Hi
I've noticed this occurring fairly regularly since BMS 3017
2 x 9.5 batteries -
House load fairly consistent around the 400 - 500w range, but the battery is losing capacity faster than the load suggests. Nearly 40% over an hour according to the below.
Quite regularly I'm down to empty overnight, then fully charged by a combination of overnight charging / solar the next day so I thought a recalibration wouldn't be required?
Thanks
lam22 that chart is probably showing a composite ("virtual") battery state. If you check the individual batteries, are their SoC roughly the same ?
Yeah they are roughly the same - both had the same accelerated loss as well.
Would SOC corrections be almost immediate, or gradual but fast like the above?
Could be an SoC thing. Maybe try a battery calibration run?
Will have to say, having jumped to 3017 I am now seeing some pretty big drops when I get down to 20%. I've had 2 drops down to BMS LV cutoff (which then triggers a force charge to 4% /15%) which is something new given I've managed to escape SOC drops since install in 2020 through pretty much every firmware in existence since then.
Having been on IOF all summer & only changing back to IO Go on Friday, I'm of the mind that it's constant target of 20% minimum by the end of each day has perhaps lead the BMS to learn some sort of false goalposts between 20 & 100% SOC (given my sudden drops at sub 20% this does seem a little too coincidental) so calibration it is and see how much it can shove in before I force discharge to empty again.
If not then I may be getting near the retention limits after 4 years/18MWh which is a bit disappointing.
(Thankfully system 2 is fine so I'm really just shunting energy back and forth more than anything)
hoggy That's what I expected would happen with 3017.
5.83kWh from 100% to 4% it seems even after calibration (including waiting several hours to see if it finds any more) so down from 6.5kWh from new after 4 years.
I'll add that to the battery tracker thread I have somewhere.
hoggy Of course your 18MWh (charge) figure is half of GE's "Throughput" figure so 36MWh by their reckoning.
11% loss in capacity on how many cycles?
Vestas I'm not at home but something over 1500 cycles.