Powerwall in Backup Mode - Charge only to 80%?

Powerwall in Backup Mode - Charge only to 80%?

I have PW2 that is exclusively used for backup purposes. We have frequent outages in winter, but not in summer. I am not a big fan of letting the battery sit at 100% charge for months at a time during summer. Most EV’s have a charging option that allows the user to only charge only to a certain level (i.e. 80-90%) to extend the longevity of li-ion batteries. Is there a way to accomplish this with PW2? Maybe switch off the battery manually?

uwenancyheine | February 25, 2020

I am not sure if Powerwall has excess capacity engineered into the system and may be OK at 100% SOC. However if you look in the app under "customize" you can select backup only and set a power reserve level there. Probably wouldn't hurt to set it at 90%. I too would like to know what the best method for preserving the life of the Powerwall is. Just leave at 80-90%? Do a discharge/charge cycle occasionally? I would really like to know this too.

bp | February 25, 2020

There is a discrepancy between the current charge level shown in the app and when using a browser to connect directly to the Tesla Gateway.

The reason for the discrepancy appears to be that the app is designed not to charge the PowerWall completely - when the app shows 100%, there may still be some amount of the batteries that haven't been charged.

This was probably done intentionally so that the PowerWalls don't sit for extended periods fully charged.

But still seems prudent to charge to less than 100% if you intend to leave it sitting at 100% for an extended period.

BIC | February 26, 2020

Here's a good article. Best lithium-ion storage is at 40% & 32F. That would be a bit low for an unexpected outage. It isn't always predictable weather. Could be a squirrel (they like to commit suicide in transformers), although that's quickly fixed.

BIC | February 26, 2020

My PW2 was installed a couple of days ago. Came with 18% charge. After some sunshine yesterday, app showed 99% charge. With all sun today, showed a 98% charge. Does this sound right? Thanks.

jeff | February 28, 2020

98% is considered full charge by Tesla. We've seen ours go to 100%, something they said was impossible, then the gateway would switch the house to the battery and bleed it down to 94%, approximately, run the house on the PV's and recharge it to 98% and run the house on what's left until sundown.

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