Strange behaviour of my battery? or bms?

[ramstein]

Hi,
My van is parked since a few hours under my window, (it's the night, 11pm here) and I was checking the day's stats on my phone when suddenly there was a big drop of capacity almost under my eyes (SOC went from 200Ah to 157Ah). That's crazy. There is just a small fridge inside the van, pumping 3Ah from time to time, that's it. There are 300w panels on the roof charging the battery when there is sun, but there is not much nowadays.
Could you please tell me what's going on?? Going suddenly from 200Ah to 157Ah without anything else than a 25L vevor fridge inside the van is not normal....
Attached pic of stats from the xiaoxiang app, you can see the drop at the end of graph. My battery is a 4S 200Ah
Thank you

 

[sunshine_eggo]

In some cases, the BMS reverts to using the voltage levels to approximate SoC. If power is lost, and the SoC data is lost, the BMS reverts to voltage.

The drop is coincident with the application of a load and as it crossed 0A.

Seems like something is amiss.

 

[ramstein]

In some cases, the BMS reverts to using the voltage levels to approximate SoC. If power is lost, and the SoC data is lost, the BMS reverts to voltage.

The drop is coincident with the application of a load and as it crossed 0A.

Seems like something is amiss.

thanks, yes it seems to be coincident with a load, which can only be the fridge. It is on eco mode, it only need current from time to time.
It happened when the fridge needed current, but usually the SOC doesn't move hugely like this time.
Is something wrong with the battery or the bms or the fridge you think?

I am now waiting for the next time the fridge will need current, so I can see what will happen...
thanks

 

[sunshine_eggo]

What it looks like to me is something that happened with one of the new heated batteries...

Basically, that particular battery would momentarily cut discharge/output to 0A and present very low system voltage as it transitioned from charge to discharge - essentially cutting off all loads momentarily even if the battery is full.

This behavior looks something like that, but I don't think it is because I doubt the BMS is losing power. It's just weird.

I'd keep an eye on it and confirm cell voltage with a seperate meter.

 

[ramstein]

What it looks like to me is something that happened with one of the new heated batteries...

Basically, that particular battery would momentarily cut discharge/output to 0A and present very low system voltage as it transitioned from charge to discharge - essentially cutting off all loads momentarily even if the battery is full.

This behavior looks something like that, but I don't think it is because I doubt the BMS is losing power. It's just weird.

I'd keep an eye on it and confirm cell voltage with a seperate meter.

Thanks. When you say "one of the new heated batteries" what do you mean please. I have lishen cells they are quite new but not heated.
I checked the voltage with the victron app too, the bms and victron both show the same voltage at 13.3V

 

[Bob B]

Hi,
My van is parked since a few hours under my window, (it's the night, 11pm here) and I was checking the day's stats on my phone when suddenly there was a big drop of capacity almost under my eyes (SOC went from 200Ah to 157Ah). That's crazy. There is just a small fridge inside the van, pumping 3Ah from time to time, that's it. There are 300w panels on the roof charging the battery when there is sun, but there is not much nowadays.
Could you please tell me what's going on?? Going from 200Ah to 157Ah without anything else than a 25L vevor fridge inside the van is not normal....
Attached pic of stats from the xiaoxiang app, you can see the drop at the end of graph. My battery is a 4S 200Ah
Thank you

Have you written any settings changes to the pack recently? It looks like it isn't doing coulomb counting .... but it tracking SOC based on cell voltages.
I'd try charging it til at least one cell reaches the battery full voltage setting and see of it will start tracking SOC via current in and current out instead of voltage.

 

[ramstein]

Have you written any settings changes to the pack recently? It looks like it isn't doing coulomb counting .... but it tracking SOC based on cell voltages.
I'd try charging it til at least one cell reaches the battery full voltage setting and see of it will start tracking SOC via current in and current out instead of voltage.

I can do this but honestly I didn't touch anything these last days in the bms settings. It's a good remark though.
This glitch happened a few minutes ago out of nowhere after a whole day without any issue I found it very strange.
The fridge has currently started consuming some energy, I will post a new screen capture after it stops in a few minutes. Thanks

 

[ramstein]

Ok the next fridge session has ended, it seems to be fine this time, no SOC drop

 

[ramstein]

The SOC returned back to normal (200Ah) suddenly this morning. Weird behaviour if you ask me