Suddeny capacity drop from 300Ah to 0. And undervoltage falut

[Picachuu]

Hello Thanks in advance.
Im a newbie who just installed my system with 15s 1p 302Ah Chinese so-called catl cells, 300A jbd bms, growatt 8000kw dvm mpv inverter.

I was running my system very well for 1 night for some security lights. Xiaoxiang app sad I have reamining capacity close to 300AH
Than next morning as soon as I get up around 6am, all the light turned off. The inverter went off. I checked Xiaoxiang, my cells were undervoltage, especially 1 was the worst at around 2.4. and the remaining capacity has dropped to 0 from about 300Ah. I cant understand how this can happen.

I am not sure if my cells are balanced because the cheap dc power supply smoked out when I attempted it. And when I saw Xiaoxiang app, it says the voltage difference is very low at around 3.31v. So I assumed it is balanced and skip that step.

I am wondering is this a coincidence or not that this happend around when sun comes out. I live in desert and sun is very strong.
Inverter showed undervoltage fault and right now I can't turn it on...
Please give me an advice...

This is the graph i see. Is it really possible remaining capacity suddenly just drop to 0? Or it is some problem of bms??

 

[sunshine_eggo]

Hello Thanks in advance.
Im a newbie who just installed my system with 15s 1p 302Ah Chinese so-called catl cells, 300A jbd bms, growatt 8000kw dvm mpv inverter.

why 15S? Not common.

I was running my system very well for 1 night for some security lights. Xiaoxiang app sad I have reamining capacity close to 300AH
Than next morning as soon as I get up around 6am, all the light turned off. The inverter went off. I checked Xiaoxiang, my cells were undervoltage, especially 1 was the worst at around 2.4.

What were the others?

and the remaining capacity has dropped to 0 from about 300Ah. I cant understand how this can happen.

By using more energy than the battery can supply.

Also, I don't know your unit specifically, but that brand has notoriously high self-consumption - they gobble power even when they are providing not loads. Whatever your loads are, you likely need to add about 150W to account for the Inverter's consumption.

150W * 24h = 3.6kWh
300Ah * 248V = 14.4kWh

3.6/14.4 =0.25

YOUR INVERTER CONSUMES ABOUT 25% OF YOUR BATTERY CAPACITY IN 24 HOURS.

I am not sure if my cells are balanced because the cheap dc power supply smoked out when I attempted it. And when I saw Xiaoxiang app, it says the voltage difference is very low at around 3.31v. So I assumed it is balanced and skip that step.

They are not. You assumed wrong. "Balanced" doesn't mean "same voltage." Balanced means "same stage of charge." Top balancing deliberately sets all cells to the same true 100% SoC.

Inverter showed undervoltage fault and right now I can't turn it on...
Please give me an advice...

If you have a generator, you should see if you can get the inverter to charge the battery in standby mode.

 

[Picachuu]

I ordered 16 cells but I shorted one really bad and the threads are gone. Until I fix that one cell I decided to go with 15 cells since it showed over 48v in the app. I do have generator I think now I need to buy a better dc supply and do another attempt to balance the battery... thank you for your advice

 

[sunshine_eggo]

I ordered 16 cells but I shorted one really bad and the threads are gone. Until I fix that one cell I decided to go with 15 cells since it showed over 48v in the app. I do have generator I think now I need to buy a better dc supply and do another attempt to balance the battery... thank you for your advice

And you are using a 15S BMS instead of a 16S BMS?

Additionally, since you only have 15S, you need to lower your inverter low voltage cut-off accordingly.

You might as well post all your BMS settings.

 

[Rossman]

I feel like, if you did not successfully complete the top balance, the state of charge reading on the BMS may not be accurate?