Adding battery storage to Tesla system

[Austintatious]

I am wanting to add some battery backup to my home. I currently have Tesla 17.5 Kwh solar, no powerwalls, 2 Tesla inverters each feeding one of the independent 200a panels on my 400 amp service.

I am considering two powerwall 3's, but they are pretty expensive... The Pro's to them are that they match the solar, I wont be installing them and they will 100 percent meet my needs. However if I can DIY and save some money or get more storage (I really only need about 25Kwh) I may abandon the PW route.

So, what I want to be able to do is charge batts at night, use that power between the hours of 5am and 11am. Then from 11am until about 430pm, recharge the batteries as much as possible, then use this power between about 430pm until 8pm and then go back to grid powering the home and charging batts. I want to be able to run some of the home in a power outage off of batteries and solar (currently solar can not power when grid is down). Furthermore I need the system to be able to deal with a situation where the power is down, the sun is shining full, my power demand is low and the batteries are full.

Any recommendations?

 

[Austintatious]

nobody? nuthin?

 

[Solar Guppy]

DYI means you do the design, permit package, purchase and install. It can be done but it requires many skills, for most the reality of this means it maybe better to earn more with your current skills than try to learn all the other trades needed for DYI.

 

[Austintatious]

DYI means you do the design, permit package, purchase and install. It can be done but it requires many skills, for most the reality of this means it maybe better to earn more with your current skills than try to learn all the other trades needed for DYI.

Odd advice for a DIY forum... You know nothing about me or what skill sets I have.

 

[Jansen Lee]

Check your DM

 

[JJJJ]

I may be mistaken but it might be possible that Tesla inverters are specifically designed for their own technology, eg powerwall. They tend to be proprietary. Now if you were using off the shelf panels and inverters there would likely be a lot more help available.

Frankly I don’t know if a system designed around lithium ion technology would work with another battery type and I have been working with this over three years.

 

[Jansen Lee]

The Tesla PW2, PW2+ and PW3 are all AC coupled so they can be added to most any solar setup that does not already have a battery. The PW2 is the only one those that doesn't have a built-in MPPTs and requires either the Tesla Backup Switch sandwiched behind the meter or a Tesla Energy Gateway to work; the PW2+ and PW3 have the MPPTs as well as a Gateway built-in and can isolate from the grid when the power goes down, somewhat similar to how the EG4 GridBoss functions.

It does becomes a little more difficult when adding different battery types, but the Tesla ecosystem does not rely on the main inverter to control DC battery charge levels so they can coexist with other battery chemistries, depending on how they are connected.

 

[chrisski]

Seems you have Tesla Grid Tied inverters. Grid tied inverters get to DC batteries through an addition of an AC coupled inverter.

I'm not recommending the Outback Mohave AC Coupled Inverter; I am familiar with it so including the block diagram:


Seems you have two different inverters feeding separate 200 amp panels, so you could get two of the above.

Other companies make AC Coupled inverters, but I can't recommend one.

My Installer recommends Franklin Power AC Coupled inverters or the Tesla Powerwalls. The Powerwalls will automate much for you; Franklin gives you more options. Neither option is cheap, but locally the Tesla Powerwall is a fair price for a good installation. I think Enphase makes a system, but know nothing of it. Don't know if Franklin, Enphase, or Tesla is DIY an option.

Beware that not all AC Coupled inverters will provide power after the battery dies during an extended power outage. Some need an AC voltage to restart charging.