60280 cell problems

wiredcom

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Joined
Aug 23, 2021
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Hello everyone,

I purchased 64 of the 60280 cells from battery hookup. I have them in an 8s8p configuration for 24v 440Ah with one BMS controlling the entire battery.
The issue I have is that the 5th cell in every pack of 8 charges and discharges faster than any of the other cells. So I thought to correct the issue I put a heltec balancer on each of the 8 packs to bring cell 5 to the voltage of all the other cells. After a couple of days I started losing cell 5 from some of the packs (2), what I mean by that is under a load the cell drops to 0 volts. I emailed battery hookup but that didn't really get me anywhere, they said they would forward the info to someone named David Paz and that he was answering technical questions for them. At this point I'm looking for any input that may help me get this issue corrected. I know battery hookup is a clearing house for used batteries but for the $2600 I spent with them I was hoping they would have some tech folks that could point me in the right direction. Is the 8s8p configuration the problem? Can the cells take charge and discharge at the same time?

Thanks!
 

Bob B

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The batteries themselves with be either in storage, charging, or discharging. Your system, however, can be doing both charge and discharge at the same time.

If you have a load and a charge source, the charge source will supply the load up until there is no longer enough charge to do that and then the batteries will begin supplying load.
If there is more charge power available than there is load, the excess charge power will charge the batteries until they are fully charged.
 

Mcgivor

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Jul 24, 2021
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187
Hello everyone,

I purchased 64 of the 60280 cells from battery hookup. I have them in an 8s8p configuration for 24v 440Ah with one BMS controlling the entire battery.
The issue I have is that the 5th cell in every pack of 8 charges and discharges faster than any of the other cells. So I thought to correct the issue I put a heltec balancer on each of the 8 packs to bring cell 5 to the voltage of all the other cells. After a couple of days I started losing cell 5 from some of the packs (2), what I mean by that is under a load the cell drops to 0 volts. I emailed battery hookup but that didn't really get me anywhere, they said they would forward the info to someone named David Paz and that he was answering technical questions for them. At this point I'm looking for any input that may help me get this issue corrected. I know battery hookup is a clearing house for used batteries but for the $2600 I spent with them I was hoping they would have some tech folks that could point me in the right direction. Is the 8s8p configuration the problem? Can the cells take charge and discharge at the same time?

Thanks!


So what you're saying is one cell within a cell block of 8 in parallel is lower than the others? When describing an 8P 8S battery it's easier to use the term cell block to reference the 8P arrangement because it reduces ambiguity.

When 8 cells are connected in parallel to create a cell block, all individual cells should be at the same voltage , if an individual cell differs from the other 7, that would indicate either a poor connection or a failed or failing cell.

Were the cells checked for voltage before being put in parrallel? They should all be within a few mV of each other.
 

wiredcom

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Aug 23, 2021
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Hi,

Yes the 5th cell in each cell block of 8 started charging and discharging faster than all of the other cells. All of the cells and all of the cell blocks were within 30-40mv of each other before the packs were assembled and before each pack was put in parallel they were all brought to an equal charge and all connections torqued to the same fp.
This battery has been assembled and working fine for about 3 weeks. I never started seeing the deviation from cell 5 on each cell block until last week. Since I don't have a bms for each cell block I added a heltec active balancer to each one but after 2 days 2 cells are dead and I have had to pull those cell blocks. At this point the battery is just sitting until I can find a solution. Today I ordered 8 more cells from BH to replace the bad ones but I don't understand why they are going bad. Is 8s8p a bad configuration? What would cause only cell 5 in each block to get so far out from the rest while charging and discharging?
 

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Mcgivor

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Something looks wrong, the image 3rd from left appears to be 8 cells in series, can you draw how the cells are arranged? Attached is a file which shows the verious methods after cell arrangement.
 

