Can't set reserve above 80% (but it worked yesterday)

[youzer-name]

I use my home automation hub to set my PW reserve level to the current battery level whenever one of my cars is charging. This means I always charge from the grid, which I prefer to do to avoid the 10% round trip penalty from charging and discharging the batteries. I also have it set to notify me if the Powerwalls are being discharged rapidly, since every once in a while something glitches and the reserve doesn't get set.

Tonight I got that notification, and when I checked, the PWs were at 84% and discharging at 10 kW. PWD showed that the reserve had been changed from 70% (where I've been keeping it lately) to 80% when the car started charging, but the home automation logs showed it should have been set to 84%.

I tried with both the home automation and the Tesla app to set the reserve to the battery level which was about 83% at that point. The Tesla app would let me select that, but after a minute or so the app refreshed and the reserve was back to 80%. When the car stopped charging, the automation fired as expected and set the reserve back to 70%. I then tried to set the reserve to 85% in the Tesla app, and it refreshed and showed only 80%. It seems I can't set any value higher than 80%, and this is a brand-new behavior.

I checked PWD and confirmed that yesterday one of my cars started charging when the battery was at 85% and the reserve successfully was set to 85%. I have not received any firmware updates since June 28, and am on 25.18.4, so nothing should have changed today.

I'm not sure if I should open a ticket with Tesla to see if they have any insight on what's going on. A quick web search didn't turn up any relevant reports. Has anyone here seen anything like this with their system?

EDIT: I re-checked the system this morning. I tried a few reserve levels below 80% and they all worked. I also tried 100% and it worked, with the system still having the annoying behavior of charging from the grid to get to the selected level even when the 'charge from grid' toggle switch is off. But attempting to set any level from 81% to 99% results in a reserve of 80%. I emailed Tesla support and will wait to see what they say.

[youzer-name]

I'll keep this short here. Tesla made an un-announced change to the system. More info here:

https://teslamotorsclub.com/tmc/threads/powerwall-charge-throttled-at-80-with-25-18-4.347099/

TLDCL (Too long, didn't click link 😄 ) - You can't set any reserve level between 81% and 99%. Supposed to be to reduce battery degradation and reduce warranty claims according to the support rep I talked to today.

[mcbirse]

I did click the link, but it doesn't work 😉 (copy paste does).

Although it doesn't affect my use cases directly (at the moment), seeing this from Tesla is really disappointing. They are taking away control from end users (their customers, who have invested in them), without any consideration for how they may be using the system.

There are so many variables at play when managing and optimising power systems / solar / batteries / EVs / pricing / usage, etc., why reduce the ability to manage this effectively! It's crazy. 😮

And to say it's to reduce battery degradation seems kind of moot/pointless, since you could set your reserve to 100% still and just leave it.

[youzer-name]

Lots of good discussion on the TMC thread. It looks like Tesla made an API change. Some have suggested this might be a way to ensure PW3 units with LFP cells are cycled through a wider range.

Based on a suggestion over there, I'm now setting my system to 'Backup Only' mode when my car starts to charge, rather than trying to adjust the reserve level. This holds the battery at whatever level it is at, and my home automation sets the mode back to 'Self Powered' when the car is done. Backup Only still works via the API, but isn't an option in the Tesla App anymore, so fingers crossed that they don't kill the feature in the API.