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Almost Needing a Generator

Long-suffering readers know that I like to poke fun -- gently I hope -- at campers who are Gandhi or Thoreau wannabees. They also know I am not a solar purist. A rational consumer uses technology up to the point of diminishing returns. (Or more correctly, the point of diminishing marginal utility.)

And yet there are solar purists who make it work for them. People who have vans or motorhomes probably don't count, since they can always charge their house batteries from their engine battery on a cloudy day. So let's only discuss trailers.

A trailer-puller can connect their tow vehicle to the trailer, and run the engine. But that charges too slowly, perhaps 7 Amps.

So what do you do after finally admitting that even Arizona is not sunny every day, or that you occasionally park under trees, or near the perpetually cloudy Coast? Buy a windmill? No... you need to complement a solar system with a secondary system that doesn't depend on the weather.

What is so bad about the quiet-running Honda 1000 watt inverter-generator? Besides the $850 cost, that is.
  1. You must put it inside at night, worry about it walking off, or increase your insurance. Lifting a 30 pound device into a vehicle is asking for a back injury. You must be careful.
  2. Do occasional maintenance, and drag a gasoline can around. Invariably you will forget to fill the gas can when you fill your vehicle.
  3. Find space for it. (probably in a plastic tub, that won't leak oil.)
I reject the boondocking-ghetto approach of some noisy, yellow, off-brand, P.o.S. generator from China. Here is what I did instead:

  1. Hook an adequate inverter to the battery of the tow vehicle, and run the engine.
  2. Run the output of the inverter to a battery charger for charging the house battery.
Obviously I run the van's engine when the inverter is sending 500 Watts to the battery charger in the trailer. I use a common outdoor 25 foot long extension cord to connect to the charger in the trailer.

The furring strip screwed to the bottom of the plywood keeps the whole thing from sliding off. I added an external fuse to the positive line of the inverter and the charger.

So far, so good. Remember, this is only to be used occasionally, as an alternative to buying a generator. (About 20 days per year.) You wouldn't want to make a daily habit of idling your tow vehicle's engine. I plan on shutting everything down after 20 minutes.

I did learn not to take the nominal ratings of the 1000 Watt inverter literally [1].  So I downsized the battery charger to a Samlex 30 amp charger [2]. Initially it eats 500 Watts from the inverter. 

You might consider this solution a bit of an extravagance: the pure sine wave inverter did cost $250, after all. I could have used a cheaper modified-sine-wave inverter, but I have had mixed with results with these. 

And the new inverter will be the backup inverter to the one I already have in the trailer. It will also be able to power a 110 VAC tire inflator or powerful tools with it.

Although I did have to buy a $200 battery charger for this project, this is not really a cost of the project per se, since a battery charger is needed anyway for the times you are plugged into shore power.


Epilogue: By midyear I have used this arrangement only 3 or 4 times. Perhaps it will get more use if I camp underneath ponderosas for shade, or when the monsoonal rains begin. So far, this is successful because it was meant to be a back-up system for a not-quite-perfect solar charging system. And it is a lot better and less expensive than dragging a generator around. 

[1] A 45 amp IOTA battery charger was too big for a 1000 Watt pure-sine-wave inverter (Xantrex ProWatt SW 1000), even though the nominal ratings would suggest otherwise.

[2] I always buy electrical controllers, inverters, etc., from in Oregon.