that has a 3S Li Ion 3.7 per cell setting.
I have never used it, no idea if it is any good. This 10 amp version could take up to a 250-300 watt solar panel, but you will only get about 130 watts of charge power out of it. They also list a 20 amp version. But the single panel would still only charge at about 130 watts, you would need parallel panels to get the current up to 20 amps. This thing can't step voltage, so anything above 15 volts or so is wasted under full sun, but a 30 volt 300 watt panel will make that 130 watts under less sun, so it is not all bad. The unit actually has some pretty good reviews.
Click to expand...

Great info, thank you.

I plan on using up to four panels, and being in AK I am thinking MPPT is the way to go since I also want the panels to be able to fully charge the unit and not just top off.

I am going to transplant everything into a new case that will fit the BMS better along with a quality MPPT. TBH the wiring is all driving me crazy anyways, the charger needs to be taken out anyways, and I accidentally fried the fan on install. Time for a trip to my hardware store for a rolling case.

After not finding any large example builds with these pouches hooked up to a large Inverter I started wondering why. I went through so many of wills videos, Jehu's and website pics and nothing. I started thinking About C rating. These are a 0.5 C battery. Am I doing this calculation right?

80x4400mah = 352,000mah /350ah

350ah x .5c = 175a discharge rate

If I am correctly learning this, how does that low C rating affecting using a inverter with a peak of 2kw. Could that damage the batteries with a 200a discharge BMS?
 
You are a little off on the math. You only have 26 cells in parallel. 4.4 amp hour x 26 = 109 Amp Hour. Then you have 3 in series to get 11.1 volts nominal. 109 x 11.1 = about 1,200 watt hours. The 1C rate would be 109 amps. If these are the cells from Battery Hookup, I think they tested them to nearly 1C without a problem. So 100 amps is fine, I would not push much further for any long term, but a start surge to double might hold. Since you are only a 12 volt system, you could add one of those huge capacitors they put on car stereo systems to help feed the power amps. As long as your constant current stays under 100 amps, you should be fine. 1,000 watts is a lot of power. With the capacitor, you could pull a huge surge for starting a motor like the compressor in a refrigerator or air conditioner.
 
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