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Camper Tech

Camper Batteries 101: The Basics

Jim: If your camper is just sitting and there are no lights on and your refrigerator is on LP gas, your camper will pull about one-half amp an hour.  If you have two Group 27 batteries, you have about 80-90 amps available to use.  That’s thirty-six amps that you would use in three days if your camper is just sitting.  One camper light uses about one and a half amps an hour.  So for twelve hours, one camper light uses eighteen amps plus the six amps you need to add for the camper just sitting.

TCM: If you boondock for a few days, how long will your batteries last?

Jim: It depends on the weather you are camping in.  In warm weather, when you don’t need anything but a small fan once in a while to move air around, two Group 24 or Group 27 batteries will last about three days.  Just being in weather below 40 degrees will reduce your battery capacity about 20% without discharging them.  So if you had 80 amps to play with at 70 degrees you would only have about 64 amps available at 40 degrees.  You can go through the capacity of your batteries in one to two days.

In cold weather, a standard Atwood heater, in heat mode, fan motor running uses seven amps.  My camper heater goes for about five minutes every fifteen minutes.  So, there’s about twenty minutes of run time every hour, which means that every three hours your heater runs for an hour.  That’s seven amps used up ever three hours.

For every hour of heater usage, three actual hours, seven amps of power is pulled out of the battery.  Plus, there are another one and a half that’s being used for your camper just sitting without any lights on.  So, twelve hours of running your furnace to warm yourself results in about thirty-two amps drawn out of your batteries and you haven’t turned on any lights.

“Always replace your batteries as a pair. It is not good to have one weaker and one stronger.”

TCM: What brand of batteries do you suggest for truck campers?

Jim: In my opinion, the AGM batteries are the best.  They don’t require any maintenance and they are a lot more forgiving.  AGM batteries are also good because they are packaged differently.  You can put them in a cabinet right in the camper and you don’t have to worry about leakage of sulfuric acid or outgas like a regular wet cell battery.

The capacity of the AGMs also provides more available power as they can be discharged to 50% repeatedly.  If you keep the AGM battery in your camper, they stay warmer and you will get more battery capacity.  They also are capable of charging faster than wet cell batteries.  The downside to the AGM battery is that they cost over $200 for the standard sizes.

TCM: What does AGM stand for?

Jim: AGM stands for Absorbed Glass Mat.  The electrolyte is held in the glass mat.  AGM batteries are sealed, so you don’t need to maintain them.  If you were to turn them upside down they wouldn’t leak.  That’s the advantage to having them.  If you get an AGM battery make sure your converter is compatible with AGMs.  They are different in how they work.  Battery companies will be able to tell you if your converter is compatible.

TCM: What if you don’t want to spend that much on AGM batteries.  Are there other batteries you recommend?

Jim: You could get flooded wet cell deep-cycle, trolling motor, RV-type marine batteries.  Trojan batteries are very popular.  Also, some people get the generic WalMart batteries or Costco deep-cycle batteries because they have a good warranty.  They are about  $60-$80 each.

When replacing your batteries, first check your battery compartment and document the depth, height and width.  Look for Group 24, 27, or 31 deep cycle batteries.  Each group is a different size physically and some batteries are slightly bigger in some dimensions so you will know if the battery(s) your purchasing will fit.  Make sure you get deep cycle batteries and not a starting deep cycle or cranking battery.

Also, you can’t mix AGM with flooded wet cells.  The size of your battery compartment will dictate the size of battery(s) you will be able to use so if you had two group 24s and have the room for 27s you can do that and get another 30 amps of capacity.  Normally campers don’t come with Group 31 batteries.

“When your batteries are not in use they will deteriorate 10% capacity per month, which diminishes the life of your batteries.”

Some individuals switch to six-volt batteries.  It takes two of them to get 12 volts.  The six-volt, “Golf Cart” batteries are the ones of choice.  They can be discharged deeper than the above mentioned and have a longer life.  Again the physical size will sometimes be a problem so check carefully.

TCM: We had a great battery survey.  TCM readers told us about the batteries in their campers.  When would those readers know if they need new batteries?

Jim: There are two reasons why you would want to replace your batteries.  First, you may decide that you need more capacity.  And second, if your batteries have aged or they haven’t been taken care of, you may want to replace your batteries.  Camper batteries over six-months old can begin to fade.  You’ll know if your batteries are too weak because they will only last a couple of hours when you are out camping.  Always replace your batteries as a pair.  It is not good to have one weaker and one stronger.

Hydrometer to test camper batteries

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