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Old 07-02-2012, 07:19 PM   #61
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Yes, the Prius is a wonderful self-propelled/self-charging/self-managed battery that one can simply hook an inverter to. I did think about getting a Prius to have that backup function and to tinker with. But one of my existing cars must die first.
I think was discussed a while back, but you can hook up an inverter to any car. If you want high watts, you need good, heavy cables and solid connections, regardless of the car model.

IIRC, the only advantage to the Prius is that it could be set to auto-start as the battery runs down. I think people said that many after-market auto-starts do the same thing.

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Old 07-02-2012, 07:33 PM   #62
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For low power levels (<2KW), there are many ways one can go. A lot cheaper than a Prius.

I thought I read about some guys tapping into the high-voltage propulsion battery bank of the Prius, not just its 12V battery. That gives more power, and more capacity for a longer shutdown duration between the engine runs. And I figure a Prius would be a lot quieter when it runs than a generator of a much smaller size. And it also serves as a vehicle when you need to get around.

Hmm... Am I describing a wheeled self-propelled power source that also serves as a vehicle when needed? Guess my nerdy nature gets the functions all backward.
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Old 07-02-2012, 07:55 PM   #63
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For low power levels (<2KW), there are many ways one can go. A lot cheaper than a Prius.

I thought I read about some guys tapping into the high-voltage propulsion battery bank of the Prius, not just its 12V battery. That gives more power, and more capacity for a longer shutdown duration between the engine runs. And I figure a Prius would be a lot quieter when it runs than a generator of a much smaller size. And it also serves as a vehicle when you need to get around.
Maybe some are tapping the HV battery, 12V connections was all I recall seeing....

ahh, some googling shows that the HV battery does keep the 12V battery charged, so I guess you'd get longer cycles between starting the engine. But for the occasional, rare emergency, any vehicle should function for this - a 'regular' car might need a bit more attention.


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Old 07-02-2012, 09:47 PM   #64
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The storm Friday night around the DC area was bad. I was only out for 5 minutes, but some people I work with have had no power for three days, and they only live 4-5 miles from work. Lots of people lost $100's in food.
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Old 07-02-2012, 10:19 PM   #65
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One of the problems with buying a generator is lack of use... if you run gas through them, it gums it up if it sits.....
Got a yamaha generator about 10 years ago from us carburation , ordered the tri-fuel option. runs on propane, natural gas , or even gasoline. Only had it on gasoline once to test. On camping trips and when in a rare 100+ for 3 day weather a transformer blew, running on Propane. Nothing to gum up or clog. Have it set up to run on a natural gas BBQ outlet now too. Biggest problem is 12 ga. extention cords running to neighbors houses are quite$

Was quite popular with neighbors that hot day .

P.S. , always ground your generator !
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Old 07-02-2012, 10:49 PM   #66
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One of the problems with buying a generator is lack of use... if you run gas through them, it gums it up if it sits....

Also, I would probably leave and go visit someplace that HAS electricity... it is what we did the last hurricaine when we were out for 7 days... (we left after 1 1/2 days)....

If I had to be concerned with a sump pump or other critical needs, then I would have one for that.... but, you still have the problem if you are not there.... we went camping a couple of months ago and the electricity was out about 12 hours.... nobody to pull out a portable one to plug in the refrig...
Having a riding lawn mower that sat for a year and a half due to the drought, stabil added to the fuel avoids the gumming problem even if all the fuel evaporates. Its about 2 oz per gallon. Put a new battery in the lawn mower and it started in about 40 seconds.
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Old 07-03-2012, 06:10 AM   #67
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You can connect that to your car battery (you need heavy cables and rock-solid connections) and start up the car to recharge. And/or add a heavy duty battery which could also be recharged by connecting to the car. The separate battery will keep you from running down the car battery (but these do shut down when the battery gets down to ~ 10.2V) and provide some power with no car around.


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+1

Just got back from a couple weeks of dry camping in the Rockies using our Aliner hard-sided pop-up. Not wanting to drop big bux for a generator or solar system, I just recharge the Aliner battery from the tow vehicle system (using jumper cables to get a fast, high current charge not limited by the small guage wiring in the hitch hookup) and all went well.

We don't run any high consumption appliances when dry camping. Roof vent fan when it's hot and furnace blower motor when it's cold would be the worse offenders. The LED lights, radio, CO detector, etc. are negligible. I'm sure that helps.

