I have the 12 800 35 MultiPlus connected to AC in, some load on AC out and 2x100Ah 12V Lithium batteries. From AC to inverter mode it switches seamlessly. After an Inverter cycle it will charge the battery but the Voltage goes up and peaks over 16V. The protection in the battery trips and that trips the whole unit for about 30seconds to a minute. In that time the 220V Load is also switched off. Then the unit starts up and it charges up again till it trips again. This happens a few times and then the inverter goes into a mode that I assume is float charging. I have set the dip settings 2=on and 3=off with no improvement.
I do not have the USB cable and app to adjust.
I have taken the unit back to the supplier. They say they have re-programmed it but the problem persists and they have stopped responding to my emails.
As the situation stands now the system is of very limited/no use to me as UPS for critical equipment.