I've started having a similar issue with my SuperBase Pro 2000.
About three months ago I tried to turn it on, but it would not turn on. So I plugged it into an AC outlet and after a few minutes plugged into the AC outlet I finally got it to turn on, but then it said 100% battery charge when, in fact, I think the batteries were completely dead. I charged it up to 100%, ran a vacuum off of it until it was at 60%, then turned it off and stored it.
Then, tonight (three months later), I pushed the green power button to see how the unit was doing and it again would not turn on until I again plugged it into an AC outlet and waited a few minutes before it would even power on. Similar to the previous time, once powered on it showed 100% battery life and proceeded to trickle-charge at about 110 watts.
Wanting to see if the unit was working properly I then turned on the AC port and plugged a small Blueair air purifier into one of the unit's AC sockets. The air purifier would NOT turn on. Additionally, after a minute, or less, the AC port would turn itself off again, as if not detecting a load or not having any power left in the battery.
So, I unplugged the SuperBase from the AC wall outlet and watched the battery % meter. It fell probably a good 20%, or more, just sitting there for less than 10 minutes, WITHOUT any load on the unit (I had by now removed the air purifier from the unit's AC outlet)
I'm beginning to suspect these units have some major flaws - either with the BMS, or the batteries, themselves. I will reach out to Zendure and see what they say.
Either the batteries have a charge, or they don't. And there's no way that Li-NMC batteries should just lose their charge like that after the units has been sitting for three months completely turned off.