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using Leaf as house backup power

Posted: Wed Jun 26, 2019 4:21 pm
by RustyShackleford
I'm curious how easy it would be, and if anyone here has managed, to use their Leaf as backup power for their house during power outages. Mine has a 40kwh battery. That's enough to run the fridge and cable modem for a couple of days, and the well pump enough for drinking water and a little washing. (Of course it's not gonna be enough for HVAC or water-heating). And obviously that battery is cable of providing more than 10kw of power (at 150 miles range, if you average 40mph you're going to run it dry in 4 hrs). So the rub is how to access a few kilowatts of that power output (the well pump driving the peak power required). Figure that out, add a 240v inverter, and Bob's your uncle. I believe I've read that the cigarette lighter outlet can supply 10 amps, so that 120 watts might run the fridge if one could disable auto-defrost mode, but not even close for the well pump.

Re: using Leaf as house backup power

Posted: Wed Jun 26, 2019 4:39 pm
by Nubo
This should help viewtopic.php?t=13097

Re: using Leaf as house backup power

Posted: Wed Jun 26, 2019 9:40 pm
by RustyShackleford
Nubo wrote:This should help viewtopic.php?t=13097
Thanks for the link; my search kung-fu is not that good I guess.

The rub for me is the well pump, which is on a 2-pole/20-amp breaker; I don't know how much power it actually draws, but I gotta figure it's more than the rig in the link. They don't seem to be harvesting nearly all the power the Leaf is able to provide to its motor. I see a DC-to-DC converter mentioned. Does this mean the battery's output to the motor is at a voltage higher than 12vdc, and the 12v power out is limited by that converter ? If so, I guess I'm SOL as far as the well is concerned, unless I can somehow tap directly into the battery's output and find an inverter than runs on that (presumably higher) voltage. Probably not likely.

Maybe I have to put a stage of 12v batteries plus 240vac inverter big enough to handle the well pump, and keep that battery bank charged from the Leaf ? Yikes.

Re: using Leaf as house backup power

Posted: Thu Jun 27, 2019 1:03 am
by Nubo
RustyShackleford wrote:The rub for me is the well pump, which is on a 2-pole/20-amp breaker; I don't know how much power it actually draws, but I gotta figure it's more than the rig in the link. They don't seem to be harvesting nearly all the power the Leaf is able to provide to its motor. I see a DC-to-DC converter mentioned. Does this mean the battery's output to the motor is at a voltage higher than 12vdc, and the 12v power out is limited by that converter ?
Yeah, much higher. The "traction battery" is on the order of 400V. Think of the converter as the analog to an ICE car's alternator in that it keeps the 12V system supplied.
I guess I'm SOL as far as the well is concerned, unless I can somehow tap directly into the battery's output and find an inverter than runs on that (presumably higher) voltage. Probably not likely.
Definitely a more complex proposition. Nissan keeps threatening to bring their "LEAF-to-Home" product to the US, and that system would be what you're thinking off; deriving its power directly from the main 400V bus. I believe it can output up to 6kW. It's been in Japan for years but I'm not sure what the status is for the US market.

Re: using Leaf as house backup power

Posted: Fri Aug 09, 2019 2:08 am
by tannerj
Never thought that the leaf's battery is that powerful.

Re: using Leaf as house backup power

Posted: Fri Aug 09, 2019 2:20 pm
by Oilpan4
No "12v inverter" is going to be able to run a 240v well pump on a 20 amp breaker.
Your best bet to run the well pump is a generator.
Or build a well pumping system designed from the water level of the well and up to use lower voltage DC power. Like I am.
I will likely include a non electric backup to the electrical pumps.

Re: using Leaf as house backup power

Posted: Fri Aug 09, 2019 3:23 pm
by RustyShackleford
Oilpan4 wrote:
Fri Aug 09, 2019 2:20 pm
No "12v inverter" is going to be able to run a 240v well pump on a 20 amp breaker.
Not so sure about that. For one thing, apparently my 1/2HP pump would normally be put on a 15-amp breaker, so we'd be talking 30amps at 120vac (using a 120->240vac step-up transformer). But the pump really uses about 1000 watts while running and double that startup surge, perfectly reasonable for a big 12vdc inverter.

Now I worry about damaging the Leaf's DC-to-DC inverter by trying to pull that surge with the big inverter straight off its 12vdc battery. So maybe AC couple it using a smaller inverter attached to the Leaf and some bigger 12v batteries to supply a larger charger/inverter's surge. That's just what @BrockWI apparently has done (or used to do) at the thread (especially see the last page or two): https://mynissanleaf.com/viewtopic.php? ... 92#p564092

But yeah, a lot of complexity.

So ...
Or build a well pumping system designed from the water level of the well and up to use lower voltage DC power. Like I am.
I will likely include a non electric backup to the electrical pumps.
I'm looking at using a pump like one of these: https://www.gopronow.biz/plastic-groundwater-pumps and running it directly off the Leaf's 12v battery. Less than 2" diameter, so can slip it down ride beside the pipe for my main submersible 240vac pump. But of course this pump couldn't pressurize my house's water system (unless I build a water tower ;) )

Re: using Leaf as house backup power

Posted: Fri Aug 09, 2019 3:51 pm
by Evoforce
Please keep us informed of your progress!

Re: using Leaf as house backup power

Posted: Fri Aug 09, 2019 11:03 pm
by Oilpan4
A half horse well pump might be able to start with inverter.
But you are going to need a big battery. If the battery voltage drops below 10.5v it's going to fault. I have a heck of a time starting my skil saw and 8 inch grinder on my samlex 2000w pure sine wave inverter. That's a pretty good $400 inverter running off a 60ah LiFePO4 battery.
Might want to see if there is a soft start available for your well pump.

Re: using Leaf as house backup power

Posted: Sun Aug 11, 2019 9:10 am
by BrockWI
You would need a 3000 + pure sine wave inverter or better to start a 240 well pump. Along with the large inverter you would need at least 300 amps at 12v of lead acid or about 150 amps of LiFePO4 and a short run of 2/0 cable, way heavier than what comes with most inverters.