Your idea of using a high wattage inverter hooked to your car's electrical system for short term sump pump backup and refrigeration is excellent. Beyond keeping the basement dry and the beer cold, there isn't much else worth worrying about during a power outage lasting no more than a few days.
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Old 07-03-2012, 06:45 AM   #68
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A Note: The startup loads on some of these items are 2-3 times the running loads. A refrigerator that uses 600 watts when running can often need 2000 watts to start. An inverter or generator has to be sized to meet that startup load (together with anything else plugged into it when the startup load occurs). Also, a car alternator is not designed to put out its maximum rated power for hours on end, so we should accept we'll be reducing its life somewhat if we load it down. Other than that, using a big inverter for emergency power can be practical. An inverter big enough to start and run a fridge is going to cost about $150, a generator big enough to do that job is about $200. The inverter has low/zero maintenance needed to keep it ready for use, which I think is the biggest plus.
If your car's alternator is rated at about 60 amps=approx 720 watts= approx 1 HP. That's all the power it will produce at a steady state, so anything above that, regardless of the size of the inverter, is coming from the car's battery and will be very temporary. Larger alternators are available, but that's more money.
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Old 07-03-2012, 07:13 AM   #69
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Got a yamaha generator about 10 years ago from us carburation , ordered the tri-fuel option. runs on propane, natural gas , or even gasoline. Only had it on gasoline once to test. On camping trips and when in a rare 100+ for 3 day weather a transformer blew, running on Propane. Nothing to gum up or clog. Have it set up to run on a natural gas BBQ outlet now too. Biggest problem is 12 ga. extention cords running to neighbors houses are quite$

Was quite popular with neighbors that hot day .

P.S. , always ground your generator !
My neighbor has a whole (most) house generator, which is hooked up to their propane tank. It kicks on every Wednesday morning. I'm sure they didn't set that up on their own so the installer must've recommended it and set it up. I don't know if it's unnecessary or if you need to start propane fed generators regularly as well. It's not that loud but it's kind of annoying. I guess it's nice to actually have power when others don't, but I can't see spending thousands of dollars plus the regular fuel costs to save some food. In 11 years here, this 15 hour outage was the longest I can remember. Our power lines are buried so that helps a lot.
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Old 07-03-2012, 07:15 AM   #70
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Feeling for you Khan! Is your power back on yet??
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Old 07-03-2012, 07:15 AM   #71
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Those are good points samclem. No doubt, someone who isn't fairly familar with the typical duty cycle of their refrigerator compressor or who can't understand that having the sump pump and refrigerator both trying to simultaneously start from one 1500 watt inverter isn't going to work should look for another solution. A whole house, automatic generator (for 6 - 10 kilobucks), professionally installed, might be more appropriate. And that will go into service automatically even if you're not home, a big plus.

In my case, I can't afford that. And I haven't needed an alternative power source in over 35 years of living in this house, although we've had a small handful of power outages lasting a few hours. It's hard for me to justify big bux for a whole house unit.

The alternator concept is minimal cost and would easily power the sump running intermittently. If the weather is dry, then the fridge gets to run.

I do wonder about the quality and reliability of those $200 2kw generators. There has to be some reason that Honda and Yamaha get five times that for theirs.

Edit: Since it's July, my mind was off the furnace. We have natural gas heat but I'll have to check the specs on the blower motor. The furnace could be just as critical as the sump pump if the power outage continues for a long time.
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Old 07-03-2012, 07:21 AM   #72
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I don't know if it's unnecessary or if you need to start propane fed generators regularly as well.
The Generac system I initially looked at was set to to perform an auto-test every month, not only to check out power generation, but also to ensure the transfer switch worked properly.

You are correct about the noise. We have a few in our neighborhood (various brands), and while they are not really that loud, when your power goes out and the neighborhood becomes "quiet", you are much more aware of the sound that they make.
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Old 07-03-2012, 07:26 AM   #73
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I do wonder about the quality and reliability of those $200 2kw generators. There has to be some reason that Honda and Yamaha get five times that for theirs.
Based on the reviews I read of the cheap ones I agree.

I drained the entire fuel system on mine, including the carburetor bowl, so I don't have to periodically fuss with it. And I keep it in the basement so I didn't want fuel in it anyway.
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Old 07-03-2012, 09:28 AM   #74
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+1 on storing the generator dry. No periodic maintenance.

