Using an EV Car as your Emergency Backup Battery

[svetz]

Many people would like to have emergency backup up power for when the lights go out. But batteries are still pretty expensive (e.g., a BattleBorn is ~$800/kW and even the cheapest of DIY battery banks are still around $200/kW). If you're using a kW/h of power, than just for 8 hours you'd need ~9 kWh (taking losses and depth of discharge into account). For most people that's not practical as they can get a high kW rated generator for under $1000. But even buying a generator is still having to pay an extra $1000 for something you'll hopefully rarely use.

But suppose you could get emergency backup power, not have to pay anything extra, and not need to worry about storing fuels or extra maintenance?

Not sure how true it is... But when Dorian was threatening Florida just a bit ago, I heard Tesla offered to let owners reverse the power out of their cars (perhaps you needed their panels/powerwall or something).

Even if the Tesla story is an old wive's tale, EVs do have big batteries. Honda announced something called the Power Exporter to let you get backup power out of their EVs. It's been around for a while, but isn't released as far as I know (first heard about this in 2015).

So, perhaps you don't need a generator or battery bank for those emergencies? Perhaps a car-trade is a smarter approach.

Seems to good to be true, anyone know why we don't hear more on this?

Note: On the old forums @suneater posted an intriguing thought; vehicles were also portable power - so in the event of a crisis (e.g., natural disasters) neighbors could help neighbors. Hopefully he'll repost about his electric car (he's already doing this!)

 

[svetz]

Here's an article where if your 12V battery system is charged by the high voltage battery, you can use your EV for backup power.

This article talks about Mitsubishi coming out with something like Honda's power exporter.

 

[Cape Coddess]

Transport Evolved has a yt vid hooking her Leaf up for home backup power using an inverter and extension cords. There are also posts on the Tesla forums. I am so ready to do this, right down to the 1200w Giandel, but need visual direction on a Tesla. I would love to be able to keep my and my neighbors fridges cool during power outs. So much food gets thrown out afterwards, it's criminal. I'm hoping Will will make an instructional vid using his Tesla.
PS I believe you can also use an ice car to do this. Then you have more gas available than a generator can hold and can drive to the gas station when low, rather than hauling a few gallons home every so often. I too am wondering why everyone isn't doing this.

 

[Rider]

I believe you can also use an ice car to do this.

:scratchinghead: What is an 'ice car' ?

 

[Cape Coddess]

Internal combustion engine. The EV world calls them ice cars.

 

[svetz]

Internal combustion engine. The EV world calls them ice cars.

That's so cold!

 

[Rider]

Internal combustion engine. The EV world calls them ice cars.

lol.... never heard that. Thanx.

That's so cold!

Agree.....

 

[Cape Coddess]

Also, I'm wondering if you can have your car plugged in while it's powering your house? Once will gets his solar shed going I think I'd like to follow along and build one at the same time. It would be good to have an off-grid backup to power the car.

 

[svetz]

Also, I'm wondering if you can have your car plugged in while it's powering your house?

Regardless of if it's possible; since you always lose some power to heat when discharging or recharging, you'd be taking a double whammy. That is for every 10 watts the battery output to recharge itself, only 9 watts would come back. It would just drain the battery faster for no reason.

 

[Rider]

I'm thinking people don't use cars for that because it's not good for an ICE to run at idle for extended periods. If you had a diesel maybe....

 

[burtinator]

... I would love to be able to keep my and my neighbors fridges cool during power outs. So much food gets thrown out afterwards, it's criminal. I'm hoping Will will make an instructional vid using his Tesla.
...

Fridges and freezers are usually really efficient, so if you only want to save your food and be in the dark otherwise, you can get away with a really small battery and one 200-300watt solarpanel. Connect a 500watt inverter and you're good to go. My small freezer only uses .2-.3 kwh a day. I have already powered it a few days with 200watts of solar, a regular car battery and a cheap pwm charge controller as a test. Perfect for a really cheap emergency situation, shouldnt be used for long periods though cause the car battery will die quickly.

 

[Rolee]

Some people do this with their chevy volts or nissan leafs (one company even makes wiring kits to make it easy to tap into https://www.evextend.com/Emergency-Power-Kit.php). I have a volt as well as a chevy spark ev and according to what people on the internet say I should be fine pulling around 1500 watts or so continuously (at 12 volts) if I pull it directly from the "dc bus" that goes from the 12v accessory battery <-> dc/dc converter from the main traction battery. I have yet to try it myself since 1) i'd need some pretty thick cables to make sure things don't heat up too much under the hood and 2) I'd prefer not to have an expensive paperweight. When they get a little older if anything goes sideways with them I'll be looking forward to making them my experiment cars.

