Real-Pierre-Delecto2 t1_irfkd5p wrote on October 7, 2022 at 6:24 PM

Have one single unit got it years ago with a much better deal from GMP $15 a month lease and free install from Tesla themselves. Could not be more happy with the thing although at times they draw down to zero and while it's never caused any issues I pay for it for backup reasons not to save GMP money so if its really getting drained I take it offline. They do have a storm policy where they won't use it with a coming storm though.

How does it work? Awesome I almost can't tell if the grid goes out the switchover is sub 20ms or so almost invisible nothing electrical goes off or resets. It's rated at 5k per unit and I have pulled more 6ish for a few mins with no issues either. 2 units should be enough to power your whole house even with electric hot water although thats a hog anyways and you might want to shut that off in a long outage situation. My main complaint is it's not the easiest thing to hack but I am working on tricking it into thinking my generator is the grid so I can use it to charge the powerwall. It's also just about dead quiet liquid cooled etc. Also the app is handy just a few clicks and I can go off grid in seconds and that's real handy when a t storm is coming in as it physically disconnects the two hot lines from the pole outside. Anything else just ask.

Thick_Piece t1_irfo919 wrote on October 7, 2022 at 6:54 PM

I may be misinformed but I thought it was bad to draw those down to zero?

Does the batter put off heat?

Loudergood t1_irfur5t wrote on October 7, 2022 at 7:44 PM

Almost every lithium battery has built in circuitry to cut off before they get drawn to damaging levels.

Real-Pierre-Delecto2 t1_irfqgay wrote on October 7, 2022 at 7:11 PM

Not with the newer chemistry. They are rated for 4-8k cycles depending on the battery. They do get warm when charging but the unit is liquid cooled with a really nice radiator inside so no issues. Maybe if it was installed outside in the desert you might but not here in a VT basement or garage. Some even newer batts are rated at around 40k cycles thats about your lifetime!

SomeConstructionGuy t1_iri6pit wrote on October 8, 2022 at 11:11 AM

I think many manufactures are calling the low cutoff voltage 0% charge now. This lets them more easily communicate that the battery is at to 0% of capacity without the confusion of customers seeing a pack at 300v and wondering why it’s empty.

Edit: spelling

Thick_Piece t1_irfoz6g wrote on October 7, 2022 at 6:59 PM

As far as using your generator to charge it, I have a kill switch in my electrical box so I can directly connect my generator with a 220 plug.

Would it know the difference? I am curious as I wanted to get those batteries and figured I could just cycle back and forth. Use the battery until it is dead, start generator, charge batteries and have the house running on the generator.

I honestly have no clue how they work but they must know when the power is coming through the lines instead of a generator?

Real-Pierre-Delecto2 t1_irfrr5d wrote on October 7, 2022 at 7:21 PM

Sadly yes it does. And for disclaimer reasons don’t do this don’t try it ever unless you really understand what you are doing. It looks for a very stable frequency on the mains before it connects so you would have to have a real nice genny preferably an older very large 1600rpm unit that is more stable with lots of rotating weight. When the initial draw of about 4k comes to bear the genny will slowdown a bit until the motor catches up this causes the frequency of 60hz to drop and the Powerwall thinks that's the start of an outage and disconnects.

Also the way the unit is wired in you would have to add yet another disconnect because you would put the genny wires upstream of the Tesla box and without that you would be back feeding into the utility lines which is a big no no and can kill workers who might be in the area not expecting power to be on a line. It's not just the battery box there is also the "gateway" where the relays and brain are stored.

I want to do just as you suggest but I am not quite there yet.

Thick_Piece t1_irftide wrote on October 7, 2022 at 7:34 PM

I will take your disclaimer to heart as I have no knowledge on the matter. I was thinking of trying to figure out how to do the same with the standard deep cell marine batteries as I figure my electrician could figure out how to transfer some of the generator power over to the batteries or simply use a battery tender to do the same. Then Tesla came out with these batteries and I wondered if it was an option.

Real-Pierre-Delecto2 t1_irfvkq5 wrote on October 7, 2022 at 7:50 PM

Ya I hoped for that as well. The thing is very sensitive to power fluctuations which actually makes it work really good especially in my area. Where I live the mains have auto-breakers so if a tree or something touches the line they will trip but then re-engage a few seconds later to see if the fault has cleared. They do this up to about 5 times and it creates a huge surge in the house on-off on-off etc it's horrible for sensitive electronics. Use to have to run across the room and shut off the tube amps and other radio gear I have on. That never happens now as the Powerwall switches over so fast and wont switch back until it has about 5 mins of constant mains power.