Use car as battery for off grid storage

Considering this and would love to get some thoughts on pairing solar panels + inverter with an MG4 Excite 51 for storage (MG EV With 350Km/220m range and 51KWh LiFePO4 pack and the built in "vehicle to load" feature)

Context
- Off grid with 18KW of panels into a hybrid inverter
- hybrid inverter has generator input (where I'd plug the car's vehicle to load)
- Work from home
- 400Km driving p/week
- 5 - 7 KWh used at night

My thoughts are
Pros
- multi purpose vehicle and storage : If you need a car and energy storage to last the night this could be a 2 in one kinda deal.
- if charge slow and keep it cool-ish and dont chage it to 100 etc etc - the LiFePO4 pack could last quite a while
- Australian dollars - $0.72/Wh(with 90% battery de-rating assumed for a year old car with 5000K's on the clock) or $0.76/Wh for the LFP battery bank in a used ($33,000) or new($39,000) MG4 respectively.

Cons
- can't charge at night
- can't charge and provide battery power at the same time. One or the other
- no power to house when you go on a trip
- Limited peak power output at night (2.5KW only)

Thinking the Cons might be a deal breaker. Perhaps could be supplemented with a single 5KWh battery(+$2500AUD ruixu rack battery for example) on the hybrid inverter to take care of larger loads at night and for a backup when I take the car out.

Anyway, just spitballin'

Not so practical in my opinion.
I would definitely use solar to charge the car.
It could be a backup solution (using car's v2l and a generator input on the inverter) in case of a power outage.

Get a small battery like you mentioned, as a buffer for when the clouds pass by.

I prefer the off-grid system to have it's own battery and charge the EV as a typical load. A 10-15kwh battery would be a good start IMO.

Pause EV charging when the sun gets low in the sky.

Restart EV charging once the house batteries are topped up.

haywire said:

Thinking the Cons might be a deal breaker.

Click to expand...

I have the Essence 64.

V2L is handy as a backup source of energy in grid outages and out on the road (e.g. picnic/BBQ) but it's impractical for V2H duties.

The lack of bidirectional charging renders it an occasional use feature. The need to swap plugs and change the operating mode in the car from charge to discharge (and back) means it just isn't that practical.

I have used mine to recharge the home battery system after a daytime outage. I fed the V2L into a spare AIO inverter and used it to charge the battery. Did a test a few months back where I discharged 22 kWh from the car over ~ 15 hours. Charged the battery back up also kept the house running overnight.

wattmatters said:

Charged the battery back up also kept the house running overnight.

Click to expand...

That's pretty sweet.

pollenface said:

A 10-15kwh battery would be a good start IMO.

Click to expand...

I jumped on the forum just now to check if Australia can get those 14.3kW-h eg4 batteries Will discussed in a video. Doesn't seem like they are sold here after a quick search. Hopefully the price and availability will improve fast on good quality LFP packs, then I can get separate home storage and keep the vehicle pack degradation to a minimum.

There's just so much capacity sitting in the car - buying more for home storage can feel like a double up until you think/talk it through with other people, so thanks for the comments .

haywire said:

with 90% battery de-rating assumed for a year old car with 5000K's on the clock)

Click to expand...

It won't degrade anywhere near that much that quickly.

haywire said:

Perhaps could be supplemented with a single 5KWh battery(+$2500AUD ruixu rack battery for example) on the hybrid inverter

Click to expand...

Don't forget these batteries have a max discharge limit of 100 A or ~ 5 kW. You have to be careful what loads you expect to power. This why you use several in parallel as it provides peak power capacity.

Also note the V2L output (in Australia at least) of the MG4 is limited to about a max of 2.2 kW, but really an effective 2 kW as the output voltage is pretty low. That's enough to steady charge a battery or for outage backup of essential loads (lights, fridge, internet etc) but not for those plus boiling a kettle.

haywire said:

I jumped on the forum just now to check if Australia can get those 14.3kW-h eg4 batteries Will discussed in a video. Doesn't seem like they are sold here after a quick search.

Click to expand...

There are multiple options which are pretty much the same thing, e.g.:

haywire said:

. Hopefully the price and availability will improve fast on good quality LFP packs,

Click to expand...

I was planning to DIY a kit from Alt-tech.

Fellow Australian MG EV owner here too

wattmatters said:

There are multiple options which are pretty much the same thing, e.g.:

JAKIPER BATTERY – Professional in Batteries

aujakiperbattery.com

48v 100ah Lifepo4 Battery | Ruixu Battery

RUIXU provide the quality server rack 51.2V 100Ah Lithium Iron Phosphate Battery.

www.au.ruixubattery.com

48V Lithium Battery

EdgePower Australia your energy partner to provide cutting edge energy solutions to residential and industrial customers.

edgepower.com.au

100Ah 48V Lithium Iron Phosphate (LiFePO4) Battery

The ATG Batteries 48V 100AH Lithium LifePO4 battery is a top-of-the-line deep cycle battery that is built to withstand even the harshest conditions. Designed and engineered in Australia, this battery is made to handle the unique demands of the Australian climate. Whether you're using it for...

www.access12voltwarehouse.com.au

5kwh » LiFePo4 Australia

51.2v 100ah LIFEPO4

lifepo4.com.au

KIJO LFP48-100 Lithium Iron Phosphate Battery for Sale

KIJO Battery Online Store in Australia, wholesale Lithium Battery and Lead acid batteries, for UPS systems, Solar energy storage, and power supply. Welcome Order now!

www.kijo-battery.com.au

Click to expand...

Great resource! thanks