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PacPow 24V 100Ah LiFePO4 Battery

teosju

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Nov 28, 2022
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Hello,

I need some newbie advice. I purchased the above mentioned battery and I use a HTRC P20, 20-Amp smart battery charger in LifePO4 mode. I noticed that while charging cell 3 maxes out quicker than the other 7 cells and when discharging it discharges faster also. Can this be solved by top balancing? Also if the bus bars are laser welded how can I perform a top balance?

I hope I make sense to anyone.

Thank You


PacPow 24V 100Ah LiFePO4 Deep... https://www.amazon.com/dp/B0BB12B51G?ref=ppx_pop_mob_ap_share
 
If you have a bench top power supply (PSU), you can try charging it up slowly, to allow the BMS to balance.
The BMS probably has passive balancing, with only a few tens of mA balancing current per cell.
Your charger might be charging it too fast for the BMS balance current to keep up with.
Balancing happens at the top of the voltage curve.

Procedure is like this:
1. Make sure your battery is discharged below 27.2v (3.4v per cell). If one cell is still at or higher than 3.4v, discharge the pack even lower.
2. Set your PSU to 28.4v (3.55v per cell) and 1A constant current.
3. Connect to your battery and let it charge untill PSU shows 0 amps going into the battery. At this voltage it shouldn't harm the cells. Just don't leave it on the charger at this state for too long.
4. You might need to repeat this procedure a few times to get the cells well balanced.
5. If after a few charge-discharge cycles like this it doesn't improve, you may want to try and charge at an even lower rate (300-400mA).

In case all this doesn't work (be patient...) and you don't mind opening the case, you can still charge each individual cell using a PSU at 3.55v 3.6v. But this is only if you know what your doing...

Good luck.
 
If you have a bench top power supply (PSU), you can try charging it up slowly, to allow the BMS to balance.
The BMS probably has passive balancing, with only a few tens of mA balancing current per cell.
Your charger might be charging it too fast for the BMS balance current to keep up with.
Balancing happens at the top of the voltage curve.

Procedure is like this:
1. Make sure your battery is discharged below 27.2v (3.4v per cell). If one cell is still at or higher than 3.4v, discharge the pack even lower.
2. Set your PSU to 28.4v (3.55v per cell) and 1A constant current.
3. Connect to your battery and let it charge untill PSU shows 0 amps going into the battery. At this voltage it shouldn't harm the cells. Just don't leave it on the charger at this state for too long.
4. You might need to repeat this procedure a few times to get the cells well balanced.
5. If after a few charge-discharge cycles like this it doesn't improve, you may want to try and charge at an even lower rate (300-400mA).

In case all this doesn't work (be patient...) and you don't mind opening the case, you can still charge each individual cell using a PSU at 3.55v 3.6v. But this is only if you know what your doing...

Good luck.
Thank you so much for the advice. Quick question, if your first recommendation doesn’t work and I have to charge each individual cell, will the busbars being laser soldered to the cells be a problem?
 
Thank you so much for the advice. Quick question, if your first recommendation doesn’t work and I have to charge each individual cell, will the busbars being laser soldered to the cells be a problem?
It's harder to charge with non-removable bust bars but it's possible.

But first, you need to be very careful: You want to charge only one cell at a time, and that means you need to identify the positive and negative of the cell.

I would suggest you use a multimeter to measure the voltage of the cell you want to charge, just to make sure you have identified the correct terminals. Voltage should be in the 3v range. If you measure double or more, you are not on the correct terminals.

The problem with welded bus bars is that you need to use some alligator clips in order to get contact with the busbars. The problem is most cables with alligator clips are low quality or too thin to carry a large current. Also, you will have a small contact area that could get a bit hot, depending on how long and at what current you charge.

In your case, since your only trying to top balance, you don't need much current.
Just charge the battery pack fully and then do the individual cell top balance.
 
meetyg thank you so much I was able to balance perfectly following your advice.
 

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