Battery Blues

Traveling with all of today's modern conveniences: digital cameras, cordless tools, laptops, tablets, etc. equates to the need to charge them on a regular basis. If you frequently dry camp for long periods, do you find yourself constantly battling to keep things charged? While some of the items mentioned above can be operated with a 12- volt adapter / charger via a 12-volt outlet in your RV, others cannot.

One solution to this problem is an inexpensive, low wattage inverter (400 watt or so). An inverter coverts 12 volts DC power, which is the primary operating voltage of your RV, tow vehicle and/or dinghy, into 120 volts AC power which is what

comes out of your wall outlets in your home and RV when connected to shore power. In the United States, chargers that plug into a wall outlet require 120 volts AC. When moving between dry camps or out exploring from basecamp, plug the inverter into the 12 volt outlet (cigarette lighter for those of us over fifty) of your motorhome, dinghy or tow vehicle and the items that need recharging into the inverter. When the vehicle is running, the engines alternator provides the amps to power the inverter and in turn the item that needs recharging. This technique is much more efficient than running a generator to provide the low wattage most items need for a recharge. Your dry camping neighbors will appreciate the lack of generator noise too.

Things to keep in mind:

1) When using the inverter via the 12-volt outlet in your motor vehicle; make sure the outlet is wired to come on and off with the ignition switch to avoid the inverter draining your start battery while the vehicle's motor is not running. If the outlet is energized all the time, be certain to switch the converter off or unplug it when the vehicle is not running.

2)  Ohm's law tells us that voltage multiplied by amperage equals wattage. Therefore, if you have an item that requires 120 watts of 120-volt AC power that equates to 1 amp of power draw (120 volts x 1 amp = 120 watts). Conversely that 120-watt item when operated via a 12 volt inverter requires 10 amps* (12 volts x 10 amps = 120 watts). For most low wattage inverters your standard 12 volt outlet can deliver sufficient amperage. However, if you plan on powering something that requires higher wattage items, make sure you have heavy enough wire on the 12 volt side of the inverter. Here is a rough guide for sizing copper wire to the load: 14 gauge 15amps, 12 gauge 20 amps, 10 gauge 30 amps, 8 gauge 50 amps. Remember, the lower the gauge number, the thicker the wire. Click here to determine proper gauge for longer runs of wire.

* Actually the amperage will be somewhat higher than this as inverters are not 100% efficient, but for quick calculations this keeps the math simple.

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