by Jim (Rochester, NY)

Question: I am new to RVs. I just bought a 2005 Forest River Sunseeker 2900 and had problems with the one side of the motorhome where you plug in the TV and DVD player and a few other electric outlets on the same side not working while plugged into my house or with the generator on.

So I checked the two 12-volt batteries and I had to add a lot of water to them both. After that, the generator wouldn’t start up either. So I plugged it into my house and the TV and DVD started working again. And the generator only starts while plugged in. I don’t know anything about motorhomes and am very confused.

Anyone have any ideas?


We will go out on a limb and say that your problem is that your batteries are dead and will need to be replaced. This is based on the situation your described. Once you added water to the batteries and connected to house power, the outlets started to work and the generator started. The charging system is providing some juice to the batteries and is allowing the generator to start and has enough power left over to power the outlets. The fact that the batteries were dry was causing the charging system to divert most of its power in an attempt to recharge the batteries.

There is a lot to learn about RVs, and trial and error could prove to be costly. You may find your best option is to take the RV to a qualified RV service center where they can diagnose and resolve your current problem. If you have the time and inclination, then you can learn as much as you can about operating your RV, troubleshooting and resolving problems. You will find that as you learn about one topic, you learn something about other aspects of RVs.

Here are some facts about batteries for RVs — things we have learned in our own RV lifestyle.


Most of the lights, refrigerator mother boards, A/C control boards, furnace/water heater control boards in our RV’s rely on a good battery to provide a constant 12 volts. A weak or discharged battery can adversely affect the performance and longevity of the appliances they control.

A weak battery will also need constant charging – putting an additional load on the charging system and if severe enough, will divert power needed for other applications.


There are three major type of batteries: flooded lead acid batteries, Absorbed Glass Mat (AGM) batteries, and Gel Cell batteries. We will only address the first two, since the Gel Cell batteries are no longer the in thing to get.

There is an additional subdivision of whether the battery is a starting battery or a deep cycle battery. The difference between a starting and deep cycle battery is the way it is used. A starting battery will be rated in Cold Cranking Amps (CCA) and a deep cycle battery will be rated in Amp Hours (Ah). There is a drastic difference in how these batteries are built. The starting battery has many thin plates that provide a high rate of power over short periods of time, which is what you need to start an engine. A deep cycle battery has fewer plates but are much larger and thicker to provide power over an extended period of time. Because of this difference in design you should use the correct battery to fit the application. While you can use them interchangeably they work best when used correctly.

The primary enemy of any battery is sulfation of the plates caused by improper charging, lack of charging after use, or loss of water over the plates. Sulfation happens when sulfur molecules crystallize and form a coating over the lead plates. Sulfated plates are a triple whammy: sulfation causes quick discharge of a battery, decreases the life of the battery and prevents the complete charging of the battery. And according to one manufacturer is the primary reason why batteries fail.

Flooded Cell Lead Acid Batteries:

These are the batteries we grew up with. They require maintenance on a monthly basis to make sure they do not run out of water. Distilled water is what is recommended by battery manufacturers so you should never add tap water to these batteries. As part of the monthly maintenance, also check that the battery connections are tight and are corrosion free.

You can clean the battery casing with a solution of distilled water and baking soda. You can coat the battery posts and connectors with an anti-corrosion product that will help minimize the formation of corrosion.

Maintenance is required whether the battery is a deep cycle or starting battery. Unfortunately, many people don’t do much maintenance until they have a problem. By then it is usually too late to save the battery.

AGM Batteries:

These batteries typically cost twice as much as a flooded cell lead acid battery. However, you do get what you pay for.

They do not require you to add water because they are sealed. They also will last longer than a lead acid battery because they can be recharged more times (cycled) and can be discharged more deeply without damage. Maintenance of posts and terminals are the same as a lead acid battery.

Application – House Batteries:

AGM and Flooded Cell Lead Acid Deep cycle batteries come in two flavors: 12-volt and 6-volt (golf cart batteries). These batteries are what allow you to use your RV while not connected to power (we call this boondocking).

These batteries are commonly found in RVs to deliver power to the house part of the RV : things such as internal lights, vent fans, furnace fans, control boards on refrigerators/furnaces/air conditioners any other 12 Volt appliance residing in the RV (house). Because of this they are typically called house batteries.

House batteries take hours to fully charge. When they go bad, they appear to charge quickly and just as quickly loose the ability to deliver power.

Charging Do’s and Don’ts:

  • Use a good quality three stage charger to charge your battery. If you have an AGM battery, make sure the charger has an AGM setting. If your charger does not have an AGM setting, consider not buying an AGM battery. Shortening the life of an expensive battery is not in your best interest.
  • Always fully charge a battery after use.
  • Don’t skip battery maintenance.
  • Never add tap water. If you have to add water, use distilled water only.
  • Don’t mix old batteries with new ones on a battery bank. A battery bank is one or more batteries connected in a common circuit.
  • If you store the RV without being connected to power, you may want to disconnect the batteries. The decision to disconnect the battery depends on how long you plan to store the RV, and phantom loads that draw down your batteries. In our coach, these phantom loads consist of a number of things that run in the background. Examples include engine and transmission ECMs (electronic control modules), LEDs, the electronics for the refrigerator and other things we probably are not even aware of. We have added solar panels which serve to keep batteries charged when storing the RV in the sunshine.

    If you decide to disconnect your batteries, use your battery disconnect switch if you have one. You could then use a clamp-on amp-meter to check that there were no remaining draws that might discharge the batteries. If you do not have a battery disconnect switch or want to be sure the batteries are completely disconnected, the proper sequence is to first disconnect the negative terminal, then the positive. When reconnecting, connect the positive, first then the negative. If you have multiple batteries, you might want to take a picture or draw a diagram before you start disconnecting things, as a reminder for when you hook things back up.

    If you are going to store the RV for a long period of time with disconnected batteries, it is best if you take out the batteries and put them on a charger. A fully charged battery not connected to a charger will self discharge 1-15% per month.

  • If your charger has a setting for equalization use this setting as recommended by the battery manufacturer. Periodic equalization helps to break up sulfation of battery plates and will improve the overall performance of the battery.

Now you know just about everything we know about batteries. Other input is welcome.

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