How to Diagnose Motorcycle Battery Problems on a Honda VTX 1800

When your motorcycle won't start, a battery problem is usually at fault. If it is, you need to find out whether the battery needs charging or replacing. 

You'll need a multimeter to diagnose your motorcycle's battery, so if you don't already own one, now is the perfect time to get one

Follow this step-by-step walkthrough and watch our Honda VTX 1800 battery diagnostics video above to learn how to diagnose motorcycle battery problems.

NOTE: We tested the battery on a Honda VTX 1800 motorcycle, but the steps for diagnosing problems are the same or similar for any motorcycle battery. 

Honda VTX 1800 motorcycle battery diagnostics

Tools Needed - Honda Motorcycle Battery Diagnostics

Accessing the Battery - Honda VTX 1800

Step 1. Remove the seat by taking off the 6mm Allen bolt from either side of it.

Step 2. Unclip the engine control unit (ECU) from the top of the battery cover and move it out of the way.

PRO TIP: Don't disconnect the ECU because the pins in the connectors are fragile and if a pin is broken, you'll have to replace the entire ECU.

Honda VTX motorcycle battery diagnostics

Step 3. Remove the three screws holding the battery cover, followed by the cover itself.

Honda VTX motorcycle battery cover

Testing the Battery - Honda VTX 1800

Step 1. Set a multimeter to DC volts, connect it to the positive and negative terminals of the battery, and measure the battery's voltage. A charged, healthy battery should register somewhere around 12.5 volts to 12.9 volts. A battery that is charged but registers under 12 volts has probably reached the point at which it needs to be replaced.

Honda motorcycle battery testing

Step 2. If the battery's voltage is around 12.5 volts, try starting the engine and measuring the voltage. A dramatic drop in voltage when the starter is engaged is an indication that the battery isn't healthy, and further testing is required.

Step 3. Disconnect the negative battery terminal first, then disconnect the positive terminal and remove the battery. Use needle-nose pliers to grip the battery's terminal posts, and lift the battery out of the box.

PRO TIP: Disconnecting the negative terminal first eliminates the possibility of accidentally creating a short circuit when disconnecting the positive terminal.

Honda VTX 1800 motorcycle battery testing

Step 4. Analyze the battery's condition with a battery tester. This will give you a very accurate picture of the battery's health, and tell you whether the battery needs replacing or not. 

Preparing a New Battery - Honda VTX 1800

Step 1. Add the electrolyte to the new battery by removing the plastic cap from the electrolyte container, pressing the electrolyte container down onto the battery cells and letting the electrolyte fully drain into the battery.

Motorcycle charging problems electrolytes

NOTE: Don't discard the plastic cap from the electrolyte container because you'll need it to seal the battery once it's charged.

Step 2. When the battery is filled with electrolyte, let it sit for at least 20 minutes so the electrolyte gets absorbed into the glass mat within the battery.

Step 3. Charge the battery using a smart battery charger or battery tender. A smart charger/tender won't overcharge or damage the battery.

 Battery tender motorcycle battery smart charger

PRO TIP: Charge the new battery with its cells open. Don't seal the cells until the charging is complete.

Step 4. When the battery is fully charged, take the plastic cap that was on the electrolyte container and use it to seal the new battery's cells.

Honda VTX 1800 battery test charging

Installing a New Battery - Honda VTX 1800

Step 1. Install the threaded inserts into the new battery's terminal posts.

Step 2. Install the new battery into the battery box.

Honda VTX motorcycle battery installation

Step 3. Connect the positive battery terminal first, then the negative terminal.

PRO TIP: Connecting the negative terminal last eliminates the possibility of accidentally creating a short circuit when connecting the positive terminal.

Step 4. Reinstall the battery box cover, then clip the ECU back onto the cover and reinstall the seat.

Honda VTX 1800 motorcycle battery diagnostics

Still having starting problems with your motorcycle? Watch the video below to learn how to test a Honda VTX charging system.

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