I have a small system (Class B RV) with a BMV 712 which generally works great. One issue is that if I leave the van sitting for a while (weeks) the battery will eventually run down. While this is happening, the BMV claims the SOC is at 100% and the current is 0.00.
In reality, the van has a very small idle draw (about 1W), but the BMV is not detecting it.
Today I calibrated the zero current:
- disconnect all connections to the load side of the shunt (leaving the battery side connected)
- using Victron Connect, go to Settings / Battery / Zero Current Calibration. Click OK
- reconnect the shunt
At this point, everything seemed to be working properly: The BMV was now showing -0.11A (1 W) which is very close to the true idle draw.
Then I put some mild loads (turned on a few small lights using about 10 watts) and the BMV was showing this correctly too.
However, after turning off the lights, the BMV shortly went back to showing 0.00 amps again. I let it sit for 15 minutes, and it stayed at 0.00.
1. Is the BMV712 simply unable to reliably measure small currents (around 100 milliAmps?)
2. Is there any way to manually configure a small negative offset?
