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I live in the SF Bay Area, where the utility company, PG&E, has decided to start shutting off the power for days at a time when they feel like it.

I've got 7kW of solar panels on the roof, and a 64 kWh battery in the car in the garage, which is all the pieces I'd need to be able to ride out an outage indefinitely (as long as the car was home), they just can't work together to do that. I'm wondering if I can come up with some kind of home brew partial solution to this problem. Even if I can't use the solar panels, I'm thinking I could use a third-party inverter to run my refrigerator off of the car battery. Has anyone tried something like this?

My main concern is that unless there's some way to connect directly to the high-voltage battery, I'd probably need to connect via the 12v battery. What's the capacity of the system that recharges the 12v battery from the main battery?
 

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I live in the SF Bay Area, where the utility company, PG&E, has decided to start shutting off the power for days at a time when they feel like it.

I've got 7kW of solar panels on the roof, and a 64 kWh battery in the car in the garage, which is all the pieces I'd need to be able to ride out an outage indefinitely (as long as the car was home), they just can't work together to do that. I'm wondering if I can come up with some kind of home brew partial solution to this problem. Even if I can't use the solar panels, I'm thinking I could use a third-party inverter to run my refrigerator off of the car battery. Has anyone tried something like this?

My main concern is that unless there's some way to connect directly to the high-voltage battery, I'd probably need to connect via the 12v battery. What's the capacity of the system that recharges the 12v battery from the main battery?
I know people have talked about ways to use EVs as grid storage but I don't think anyone has actually demonstrated the concept. Trying to connect to the traction battery is wildly dangerous and would likely result in some combination of damage to your car, your house and you personally. :eek: Plus I doubt any commercially available inverter is capable of handling the 356V out of the traction battery.

Like you I'm not sure of the capacity of the DC/DC converter that runs the 12V accessories. For comparison most conventional cars have alternators in the 100A - 200A range. I would assume that an EV would have a similarly sized 12V supply, maybe a little more.

For example, a stock Kia Forte has a 110A alternator. If we assume you can safely draw half of that continuously that's 55A which works out to 660W. Inverters have an efficiency around 90% so that equates to just under 5A @ 120VAC. That's not a lot. Even if it's 200A you still looking at less than 10A @ 120VAC. Domestic refrigerators use about 200W but that doesn't count start up current which can be a lot higher.

TLDR, I doubt it's possible to power home appliances from your car easily or safely.
 

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I believe the Leaf is the only EV that is capable of such a connection. The car's programming has to allow the electricity to flow out instead of in. It's referred to as V2G, or Vehicle to Grid, although you obviously wouldn't want the power actually flowing to the grid under these circumstances.
 

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I believe the Leaf is the only EV that is capable of such a connection. The car's programming has to allow the electricity to flow out instead of in. It's referred to as V2G, or Vehicle to Grid, although you obviously wouldn't want the power actually flowing to the grid under these circumstances.
That's pretty cool. To take the discussion further off topic I do wonder about the real world utility of this concept though. From this article:

Our own Kyle Field says V2G could be perfect for electric school buses, which spend most of the day parked and waiting for school children to transport. Think of the energy that could be stored in all those yellow vehicles and how it might be cheaper to tap into it rather than building dedicated fixed battery storage facilities.
If you use the power stored in an electric school bus to supplement the grid during the day how do you use that same bus to drive the kids home in the afternoon? Do they really sit there fully charged for hours on end?

Here's what seems to be a typical electric transit bus. It takes 2.5 hours to recharge its 500kWh traction battery. If a similar school bus finishes its morning route at 9:00 it will be fully charged by 11:30 assuming it was completely discharged. Let's say it has to start picking up kids at 3:00. That means if it discharges by 50% supporting the grid it needs to start recharging before 2:00. That gives us 2 1/2 hours of grid support time. Is that worth the extra cost of infrastructure and maintenance? Obviously these are worst case numbers and it may be that the bus has significant range left over after its morning route. In any event the amount of time that a school bus could be used for grid support is limited by its fixed schedule. Sure, the math works much better overnight, but generally we're concerned about peak usage hours.

