Losses During Standby with PowerWalls

[SD Solarguy]

I'm wondering what is a normal 24-hour loss rate for PowerWalls in Standby? Mine have been losing about 5% per day, and that seems excessive. I have a couple of Powerwalls on our house, with a 7.5kW PV system. We are in Oceanside, CA, so the weather is pretty mild, although we have been approaching mid-30's some nights (usually 60-70's in the day).

 

[gpez]

I don't understand all the tech talk, but here's my experience. I only use the PW2 as emergency backup power, set at 100% charge. Nonetheless, it discharges 0.5 kW every day and variously charges about 1-2 kW every day. It usually shows 97, 98 or 99% charge, sometimes 100%. I don't know the meaning of this, is it normal? Thanks.

Yes, strange but quite normal. Mine does the same: drops to about 96-98% through the night then charges back to 100% in the morning when the sun comes up.

 

[Redhill_qik]

I'm wondering what is a normal 24-hour loss rate for PowerWalls in Standby? Mine have been losing about 5% per day, and that seems excessive. I have a couple of Powerwalls on our house, with a 7.5kW PV system. We are in Oceanside, CA, so the weather is pretty mild, although we have been approaching mid-30's some nights (usually 60-70's in the day).

I have been tracking mine and the assuming 90% recharge efficiency the losses were 200-250 W per Powerwall (<2%) until the 21.44 update on 12/16. Now I am seeing and now I'm seeing 400-450W per Powerwall in losses. It is colder, but my Powerwalls are in my garage and the last year at this same time/temp it wasn't this high.

 

[RGKresek]

I have two Powerwalls and currently allow them to go down 60% before going into standby. Starting at the beginning of this year I have noticed a 3-5% drop in available power before it starts to recharge in the morning (never occurred before). Strangely most of the drop seems to occur shortly after going into standby, so I don’t think it has anything to do with keeping the PW warm since the drop would be more gradual across the night and early morning. Glad to hear that I am not alone, but hope that someone figures this out andTesla gets this fixed.

 

[nyprepper]

I don't understand all the tech talk, but here's my experience. I only use the PW2 as emergency backup power, set at 100% charge. Nonetheless, it discharges 0.5 kW every day and variously charges about 1-2 kW every day. It usually shows 97, 98 or 99% charge, sometimes 100%. I don't know the meaning of this, is it normal? Thanks.

Yes, I leave my PW's set at 100% and I observe the same behavior with mine.

 

[BGbreeder]

I have been tracking mine and the assuming 90% recharge efficiency the losses were 200-250 W per Powerwall (<2%) until the 21.44 update on 12/16. Now I am seeing and now I'm seeing 400-450W per Powerwall in losses. It is colder, but my Powerwalls are in my garage and the last year at this same time/temp it wasn't this high.

I can't say that I see this behavior on 21.44, but perhaps the behavior is dependent on hardware/battery condition? i.e. they a have new / better / different battery / cell management strategy that is drawing an increased load for some units.

Tesla seems so black box about their support and updates.

All the best,

BG

 

[Grayson73]

My 2 Powerwall 3s are discharging about 2 kWh per day. I assume it's because they are mounted outside and energy is being used to keep them warm.

 

[Redhill_qik]

I can't say that I see this behavior on 21.44, but perhaps the behavior is dependent on hardware/battery condition? i.e. they a have new / better / different battery / cell management strategy that is drawing an increased load for some units.

Tesla seems so black box about their support and updates.

All the best,

BG

This was an old post (2 years ago) and I would be very surprised if any Powerwalls are still running that firmware. I wasn't logging all of the firmware updates that were being applied to my Powerwalls until things went sideways with the 22.1.1 release that hit my Powerwalls on 12/16/2021. Prior to that (which I am assuming was 21.44 and earlier based on my post), I was seeing on average low of ~230Wh per day per Powerwall. With firmware 22.1.1 I was seeing on average ~470 Wh loss per day per Powerwall. My next firmware update on 4/13/2022 was to 22.9.1 and my losses reverted back to ~230Wh per day per Powerwall and this has remained roughly the same since and although it has been trending towards ~200Wh loss over the last 6 months or so.

My two Powerwall2 units are inside a garage and don't see large temperature swings that others might experience.

My methodology to compute the losses is to log in to the Gateway local REST API /api/meters/aggregates page and to log the energy_exported and energy_imported about once a month (I was doing this daily, but stopped) and then use this formula:

Loss/day/powerall = ((energy_imported_day1 - energy_imported_day0) * 90% - (energy_exported_day1 - energy_exported_day0))/(day1 - day0)/num_powerwalls

Where day1 is the current data and day0 is the last time it was logged. The energy imported is derated by 90% for the efficiency loss during charging.

There is no significant difference in the calculated loss during the summer months when I discharge the Powerwalls more (4.0kWh each) than during the winter months with minimal discharge (0.8kWh each) during Peak.