Batteries charging without being told

[alexkay]

Hi all,
I have a bit of a weird one. Currently I have no grid charge settings set, so the battery should never charge other than when solar power is available.
However the last couple of evenings, just as the clock turns over it starts to charge. It charges at a relatively slow rates (0.600W) but it will do this through the night until it reaches 60%.

When I caught it doing this yesterday I opened up foxesscloud and saw that non of the battery charge settings were set to allow it to charge from the grid.

I do have the Foxess energy management in HA setup but it's currently set to disable auto charge. Furthermore I can't see anything in the logs suggesting it caused the battery to charge.

My only other thought could be the temperature dipping below 12c and the bms kicking in?

Has anyone else experienced this or have any thoughts as to what it could be?

For now I've disabled the HA integration to see if we have the same tonight.

Alex

[alexkay]

Have disabled and removed the foxess em add on and the batteries continue to charge at their own accord. It hit 50% and started to charge. Min soc for both is 15%.

[alexkay]

After a weekend of playing, this is what is happening:
Battery reaches lower than 50% SOC, battery is charged (at 600w) up to 60% only. Rince and repeat.

My guess is the temperature of the batteries have gone below a threshold (current guess is 13c) and it won't allow them to discharge beyond 50%.
I've added a 55% min grid SOC for now.

I'll contact foxes support to see if they know anything about it.
FYI I'm using the V2 HV2600 batteries and BMS.

[bvarsani]

I had my batteries installed on 10 December 2022. With overnight temperatures plummeting to sub zero, my batteries in the shed are behaving in exactly the same way as the post above. My batteries are in a solid wall garden shed, which is unheated/uninsulated.

Will be good to know if this is expected behaviour to keep the battery cell healthy.

My install sounds the same as your one. If you receive any further information, please do update me via this post. Glad I'm not the only one in this scenario.

[Pam36]

Hi. I wondered if you people have made any progress with your problem. I have two Mira- HV25 batteries fitted on 25th November and an H1-3.7 E inverter. On 16th December at 6:30pm my batteries started charging up, till they reached 100% by about midnight and have been discharging very slowly since then. 73% today. So although there was some sun today, my batteries don't seem to be charging from it and the house is not using any of the power in the battery. So either the batteries were too cold, - they are in a cold utility room- or there was a forced charge because they weren't getting enough charge from the sun. The battery settings are set to not allow force charging or force charging from the grid . The minimum Soc is 20% and the minimum from the grid is also 20%. These were the settings when I had it installed and I haven't touched anything. I am hoping that when the level drops to 20% again that all will return to normal, providing we get enough sun. But at the current rate that is going to take days and days. Any information would be most helpful
Thanks.

[Jez1987]

Also having the same issue. My battery reaches min SOC then charges from the grid occasionally until it goes back to or just above Min SOC. is this normal behaviour?

[Dave Foster]

Also having the same issue. My battery reaches min SOC then charges from the grid occasionally until it goes back to or just above Min SOC. is this normal behaviour?

Yes, when there is no solar the batteries provide the power that keeps the inverter from going into standby. What happens is that when your batteries reach minsoc they disconnect and the house load is provided by the grid, but the inverter is still taking a small drain from the batteries.

After about an hour the charger will turn on at low power to trickle charge the batteries and get them back over minsoc, it then turns off and it continues this cycle until the batteries are either charged or solar returns to take over.

This is most obvious at this time of year as solar power is very low during the day, and the days are short - quite a few people change their tariffs to get a low overnight tariff such as economy 7, or Octopus Flux - those with EV’s will have low overnight charge periods and fully charge the home batteries at the same time to take advantage.