I love the idea of being able to use MY personal EV to power MY personal home when needed. I can trade off vehicle range for home power if I want / need to. I'm not sure about having my neighbor power his man cave with my range leaving me stranded when I want to go pick up pizza in the evening. :D
 

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Don't even think of using the car's 12 volt system to power the house. So many issues. Yes, an outside inverter from the traction battery would be the way to go, but you would need to watch the charge level on the battery closely. You don't want to damage it by dropping too low.
 

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Assuming:

1: You don't damage your car hacking the traction battery to connect your inverter
B: You don't kill yourself in the process
III: You have a bunch of money

Something like this would probably work:

https://www.schaeferpower.com/content/products/dcac-inverters/

If you are a true wizard you could address yticolev's concern about discharging your battery using the CAN bus interface on this model:

https://belfuse.com/product-detail/power-solutions-custom-value-added-solutions-emobility-350inv60-auxiliary-inverter?navCategory=eMobilityDcacInvertersundefined

If you try it, take lots of pictures and make sure they upload to the forum automatically in case you're not around to do it. :D
 

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Yes don't use the 12v. outlets at all for powering anything in the house. It can charge you cell phone and things like that. Try looking at www.priuschat.com and see if the discussion there can b apply to the Niro. I know when I had my Prius and use to hang out there, there were lots of discussions about this. I believe there was a kit available where you could just plug your house into the car and just use the car like and emergency generator to power your house. I don't know if the "kit" could be used in the Niro but there seems to lots of people there that are very educated about this electrical stuff. Most of it was "over my head".
 

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I live in the SF Bay Area, where the utility company, PG&E, has decided to start shutting off the power for days at a time when they feel like it.

I've got 7kW of solar panels on the roof, and a 64 kWh battery in the car in the garage, which is all the pieces I'd need to be able to ride out an outage indefinitely (as long as the car was home), they just can't work together to do that. I'm wondering if I can come up with some kind of home brew partial solution to this problem. Even if I can't use the solar panels, I'm thinking I could use a third-party inverter to run my refrigerator off of the car battery. Has anyone tried something like this?

My main concern is that unless there's some way to connect directly to the high-voltage battery, I'd probably need to connect via the 12v battery. What's the capacity of the system that recharges the 12v battery from the main battery?
I share your interest in this, but ...

What many people don't realize about backup power systems is that they need to guarantee that they don't backfeed into the grid during a power outage. This is a legal requirement, and its primary purpose is to prevent your backup power from electrocuting some poor power-company lineman who is trying to repair the grid and thinking that it's de-energized because they've switched off the feed from the power company end.

For this reason, most PV installations (including mine) use an inverter that automatically shuts down when it doesn't sense electrical power from the distribution grid.

There's a simple model to do what you want to do (but it doesn't involve your car battery). You purchase a portable, gas powered generator. When the power goes out you wheel it outside, put some gas in it (or hook it up to a natural gas supply line if it's designed to run on natural gas), and run a long extension cord into your house to run the refrigerator, maybe your wifi and a phone charger, but not much else. You can do this for maybe $300 - $500.

There's a more complicated model (and it still doesn't use your car battery): You hire an electrician to install a generator outlet and generator switch. You purchase a (possibly larger) gas powered generator. When the power goes out, you wheel it outside, provide it with fuel, and connect a special cord to the generator outlet that the electrician installed. You flip the generator switch, which physically disconnects your house wiring from the grid, and simultaneously connects your house wiring to the generator outlet. Now your whole house is running on generator power, legally. You can probably do this for about $1200, if you find a reasonable electrician.

The fuel part is kind of a challenge: when the electricity goes out, the gas stations can't usually pump gas. So you need to store a few gallons of gas, and you need to replace it every few months or put fuel stabilizer in it to keep it from going bad while it's sitting around in a gas can. And storing it has its own set of concerns.

There's a "Mickey Mouse model": you can purchase a 120 volt inverter that will plug into the 12V power outlet on the car. That would be capable of running something like a wifi router, but plugging even something as small as a crock pot into it might be too much power draw. The higher end Niro trim packages have a 120 V inverter built in, but I think the same power draw limits apply: maybe you can pump up an air mattress or run a router, but I think mine still won't run my crock pot.

If you want to substitute your car battery for the gas generator in either the simple model or the more complicated model, you need to find an inverter that can deliver higher current loads and you also need a safe way to connect it to the battery without electrocuting yourself. And then you're either stuck with the simple model's limitations (anything you run has to be plugged into an extension cord) or the more complicated model's requirements (need a generator switch and a generator outlet and a generator cord).

