How to Charge the Battery on a Harley Davidson Fat Boy

by Chris Gilliland
Justin Sullivan/Getty Images News/Getty Images

While the motor is considered the heart and soul of a Harley-Davidson Fat Boy motorcycle, it relies heavily on the battery to keep that metal heart beating. Powering everything from the lights to the ignition system, the battery's electrical supply is refueled by the motorcycle's charging system. This system, however, only works while the motorcycle is running. With motorcycles being ridden mainly on fair weather days, the battery slowly loses its charge as most find themselves in periods of inactivity. Recharging the battery with a battery charger is a simple fix, requiring only a few minutes to remove and install the battery.

Step 1

Park the motorcycle on a smooth, level surface and turn the ignition switch to the "OFF" position. Locate and unscrew the bolt that secures the seat to the rear fender, using the appropriately sized allen key. Then, locate and remove the two allen head bolts under the leather flaps of the seat. Pull the seat upwards and to the rear of the motorcycle to remove.

Step 2

Disconnect the negative (-) terminal's Phillips head screw and place the wire lead aside, making sure that it does not contact the frame or any metal parts. Disconnect the positive (+) terminal's Phillips head screw and place the wire lead aside.

Step 3

Remove the rubber battery retention strap, if equipped, then lift the battery vertically to remove it from the frame.

Step 4

Connect the battery to a charger, attaching the positive (+) wire lead first, followed by the negative (-) lead. Allow the battery to charge completely.

Step 5

Disconnect the charger's leads, negative terminal first, and slide the battery into the motorcycle's battery tray. Connect the positive (+) wire lead first, followed by the negative (-) wire lead. Reconnect the battery retention strap, if equipped.

Reinstall the seat by sliding the metal tang on the front of the seat into the slot on the frame. Once seated, press down on the back of the seat and secure it to the rear fender. Reinstall the final two bolts under the seat's leather flaps.


  • Inspect the battery for signs of damage, such as cracks or leaks, and remove corrosion buildup from the terminal posts using a solution of water (1 pint) and baking soda (3 tablespoons).
  • Depending on the type of charger you have selected, you may charge the battery while it's installed on the motorcycle.
  • Refer to the battery charger's manual for estimated charge duration.
  • If you do not feel that you can complete this project, have the work done by a qualified technician.


  • When disconnecting the battery, do not let the terminals contact the frame, preventing grounding and electrical shock.
  • Double check that the seat is locked into position. A loosely mounted seat can shift while riding and cause a loss of control.

Items you will need

  • Screwdriver, Phillips
  • Allen keys, SAE
  • Battery charger

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