bmv-712; SOC is wrong after expanding battery storage

Q&A and troubleshooting
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1

Hello,

I’ve recently added some extra capacity to my system, going from 560Ah packs to 1120Ah,

I updated the BMV-712 settings to say that I now have 1120Ah instead of 560 and now the SOC is wrong. It is telling me I have more capacity left than I actually do when I look at how many Ah I have consumed.

I’m pretty sure this was not an issue before and that it would say 50% when I had consumed 280Ah.

It now tells me, for instance if I have consumed 218.8Ah, that I have 86.5% SOC, when it should be around 80%.

Batteries have been fully charged and it sync’d to 100% SOC at least twice since I added the extra capacity.

I use all default values on the BMV except Ah capacity (1120) and Charged Voltage (27.6).

Any ideas?

Cheers,
Magnus

2

The c rating draw would have changed from the bank. What your peukerts is would affect the way soc is calculated. And peukerts is related to the c draw from.the bank.

https://www.victronenergy.com/media/pg/BMV-712_Smart/en/battery-capacity-and-peukert-exponent.html#UUID-9edd31c8-fda5-b4d7-0281-fc289fd6e71b

3

Sure but does that account for why SOC and Ah used isn’t lining up even though both numbers, I assume, come from the BMV?

4

Is your bank lead acid?

5

No they’re LiFePO4 prismatic cells