FoxESS Community - Owners & Installers Forum

Hi,

I've very recently had installed an EP11 battery and AC1-3.7-E-G2 inverter. I had solar installed many years ago under the FiT tariff so could not have a hybrid inverter. My solar array is very small compared to most systems and has performed well over the years.

The inverter and battery are performed as well as I was expecting but have noticed a small anomaly. This afternoon, as the battery was charging up steadily, then, it jumped from 80% to 100% within a matter of 2 minutes. This is the first time the battery has reached full capacity, so don't know if this normal behaviour, or whether it's something else.

Any advice would be greatly appreciated.

Steve

Hi, it’s because the battery has never been to 100% that the soc jumped - the BMS works out the soc based on the cell voltage and on LFP batteries such as this the cell voltage remains flat across the majority of the charge range with a rapid rise as it approaches 100%. The BMS uses this to calibrate it’s counters, and for best accuracy it is advisable to charge the batteries to 100% at least once per month (or as often as you can).

Hi Dave,

Thanks for the prompt reply. It would have been nice if my installer had mentioned this, but at least I know now.

Cheers,

Steve

I set up an automation to charge up to 100% weekly (if it did not hit 100% naturally within that time), and down to 10% once a month (again, if it did not reach 10% by itself in that time). That helps keep the battery system happy

You might notice that charging seems to pause at 96%. This is when different modules within the battery system are being balanced with each other (if you only have one module, that won't happen obviously).

Thanks very much for the response. All good to know what is to be expected with battery and BMS behaviour. With the sunny weather the battery has steadily climbed back up to 100% today.