A motorcycle’s battery is the heart of the entire electrical system. Waiting until the battery light comes on is not the ideal time to test its health. The basic health of a battery can be determined by conducting a few simple tests with a common multimeter. In this article you will be provided with instructions on how to perform these tests and any necessary preparation steps.
The first preparation step is to fully charge the battery. To accomplish this you can either hook the bike up to a charger or, if you know the bikes charging system is in good health, go ride the thing. Both will be sufficient but the second option will also charge your soul. After charging the battery you will need to remove any surface charge that could provide an inaccurate reading. One way to do this is to let the bike sit for 3-4 hours. Another way this can be done is by switching on the headlight (on high beam) for 1 to 2 minutes. How you remove the surface charge does not really matter; just be sure to do so prior to conducting any tests.
Next you should gain access to the battery. While it is possible to obtain an accurate reading by utilizing the battery charger plug (if the bike is equipped with one) this method is not recommended. Accessing the battery is usually as simple as removing the seat or a cover, and enables a proper physical inspection. The battery should be checked for any leaks or damage. It is also good practice to brush any corrosion off of the terminals and ensure they are secured.
The final preparation step is to set the multimeter. Place the leads in the correct ports and select the appropriate scale. On the multimeter pictured the black lead goes to COM (common ground) and the red to V (voltage) with the correct setting being 20 in the DCV (Direct Current Voltage) scale. Once the meter is set you may begin testing. For all of these tests you will place the meter’s red lead to the battery’s positive terminal and the meter’s black lead to the battery’s negative terminal.
Begin the series of tests by checking the battery’s static voltage. This is the simplest of the tests and will tell you the battery’s state of charge. With the bike completely powered off, place the multimeter leads to the corresponding battery terminals. A reading of 12.6 volts and above generally means that the battery is 100% charged. Every tenth of a volt below 12.6 represents about a 10% decrease in charge. Consider replacing a battery that will not take a charge above 12.2 volts.
Next up is the starting load test. This test will demonstrate how much battery voltage drops under the load of the starting system. For this test you are going to crank the engine over with the multimeter leads in place. From the time cranking begins until the time the bike starts, monitor the reading on the meter. An acceptable reading would be 9.6 volts or higher. In most cases a reading below 9.6 volts indicates the battery has a low capacity and is in need of replacement. Once you have gathered your reading leave the bike running to conduct the final test.
Conclude your testing by checking the bikes charging output. This test is directed more toward the charging system but the reading is taken at the battery. With the multimeter leads in place run the motorcycle from idle up to approximately 3,000 RPM. As you increase RPM the voltage should rise to a range between 13.7 and 14.5 then remain there. Any extreme fluctuations in the reading or a reading outside of this range indicates that a more detailed inspection of the charging system is in order.
Completion of these few simple tests can save you from being stranded on your next long ride. In addition, these tests will typically be where you begin when inspecting or troubleshooting a motorcycles electrical system. Keep in mind that the voltage specifications provided in this article are only a reference point. Exact specifications may vary from bike to bike. Now go make things happen.
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