What Kind of Battery Do I Need for My RV?

All RV’s are very dependent on our 12 volt battery systems. From the time we unlock the power door locks, open our entry door (step extends), turn on an interior light, cool the RV refrigerator (circuit board needs 12 volt to operate on gas or 120 volt electric), control interior climate with furnace or air conditioning (thermostat operates on 12 volt) the batteries must be providing us the necessary power to allow this to happen. This is the most important and probably the most neglected system in the RV.A picture of a RV battery.

We complicate our 12 volt system by using deep cycle and automotive style batteries. We also use two 6 volt batteries connected in series, one or more 12 volt batteries connected in parallel and finally we use four or more 6 volt batteries connected in series/parallel.

Let’s start with clarifying the difference between automotive and deep cycle batteries. An automotive style battery is constructed to allow a high rate of amperage output as is needed to start an engine. This battery can only be discharged at a high rate for a short period of time before it is completely discharged or dead. Deep cycle batteries are constructed of thicker plates which allow for a lower rate of discharge for a longer period of time. Now you can see the importance of choosing the correct battery. A deep cycle battery being used to start the engine may not be able to provide enough amperage for the starter to function properly. As well as an automotive battery used for the house application will discharge quicker. Another advantage of the deep cycle is the ability of the battery to be completely discharged and recharged without damage. An automotive style battery can only be completely discharged a few times without causing damage.

Our next choice will be 6 volt or 12 volt batteries. The most common automotive system is a 12 volt battery to start the engine. In most diesels we see two 12 volt batteries connected in parallel to provide enough power to start that big diesel engine. When batteries are connected in parallel the voltage stays the same but we add the power (amperage) of both batteries. Most commonly the manufacturers use two or more 6 volt batteries in series for house power. When connected in series voltage is added and the power is not added. There are pros and cons of both systems. For the average RV’er, staying connected to shore power and only dry camping for short periods of time makes the 6 volt batteries in series the most efficient system. However, if dry camping for extended periods of time 12 volt batteries connected in parallel will provide more power. Space and weight will also play a part to determine which system we use.

When replacing batteries it is important that the same size of battery is used. Batteries are rated in Cold Cranking Amps (CCA) or Amp Hours (AH). This is what we use to determine the power or size of the battery. The physical size of the battery is important but doest not determine the power in a battery. Some things that determine the price of the replacement battery will be the rating  and warranty period.

Deciding on a water filled, AGM or Gell Cell can be done by answering a few simple questions. Do you want to check your water filled batteries monthly? Are they are installed with easy access for monthly maintenance? If your answer is no then you need to look at AGM or Gel Cell. These are both true maintenance free batteries. If this is the case I would recommend AGM over Gel Cell. AGM batteries are less expensive and provide the maintenance free service. Gel Cell batteries were more common before AGM technology.

When replacing only one battery in a bank of batteries most technicians will tell you that you must replace all of the batteries in the bank. This can be very expensive if you have 4 batteries. My advice is to just understand that a new battery will not  improve old batteries but old batteries will bring down that new battery to their level as soon as they are connected. If the remaining batteries are one or two years old and in good condition it could be OK to add just one new battery. However if they are older or in a deteriorated condition then they all should be replaced. Also remember anytime we have a bank or group of batteries they must all be identical.

The newest battery entering the market is the Lithium-ion battery. Some RV’ers are experimenting with these batteries. Currently the problem is our charging systems are not  designed for Lithium-ion batteries plus they are very expensive. I think I would wait for this technology to be  advanced.

Come back next week for more information on batteries.

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