How to Charge an RV or Trailer Battery

How to Charge an RV or Trailer Battery

Your RV, trailer, or camper has two distinct batteries - the starter battery for your engine, and what we call a “house” battery, which gives power to all the appliances and electronics in the trailer. In most cases, house batteries come chained in parallel or in a series, and if one goes out or runs low, your electrical appliances and power won't work properly.

Before you start looking for replacements for your deep cycle RV battery, you should attempt to recharge it as it’s a much more affordable and less time-consuming. More often than not, you’ll be able to recharge your house battery using tools that your likely already have on hand.

First, check your battery's voltage level with a multimeter. An ideal 12v house battery reading will come in between 12.4 - 12.6 volts. If you're seeing less than that, then your battery could use a charge. There are potentially 3 ways the trailer battery is recharged.

METHOD 1: Use Your Vehicle's Alternator

The charge line traveling from the tow vehicle alternator to the trailer allow you to charge your house battery while your engine or vehicle is running. This requires more than a 4-pin connection. A 4-pin connection only provides running light functions. Typically a 7-way trailer-to-tow vehicle connection is used when brakes or a charge line are required. The problem with using the tow vehicle to recharge the battery is that it is typically very slow and only works when your truck is running and connected.

METHOD 2: Using an RV Solar Battery Charger

This is becoming an increasingly popular option for RV and vintage trailer enthusiasts. With a voltage regulator inline between the panels and your trailer battery, the solar panels will provide a trickle charge or better (depending on solar panel wattage) to your battery. There are a wide assortment of "trickle" solar chargers available online. We recommend having these on hand even if you can charge from your alternator or with a power converter. Solar charging panels prevent you from having to rely on shoreline connections and readily available power.

METHOD 3: Use an RV Power Converter/Charger

This is the #1 way house batteries are recharged. A power converter is simply plugged in to 110 volt AC electrical outlet which can be found all over your house, garage, and exterior. It provides clean, efficient 12VDC power to run interior lighting AND to recharge the battery. A good converter/charger recharges batteries very quickly and safely maintains the batteries at the correct voltage level to prevent overcharging (which shortens life of the battery). Obviously, the battery is only recharged when the trailer is plugged into shore power.

All three of the above RV battery charger methods have a place and the ideal 12VDC system incorporates all 3. If you are having a long driving day while on the road, you may find METHOD 1 is very important. If you are parked off grid for long periods of time, you may find METHOD 2 is very important. If you are frequently camping at campgrounds where you can be plugged into shore power, you will find METHOD 3 is essential.

One additional trick is to bring along a small generator that can provide 110V power to your converter/charger when you are not able to plug into shore power.

For more trailer maintenance and upkeep tips, check out our Resources & Guides section.