Maintaining an RVs Battery

Batteries are the highest-maintenance item on an RV. They tend to get abused because people don’t know how to take care of them, and the electrical system of the RV may not be designed to optimize battery life. Batteries will discharge over time, even if no lights or accessories are turned-on. Modern vehicles have various devices that consume a small amount of electricity from the batteries all the time, such as the memory for radio settings, engine computer, LP detector, etc. When a battery is left for a period of time without being charged, it will gradually be discharged. A partially discharged battery deteriorates much more quickly than a fully charged battery, so the normal life span of the battery will be shortened if it is not kept fully charged. A discharged battery will be completely ruined very quickly if left uncharged. Water evaporates from batteries, and if the water level drops below the top the plates the battery will be ruined. Therefore, once a month, check the water in the batteries (if they have removable caps) and top-off with distilled water only to bring the level up to the”full” indicator. Distilled water is available in most grocery stores.

While you are looking at the batteries, take a look for corrosion on the cable terminal connections and on any metal surfaces around the batteries. Use battery terminal cleaner spray to neutralize the acid that is causing the corrosion. After it dries, coat the terminals and the metal areas with battery terminal protector spray. You can find both of these products in auto parts stores, or go to and select “Automotive”, and then enter “battery spray”.

It is not a good idea to leave the RV plugged-in to shore power unless your coach has a modern (less than 10-years old) Inverter/Charger. Most rear-engine diesel motorhomes come with this feature, but most towable RVs and front-engine motorhomes do not, they come with a Converter/Charger. The modern Inverter/Chargers usually have a sophisticated charging program that will keep the house batteries charged optimally when the RV is plugged into shore power or the generator is running. However, the unsophisticated Converter/Chargers that come with most other RVs provide only a constant voltage output, so they usually either overcharge or undercharge the house battery; either way, that shortens the lifespan of the battery. If you plan to keep your RV plugged into shore power for extended periods of time while camping or in storage, you should consider upgrading the Converter/Charger to a model that adjusts the voltage output according to the state-of-charge of the battery. A good example of such a product is the Progressive Dynamics Intelli-Power 9200 Series Converter/Charger With Built-in Charge Wizard. These are available at most RV dealers, or you can go to, then select “Automotive” and then enter “Progressive Dynamics converter”. Select the model that has the same amperage output capacity as the one in your RV. If you want to know whether your RV has a Converter/Charger that has similar advanced voltage regulation, ask your RV dealer, or find the brand and model number on your existing Converter/Charger and look it up online. Many RVs have a Converter/Charter that is built into the 110-volt circuit breaker box. With this type, you would bypass the built-in Converter/Charger and install the better Converter/Charger as a free-standing unit nearby. This is something that would best be done by an RV dealer; their people should know how to do the wiring to avoid failures and fires. Another option is to disconnect the ground cables from the batteries when parked and then use battery tenders to maintain the batteries.

It is important to realize that most motorhomes are designed so that only the house batteries are being charged when plugged into shore power or when the generator is running. The “chassis” battery(s) (the battery that starts the engine) receives a charge only when the engine is running. Have you ever wondered by most motorhomes have a “battery boost” switch? Its purpose is to (hopefully) enable starting the engine if the chassis battery is discharged. While you hold that switch, it uses the house battery to jump the chassis battery. The theory is that since the chassis battery is not being charged while you are camping and plugged into shore power, but the house battery is being charged under those conditions, the house batteries should have the power to start the engine so that you don’t have to drag out the jumper cables. But think about this: the RV manufacturers must expect the chassis battery to be discharged often, or they wouldn’t go to the expense of providing the battery boost feature! That line of thinking confirms that chassis batteries often get discharged, and I have already explained that that shortens the lifespan of the chassis battery. How do you protect your chassis battery? The best way is to install a battery tender on the chassis battery and plug it in whenever your motorhome will be parked while camping or in storage for more than a week at a time. Battery tenders are available at RV dealers or go to, then select “Automotive” then enter “battery tender”.

What to do about maintaining batteries if the RV is parked for more than a week at a time where there is no access to electricity? If you have a towable RV, the easiest thing to do is take the battery home and keep it connected to a battery tender. If you have a motorhome, the easiest thing to do is drive it for ½-hour every week. If you can’t attend to the motorhome every week, you could take the batteries home and keep them connected to battery tenders. But that is a lot of work because there are usually multiple wires and cables, difficult access and awkward lifting involved. If you think you could attend to the motorhome at least once a month, you could disconnect the negative cables from the batteries or have an RV dealer install a high-quality battery disconnect switch on the negative (chassis ground) cable of each set of batteries. If your motorhome already has one or two battery disconnect switches, you should verify that there is absolutely no draw of electricity from the batteries when the switches are in the “off” position. You wouldn’t think so, but some RV manufacturers design their systems so that even with the battery switch(es) turned off, there are still some devices that draw power, such as LP alarms or engine computer. This doesn’t have to be do-it-yourself work. RV dealers are used to dealing with these issues, and not a huge labor bill will be required to have it professionally done. The investment will save the aggravation of discharged batteries, and the expense of prematurely replacing batteries. Note: Do not use the small battery disconnect switches that mount directly on the battery terminal, whether the knife-switch style or the type with the knob to tighten the connection. Both types tend to make poor connections after not a long time in use. The marine-style switches with a large selector dial are the best because they resist corrosion. If you do-it-yourself, be sure that you buy a switch with sufficient amp rating to match the batteries that you are connecting it to.

Why do they call it “shore power”? Because much of the technology and equipment for RVs came from the boating industry, and boaters called it shore power before RVing became popular, so the name stuck.