How to inspect your motorcycle battery?
Step 1. Check to make sure you actually have a mechanical problem
Is your sidestand up? Is your clutch pulled in? Often on modern bikes there are electrical switches that will not allow a bike to start if these two conditions are not met. Is the bike’s key in the ignition position? These not battery problems, but they will mimic the problems a bad battery displays.
Step 2. Once you verify you have a problem, make sure it’s a battery issue
Mechanics never describe a starting problem as “not running.” Starting issues are either “no crank” or “no start.” If the bike’s starter sounds like it’s turning over the engine at the appropriate speed, odds are good your no-start condition is not a bad battery. Though your bike’s electrical system is pretty complex, the starting system really is not. Cranking issues are often battery related. Starting issues are usually not.
A quick test, even if you are by the side of the road, is to turn on your bike’s headlight and walk around to the front of the bike. A weak, dim headlight is an excellent indicator your battery’s not up to the task of starting your freedom machine. Note that many modern motorcycles have a circuit to turn the headlight on only after the bike is running, so this test won’t work on those
Step 3. Perform a standing voltage test
What we’re about to discuss holds true for standard lead-acid and AGM (absorbed glass mat) batteries. Batteries of a different construction type may well have different testing procedures and specification. (Lithium batteries spring to mind immediately as a battery that has a different usage and test scenario. If you’ve got one, refer to your battery manufacturer’s recommendations.)
Batteries need both voltage and current, but testing voltage is easy — all you need is a multimeter, also known as a DVOM (Digital Volt and Ohm Meter). Plug the leads into the multimeter. The black lead will go into the port that says “COM” (common ground) and the red lead will get plugged into the port that has a capital “V”. Turn the multimeter on to the 20V DC section of the scale. (If you have an autoranging meter, just go to “V,” because you won’t have a scale.) With the bike completely turned off, touch the black lead to the negative post of the battery, and the red lead to the positive post. Record the voltage.
Step 4. Perform a cranking voltage test
You can perform a test with the battery under load (working) to get an idea of the current flowing through it. Note that this isn’t the “right” way to do this, but it’s another clue to help you confirm or deny your battery’s health. Hook up your DVOM in the same manner you did for the standing voltage test, and have an assistant thumb the starter. While the starter is spinning, observe the voltage. The starter should be running at normal speed. A good battery should not drop below 9.6 volts over 10 seconds or so.