How to Install a Battery on a Fifth Wheel Trailer


RVs, travel trailers and fifth wheels have the advantage of being self-contained whenever they travel beyond an external power source. Fifth wheel trailer batteries can last for two or more days without losing their charge and still feed enough current to work all the trailer accessories. Battery selection and placement can be the most important purchase a trailer owner can make, since the battery functions as the electrical heart of the system. Any trailer owner can install the proper size and amp-hour battery in their trailer, using a few tools and simple steps.

Things You'll Need

  • Owner's repair manual
  • Socket set
  • Ratchet wrench
  • Battery strap
  • Baking soda
  • Bucket
  • Scrub brush
  • Towels
  • Battery cleaner tool
  • Paint (optional)
  • Battery washers (felt)
  • Vaseline
  • New battery cable (optional)
  • New battery clamps (optional)
  • Select the highest amp-hour, deep cycle battery that will fit in your battery box. Refer to your owner's manual for the most powerful battery allowed. If you need to replace your 12-volt battery with two deep cycle 6-volt batteries, make sure you measure your battery dimensions, allowing room for the dual battery installation. Make sure the replacement battery has a full charge before installing it.

  • Locate your main battery cutoff switch at the control panel and turn it off. Disconnect any external power source hookup to your trailer. Open your battery box. Use a socket to disconnect the negative battery cable from its post. Use a socket to disconnect the positive battery cable. Unscrew the battery hold-down clamps and pull the hold-down mechanism off the battery.

  • Use a battery strap to secure the old battery and transport it out of the trailer. Clean the battery box with baking soda and water. Scrub the battery cable ends with baking soda and a brush, if you intend to reuse them. Remove all battery acid corrosion.

  • Dry the box with a towel, and paint it with a rust inhibitor paint if you want extra protection. Install the new battery in the battery box, using a strap to lift and place it. Replace the battery hold-down bracket or clamp and tighten the bolts with a socket.

  • Clean the inside of the battery cables with a battery cleaner tool until the insides shine. Insert two felt washers over the battery posts. Place the positive and negative cables over their respective terminal posts and tighten them with a socket. Apply a liberal amount of Vaseline gel to all surfaces of the battery cables, including the undersides. Turn your main cutout switch to the "on" position and test your trailer accessories.

Tips & Warnings

  • To hook two 6-volt batteries in series, connect the negative post from the second battery to the positive post of the primary battery. Change the chassis ground from the primary battery to the second battery.
  • To hook up two 12-volt batteries in parallel, hook up an extra cable from the positive terminal on the second battery to the positive terminal on the primary battery. Run an extra cable from the negative post on the second battery to the negative post on the primary battery. Allow the negative post on the primary battery to remain grounded to the chassis.


  • Photo Credit construction security, trailer image by Greg Pickens from
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