It drives me crazy to think that I have a PV system on the roof that generates more electricity than I use in a day (most of the time), but if the grid goes down, I can't use any of it. But when I look at what it would take to be able to use that in a power outage, it's up around $10,000 to install something like a Tesla Powerwall and all of the additional switching technology. Compared to a gas generator and a small amount of electrician work, it's about 10 times more expensive to install the Powerwall.

If you find a solution that strikes a happy medium, I'd love to hear it.


If you go the generator route, be aware that the less expensive high power ones can be really loud.
 

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Actually its very simple. When ever you turn on the ignition in the EV (it can be any EV, leaf / niro / tesla) the DC-DC converters kicks-in and it will provide 12v supply (from main 64KWH lithium-ion batteries). This is essential, without this your AC/ Heater/ head lights/ fans / lights/ display / audio / wipers / safety systems / sensors etc.etc will drain your small 12v battery in just couple of minutes. So, DC-DC (400v DC to 12DC) will need to provide good amount of power for all these accessories to work. In case of Tesla this DC-DC converter can deliver up to 180 Amps, which is about 2.2KW. In case of nissan leaf its 135 Amps (about 1.7KW). If you have a 12v DC to 120v AC inverter, you can generate good amount of power, which is good enough to power a home essentials. Obviously you need to take care few things like, how much power you are drawing (need to make sure you should not draw more than 90% of DC-DC converter capacity), how to hook up safely to home and inverter efficiency, surge load capabilities, waveform of inverter. When you connect inverter to 12 battery terminals, make sure to turn all possible accessories in the car. This makes no extra loads in-side the car. I have nissan leaf and I am able to run my 120volts 1500 watt heater by connecting with a proper inverter. Nissan leaf is able to power this heater whole night, without any issue. Why I have limited my heater to 1500 watts is, my DC-DC converter can do at 1700watts, but out of this 1700 about 60 watts gets wasted inside leaf for few electronics, which are ON aslong as car is in ON mode (gear is in parking only). and another 150 watts of loss (efficiency) inside inverter. So, 1500 watts from nissan leaf is easy. I believe niro also has similar specs, so if you hook up your car to home all you need to take care is safety and make sure you are not turning appliances which makes total power draw more than 1500 watts.
I have some simple system with some safety additions to power a house from EV car. Here you are not hurting car, as safety fuses will turn-off power if the power draw exceeds allowed limits. Frankly EV manufactures don't want their cars to use like this, as it causes more cycles on Li-ion battery, which they cannot trace. So, if the battery degrades quickly (assuming you are using this method rigorously ), it comes to car manufactures to replace the battery, as the odometer will show less miles, but battery has large number of charging/discharging cycles with-in the specified age and battery not holding enough charge. But drawing power couple of times in a year is not a big deal.
Inside the car 1500 watts draw is nothing, its exactly same as turning all interior lights, max Heater+ high beam head lights +fans @ max speed + max display brightness + max audio vol + fast wipers + safety systems + sensors, drawing 180 watts from cigarette lighter slot etc.etc . If you add all them it comes to 1700 watts. This is the reason why car manufacture created a DC-DC converter which delivers 1700watts.
 

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I share your interest in this, but ...

What many people don't realize about backup power systems is that they need to guarantee that they don't backfeed into the grid during a power outage. This is a legal requirement, and its primary purpose is to prevent your backup power from electrocuting some poor power-company lineman who is trying to repair the grid and thinking that it's de-energized because they've switched off the feed from the power company end.

For this reason, most PV installations (including mine) use an inverter that automatically shuts down when it doesn't sense electrical power from the distribution grid.

There's a simple model to do what you want to do (but it doesn't involve your car battery). You purchase a portable, gas powered generator. When the power goes out you wheel it outside, put some gas in it (or hook it up to a natural gas supply line if it's designed to run on natural gas), and run a long extension cord into your house to run the refrigerator, maybe your wifi and a phone charger, but not much else. You can do this for maybe $300 - $500.

There's a more complicated model (and it still doesn't use your car battery): You hire an electrician to install a generator outlet and generator switch. You purchase a (possibly larger) gas powered generator. When the power goes out, you wheel it outside, provide it with fuel, and connect a special cord to the generator outlet that the electrician installed. You flip the generator switch, which physically disconnects your house wiring from the grid, and simultaneously connects your house wiring to the generator outlet. Now your whole house is running on generator power, legally. You can probably do this for about $1200, if you find a reasonable electrician.

