[seharper]

I am trying to come up with a simple way to keep the frozen food frozen in another power outage.

A few years back, I bought a 800W inverter to connect to my car's battery. it can run a 21" TV, the cable modem, the wifi router, a laptop, but it cannot run the refrigerator which draws 11.6 A.

Priorities, eh? I know exactly what you mean

Here's a useful tip, many of the things you list there will run on 12V, or versions can be obtained that run on 12V. So it's possible to avoid the vampire load of a double conversion.

As far as the refrigerator, you have the right concept. My rule of thumb is refrigerators take 1 kilowatt-hour per day. That's not bad at all, it only averages 42 watts. But it's the startup surge that kicks you in the pants!

I was doing the calculations and for the refrigerator alone, I need a generator that can output 1392 watts but probably more like 2800 watts peak.

Yeah, that's startup current for you! But you're on the right track. You just need to upsize the inverter to handle the startup load.

Or you can take the mountain to Mohammad, and shop for an inverter refrigerator (that is to say: one that has a VFD driving the compressor motor). Those inherently "soft-start", which may be easier to drive from the inverter.

Would it make sense to buy an ice maker and run it on the inverter and fill an Igloo cooler with ice and the frozen food?

No, that would not work at all, it would have the same startup surge problem as the fridge, and the ice wouldn't keep your frozens frozen. Frozens need to be around 10F, your ice will be at 32F. Ice works for the *refrigerator* part, that's all.

Matter of perspective. Smaller than a 22K whole house generator. I don't see the reluctance to go the generator route.

*penguins climb off boat, finally reaching Antarctica*
*they take it all in*
"This sucks."

That's generators for ya. Like any small engine, they are balky and fidgety.
- The battery went flat
- The fuel got old
- The fuel filter is plugged, For, No, Reason
- The carb needs rebuilding.
- The plug is fouled (why??????)
- The magneto quit.

Nothing is "NO" maintenance. Not even my wife Keep it up and it will run for years.

I knocked together a simple solar system to sustain an old Edison battery (itself 40++ years old). MorningStar SunGuard ($30), 20-watt solar panel, that's pretty much it. Nine years on, and the thing just keeps on ticking. Zero maintenance for something *that* much of a hobby-hack, that's impressive.

Granted, the "emergency generator" application is a very hard one, because you need it so rarely, and when you do it's critical. But this is exactly what small gas engines are particularly bad at.

 

[seharper]

I'm sorry, but if you're happy with the "inverter off the car battery" approach, that's good enough. Just size the inverter and load properly.

- Modern fridges take ~500-2000W to start. (40-160A at 12V)
- Once the motor is spun up (<2 seconds), they draw about 120W (10A @ 12V)
- Average total draw over a day is 1 KWH or ~42 watts average. (3.5A @ 12V)
- The refrigerator light draws whatever it says on the bulb, when the door is open.
- A "Kill-a-Watt" device can give you the hard numbers for your fridge.

An inverter pulling 1500W off a battery will draw 125 amps, so you need to have SERIOUS wiring to that battery. You cannot do it off the cigarette lighter.

You can get away with hooking up the inverter to the car every 8 hours and running it (THE FRIDGE not the car) until the fridge has fully cooled back down and cycles off. Then you can unhook it until the next round. I wouldn't go longer than 8-9 hours if you can avoid it. You don't want the frozens thawing and re-freezing.

You don't want to idle a car for hours, so I'd do it for 5 minutes every hour to keep the battery from getting wacked. DON'T look up the amp-hour capacity and go thinking you can use all that, that number has a HUGE asterisk that will destroy your battery.

The leakage through the fridge and freezer's insulation will be the same rate regardless of what's in the freezer (and that's what decides how long the refrigerator must "catch up"). However, adding "thermal mass" to both fridge and freezer will increase its "coasting range" (time before it thaws/gets warm). The best thermal mass known is depleted urani-- I'm just kidding, it's actually WATER for awesome scientific reasons. So, plain ice-packs (ziploc freezer bags full of ice, even) will help a lot in the freezer, and for the fridge, just pack it full of 2-liter soda bottles full of water.

 

[seharper]

My car has a 230 amp alternator. That figures out to 2760 watts. I'm not suggesting I would run the car to supply power to a 3000 watt inverter but in reality it would work like a champ. Inverters cost about as much as a generator but they end up eating more. :devil3:

You aren't limited to 2760 watts, since your car's electrical system can borrow off the battery. However that figure is at some *idealized engine speed*; running at idle will certainly reduce that. Your fuel economy will also suck because a 100-200KW engine is wildly mismatched (much too large for) the 3KW generator.

Check your owner's manual as to whether you're *allowed* to idle the car for extended periods. Remember if it's part of your house's electrical system NEC 110.3(B) must obey instructions and labeling LOL J/K...

I would say inverters cost as much as cheap generators...