FoxESS Community - Owners & Installers Forum

Hi, my Mira hv25 batteries (4 of them, about 10kwh) have started getting enough sunshine to fully charge which is great.

However, when they get close to 100%, they take an awful lot of energy and just stick on 99%

Not sure how to in-line the attached photo. It shows that the soc hits 99% but charging continues around 1kw for about an hour. That’s using home assistant for the graphs. The data comes direct from FoxEss cloud and matches what I see in the app.

Temperature of the batteries doesn’t look like it should be an issue: near to 20 degrees c.

The questions

• Is this expected behaviour?

• Can I limit the max soc to eg 95%?

• If not, could I switch the inverter mode to stop charging in some way?

Reason being - I could be getting export tariff for those kWh that don’t seem to be helping at all.

When the batteries near full the battery voltage rises rapidly and so the charger will reduce the current to allow the batteries to continue to charge for as long as possible, this is known as top-balancing the cells and allows the cells time to absorb the maximum charge which helps maintain their health and to calibrate them which improves the SoC reporting accuracy.

The 99% is the maximum SoC that can be reported (in effect it is 100%) - In the very latest firmware versions Foxess have changed this behaviour to report 100% (which is much less confusing)

Thanks Dave, that’s interesting to know. I’ll see what behaviour I get with the newer firmware. Would be great if that last top up is skipped or if was just a calibration issue.