 

[L-P-G]

The whole concept is called vehicle to grid (V2G) but I haven't really seen anyone implement it yet. I know Elon Musk was asked about V2G in an investor meeting and he said probably not since the batteries aren't designed for that many cycles. Someone also mentioned that people with unlimited free supercharging would abuse the system by charging for free and using the power at home. I remember back during the BitCoin bubble someone setup a mobile mining rig in the back of their car and used the superchargers to keep the car charged.

As for Tesla offering V2G during Dorian. I wish, I already have a Tesla battery pack powering my off grid inverter but that one is only 60kWh, the one in my car is 90kWh. I didn't see any emails or push notifications. They did however send out notifications that all supercharging would be free and anyone with a software locked battery would have the lock disabled.

 

[svetz]

V2G? That's scary, one more thing to Vote NO on. I'm not a fan of the utility controlling my solar, I sure wouldn't want them controlling my car's battery.

I just want V2mG (vehicle to microGrid, ideally it works with my AC battery , seriously the utility doesn't pay enough for me to use battery cycles for their purposes)

 

[L-P-G]

V2G? That's scary, one more thing to Vote NO on. I'm not a fan of the utility controlling my solar, I sure wouldn't want them controlling my car's battery.

I just want V2mG (vehicle to microGrid, ideally it works with my AC battery , seriously the utility doesn't pay enough for me to use battery cycles for their purposes)

The only control the grid has over any production/storage devices on the grid is frequency control. As long as you use a battery based inverter that can curtail its frequency output (theoretically) you could use V2G to offset the loads being consumed off the battery inverter.

Than again since no one is doing V2G it's all theoretical at the moment.

More in line for what you're referring to would be this.

PriUPS-getting electricity FROM your hybrid vehicle

Using a Prius as a UPS with the engine topping off the battery as needed.

 

[svetz]

The only control the grid has over any production/storage devices on the grid is frequency control.

We're saying slightly different things. You're saying you might be able to make use of it in a microgrid (no arguments there), I'm saying voter beware.

Rule 21 in California (Hawaii and Puerto Rico have similar laws) is so the grid can control residential inverters. Any new inverter has to be compliant to be on the grid. What it allows them to do is ramp down/up the amount your PV system can put onto the grid.

It's one of Sol-Ark's selling points, they have a CT on the grid line so they can ramp power down to the grid at it's request without affecting incoming solar power to recharge the batteries, power the house, etc.

Haven't seen any laws regarding the grid reaching into your batteries, but there's been talk like V2G for years where the grid uses your solar/batteries for peak demand, from Wikipedia (bold is mine):

Vehicle-to-grid (V2G) describes a system in which plug-in electric vehicles, such as battery electric vehicles (BEV), plug-in hybrids (PHEV) or hydrogen fuel cell electric vehicles (FCEV), communicate with the power grid to sell demand response services by either returning electricity to the grid or by throttling their charging rate.

Rule 21 and the other laws got passed because they needed to be. Grid-tied assumes the grid's an infinite sponge that can absorb all the solar you throw at; which isn't true - especially in small grids like Hawaii or Puerto Rico. In CA, they added it when all new homes were required to have solar. Could they pass a law to dip into your batteries? I don't see those politicians having much of a career or it being upheld in the supreme court, but why let it get that far? (I don't believe all new homes being required to have solar would stand up in the supreme court if challenged and yet it is currently a law and became the reason for Rule 21).

 

[Rider]

Vehicle-to-grid (V2G) describes a system in which plug-in electric vehicles, such as battery electric vehicles (BEV), plug-in hybrids (PHEV) or hydrogen fuel cell electric vehicles (FCEV), communicate with the power grid to sell demand response services by either returning electricity to the grid or by throttling their charging rate.

Well, wouldn't that be dandy. Power gets sucked from your vehicle overnight when you have a long distance drive planned for the next day.....

 

[Rolee]

Well, given that demand is usually far lower at night I wouldn't expect the grid to pull from my vehicle but I don't trust PGE at all and would not want to give them any control over how my car gets charged. I like the idea of V2mG where I define the microgrid as my house and it is entirely under my control. My main panel is old (125amp service) with no main breaker. Instead it has 2 large breakers that run to subpanels in the house. I've entertained the (expensive) idea of having my existing solar take up one of the breaker slot and then decoupling the subpanels from the second slot (making the microgrid) and my microgrid has 2 inputs: "shore power" from PGE and "generator input(s)" from my grid-tie solar+ batteries + car battery. Yes it is convoluted but i'm not starting from scratch or with an unlimited budget unfortunately.

 

[svetz]

 

[svetz]

​

...Other standard features include on-board power inverters for supplying both 120 and 240-volt electricity, allowing use of power tools without a portable generator.

Didn't see anything on the size, but Jack Rickard thought it might be as high as 10 kW.