The fuel part is kind of a challenge: when the electricity goes out, the gas stations can't usually pump gas. So you need to store a few gallons of gas, and you need to replace it every few months or put fuel stabilizer in it to keep it from going bad while it's sitting around in a gas can. And storing it has its own set of concerns.

There's a "Mickey Mouse model": you can purchase a 120 volt inverter that will plug into the 12V power outlet on the car. That would be capable of running something like a wifi router, but plugging even something as small as a crock pot into it might be too much power draw. The higher end Niro trim packages have a 120 V inverter built in, but I think the same power draw limits apply: maybe you can pump up an air mattress or run a router, but I think mine still won't run my crock pot.

If you want to substitute your car battery for the gas generator in either the simple model or the more complicated model, you need to find an inverter that can deliver higher current loads and you also need a safe way to connect it to the battery without electrocuting yourself. And then you're either stuck with the simple model's limitations (anything you run has to be plugged into an extension cord) or the more complicated model's requirements (need a generator switch and a generator outlet and a generator cord).

It drives me crazy to think that I have a PV system on the roof that generates more electricity than I use in a day (most of the time), but if the grid goes down, I can't use any of it. But when I look at what it would take to be able to use that in a power outage, it's up around $10,000 to install something like a Tesla Powerwall and all of the additional switching technology. Compared to a gas generator and a small amount of electrician work, it's about 10 times more expensive to install the Powerwall.

If you find a solution that strikes a happy medium, I'd love to hear it.


If you go the generator route, be aware that the less expensive high power ones can be really loud.
To make a simple system to power your home with EV will costs just around $500. Once you have EV, you really don't need power wall. Its a legal way to power your home safely. Instead of a gas generator, you are going to use EV. Keeping a limit of drawing about 1500 watts at any given time. This will make sure your EV is not getting screwed up, and things will work with-in the specified limits. Even with 1500 watts you can power more than 150 LED bulbs (assuming each bulb consumes about 10 watts). So in case of emergency, 1500 watts is a very good amount of power. By drawing 1500 watts continuously, your fully charged 64KWH EV can power you about 40 hours easily.
 

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To make a simple system to power your home with EV will costs just around $500. Once you have EV, you really don't need power wall. Its a legal way to power your home safely. Instead of a gas generator, you are going to use EV. Keeping a limit of drawing about 1500 watts at any given time. This will make sure your EV is not getting screwed up, and things will work with-in the specified limits. Even with 1500 watts you can power more than 150 LED bulbs (assuming each bulb consumes about 10 watts). So in case of emergency, 1500 watts is a very good amount of power. By drawing 1500 watts continuously, your fully charged 64KWH EV can power you about 40 hours easily.
If you are a PV system owner and have enough money, you can replace your old solar inverter with anew one, that will allow limited use during power outage e.g. 1500 W from a new Sunny Boy model (it will automatically disconnect from the grid to eliminate islanding).
 

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If you are a PV system owner and have enough money, you can replace your old solar inverter with anew one, that will allow limited use during power outage e.g. 1500 W from a new Sunny Boy model (it will automatically disconnect from the grid to eliminate islanding).
I have PV system. The problem here is in case of power-shutoff, mostly we need power during night time. As these PV system doesn't generate power during night time, it becomes useless. More over this 1500 W is not constant, as it depends on clouds and weather at that point of time.
The system that I have is, powering home with Car (it can be gas car or electric car).
With gas car, I can get only 300 watts of power, which is good enough to run 10 (LED) lights, some communication equipment like modem/router, while keeping the car in idling mode continuously. A full tank of gas in car, gives me about 2 days. Which is decent in case of power-shut off.
With Electric car, I can get about 1500 watts of power. With this power I can run 40 (LED) bulbs + communication equipment like modem/router + laptop + LED TV / mini fridge + small space heater / ceiling fan + gas powered water heater. This whole setup is very interesting and it costed me only $500. My electric car (Nissan leaf - 40KWH battery) on full-charge it powered my house for 3 days continuously, as we used TV & lights intermittently.
Note: During my power outage, my PV system is completely OFF.
 
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