Up and Running, and a Powerwall Question

[RHinCT]

My Solar install was last week, Thursday and Friday Dec 1&2. (Ordered late July 2021, so 16 months. This is in Connecticut.) 32 panels on a south-facing roof, and two Powerwalls (2 and +).

It went great! The two crews, roof and electricians, were excellent from all I could tell. Of course I can't sell anything back to the grid yet, but I am charging the Powerwalls, and running the house on a mix of Solar, Powerwall and grid. I could use more sunny days, though.

I heard the guys talking when they came to take pictures and put on stickers yesterday. There are Powerwall 3's already at their location, shrink-wrapped on pallets of course, so the guy who saw them couldn't investigate much.

My Powerwall question: When they showed me everything, and told me the do's and don'ts, there was a warning about not running the battery to zero. Fair enough, I know not to do that with my Y. What I am unsure of is how low is a practical, safe limit, one that keeps the battery in good shape? 20%? 10%? Any pointers to official information would be appreciated, as well as any related experience.

Thanks!

RH

 

[zƬesla]

My understanding is that PWs will not drain all the way to 0. They reserve a small amount (5%?) so that the system can be restarted after an outage. If they do run to 0, there are jump start instructions online. So set it to what you are comfortable / your goals.

 

[jrweiss98020]

In the winter time, keep them at 100%. if you have an outage, you may not have enough solar to recharge them for several days.

In the summer time, IF you want to cycle them, I would not go less than 25%, assuming you can recharge them to 100% in 1 day.

 

[jjrandorin]

My Solar install was last week, Thursday and Friday Dec 1&2. (Ordered late July 2021, so 16 months. This is in Connecticut.) 32 panels on a south-facing roof, and two Powerwalls (2 and +).

It went great! The two crews, roof and electricians, were excellent from all I could tell. Of course I can't sell anything back to the grid yet, but I am charging the Powerwalls, and running the house on a mix of Solar, Powerwall and grid. I could use more sunny days, though.

I heard the guys talking when they came to take pictures and put on stickers yesterday. There are Powerwall 3's already at their location, shrink-wrapped on pallets of course, so the guy who saw them couldn't investigate much.

My Powerwall question: When they showed me everything, and told me the do's and don'ts, there was a warning about not running the battery to zero. Fair enough, I know not to do that with my Y. What I am unsure of is how low is a practical, safe limit, one that keeps the battery in good shape? 20%? 10%? Any pointers to official information would be appreciated, as well as any related experience.

Thanks!

RH

There arent any pointers to official information that I am aware of. You set the reserve at whatever you think it will take to make you feel comfortable / get you through a period without power, given whatever your goals with the system are.

There are also 10% round trip power loss from the PV so you have to take that, and time of year into account (or not, if it wasnt part of your plans).

During the colder months (what passes for colder out here in southern california anyway ) on my own personal system, I have it set at 80% reserve right now because I am not generating enough to power my home and charge both my vehicles. It really should be set to 100% but I like to run the powerwalls daily.

One thing of note on these, 100% isnt really 100% and 0% isnt zero (in the tesla app anyway). I think 0% in the app is like 5%, and the system will shut itself down and check for solar the next day in the morning till it can charge, and 100% is based on 13.5kWh of storage, but most powerwalls have a bit more than that for a top end buffer.

 

[h2ofun]

In the winter time, keep them at 100%. if you have an outage, you may not have enough solar to recharge them for several days.

In the summer time, IF you want to cycle them, I would not go less than 25%, assuming you can recharge them to 100% in 1 day.

I have mine at 80%, and still cannot get them to 100%

 

[sunwarriors]

I had mine at 40% today and got to 100% by 1pm. Since I don't think it's really worth it to try to totally be self powered (more cycles of batteries), I usually go with 40-90% depending on what the general weather is or next day is. If it's really sunny, I go 40% and can get back to 100% tomorrow in the winter. If it's rainy/cloudy, it might be 80%.

I sorta micromanage my reserve.

What you choose, as mentioned depends on your weather.

 

[h2ofun]

I had mine at 40% today and got to 100% by 1pm. Since I don't think it's really worth it to try to totally be self powered (more cycles of batteries), I usually go with 40-90% depending on what the general weather is or next day is. If it's really sunny, I go 40% and can get back to 100% tomorrow in the winter. If it's rainy/cloudy, it might be 80%.

I sorta micromanage my reserve.

What you choose, as mentioned depends on your weather.

You may not have electric heat? I use like 80 to 100kwh a day with heat pumps. Only at best make 35kwh per day, at best

 

[sunwarriors]

You may not have electric heat? I use like 80 to 100kwh a day with heat pumps. Only at best make 35kwh per day, at best

No, gas heat and we haven't even turned it on yet cuz I'm a cheap bastard. I'm still using credits from my True-up bill as well so haven't paid for gas neither the last few months.

I use like 15 - 20 kWh during the winter normally and we generated 30+kWh today on my ~8kW setup. So. Cal sun and no AC use makes it easier for us honestly to probably be grid free during the sunnier cool months.

 

[RHinCT]

My question on where to set the battery had more to do with avoiding damage to the battery than anything else.

Once I can send excess to the grid after the Powerwalls are at 100% I think I'll set to 100% and do give-and-take from the grid with the difference between what the house needs and the roof provides. That assumes - I have no idea about this - assumes that my credit for pushing a kWh to the grid is similar to what I pay for pulling the same from the grid. If the difference is significant I might exercise the Powerwalls more.

I'm sure learning a lot about my power usage using the app. Having more or less real time monitoring, with some history, has been enlightening. Looking at the history from Eversource, my usage peaked last summer at around 50 kWh per day. November thru May stayed under 30.