Battery Maintenance – BMW 650 GS and Dakar

Battery maintenance is important and fortunately it’s easy. The original battery that comes with the GS and Dakar is unsealed, meaning you periodically need to add water. How often varies but it’s best to check it every few thousand miles or so. If you do a lot of off road riding, it’s best to check it more frequently.

If the water is low, damage to the battery can occur and it won’t hold it’s charge as long. If you find that the battery is consistently low on water, there could be an over-charging problem where the voltage rectifier is pushing too much voltage to the battery. Since it’s right near the battery, we can check that with a volt meter at the same time we check the water levels.

Adding Water to the Battery

  • Go buy some distilled water at the supermarket. It must be distilled. You cannot use regular water.
  • Leave the bike turned off. You do not need to disconnect the battery.
  • Unlocking and opening the rear compartment. Pull the seat release cable and lift the seat at the same time.
  • Remove two screws on the left side body panel; one is where the seat normally covers and the other is up underneath the handlebars where the oil dipstick is located. Remove the same two torx screws located on the right side body panel.
  • Unscrew the 2 torx screws on the center body panelwhich are also located underneath the handle bars. There is enough flex in the side panels that you should be able to pop out the center body panel.
  • Once the center body panel is removed, you will see the battery. The battery is held in place with a rubber strap. Pull and lift the strap. You do not need to remove the battery unless you want to (it’s easier to see the water levels but again isn’t necessary). To remove the battery you need to disconnect the terminals and pull the battery straight out. Note: As with any vehicle battery, disconnect the black terminal first. When reconnecting, connect the positive (red) terminal first.
  • Get a small damp towel and clean around the top of the battery, especially around the white plastic circular caps. You don’t want any debris to fall into the holes.
  • Once cleaned, remove the first plastic cap with a pair of needle nose pliers. If you look down into the hole with a flashlight, you may be able to see some metal slats. I typically poor in enough distilled water to fully submerge the metal slats. Replace the white plastic cap and repeat the process for each plastic cap.
  • Reattach the center body panel and snap the side body panels into it. Re-insert the torx screws into the center and side panels. Reattach the seat.

Checking voltage Rectifier

  • While the bike is turned off, use a voltage meter to test the battery voltage. Connect the red lead to the positive terminal on the battery. Connect the black lead to the negative terminal on the battery. It should read right around 12 volts DC.
  • Start the bike and leave it running. Connect the red lead to the positive terminal on the battery. It should read around 14 volts DC this time. If the charging voltage is significantly higher than 15 volts, there may be a problem with your voltage rectifier and your battery is getting charged to quickly. This could result in low water levels and could also damage the battery.

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