Hi Guys

My current setup is 1x Pylontech US3000 battery (SOH 87%, BMS Version 0), a Goodwe 5048D-ES inverter and 16x 400W solar panels.

There appears to be a problem with how my inverter reads or measures my battery's SOC%, or how the BMS communicates it to the inverter.

As an example, on 8 September I consistently used about 510W of my battery between 18:00 and 19:55. Between 18:15 to 19:40 the battery SOC% declined from 100% to 76% which is an average of 1% every 3.5 minutes. But then between 19:40 to 20:00, while still using only about 510W of battery power, my SOC% drops from 76% to 20% which is an average of 2.8% every minute even though the battery consumption remained approximately the same.

I have tried a reset of the battery and the inverter by switching everything off - battery, panels, grid - and then restarting again in the same order - battery, panels, grid - but it does not seem to fix the problem. Goodwe has now installed new firmware but that does also not seem to fix the problem. I don't have access to a cable and software to connect to the battery to upgrade any firmware or make changes to the battery so that is still the same as when it was installed in 2020.

Has anyone had a similar issue, and if so how, if at all, did you manage to sort the issue out?

There appears to be a similar issue on the charging side. This morning while charging consistently at 185W between 00:00 and 05:50 the SOC% climb consistently from 20% to 53%, but then while actually discharging from 05:50 to 06:00 the SOC% jumped from 53% to 97%.

Your graph is showing SOC but your heading and first line is referring to SOH (SOH 87%, BMS Version 0).

SOC is state of charge while SOH is state of health. If your battery is reporting a SOH of 87% then you no longer have a full capacity battery (3.5kw * 87 = 3kw) this will account for the increased % per minute you calculated.

The spikes in the SOC graph might be indicating bad cells and I would try to see what the cell voltages of the individual cells are in the pack. A sudden dip on discharge is SOC could mean cells have dropped to low on voltage. The sudden jump from XX to 100 is similar but this could be that bad cells are overcharging and causing a Over volt protection mode to kick in.

I had a battery drop from 100% to 87% SOH and it was a result of bad cells due to inadvertently depleting my batteries due to how the SOC on the inverter was read for a multi battery setup as it only reads the avg value and caused a battery to deplete multiple times damaging cells.

You however state you only have 1 battery so the cause might not be the same but I think you still might want to start by checking the cell voltage to see if you don't have bad cells.

Edited September 12, 2025Sep 12 by -cK-

2 minutes ago, -cK- said:

Your graph is showing SOC but your heading and first line is referring to SOH (SOH 87%, BMS Version 0)

Yip, sorry. Heading should have said SOC not SOH.

Do you perhaps know ho to check the cell voltages without access to a cable a specific software? Or should I rather just take the battery to Segen and have them test it?

Regards

If the battery doesn't have an onboard display the only other way will be with a cable and BMS software to my knowledge. Luckily my battery have a little onboard display with the option to check various outputs like the cell voltages, temps etc. But if it only have lights to indicate the charge I think you might need to get it tested.

Thanks, I have contacted Pylontech to try and figure out what my options are.