diyBMS-CurrentShunt
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stuartpittaway
Shunt resets only to 99%
the shunt reset to 99% not to 100% looks like a bug.
[Release-2023-01-25-12-26]
Do you have "Charge efficiency factor %" set to 99% ?
That will have the effect of subtracting 1% from the 100% on reset.
yes charge efficency was at 99%
interesting, if the shunt should reset to 100% at full charge it reset to the Charge efficiency factor % value
this was not the case with older firmware
The whole SoC calculation is different in this version - the previous one was incorrect.
It doesn't set to the charge efficiency factor % directly. The SoC is calculated on the amps in vs out, and the factor % is applied to the "in" value to determine the SoC.
what is the charge efficency factor for, if it has to be set to 100% ?
make no sence for me, ok i will set it to 100%...
When you charge any battery, some energy is lost - thats the efficiency.
Lithium cells are very good - hence 99%+ - lead acid less so, probably 90%
i undestand, but in this case if i set 99,5% efficency it wil never reset to 100%... but it has to
Hi @stuartpittaway I have firmware 40792eb5 and I'm thinking of SoC calculation. Bank is 14S Lithium and fully charged voltage is set for testing to 58,8V. Charge efficiency factor is 100% SoC goes a bit over 100% at 58,8V max, but after a while returns to 100%.
When discharging, voltage drops for example to 53,14V, SoC changes to 72,34%. With linear voltage drop calc between 58,8 and 50.4, the SoC at 53V is 30%
Maybe there's something, which I don't underestand. Any ideas ?
Voltage has nothing to do with the SoC calculation !
Its only used to identify when 100% fully charged has been reached - 58.8V in your case.
After that, its down to amp-hour counting.
You can't apply a linear voltage drop calc to Lithium cells, they don't have a linear charge curve.
The state of charge does indeed reset to 100% when the conditions are met, however from that 100% value the charge efficiency is removed, typically this introduces the 99% value you see.
hmm, so i have to live with the 99% on full? if i set the efficency to 100% then the soc calculation is to high if the battery dont charge full for a week
victron shunt does it right, it reset to 100% but still a "charge efficency" can be set seperatly
There has been a code change submitted by another use to change the behaviour so that the soc goes to 100%, but that's not been incorporated into the main code base.
could you please integrate it in the external shunt firmware, if its not to much work? i dont know how to do it. thanks
This is related to issue https://github.com/stuartpittaway/diyBMSv4ESP32/issues/232