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I have a 2020 Niro EV and the power went out last week but is back on now. It brought a question to mind, can I use a gas-powered generator either a 120V or 240V to charge my car with either the Level 1 or Level 2 charger?

Luckily the car had 60% battery when the power went out so I didn't need to charge. But if it had gone on for a few days I thought maybe I could use my Ryobi 6,500W generator to charge an EV battery.

My generator has 4) 120v GFCI 20 amp outlets and 1) 120v/240v 30 amp outlet.

Will this work in emergencies or am I asking for trouble?
 

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I have a 2020 Niro EV and the power went out last week but is back on now. It brought a question to mind, can I use a gas-powered generator either a 120V or 240V to charge my car with either the Level 1 or Level 2 charger?

Luckily the car had 60% battery when the power went out so I didn't need to charge. But if it had gone on for a few days I thought maybe I could use my Ryobi 6,500W generator to charge an EV battery.

My generator has 4) 120v GFCI 20 amp outlets and 1) 120v/240v 30 amp outlet.

Will this work in emergencies or am I asking for trouble?
Probably? Caveats:
1. Some generators (inverter based like the little Hondas) don't generate a true sine wave AC signal. This might interfere with the operation of the onboard charger.
2. You'd need to make sure the charge current limit was set below the max rating for the generator.

It would certainly be the least efficient way to charge your vehicle but it would most likely work.
 

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Probably? Caveats:
1. Some generators (inverter based like the little Hondas) don't generate a true sine wave AC signal. This might interfere with the operation of the onboard charger.
2. You'd need to make sure the charge current limit was set below the max rating for the generator.

It would certainly be the least efficient way to charge your vehicle but it would most likely work.
The little Honda's do in fact generate a true sine wave. That's one of the reasons why they are so expensive. That said: True sine wave is not even very important to a AC-to-DC charger in an EV. True sine wave is most important for AC motors but most devices that take alternating current and rectify it to DC usually run fine on modified sine wave because once the AC is rectified to DC the waveform of the original AC is really no longer important. There could be sensitive electronics in the EVSE itself that may not work well on modified sine, but the car's onboard charger itself should be fine.

But again I've not seen any "Inverter" based portable generators that produce modified sine. The most popular models from Honda and Yamaha all produce true sine wave because their primary market is recreational vehicles where those little generators have to run air conditioners and air conditioner compressor motors need pure sine to run correctly.

Your point #2 is quite valid, and I would go even further and stress that you need an EVSE that allows you to adjust the charging current without an Internet connection. Many "smart" EVSE models like the JuiceBox will only allow you to adjust settings via the cloud over the Internet. If your power is out then chances are your Internet is down as well, and you wouldn't be able to modify the charging current on the JuiceBox EVSE. So having an EVSE where you can adjust the charging current up/down without Internet would be very important. It looks like OpenEVSE allows making changes to this without an Internet connection so that might be a viable alternative to JuiceBox.

An additional important note on charging on a portable generator is that most EVSE's will perform a "ground check" before they allow charging: They attempt to verify that the ground pin on whatever plug you plug it into is actually connected to ground. They do this by checking the voltage between the "hot" wire of the plug with the ground wire. If there's no voltage that means there's no ground wire connected and the EVSE will refuse to charge because it thinks it's not safe to do so.

Many portable generators, especially the Inverter based ones from Honda, do not bond the neutral to ground, and thus this ground check will fail. This is perfectly safe because on a portable generator there's no need for earth ground as the generator itself is sitting on rubber wheels and/or rubber shock absorbing feet and isn't earth grounded anyway. You can trick the EVSE into passing this test by simply connecting a very high Ohm resistor (Like 100k) between "neutral and ground" and between "hot and ground". This was thoroughly discussed on the Nissan LEAF forums back in 2012 and "Ingineer" (Who used to own/operate the evseupgrade.com website) offered instructions for how to create your own charging plug that would allow charging on a portable generator with a floating ground. You can read that thread here:


I have tested charging my EV on my motorhome's 6,000 watt diesel generator and it works great. I actually get about 25 miles of range per gallon of diesel burned so while it's not the most efficient way to add range to the car it's not exactly terrible compared to the average ICE vehicle.

"The Fast Lane Car" did some testing with charging EVs on portable generators and they found that the generators with 240v outlets are able to charge at level 2 speeds:

They also discuss the floating ground issue on the TFL videos. You'll notice they have a special "ground plug" plugged into the 2nd outlet of the generator in their 2nd video (It's a 3 video series) which contains the resistors I mentioned earlier to make it pass the ground check. I did some checking and I found you can buy pre-made plugs on Amazon for around $12:


However most of the larger 240v generators do bond neutral to ground which alleviate the need for the bonding plug. The 6,000 watt diesel generator on my motorhome charges my EV just fine without any special bonding plugs so it really just depends on the generator. If you have a 240v generator you probably don't need the bonding plug.
 

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The little Honda's do in fact generate a true sine wave. That's one of the reasons why they are so expensive. That said: True sine wave is not even very important to a AC-to-DC charger in an EV. True sine wave is most important for AC motors but most devices that take alternating current and rectify it to DC usually run fine on modified sine wave because once the AC is rectified to DC the waveform of the original AC is really no longer important. There could be sensitive electronics in the EVSE itself that may not work well on modified sine, but the car's onboard charger itself should be fine.

But again I've not seen any "Inverter" based portable generators that produce modified sine. The most popular models from Honda and Yamaha all produce true sine wave because their primary market is recreational vehicles where those little generators have to run air conditioners and air conditioner compressor motors need pure sine to run correctly.
Good to know, I've seen some older ones that produced a fairly crappy sine wave with obvious stair stepping. Some equipment (oscilloscopes and the like) really didn't like it. To the point we had to put a UPS that had a whole bunch of filtering in between to get stuff to work.
 
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