Problem with battery and BMS 16S 48V 300A

[Jovan Ristov]

Hello,
I was to make conversion on Daewoo Matiz to electric. EV work on 48V 16s CATL battery,302A, with Daly BMS 300A. Everything was ok since have trouble with battery. When its start charging with ~SOC 30% , all 16 cells going around 3.350V (+-0.05). After 30-60min some batteries, 4 pcs going to 4 to 4.2V while charging (Attach screenshot). After that BMS turn off charging, suppose some cell is full charged. Result is that I can't fully charge the battery and I haven't idea what is going wrong. Maybe need manually to charge, with 12V charger 4 cells?
If anyone can help me, I would be grateful
Best regards,

[Sean Moore]

I suspect you are trying to charge far to quickly, when cells start reaching their vMax you need to reduce the overall charge rate to allow the balance/bleed system to work - I'm unsure how that BMS is communicating with your charger, but it should be able to modify charge rates based on states of charge - I'm aware that BMS is aimed at hobby/DIY projects so may not be as capable as others.

[Jovan Ristov]

To clarify, I'm not trying to charge quickly, I don't have such an option ..... BMS does not work with the charger, they are two separate systems ... The charger is intended for LiFePo batteries 48V, 15A and so far it has worked well .....
I don't understand why it doesn't level the cells with a lower capacity with those with a higher capacity first, but it seems to charge them all equally?
Anyway, I appreciate your interest in the issue.
Have a nice day,

[Sean Moore]

What is the charge rate ?

I sounds like you are expecting charge from full cells to be shuffled to other cells ?

[Jovan Ristov]

15A charger charge 300A battery ... that's become about 20h or 0.05C

When I put the batteries under load, they equalize after a while, and when I start charging them, then they're going in an imbalance, some go up to 4.2V.
I think it will be clearer now, sorry i didn't say all the info inputs at the beginning

[Sean Moore]

so 15A charge rate, what is the maximum bypass or bleed current that BMS is capable of ?

[Jovan Ristov]

Suppose, 15A .... but BMS is 300A ... if I have stronger charger I will send more current ...

[Sean Moore]

You need to be able to control the charger, it can't just be on or off.

[Jovan Ristov]

Charger is Smart ... unloaded, not working and is intended for LiFePo4 battery 48V

[Sean Moore]

I feel like this is an uphill struggle .... if you want detailed help you will have to provide as much detail as you can - calling the charger "smart" is great, but that's a marketing description.

What make/model is it ?

[Jovan Ristov]

Same like this, only 15A ...

[Sean Moore]

That isn't a smart charger, and your BMS will only be able to tell it to turn off.

You need a BMS and charger that talk to each other, so that when cells reach their Vmax, and therefore start bypassing (at likely less that a few amps), the BMS tells the charger to reduce its rate of charge.

The behavior you are seeing is exactly as would be expected when using such a BMS and charger combination that you currently have - simply, its not suitable for your intended use.

[Jovan Ristov]

Sorry for being gone.....private matters, thanks for your dedication to solving the problem, can you give me a link so I can look at the charger with your specs?
Best Regards,