Suddenly charging out of schedule.

[elliott]

Good afternoon all.

I've noticed during the last two days, my MIRA HV25 system has been initiating a charge at some point in the afternoon (today about 20 minutes ago around 13:30), yesterday around 15:30, drawing around 1KWh from the grid.

The SoC right now is 40%, yesterday was around 50% when the charging kicked in, but it shouldn't as minimum SoC is set to 15%.

I've checked my work-mode, which is still set to self-use.

I've checked for any force-charge settings, both are disabled.

I've got mode scheduler enabled with the following settings:

00:00 - 05:30 - Force Charge, minimum SoC 15%, no force discharge.
05:31 - 23:29 - Self-use, minimum SoC 15%, no force discharge.
23:30 - 23:59 - Force Charge, minimum SoC 15%, no force discharge.

The batteries are COLD, dropping to around 3c today (installed in a double garage).

Yesterday the only way I could stop the import from the grid was to turn the batteries off and restart them, then the inverter (H1-5.0-E) picked them up again and resumed self-use as expected. Charging overnight occurred at the expected scheduled time, though I did notice that the charging rate was reduced, again, assuming something to do with the cold temperatures.

Is this somehow expected behaviour for cold temperatures? Will the system stop charging at a certain SoC, or will it charge until full?

[Will]

It sounds like you've checked all the normal stuff, random charging like this is normally the battery protection system trying to keep the battery within safe temp and soc.
On the v2 fox app, devices > battery what is the battery temp currently? single figure temps will cause that you're seeing.

Solution is to insulate the battery.

[elliott]

Indeed, the battery is down to 3.3c currently.

I have tried to insulate them with a wooden enclosure and some old fabric (curtains, sheets, etc), but the temperature remains incredibly cold.

What makes little sense to me however is that earlier this morning they were at 2.9c and were happily providing rather than consuming energy from the grid.

[Will]

The exact algorithm that the bms uses is still undocumented but what you see in the app doesn't mean you don't have one cell slightly colder that causes the battery to stop discharging.