Jumping SoC with BMS v1017.03 AC200MAX


since updating to latest version of BMS, I see now sudden jump of SoC.
It was SoC 29% . Turn solar input on it jump to 98%, than to 60%. after back to 98%
I checked the voltage in the BMS submenu and all cell nicely show 3.30 V, as expected for below 30%…

Can I reset the BMS? Shall I first discharge or first fully charge to recalibrate?

Turn on/off , even applying AC 300W load does not show any correction to SoC but slowly goes down now to 97%…

Hi @mini_PV

you should recalibrate the Unit.

To do this, discharge the unit until its shutoff the AC and then recharge it at a constant rate from the grid. Wait until the input is at 0W and discharge your unit at a constant rate until it turn of again. For the best results, you charge the unit now again with a constant AC Rate. The jumps should be gone.

If they dont. Re do what i say until you have reached two full “empty - full cycles”

Let me if it worked for you!



Many thanks, yes after discharging an charging seems to work fine.

Maybe the slow charging via Solar in winter < 20W, was not really considered in SoC update over 2 weeks. Though first its high internal consumption… but the SoC of 29% was wrong, as the discharge was much more that 1kwh…

Will check now how it behaves…

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As sun in winter is fairly rare, it mostly only charges with 10-150W last weeks, mostly around 50W.
Below 5W solar input, I turn the Solar input off via a solid state relay to avoid internal discharge.

Nevertheless, the SoC is again jumping. Seem that low inputs are not really well considered vs charging with 500W supply.

It moved some %, when charging was in range of 100W+ from 62-68%, but this morning I recognized, solar input is in-active, because SoC=100% is reached suddenly (jump to 98 then 99&100% in few minutes).

Supprisingly the cell voltages are not really balanced by the BMS as-well , see picture.
Turning on the B230, solar charges again, but I see no improvement on the AC200Max. cell voltages itself.

  1. Is that a common problem, that small charing inputs are not correctly considered by the SoC controller?
  2. Does the balancing only work with normal power supply (500W)?

Hi @mini_PV

The cells should automatically balance themselves. When you do this calibration cycle to 100%. You can leave your unit over night (turned off) and on next morning it should be back to 99%. AC back in and charge it to 100% again. At least that was the case with my Ep500Pro