Trouble with a Single LiFePO4 Cell in My Battery Pack – Need Advice!

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Asked By User1234!@# On

I'm dealing with a 48v battery setup made up of 16 LiFePO4 cells in series, and I'm having some issues. My system keeps shutting off because the BMS is detecting low voltage, and it seems to be a particular cell that drops in voltage quickly. I'm pretty sure this cell is faulty, but I'm not sure how to go about fixing it. I've come across some threads suggesting that I can't just replace this single cell, which is concerning because replacing the whole pack would be quite costly.

I'd like to know if there's a reliable way to confirm if this cell is indeed bad. I tried swapping it out with a different one in the series, but the BMS didn't respond well, so I'm guessing they have some identification mechanism. Would resetting the BMS help? Or would that be a bad idea? Also, should I consider charging all my cells to full? I've got a 12v car battery charger, and I've read that I can charge groups of 4 cells at a time. As of now, my cells never reach full charge, with the BMS reporting under 3.4V, which I think is the threshold for full charge. I'm relatively new to this, having run the batteries since September, but they were unused for about 14 months before that. Any advice would be appreciated!

3 Answers

Answered By BMS_Enthusiast On

To check if your cell is really bad, you might want to disable the BMS temporarily and then charge and discharge that specific cell independently. That way, you can verify its capacity. And remember to check your BMS model since some don’t even support cell balancing! It sounds like you might need a better charger than that car one to fully utilize your setup.

User1234!@# -

Thanks for the tip! I’ll see if I can find a BMS model that suits my needs.

BatterySavant77 -

Definitely look for a dedicated BMS. It can make a big difference!

Answered By TechGuru001 On

First off, it's great that you're digging into this! Yes, you should definitely check if your BMS balances the cells, either actively or passively. If it's passive, try to balance them manually by connecting them all in parallel without load. It can really help! Plus, balancing them before use is key to get the most out of your battery.

BoatLover24 -

That makes a lot of sense! So, I just disconnect everything and connect the cells in parallel? I’m eager to try anything to get them working better.

WaveRider99 -

Exactly! Just make sure to keep an eye on the connections, and you should be good to go.

Answered By BatteryExpert43 On

Charging each LiFePO4 cell to around 3.6V is crucial. The BMS usually balances when it’s nearing full charge; if the cells aren't balanced from the start, the BMS won't be able to fix that. Using a charger specifically designed for LiFePO4 is recommended since it will optimize the full voltage. If a single cell is failing, you *can* replace it, but note that new cells might not match the capacity of older ones, leading to potential issues later on. Just make sure you have the right charger for the task!

User1234!@# -

I’ll definitely look into getting a proper charger. So, doing it in batches of 4 is a way to go? That could really simplify things.

NewbieTech -

For sure, just be cautious and monitor the cell voltages as you go.

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