Hi,

Exactly:

http://hiwaay.net/~bzwilson/prius/priups.html

Some hybrid-electric vehicles have an option for an inverter, typically 1-1.5 kW. These are usually thought of for camping activities but it turns out they can make a power outage quite livable.

I've had occasions to use the same 1 kW inverter in the winter to power a gas furnace and now in the summer to power a 5,000 BTU window air conditioner. This means we can deal with power outages regardless of the season.

Bob Wilson

 

Wow, that is intriguing. Thanks for the explanation Bob. When I look at your linked website and the technical diagrams I wonder how much of this is something a person without a degree in electrical engineering could tackle.

I have rewired my entire house as much to code as I am aware but messing with a system that has 500V of charge ready to kill me is a bit more intimidating. Are there more plug-n-play inverter mods out there I can read about? Additionally, I assume you have already touched on this originally but what are the concerns about severely limited battery life by inverter drain/cycling.

Thanks in advance.

 

Hi,

In my approach, we're always dealing with the 12 DC system. The highest voltages are 110-120 VAC that comes out of outlets on the 1 kW inverter. This is not a hazardous system as long as you stay within the vehicle limits.

As for 'limited battery life by inverter drain/cycling', it is a risk I'm willing to take. From a risk assessment standpoint, compared to my daily commute, 10 miles each way, and other ordinary driving, this is nothing. If this infrequent, once or twice per year for 4-12 hours, is enough to fail the car, it should have died a long, long time ago. To keep things in perspective, a full 1 kW load is about 1.3 hp. Regardless, I want to know about this before buying another hybrid-electric.

Bob Wilson

 

Also, just to point out, the Prius won't let you completely cycle the battery at any time. It likes to keep it around 60% for narmal driving, and lets it get no fuller than 80%, but when it's in use as a stationary power system it will drop down to 40-45% then charge back to 50-55%, minimizing any kind of stressful wear on the battery. When you push the car to it's limits by flooring it to maximum speed, you might see the battery drop to 30%, but in normal use it's limit is 40%, the computer just won't let the battery deep cycle, so there isn't much you could do to hurt the battery, short of serious modifications to the HV systems.

 

very interesting replies all, thanks. I just received my 2006 Prius last night and appreciate the insight. Do you need to manufacture the inverter mod yourself or are their kits that are nearly plug and play?

 

My 03 Prius, NHW11, is different from your 06, NHW20. I did all of the mechanical and electrical work from scratch with a couple of excellent suggestions. I think Doug recommended running the AC wires into the cabin.

For the NHW20, you're on your own because the body style is so different. Given what I've seen of the battery storage for "plug-in" Prius, there should be some nooks and cranies to locate the inverter.

I was lucky and my 1 kW 12 VDC to 110 VAC inverter matched what may NHW11, 12 VDC inverter supplies. I suspect the NHW20 has at least 1 kW capability on the 12 VDC bus and possibly a bit more. But without an NHW20 and measurements, I'm loath to say for sure.

One alternative would be a 12 VDC, high current power plug setup so the cables are permanently connected to the battery. You could then plug-in the inverter as needed, getting the low resistance contact needed, and away you go.

Bob Wilson

 

We've had our 2006 Prius for about a week, and I've already successfully tested using it to generate emergency power. Here in California the most likely emergency is an earthquake. In the event on an earthquake, we need to be able to be self sufficient for at least 4 days, and possibly a week. We are experienced campers, and camping in the back yard for a week shouldn't be a problem. Water can be a problem. Food will be a problem. After just one or two days, the food in most refrigerators will have gone bad. But the prius can help.

I already had an inverter. I'd recommend getting one like I have, 2,000 watts continuos, 4,000 watts peak. Modified sine wave. This gives as much power as any standard outlet. Trying to run a refrigerator on much less will give you problems as the energy draw when they start up can be large. The good thing is that it doesn't last very long and so you don't need to be able to provide that much power continuously. In fact I have used my inverter with a good battery and found it was able to handle the Refrig for at least an hour.

So what does it take to make the Prius an emergency power supply? Pretty much the same as any vehicle, just connect the inverter directly to the battery with the 2 gauge (large!) cables that it came with. Why is the Prius better? Well it does have a 150 amp fuse so it appears that it can provide almost 150 amps of power to the battery. My truck has a large alternator, but not that large, and not as efficient.

Once the inverter is connected, you will want to have the car on your driveway to avoid poisonous gasses being built up, So you'll also need a long and heavy duty extension cord. Note that at 120 volts AC, transmissions loss is much less, so you don't need cables as large as you use to connect the inverter to the battery. You'll also need to have the car running, and in park. Since you may want to lock the car, you'll need a second set of keys, and remember to turn off the smart key system if you have it.

