Model S battery intact in place of net metering [DIY home storage using Tesla Car battery?]

[lolachampcar]

This is a shout out to the most nerdy of my Tesla peeps.

Florida is trying to nuke net metering (yea, I know. Instead of charging net metering customers for grid use and growing distrubuted production, FPL wants to force net metering customers back to FPL's primary mission of burning fossil fuels for power. We really are beyond repair.).

Back when I first looked at solar 8 or so years back I was going to use an 85 kWh-hr scrap battery intact with a simple low current in line buck-boost converter along with panels in series to generate around the same voltage as the pack's range. This combined high voltage would be directed to the home inverter for AC.

My question for all is has anyone followed through with this idea? I see a lot of people disassembling packs to re-arrange modules and even using the stock BMS on the module to monitor things. It seems a lot of work when dealing with the existing pack's high voltage allows you to keep all that lovely Tesla packaging and place the battery outside for fire reasons.

Thanks
Bill

 

[Ampster]

I have not seen anyone find an inverter that can accomodate high voltage battery.

 

[BGbreeder]

There are a few surplus / new high voltage inverters that I know of designed for data center use, but they aren't common, nor easy to find, and very few of them can deal with lithium batteries. My $0.02 is that unless high power DC/AC is a core expertise, I would suggest poking around to find a battery/inverter step by step website that you can follow along.

There is the added wrinkle that anything that you home brew is strictly for off grid use, and may not be something that would be covered under homeowner's insurance, both directly, and indirectly (damage to your house from your battery fire).

Just free advice, and worth what you paid for it...

BG

 

[miimura]

Bill, look through the EVTV Motors YouTube channel. I'm pretty sure Jack did exactly what you're talking about with his "Selfish Solar" system. He even advocated for skipping the MPPT on the solar direct into the battery. They also have hardware to talk to the intact pack BMS.

https://www.youtube.com/user/marionrickard/videos

 

[lolachampcar]

I've been slogging my way through the EVTV stuff and they have done a lot of what I am interested in. The problem is having to listen to the presenter belch hundreds of words to say what could be put into a single sentence. There are few if any technical descriptions. They seem to rely almost solely on the guy's videos.

There are some very interesting discussions of the approach to using battery versus PV power, charging the batteries when there is excess PV power then using the battery when there is insufficient PV power. Some of the these approaches actually comply with the requirements for grid tie PV (the UL, CA and HI applicable requirements are referred to often in the videos).

Thanks for the help.

I'll keep poking about.

 

[miimura]

Listening to Jack was always relatively painful, somewhat less so at 1.5x, if only because it's over sooner. When states start proposing things like $8/kW fees for grid tied solar systems this kind of not-actually-grid-tied system starts to make more sense. Having a big battery and the only thing connected to the grid being a repurposed EV battery charger should allow you to avoid those kind of nonsense fees.

 

[lolachampcar]

SolarEdge Home Wave Inverters

Maximize efficiency and safety with SolarEdge Home Wave Inverters - the trusted home energy managers, delivering enhanced performance.

www.solaredge.com

Just a quick look at this PV inverter

indicates it will accept up to 480 Vdc which seems more than compatible with a Tesla battery pack.

PV => Battery => above inverter
The key would be to do a MPPT with an output compatible with the full discharge to charge range of the battery.


Also found this someone linked in the comments to one of the above described videos.

30KW 30,000W PURE SINE POWER INVERTER CHARGER 300 VDC 240 VAC SPLIT PHASE​

Power Inverters, DC To AC Inverters & Solar Panels | AIMS Power

 

[lolachampcar]

I've been looking at the Enphase IQ8 micro inverters that can do solar island when the power goes down without the need for a battery. These inverters fold back power draw to match home consumption and, obviously, can be paralleled. Their 10 KW-hr battery system uses the IQ series inverters to both discharge and charge the battery to load level. In short, all of the elements are there with just some tweaking of the architecture to use a Tesla car battery.

Anyone else pondering these questions?

 

[miimura]

I've been looking at the Enphase IQ8 micro inverters that can do solar island when the power goes down without the need for a battery. These inverters fold back power draw to match home consumption and, obviously, can be paralleled. Their 10 KW-hr battery system uses the IQ series inverters to both discharge and charge the battery to load level. In short, all of the elements are there with just some tweaking of the architecture to use a Tesla car battery.

Anyone else pondering these questions?

Personally, I would not mix systems like that (Enphase + Tesla Battery) unless there was some way to programmatically find the solar headroom available for charging. You would have to have a system to modulate the big battery charging with available solar, then turn around and discharge proportionally or intermittently to keep the Enphase batteries within a nominal SOC range and/or Enphase power discharge limits. It is FAR simpler to just use a big HVDC inverter straight from the Tesla pack, a repurposed EV charger connected to the grid and a HVDC MPPT controller. You will end up with a much more robust and capable system, albeit at a higher price.