Fast Powerwall draw down?

[FurryOne]

I've got an 8K system with 2 Powerwalls, and it seems to me that for the amount of power my house draws, the Powerwalls are dropping rather too fast. My house averages 500-800W draw, and after being at 100% around 7pm, at 9:30 I'm down to 91% with a pretty steady 600W draw. Is there any way to tell if both Powerwalls are performing correctly?

 

[ptdusn]

Turn one off, watch the drain and then switch. I have a 9.45kW system with 2 PWs and that seems to be along the same lines as our draw. Now that summer is close, the A/C has been kicking on in the afternoon, mostly when the PVs are producing.

 

[ucmndd]

If you're at ~800 watts for 2.5 hours, that's 2kwh.

Two Powerwalls are 26kwh of storage when new, so 2kwh is about 7.5% of your total storage capacity. But they're not 100% efficient, with a ~10% round trip loss, so 91% state of charge under those conditions sounds just about right.

 

[holeydonut]

If you're at ~800 watts for 2.5 hours, that's 2kwh.

Two Powerwalls are 26kwh of storage when new, so 2kwh is about 7.5% of your total storage capacity. But they're not 100% efficient, with a ~10% round trip loss, so 91% state of charge under those conditions sounds just about right.

This company also saw their Powerwalls capacity (kWh) degrade 25% over 5 years. So for the FurryOne, things only get worse from here.

Interesting Deep Dive Testing of ESS (ITP, AU Market)

For the nerdy types on the TMC Energy Sub... (which is like all of them amirite?) I found this analysis about ESS as conducted by an Australian firm (ITP). It looks like they've been running some long-term tests for SoC and efficiency for the last few years. Worth a look if you're into graphs...

teslamotorsclub.com