A Hobbiest (not really RC) Electronics Question

[Valid8r]

This actually does have ties to RC. I posted earlier in the batteries/chargers forum a question about how to connect my battery charger to my prius (harder than one would think). This however led me to a site called www.priups.com which is a website devoted to using a Prius as a source of emergency power for your home. Surprisingly, this is doable and I am intrigued enough to pursue this further (I live in New England and winter power outages can result in very cold homes and frozen pipes).

My question to you all is the following. The website referenced above takes one through the process of getting 210VDC power out of the car. To invert the power to AC, the author uses a commercial UPS (expensive). I can't figure out why he didn't just use a relatively cheap commercial inverter.

As he does not have any way to contact him listed on his site, I am turning to my trusty RC Groups colleagues to see if you can help. I am also willing to ask this question in a hobbiest electronics forum if someone can direct me to one that is equally as good as RCG.

Thanks in advance for your help.

Jon

[fredhs]

Hello Jon,

most modern DC/AC inverters produce a "modified" oder "pure" sine wave and should therefore be compatible with just about any piece of line powered equipment. I agree with you that a simple inverter should suffice.

Regards,

Fred

[jeffs555]

I can't figure out why he didn't just use a relatively cheap commercial inverter.

I don't know what cheap commercial inverter you are talking about. Most that I have seen have a relatively low input voltage(ie 12VDC-48VDC), not the over 200VDC of the Prius.

PS With a standard inverter you would need some kind of a transfer switch. With a UPS the transfer function would be built in.

[fredhs]

Hi,

... Most that I have seen have a relatively low input voltage(ie 12VDC-48VDC), not the over 200VDC of the Prius.
very good point -- I got confused by the 12V mentioned
here (http://www.priups.com/ham-12v/); but the Prius battery does in fact provide 200V, a voltage ouside the input specs of most inverters.

Regards,

Fred

[Unterhausen]

that's why they are using industrial UPS. There is a section on priups.com about attaching 12v power supplies. There are a number of 12v power supplies that will take the 210-240vdc that the Prius puts out. I swear I've seen someone using a 12v inverter w/ their Prius, don't know where I saw that.

[Tomapowa]

http://www.homecreater.com/sdp/503489/4/pd-2695030/3775277-1310983.html
or
http://www.mrsolar.com/pdf/sma/SB30004000US.pdf

Not sure what output phase you are looking for but they sell a lot of models (input/output)

[Valid8r]

I did realize that the input to the inverter was ~210V but didn't realize that was where the problem was. In his articles, he mentions that he thought the home solar approach was going to be the answer (these are relatively cheap) but that all of the inverters he found actually required AC to keep the inverter working.

Sorry for the confusion.

I had hoped/thought that finding a 220V input inverter would still be relatively cheap as long as it did not have all of the associated batteries found with the commercial UPS units. That seems to be the hard thing to find I guess...

I also was not worried (now about the transfer switch as I was thinking I would simply create a manual switch rather than an automatic switchgear...

Thanks for the input, still interested in this if anyone happens to find a cheap, 220V inverter that can handle about 5Kw

[jeffs555]

There are two types of inverters for solar/wind power. One type is designed to feed power back into the power grid to sell it back to the power company. These don't have batteries and do require AC to keep them working so you don't feed power back into a downed power line and kill a lineman. The other type is basically like a UPS and uses batteries and a transfer switch(unless you are not connected to the grid). I don't think these would be any cheaper than a computer room UPS. Also, you are much more likely to find a used UPS at a good price.

PS If you plan to connect this to your home wiring, you will need an approved transfer switch properly installed(again, so you don't kill a lineman). Check your local electrical codes which most likely require compliance with the NEC.

[Ron W3FJW]

Thanks for the input, still interested in this if anyone happens to find a cheap, 220V inverter that can handle about 5Kw

There ain't no such animal. You're looking at a few thousand dollars. Probably way over 10....

[Valid8r]

Ron - no disrespect (I've followed your online RCG posts for some time), but I can buy a new 240V "industrial grade" UPS online for about $1,500. Therefore, I was thinking that I could buy just the inverter (minus the batteries which I technically don't need) for less, but that does not seem to be the case.

You have to admit, it's an interesting concept to provide a cheap E-gen for your home??? (or do you think it's crazy?).

Jon

[Ron W3FJW]

No, I think it's a great Idea if there are power outages. I'm only familiar with commercial units. Not anything bought off the IN or Ebay. & you'll have to excuse me. I misread the 5 as a 50. I live in a motorhome and although there are modified sine wave inverters, if it were me, I'd want a pure sine wave. But that's just me as I have a lot of electronics, and probably what I was thinking as well when I read your post. It's hell getting old with memory & eyesight problems.

Keep in mind those UPS don't operate from 220 vdc, but operate anywhere from 12 to 48 vdc and produce 220/240 vac.
Now you could find a 220vdc motor and use it to turn a 220v 2 phase motor and use the output of that to power the house.
Keep in mind that's it's going to be hard on the Prius battery bank which is probably a few thousand(?) to replace..

I would use a 4 or 5 kw electric start (auto upon loss of house ac) generator with an automatic transfer switch. Should be able to get by for less than a thousand $ and it would be less of a headache in the long run... But electrical installation & inspection would probably up that amount a lot unless you know a friendly licensed electrician.

But to keep the forum somewhat on track, that would probably be the best way to power your RC chargers when the power goes down...

[Zlatko]

But to keep the forum somewhat on track, that would probably be the best way to power your RC chargers when the power goes down...

I totally agree.
You could charge A123s really fast from a Prius 220V battery ;)

I've read this too and thought it would be interesting but the fact remains that a converter from 220V DC to 120V AC is not going to be easy nor cheap.

Yes , there is a possibility to run a 220V DC motor of Prius batteries and couple it to another 120V AC motor to power your house but the cost would still be "up there" and you will reduce the lifespan of your Prius batteries + you'll void any waranty ( if you had any left ).

If you search ebay you will find lots of electric start / auto start diesel generators that will do 5kW.

For instance this one
http://cgi.ebay.com/NEW-5500-WATT-5-5-KW-COMMERCIAL-DIESEL-GENERATOR-SILENT_W0QQitemZ280256437006QQihZ018QQcategoryZ106 437QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
is under $1000 delivered.

Cheers

[darkith]

Looks like if you only need <= 1kW of power (e.g. power furnace blower), you can tap 100A from the 12V auxilary battery (being charged as needed from the 200 Vdc traction battery and gas engine). Then you *could* use just a relatively cheap COTS inverter (or UPS abandoned due to dead batteries).

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

This is a 2003 Prius tho.

D.