To make it easy to connect to the battery, I bought a pair of power pole connectors from powerwerx. Rated at 350 amps at 600 volts they seem a bit big, but I have used my inverter to power a lawn mower for an hour or two, and if connections are not tight enough there is a chance that they will get very hot. Melting and causing a fire is not what you want. Especially when the fire department is unavailable. The inverter came with 2 gauge wire, and cutting them and soldering them into the connectors was easy.

I don't remember how much my inverter cost, but I did recently see one on sale for only $150 at a place like Harbor Freight. $30 for the power poles, and I'm out around $200. I think that Toyota is really missing out. I contacted them for some information before I bought the car and they did not give me any information, but said that they do not support any modifications. Have you seen the GMC truck Hybrid? It doesn't get very good gas mileage but it does provide 120 volts and 15 amps. Comes in pretty handy for a contractor to not have to haul around a generator, but it also provides emergency power. I think that many Prius owners would pay a couple of hundred dollars to have this extra security. But if Toyota won't do it for you, then many of us can do it ourselves.

My Prius is almost unmodified. If you look at the battery there are two wires connected to it, and they end in one half of the power pole connectors. The inverter will remain in my garage and will not be used except in an emergency, and for an occasional test run. If you want to do this yourself, remember that any emergency plan needs to be practiced.

 

Well done!

Pictures? Web page? How to? Any details on the 150 A. fuse and location?

This is mine.

My only suggestion is to make sure you have a spare 150 A. fuse, unless you know the inverter can not 'blow it.' Having a spare is cheap insurance and lets you get back online, with a reduced load. I did extensive load testing and doubt my inverter will blow the fuse.

I do have this 90 A. circuit breaker I've been meaning to put in the circuit along with a load indicator. I also have some in-rush thermisters I'll be putting in the TV and laptop circuits . . . when I get around to it. <grins>

Bob Wilson

 

Here in northern California about 600 of those power pole-mounted transformers have failed in the past few days due to the heat wave, leaving many localized outages. (PG&E said the transformers used here are basically rated for temperate California conditions, and haven't been able to cool down sufficiently during the 75 degree nights.) I just wanted to share my own successful realworld experience with using an inverter for backup power. Since the validity of the concept has already been proven out by the technical groupies, this is more of a novice-to-novice case study.

So this past Sunday afternoon, just a few hours after I'd finally broken down and installed one of those in-window air conditioners into the coolest room in our house, the little A/C goes quiet along with everything else. Now it turns out our street's failure was actually due to a large eucalyptus branch that failed due to the heat, but we had to wait our turn for the same PG&E repairmen who were out replacing transformers. Not really thinking too hard, we went out and came back near nightfall to find the power still out and the PG&E folks waiting around for equipment and not promising power anytime soon. We then fully realized we'd have not even a fan to cool us down that night.

Now I'd actually bought a 800W inverter after reading old posts in the Yahoo Groups about using the Prius as a backup generator, since we often have outages during winter storms, but it had been a mild winter. So I skeptically pulled the box and instructions in the waning twilight, and opened up the trunk of my '02 Prius. In not even 5 minutes I had the inverter and an extension cord running into my house and powering a fan and a lamp. It was a piece of cake!

I did run into the "inrush" problem resetting the inverter when I plugged in a power strip that had a laser printer on it, so we didn't really try anything more than a couple of lamps and two table fans. But it's nice to know for future reference that I probably could've gotten our 5100 BTU window air conditioner working on it. Also just powering a few essential items, the motor hardly came on more than a few times that night to top off the battery.

I think the neighbors that drove by were a bit surprised to see our lights on without the accompanying sound of a backup generator. Next time, hopefully at my choosing, I'll test out further the limits of what I can actually power up (probably the laptop and the cable modem would have been my next priority - well, I do live in Silicon Valley...).

I think someone hit it right on when they characterized it as a great solution for "camping out" at home. To power the entire house or even the refrigerator/TV reliably might take a greater effort and learning curve, but the inverter on the 12V battery is a <$100 solution that any novice can safely do in 5 minutes. Just having the ability to power a few devices at will - a lamp, a fan, a radio, a laptop computer - makes a tremendous difference in still feeling connected to civilization and not back in the Stone Age.

 

What a great story. Would you mind telling what your specific model of inverter you bought? I think one of these days when car payments are not as fierce for me, I will pick up an inverter on the side.