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Based on the reviews I read of the cheap ones I agree.

I drained the entire fuel system on mine, including the carburetor bowl, so I don't have to periodically fuss with it. And I keep it in the basement so I didn't want fuel in it anyway.
About the Prius, I found a guy's account of how he tapped into the main traction battery bank. He bought an industrial inverter that worked directly off the HV battery.

In a test where he put a 1,000W load on the inverter, he found that the Prius would turn itself on for 2.5 min, then off for 9 min. I was surprised that the battery could not sustain the 1KW load for longer than 9 min. Upon further research into the HV battery capacity, I thought that to be reasonable. And with a smaller load like a 500W fridge, the off time should be twice as long. On for 2.5min, then off for 18 min is quite acceptable, and of course a person inside the house would not even know the car is running.

Neglecting the higher cost and complexity, the Prius solution using its HV battery is better than having to idle a normal car for hours on end to keep a residential fridge going via the 12V+inverter setup. Or does one run the fridge (and car) on a duty cycle of something like 8 hrs on/16 hrs off?

In an emergency, I already have a 4KW generator built into my motorhome to tap into. But the drone of the thing over a long period like 48 or 72 hrs would be bothersome. And it seems a waste to run a large generator just to keep the fridge going.

A small and quiet generator (with inverter technology) like the Honda or Yamaha seems the simplest, but the price may be high for someone has no other uses than the need for power backup once every 10 years. The advantage of a 2KW ($1000) unit is that it can also run a small window A/C, if one has the A/C installed in a small bedroom to serve as the survival bunker.

And then, considering how often a normal person needs this, I do not think that a cheap "disposable" generator would be that bad a solution.
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Old 07-03-2012, 10:57 AM   #75
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A Note: The startup loads on some of these items are 2-3 times the running loads. A refrigerator that uses 600 watts when running can often need 2000 watts to start. ... Also, a car alternator is not designed to put out its maximum rated power for hours on end, so we should accept we'll be reducing its life somewhat if we load it down.

... The inverter has low/zero maintenance needed to keep it ready for use, which I think is the biggest plus.
Yes, the low/ zero maintenance of the inverter is what drew me to it, also automatic/unattended operation for my sump pump (with a battery and charger).

Regarding those start-up loads, one thing that is easy to overlook is just how solid those connections on the battery side need to be to handle that surge current. Even though my freezer is just something like 200W, I had trouble getting it started with my 2500/5000W (cont/peak) inverter. As you draw that surge if the voltage at the inverter drops to 10.2V it shuts down, and then the voltage rises and it kicks in, and keeps cycling on/off like that. So you need really solid connections, nothing shaky at all.

I had planned on (and should do it now that we have a new vehicle) to hard-wire some welding cable connectors under the hood of our car, connected really solid to the battery cables. Then it would just be a plug/unplug operation - even DW could do it.



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I do wonder about the quality and reliability of those $200 2kw generators. There has to be some reason that Honda and Yamaha get five times that for theirs.

Edit: Since it's July, my mind was off the furnace. We have natural gas heat but I'll have to check the specs on the blower motor. The furnace could be just as critical as the sump pump if the power outage continues for a long time.

I'll dig up some numbers I have and report back later, offhand a furnace fan ~ 500W.

I'll also run some numbers on the alternator issues that samclem brought up. I think I'd be OK, since I'm only looking at running a couple things at a time.

I also can give some experience with cheap generators, but later.


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Neglecting the higher cost and complexity, the Prius solution using its HV battery is better than having to idle a normal car for hours on end to keep a residential fridge going via the 12V+inverter setup. Or does one run the fridge (and car) on a duty cycle of something like 8 hrs on/16 hrs off?
When I dig up my numbers and have some time, I should be able to shed some light on this.

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Old 07-03-2012, 12:36 PM   #76
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Biggest problem is 12 ga. extention cords running to neighbors houses are quite$
12 ga. for the Jesus cord? That's impressive.

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And that will go into service automatically even if you're not home, a big plus.
An automatic transfer switch is very convenient. But I wouldn't pick it for myself. In disaster (like fire/flood), I definitely don't want it to kick in automatically to make an already difficult situation even more treacherous.

