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Friday, October 23, 2009

Inverter Requirements

I am thinking about installing a 600-watt inverter to power my 27-inch TV and dish system. My question to you is, are the two, 100-amp batteries that I have in my motorhome enough battery to watch TV for four or five hours at night and then recharge my batteries in the morning with my generator? If not, any ideas on what to do or where one would install more batteries.
Tom, (Seattle, WA)

Tom, first it will be necessary to determine exactly how much wattage the television and the dish requires. If they are rated in amps simply multiply the amperage times the voltage; the result is power measured in watts. Then multiply the wattage requirement by the number of hours you will watch the TV. This result is the daily wattage requirement, not including any other 12-volt devices being activated, such as fans, water pump or lamps. 

The bottom line is: multiply all the 12-volt devices you will be using times the amount of time to obtain a final amperage requirement figure. Then add a 30% safety factor. Assuming the batteries are in fairly good condition and you can fully charge the two of them, divide your final amperage requirement calculated above into 200. The mathematical result will determine if you have enough storage capability. 

Next, look at your charging method. Typically the RV power converter is used to charge the batteries. The generator will simply provide the 120-volts AC to power the converter/charger. The power converter with a well designed charging feature is a very good method of keeping the RV portion of the 12-volt DC system charged up, especially if your unit is equipped with a sophisticated, three or four step converter/charger, which is what I recommend. 

The typical charging converter is not capable of charging the batteries quickly. Extra batteries should be installed as close to the others as possible, but basically anywhere they can fit, though not inside the living areas. 

The AGM battery is what I recommend. Highly touted, the AGM battery has many intriguing features. Their recombinant gases are effective to about 99%. The hydrogen and oxygen are recombined inside the battery within each separator, unlike the gel type where the recombining occurs between the plates and the battery top. This keeps dangerous hydrogen gas levels to a minimum. Most AGM batteries vent hydrogen vapors at less than 2%, where 4.1% is needed to support flammability in air. The inherently low internal resistance is a welcomed benefit to RVers who store the motorhome part of the year. AGM batteries can be charged ten times faster than a same rated gel battery and five times as fast as a like-sized flooded lead acid battery. You indeed have many things to consider, so do the math first to determine your exact plan of attack.


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