Hi, my MUST pv1800 3kw/3kva Inverter reads my newly-installed (2 days) SVOLT 25.6v 2.71kwh 106ah (No COMMS but built-in BMS, naturally), at 0.5v higher than the batt. actual voltage. Load or no load.

Yet, measuring at both inverter terminals (inside) and the battery terminals are identical, and show true voltage. So the route from battery to inverter is fine.  I.e. MPPT PV Screen shows 27.1 & Battery screen shows 27.6, true is 27.1.

As the MPPT PV Screen shows the true voltage, to ensure correct values I had to offset the Bulk, Float, Cut-Off etc. by 0.5/-0.5 & observed actuals did reflect, thus - this was to success. I've not set the max charge current to above 20a yet. That, I will do carefuly & will measure things whilst doing so, though the built-in LifePo4 BMS correctly shuts the battery off if a too-high-a-value is set.

The inverter never did this with previous banks of SLA's of various combinations in LEA, GEL & USR modes. I've reset the inverter several times to no avail. The battery screen still shows +0.5 higher but MTTP screen shows actuals, and, the various configs (Bulk, Float, CutOff, etc.) appear to respond to the battery value & not the 'MTTP charge controller screen' value, thus my workaround to offset voltages to compensate - shows correct voltages on the MTTP screen, whilst the +5 incorrect voltages remain on the Battery screen.

Reset battery BMS switch - yes. Have run 1 x cycle thus far.

HUH.jpg?

 

Edited August 9, 20242 yr by ironcast

Axperts have commands to calibrate the battery voltage reading.

There is a very small chance that the Must models use the exact same commands. Axpert details here.

Edit: See next post; it seems that the procedure is vastly different. 

Edited August 11, 20242 yr by Coulomb

Growatt Inverters have a hidden Program code where the offset of battery and grid for that matter can be adjusted as well.
Press the up and down arrow keys simultaneously. Then enter program code 111
This opens a new submenu with numerous values that can all be offset/adjusted. First one is grid, second one is Battery and then follows a host of other values that I have no clue what they are supposed to adjust.