Storing generator dry helps, but a generator does need periodic exercise (under load, 30%-50%). It's a good idea to keep some oil seals/gaskets periodically lubricated once the generator is used. Also if a generator is kept unused for too long, the residual magnetic field (RMF) in the gen head could potentially diminish too low. Most portable generators in now days are based on brush-less, self-excite design. When the RMF becomes too weak, the gen head will not be able to generate power anymore. It's not fun to manually "excite" the gen head in emergency, especially in total darkness.

The small engines in most consumer grade generators are screaming at 3600 RPM to give the required 60Hz AC current with a 2-poles gen head. This high RPM not only is bad for engine lifetime, but produces a lot of noise and consumes a lot of fuel as well. So if a cheap backup generator is desired, a better solution probably would be to put it to work in conjunction with an inverter + battery bank setup. The generator will only be started to charge the battery bank and to run sustained heavy load. Still having air conditioning during extended power outage in hot summer is a nice luxury to have, but no a must necessity in most cases. Having drinking water supply, preventing food and crucial medicine supply from being spoiled, and keeping limited fuel stock to last as long as possible are far more important.
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Old 07-03-2012, 02:31 PM   #77
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Transferring power at a low voltage like 12V requires a lot of current. And at currents as high as 150-200A, it does not take much resistance to lose a couple of volts like ERD50 described. At the household AC voltage of 120V, a loss of a couple of volts may not be a big deal, but when one starts out with only 12V, that 2V loss is a lot.

RV boondockers know about this. For wiring up the inverter to the battery bank, they place the two only a few feet apart. The wiring size de rigueur is AWG #0. I used AWG#2 when I installed a 2KW pure sine wave (PSW) inverter in my RV. I thought the heavier wire was too difficult to route. I somewhat regretted that.

It is not just the resistance of the wire. Although every connection and contact point was tightened with lug nuts, I lose more than 1V between the battery posts and the inverter input posts when I run the microwave. It was very revealing when I set my DVM to the highest voltage sensitivity, and probed the voltage drop across each connection and each segment of wire. At a current of 150A, one milliohm of resistance causes a 0.15V drop. A milliohm here and there, and soon you are talking about losing 1V.

Regarding refrigeration, out of curiosity, I did a bit of investigation on residential fridge power consumption and wanted to share the info.

An average fridge of 18 cu.ft. would use something like 1.5KWhr/day. It may draw 500W when running, but the compressor cycle is sufficiently short that its average consumption is only around 60W. With that low power, we would think it should not be a big deal to keep it running. Well, not quite.

Storing 1.5KWhr worth of energy requires 125AHr of 12V battery. If we keep the depth of discharge to 50% to prolong battery life, that takes 4 batteries of the 6V golf-cart type. Then, to charge these batteries once a day, we would need a charger with a 60A capacity, run off our generator 2 hr/day. A 1KW generator is sufficient.

RV boondockers do something like the above, except that they use solar panels to charge the battery bank throughout the day. And they often use more than 4 batteries. And they still cannot use the residential fridge and most of them still use the ammonia absorption fridge that burns propane.

By the way, there is a new type of RV/boat fridge that has a high-efficiency 12V compressor. It uses freon just like the usual fridge. They are still pricey; a 6-cu.ft. unit will set you back more than $1500.

So, does the average home owner want to invest in and to maintain equipment like an RV boondocker does?

I would think that keeping the fridge going is the most important thing. I heard that some people could not even go out to eat when their food gets spoiled. All the restaurants nearby also shut down.

Here in the SW, if one wants to stay at home, a small A/C may be a necessity. Not too many are made of stern stuff like the native Americans or cowboys of yesterday who could tough out the 115+ degrees. Quite a few elderly people may expire in that heat, I am afraid.
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Old 07-03-2012, 03:01 PM   #78
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Hallelujah, the power just came back on! I think at this point, it's been off about 88 hours or so. I think what caused it, is that my uncle, who lives across the street from me, just bought a generator. :-/
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Old 07-03-2012, 03:14 PM   #79
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Hallelujah, the power just came back on! I think at this point, it's been off about 88 hours or so. I think what caused it, is that my uncle, who lives across the street from me, just bought a generator. :-/
Seems to work almost every time - too bad he didn't buy it sooner.
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Old 07-03-2012, 03:21 PM   #80
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Amazing he could still find one on the shelf to buy.

Or should I ask how much he had to pay the scalper?
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