How/why has my battery SOC decreased from 88% to 81% overnight with no battery discharge? System is 18kPV hybrid inverter with 2 - 280Ah indoor wall mount batteries.
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February 1, 2026 9:07 pm
8 Replies
February 2, 2026 3:04 pm
And it is still happening - day 2. Am I powering the universe?
I do not know if it is significant, but when I "READ" this, it always times out. So there is some sort of communications issue with the batteries.
February 2, 2026 4:38 pm
What does your vBat graph look like?
February 2, 2026 6:22 pm
Here are the graphs for 2/1/26 and 2/2/26. What do you surmise, or what would you expect to see?
February 2, 2026 7:02 pm
How cold are these batteries? My first guess is that this is caused by heater discharge.
FYI, the 18Kpv EPS standby consumption won't look like this - that discharge stays under the radar as far as SOC reporting is concerned. i.e. the SOC doesn't change if the only consumption is from EPS idle.
From the specs, the heaters will consume 448 watts, which amounts to 10.7 kWh, or 37% of your SOC in a 24 hour period if the heaters are running continuously.
February 2, 2026 8:44 pm
@jlankford These are the INDOOR wall mount batteries. Per the manual, the heaters will come on at 32 F and turn off at 41 F. My basement temps might get into the 60s but definitely not cold enough to turn on the heaters.
February 2, 2026 9:19 pm
@gtsquires I saw that they're indoor batteries, but plenty of people install those in unheated sheds so it seemed like a reasonable question. The 224 watt heater power was from the indoor spec. I have no other ideas for you, unfortunately...
February 2, 2026 11:26 pm
@jlankford Thanks for the suggestion. Actually, I did not even realize the indoor batteries had heaters. I thought only the outdoor version had them. I will have to see if there is any phone support at EG4.
February 2, 2026 8:51 pm
And another mystery. At 5 am when there is no PV activity and no battery discharge, I export power to the grid for 5 minutes.