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wiredcom

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This is the configuration but instead of 2 in parallel there are 8. 8s8p
 

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Mcgivor

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What you have is 8 separate 1P 8S batteries in parallel, a single BMS cannot be used, 8 separate BMS's would be required.
 

wiredcom

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Ok, Is there a better or any other way to configure them? How can they be configured for one BMS? Or how do you control each cell in this big of a battery. How can you put 8 BMS's in parallel?
 

Mcgivor

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The only way to accomplish this using a single BMS is to parrallel 8 cells into a cell block then series connect, this will be a 8P 8S configuration, this is what I use only with 4P 100Ah prysmatic cells.
 

Mcgivor

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Each group of 8 parrallel cells will be treated as a single cell (cell block) Screenshot_2021-08-24-11-02-23.png
 

wiredcom

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Can you explain this configuration to me? I don't understand it but I'm guessing this is how they were configured when BH got them..
 

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Mcgivor

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Can you explain this configuration to me? I don't understand it but I'm guessing this is how they were configured when BH got them..

That is a 2P 4S 12V nominal, to make a cell block all the negatives would be on one side and interconnected, same for the positives, making it 8P 1S, this would be done to all the modules then connect in series + to -, the eight BMS positive sense wires connect to each module (cell block ) positive, negative to first module negative.
 

ejfluhr

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Which cell block does your BMS monitor? I presume it only "sees" one of the 8 since you have 8 independent 8s batteries there. That cell block likely as has the best cell voltages as it's the only one getting checked and balanced.

As a simple test to prove that your "bad" cells and BMS do work ok, you may try connecting the BMS to just one of the 8s1p cell blocks you pulled and run a few charge and discharge cycles. The BMS should adequately protect and maintain the cells (assuming the #5 cell isn't damaged, and has been recharged back to match the other cells).

You probably don't have enough bus bars from BH to convert that pack to an 8s of 8p. Can you make your own? If not, perhaps you have enough to make 8 groups of 4p (as Mcgivor describes above), then serial connect those to temporarily make an 8s4p pack for use until you acquire some more bus bars?
 

Mcgivor

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Which cell block does your BMS monitor? I presume it only "sees" one of the 8 since you have 8 independent 8s batteries there. That cell block likely as has the best cell voltages as it's the only one getting checked and balanced.

As a simple test to prove that your "bad" cells and BMS do work ok, you may try connecting the BMS to just one of the 8s1p cell blocks you pulled and run a few charge and discharge cycles. The BMS should adequately protect and maintain the cells (assuming the #5 cell isn't damaged, and has been recharged back to match the other cells).

You probably don't have enough bus bars from BH to convert that pack to an 8s of 8p. Can you make your own? If not, perhaps you have enough to make 8 groups of 4p (as Mcgivor describes above), then serial connect those to temporarily make an 8s4p pack for use until you acquire some more bus bars?
Just to avoid confusion on behalf of the OP, if 8 cells are connected in series that is a battery, a single cell is a cell, a group of cells in parallel is a cell block, 8 cell blocks in series is a battery.
 
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Christopia25

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Sep 20, 2021
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Hi,

Yes the 5th cell in each cell block of 8 started charging and discharging faster than all of the other cells. All of the cells and all of the cell blocks were within 30-40mv of each other before the packs were assembled and before each pack was put in parallel they were all brought to an equal charge and all connections torqued to the same fp.
This battery has been assembled and working fine for about 3 weeks. I never started seeing the deviation from cell 5 on each cell block until last week. Since I don't have a bms for each cell block I added a heltec active balancer to each one but after 2 days 2 cells are dead and I have had to pull those cell blocks. At this point the battery is just sitting until I can find a solution. Today I ordered 8 more cells from BH to replace the bad ones but I don't understand why they are going bad. Is 8s8p a bad configuration? What would cause only cell 5 in each block to get so far out from the rest while charging and discharging?
If you connect all the 1P8S cells in parallel to make an actual 8P8S battery with busbars, top and bottom, and you can manage the whole battery with one BMS. That'd be the easiest way to fix your batter issue. You can probably get away with using flattened copper pipe as busbars if you don't have enough busbars, but you'll need to check the ratings with the draw you plan on pulling from the battery.
 

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