Now it’s very important that you use the right battery for the type of
application. The battery used to start and run the engine is referred to
as a chassis battery or a starting battery. Vehicle starters require
large starting currents for short periods. Starting batteries have a
large number of thin plates to maximize the plate area exposed to the
electrolyte. This is what provides the large amount of current in short
bursts. Starting batteries are rated in Cold Cranking Amps (CCA). CCA is
the number of amps the battery can deliver at 0 degrees F for 30
seconds and not drop below 7.2 volts. Starting batteries should not be
used for deep cycle applications.
The battery or batteries used to supply 12-volts to the RV itself are commonly referred to as house batteries. House batteries need to be deep cycle batteries that are designed to provide a steady amount of current over a long period. Starting batteries and marine batteries should not be used in this application. True deep cycle batteries have much thicker plates and are designed to be deeply discharged and recharged repeatedly. These batteries are rated in Amp Hours (AH) and more recently Reserve Capacity (RC).
The amp hour rating is basically, how many amps the battery can deliver for how many hours before the battery is discharged. Amps times hours. In other words a battery that can deliver 5 amps for 20 hours before it is discharged would have a 100 amp hour rating 5 Amps X 20 Hours = 100Amp Hours. This same battery can deliver 20 amps for 5 hours 20 Amps X 5 Hours = 100 Amp Hours. Reserve Capacity rating (RC) is the number of minutes at 80 degrees F that the battery can deliver 25 amps until it drops below 10.5 volts. To figure the amp hour rating you can multiply the RC rating by 60 percent. RC X 60 percent
The two major construction types of deep cycle batteries are flooded lead acid and Valve Regulated Lead Acid. Flooded lead acid batteries are the most common type and come in two styles. Serviceable with removable caps so you can inspect and perform maintenance or the maintenance free type. In VRLA batteries, the electrolyte is suspended in either a gel or a fiberglass-mat. Gel cell batteries use battery acid in the form of a gel. They are leak proof and because of this, they work well for marine applications.
There are several disadvantages to gel cell batteries for RV applications. Most importantly, they must be charged at a slower rate and a lower voltage than flooded cell batteries. Any overcharging can cause permanent damage to the cells. Absorbed Glass Mat, or AGM Technology, uses a fibrous mat between the plates, which is 90 percent soaked in electrolyte. They are more expensive than a standard deep cycle battery but they have some advantages. They can be charged the same as a standard lead acid battery, they don’t loose any water, they can’t leak, they are virtually maintenance free and they are almost impossible to freeze.