Charge on Solar + Battery to stay Self-Powered?

[Mardak]

We just expanded solar with first time Powerwall+, so it sounds like we shouldn't expect to see Charge on Solar in the first few days. Maybe it also depends on PTO of the additional solar + battery even though we had been exporting with old solar (but not anymore until new PTO?)? Even before batteries, I sometimes would plug in the car during the day and drop the charging amps to match solar power, and now at night, I can do a similar thing to match Powerwall continuous power availability (which seems to go up to 5.7kW).

Is there a way to automate this charging from battery and not from grid so that it reduces vehicle charging when there's additional load, e.g., water heaters turn on? We've configured it for Self-Powered as our oversized solar will result in excess utility credits that we'll just accumulate without getting value. Our daily driving typically needs only 1-2 hours to charge at full power, so there's plenty of time to transfer energy slower. And ideally it can charge at full power during the day with solar without needing to adjust charging amps for day vs night.

I suppose maybe a step back, is this even a reasonable thing to want to do?

 

[BGbreeder]

We just expanded solar with first time Powerwall+, so it sounds like we shouldn't expect to see Charge on Solar in the first few days. Maybe it also depends on PTO of the additional solar + battery even though we had been exporting with old solar (but not anymore until new PTO?)? Even before batteries, I sometimes would plug in the car during the day and drop the charging amps to match solar power, and now at night, I can do a similar thing to match Powerwall continuous power availability (which seems to go up to 5.7kW).

Is there a way to automate this charging from battery and not from grid so that it reduces vehicle charging when there's additional load, e.g., water heaters turn on? We've configured it for Self-Powered as our oversized solar will result in excess utility credits that we'll just accumulate without getting value. Our daily driving typically needs only 1-2 hours to charge at full power, so there's plenty of time to transfer energy slower. And ideally it can charge at full power during the day with solar without needing to adjust charging amps for day vs night.

I suppose maybe a step back, is this even a reasonable thing to want to do?

You might get better advice if you updated your personal information to include a better location. Details matter for this sort of question.

Is what a reasonable thing to do? Charge your vehicle from your battery? Most likely no, as you incur a 10% loss doing so, and the vehicle battery is so much larger than your Powerwall.

Tesla has a pretty automated system. Trying to do something not as Tesla programmed is doable, e.g. with Netzero, but if you like tinkering, certainly possible.

Personally, I would just have the car do charge on solar, and not sweat anything else, but that's me.

BG

 

[Mardak]

Charge your vehicle from your battery? Most likely no, as you incur a 10% loss doing so, and the vehicle battery is so much larger than your Powerwall.

After the first night, we got close to Backup Reserve level, but solar is recharging it now. Maybe it's just trying to justify our battery purchase as we knew it wouldn't be "valuable" to us, so we only got one to try it out and be part of the ecosystem, but now I better understand why people care to be Self-Powered.

Practically, if the Powerwall won't be able to stay above Backup Reserve for the whole night, it basically doesn't matter when we start pulling from the grid for the car (already scheduled to only start after TOU rates for EV charging although it's only 0.6¢/kWh cheaper now). So yeah, I think you're right to just do Charge on Solar and not bother adjusting for battery.

 

[Jeremy3292]

Is there a way to prevent your Tesla from charging via the Powerwalls (with Tesla wall connector)? I agree that is stupid to do for a lot of reasons, so I hope Tesla has figured out a way to prevent this with software. I would want that power to either come from solar and/or grid and not the Powerwalls at all.

 

[Mardak]

Charge your vehicle from your battery? Most likely no, as you incur a 10% loss doing so

I've been thinking a bit more about this, and is that still relevant for Self-Powered as opposed to Time-Based Control? If not charging from our battery, we would need to get energy from a power plant or grid storage with losses from transmission. While our meter only counts the energy actually received, presumably the per-kWh price accounts for these inefficiencies, so unclear whether local battery or grid has overall more loss?

 

[Mardak]

Is there a way to prevent your Tesla from charging via the Powerwalls… I would want that power to either come from solar and/or grid and not the Powerwalls at all

It seems like the concept of Charge on Solar could be similarly applied here as well where there's 3 charging levels: must charge (from grid), nice to charge (from solar), stop charge, e.g., charge the vehicle to at least 50% from any source then additionally up to 80% with solar and stop above that.

If there was software for a Charge on Battery, your use case would set it to "stop charge" to prevent the Tesla from charging via the Powerwalls. Whereas I was looking for a "nice to charge" of say use battery power if available as well as if Self-Powered energy level is available, i.e., stop charging if in Backup Reserve and don't bother pulling from grid.