Use the Prius as a 12-volt generator during a power failure?

Just thinking about Hurricane Irene last weekend. Our power went out and I was able to keep our 12-volt battery backup sump pump in the house running by charging its battery off the Prius. The sump pump basically runs on 12-volt marine batteries. When the battery ran down, I swapped in a fresh one, and took the depleted one out to the garage and ran jumper cables to recharge it off the Prius 12 volt battery. It seemed to work fine. The Prius would just start up once in a while. My run-down sump pump batteries got charged, then I would just swap it with the next one that needed recharging.

Anyway... I occurred to me that a lot of the problems with running home lights and appliances off the Prius (essentially using the Prius as a generator) is that people are trying to convert from 12 volt to 120 volt. So... what if I just got a bunch of 12-volt lights and small 12-volt appliances and so forth for the house, and ran a wire outside and just connected these items directly to the Prius 12-volt battery? Wouldn't this eliminate all the conversion/inverter hoop-de-doo that seems to be a big hassle?

I'm no electrical engineer, but 12-volt to 12-volt seems like it would work just fine. Just wondering what you think...

that would work, and you might be able to make a business out of selling people 12v appliances and etc., but i would think you would do better if you could come up with the 12v to 120v converter.

Id visit a local truck stop and wonder over to the "truckers" side. They have 12 volt everything, ovens, microwaves, etc. I was previously an electric wheelchair user and had a 24 to 12 volt converter attached to its electrical system. Those chairs use 24 volts. I depended on public transportation, was piss poor broke and was a full time student and then some. I managed to keep food cold and warm up and in many cases even cook food before I ate it.

This is a tradeoff. 120V needs stronger insulation and shock protection. 12V needs much heavier gauge wire to carry power any significant distance.

For a given power and distance, 12V needs 100 times heavier wire than 120V. Or put another way, the wire gauge needed to power a 120V device 100 feet way will reach only 1 foot on 12V before the losses become unacceptable.

The problem is finding " useful " 12 V appliances.

I was under the impression that it only needed wire 10 times bigger (12 x 10 = 120). I know for sure the amperage is 10x more with 12v vs 120v.

Gents,

I had a 700 watt inverter connected to my 2004 Prius for 2 days straight during Irene. I ran a a refrigerator, 15w lamp, radio, laptop, cell phone and other small items. It consumed about 4 gallons of gas. I just looked at the refrigerator specs and it reads 11.5 amps. That should be around 1380watts (oops) and I never noticed any problems like lamp dimming or alarm conditions. Hopefully 11.5 amps is just a momentary surge.

The 12volt battery is about 300 cold cranking amps so surges of up to 3600 watts would be OK. Then the battery needs charging current. The schematic shows a fusible link rated 120 amps which is probably to limit shorts to the battery. If the 12volt battery is drained too low the auxiliary inverter should shut itself down due to the inverter LVD (low voltage disconnect) circuit. One good question is how much charging current is available to the 12volt battery.

Hypothetically inverters up to 3600 watts would be OK but too much continuous power consumption would cause LVD power lapses.

Check out the used 1000watt tripp-lite units on e-bay for 30 bucks.

If this sounds insane please let me know why. I don't want to blow up my car.

V Rob

You are thinking of voltage drop, not system power loss. A voltage drop (i.e. amps * wire resistance) that causes a 10% loss in a 120V system will cause a 100% loss in a 12V system.

Put another way, wire heating loss is (wire resistance) * (amps squared). To keep the same power loss when amps increase by a factor of 10, wire resistance must fall by a factor of 100.

Ahh, true. A 10% loss on any system is a LOT, though

I'm great with electrical (the practice), not so good with the math as you can see lol.

let's keep in mind distance... there's a reason they don't make 50 ft jumper cables.. they wouldn't work.. as you have the voltage drop, it gets worse with distance and requires many times thicker cable... cable that thick cost a lot more than a cheap 120v inverter and a 30 dollar extension cord.... and a bar plug from the dollar store...

Any good RV supply facility, such as Camping World, has a good
selection of 12V accessories, inverters, 12V extension cords, etc.

