By Mike Sokol
Welcome to my J.A.M. (Just Ask Mike) Session, a weekly column where I answer your basic electrical questions. If you’re a newbie who’s never plugged in a shore power cord (or ask – what’s a shore power cord?), or wonder why your daughter’s hair dryer keeps tripping the circuit breaker, this column is for you. Send your questions to Mike Sokol at mike (at) noshockzone.org with the subject line – JAM.
NOTE from editor: Be sure to check out CarGenerator’s owner’s informative comments in response to readers’ numerous questions below.
Last month I wrote about an interesting non-generator technology for supplementing solar panels while boondocking. The biggest question most boondockers have about power is whether to take a generator or not. Sometimes this is an easy answer, since if you want to run an air conditioner or electric appliances such as an Instant Pot or convection microwave oven, then you’ve pretty much answered your initial question. Yes, any high-power appliances will require a dedicated generator (and hopefully a quiet inverter type) when you’re camping out in the great outdoors.
However, if you’re running a lot of your appliances from propane (water heater, cook stove, 3-way refrigerator, etc.) and don’t need air conditioning, then you’ve probably already figured out that you can get by with a reasonable amount of batteries and solar panels. If that’s the case then you don’t want to bother with a generator.
But what happens when the “sun don’t shine” for days on end and you’re watching your battery charge head towards empty (or 50% for conventional lead-acid technologies)? Do you really want to haul around a generator that you should start up every few months and run for an hour just to keep the fuel in good shape and the motor ready to start? I didn’t think so.
That’s why I was extremely interested in the CarGenerator™ when I saw it at the Alumapalooza® Airstream Rally last year and asked the owner, Jonathan Schloo, to send me one for evaluation. Basically this is a 1,000-watt pure-sine inverter that’s been optimized and packaged to easily connect to your tow vehicle’s alternator via its battery terminals. It then outputs 1,000 watts of pure-sine AC at 120 volts that you can plug your RV shore power into.
So what can you do with 1,000 watts? Well, it turns out, quite a lot. The primary use for the CarGenerator is charging your RV’s house batteries with your existing converter/charger.
And the basic math goes like this. Watts is watts, no matter if it’s 12-volt DC power or 120-volt AC power. And since volts x amps = watts, if we raise the voltage a factor of 10x from 12 to 120 volts, then the amperage decreases by the same factor of 10. The CarGenerator with 1,000 watts of output makes around 8 amperes of 120-volt AC power by drawing around 80 amperes of 12-volt DC power from your car’s alternator at idle. That 8 amperes of 120-volt power goes into your RV’s shore power cord where your converter/charger converts it back to 12 volts (actually closer to 13.5 volts for charging), and can easily charge your batteries at 60 amps of 12-volt DC. That’s because 60 amps x 12 volts = 720 watts. So however fast your house batteries would charge on shore power (perhaps as much as 80 amperes), that’s exactly how fast you can charge them with a CarGenerator.
All this suggests you would only need to idle your tow vehicle engine an hour at a time every few days if the sun wasn’t shining to recharge your batteries or you had no solar panels but enough battery storage. And that would be enough watt-hours to allow you to power a 12-volt DC refrigerator (like the Vitrifrigo/Danfoss model I recently reviewed HERE) and a CPAP machine you need at night (no reviews yet), even if the sun wasn’t shining on your 200 to 600 watts of solar panels.
I promised you an update, and here it is. CarGenerator is now available with a TT-30 shore power outlet making it “RV Ready.” Now this TT-30 can’t supply 30 amperes of current from the CarGenerator since that would be 3,600 watts and the CarGenerator power output is only 1,000 watts, which works out to 8 amperes or so. But it makes a pure sine-wave 120-volt output at 60 Hz with less tan 3% THD (Total Harmonic Distortion), much like a Honda inverter generator. That means all of your RV’s electronics should be happy with it, and it won’t cause any overheating issues powering your RV’s converter/charger.
Also note that the TT-30 outlet is mounted “upside-down” on the side of the CarGenerator box with the ground pin at the bottom of the outlet instead of the top. That’s because it’s designed to drape the shore power cord over the top of the mounting strap for better strain-relief on your shore power cord – which is actually a pretty clever design.
Stay tuned for my RVelectricity newsletter next Sunday, May 31st, where I’m going to do a comparison of various generators for volume level under load at 23 feet, and including the CarGenerator being connected to my Nissan Frontier pickup truck. Getting interesting, isn’t it? For more information on the CarGenerator (in various wattage classes) please visit their website.
OK, everyone. Remember that electricity is a useful and powerful force, so we all need to pay attention to safety precautions while using it.
Let’s play safe out there….
Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.
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