I Read the new Pius Plug IN will have a plug for this reason. BUT Only in Japan for 2012. No idea if we will ever have it.
I think it would sell a lot of cars in rural areas. A whole house generator installed runs from 3500.00 to 10000.00 depending on size.

The issue here is one simply cannot draw so much from a 12VDC source due to the enormous current involved. About the most you can take from a 12VDC (typical sinewave) inverter is about 3KW.

The REAL way a Prius can be used as a UPS, if you will, is by using the traction battery. All that's required is an inverter to take ~200VDC to single-phase 120VAC AC, and the Prius itself acts as a backup supply / generator. I met a guy who did just that once - see The Correct Answer Saw it in action - it works. The only issue there is whether the owner is willing to tear into his Prius to this extent - and also the cost of said inverter. 200VDC is more a specialty voltage usually used by steel mills and such. A large inverter of this size would run several thousand dollars.

-MKL

sounds like we're back to my dedicated standby.

Using the CR-Z as a backup generator - Honda CRZ Forum: Honda CR-Z Hybrid Car Forums

Following the northeast snowstorm (I just came back online after 3 days with no power), I'm wondering about running an inverter off my Prius for emergency backup power. I already tried this for a short time during this outage with a 400W inverter driving a couple hundred watt load, and it worked (but my inductive motor load didn't seem to like the "modified sine wave" output of my inverter - it made strange buzzing noises and was drawing more current than normal so I didn't run it for long). To be prepared for future outages, I'd like to consider getting a 12V sine wave inverter but am wondering what size inverter I can safely use.

I've found some examples where people think the Prius can supply up to 100A at 12V (Gen 2), but it's not as clear if this limit is from a reliable source, or if there's danger of overloading and damaging the DC to DC converter that charges the 12V battery. I read people have found a fusible link, but assuming this is any indication of the actual available power may be incorrect. Has Toyota ever published a current capacity for the 12V electrical system? I'm hesitant to follow advice of people who might be just guessing about the maximum available power.

The best article I've found is here: Prius - UPS Project for power from the 12V system, where the author did some testing on a Gen2 claiming near 1000 watts (but here, another author says the Prius can't even provide hundreds of watts and taps into the HV battery instead - it's hard to know which to believe). There's also the famous PriUPS-getting electricity FROM your hybrid vehicle that runs off the HV battery, but that's a much bigger, difficult and expensive project. I'm wondering how much power I can get with a simple off the shelf inverter running off the 12V battery, and whether the Prius will protect itself from overloads or if there's any danger of overloading and damaging the Prius charging system (HV to 12V DC to DC converter). The author of the above seems to think there's some protection, at least in the Gen2.

Since I have a Gen3, I'm wondering if the Gen3 has the same power capacity as the Gen2. Does anyone know?

FYI, normal AC power is a sinewave, but cheap inverters ouptut a "modified sinewave", which I'd call a "modified squarewave". This is fine for some appliances (incandescent lightbulbs, and similar resistive loads), but may not work as well with inductive loads (like motors) or sensitive electronics. More expensive sinewave inverters produce better power that's closer to utility AC power.

See the post I just made here:
http://priuschat.com/forums/gen-ii-...how-convert-dc-ac-2006-prius.html#post1411389

I only glanced at the above but the author (bwilson4web) has only owned a NHW11 (Gen 1) and ZVW30 (Gen 3). He's never owned Gen 2 NHW20, AFAIK. I've known about his NHW11 posts and work and I was with him at the ZVW30 unveiling in Detroit in January 09.

His pictures from the trunk definitely do NOT match my NHW20.

Thanks, my search for a relevant thread turned up this one but not that one. The only question not answered is if I can expect the same available power from the Gen3 Prius, or if it may be more or less. Does anyone know?

This is not something I'd use often, just for these rare storms with extended power outages so opening up the hood or trunk and clipping on leads to the jump point or battery is fine, I don't need a permanent installation I'm only really looking to keep just a few things running (heating system and refrigerator and perhaps a light - one at a time if necessary, so I'm not in need of a big inverter, except to handle motor startup on the above).

Oh you're right, that 2003 must be a Gen 1 (probably confirmed, from the later picture showing what looks like a trunk, not a hatch). Those pictures don't match my Gen 3 either, where the 12V battery is on the right hand side and the other bodywork doesn't look the same either.