Motorcycle Battery Testing Picture

Motorcycle Battery Testing

Before diagnosing electrical components or systems on a motorcycle, it is important that the battery be properly tested first. The battery has only two jobs to perform; 1) Cranking the engine over and 2) Supplying power when the charging system becomes overloaded. Weak or marginal batteries can often cause the unnecessary replacement of electrical parts. In addition, knowing for sure that the battery is good will keep you from wasting money on a new battery that you don’t need and will help in diagnosing other electrical system problems. We’ll show you a quick and simple way to properly test your battery using a load test. This test is called a “load” test because the battery is subject to electrical loading and the test simulates “real” conditions under which the battery has to perform.

Load testing using the motorcycle’s starter and a digital multi-meter (DMM)

TOOLS: Digital Multimeter (between $35 to $250)

For this test you’ll need a digital multi-meter sometimes called (DMM) or Digital volt/ohm meter (DVOM). The DMM is a basic tool required for battery and other electrical systems testing. The battery must be fully charged for this test to produce accurate results. See Motorcycle Battery Charging for details regarding how to properly charge your battery.

Typical Digital Multimeter/Digital Volt-Ohm Meter

 

Digital Multimeter

1. CONNECT DMM TO BATTERY: Set your DMM to read DC Voltage.  Turn the meter’s rotary dial to select voltage (marked with the symbol V).  Then choose DC or AC function by pressing the red “Select” button at the top left of the meter.  The display (upper left corner of the digital display) changes from DC to AC, or AC to DC depending on how many times the Select button is pressed.  Press the Select button until “DC” is displayed. Make sure the red and black meter leads are connected to the meter correctly—Black lead to “Com” or common port and the red lead to “Volts” port.  If you’re unsure as to how to use a DMM, click HERE. Connect the alligator clips (or touch the probes) from the meter leads directly to the battery—red to positive and black to the negative battery terminal.

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2. DISABLE IGNITION SYSTEM: The engine must not start during the test and there are several ways to keep it from starting. Disable the ignition system by either unplugging the primary leads (small wires) to the ignition coil(s) or removing and grounding the spark plug cap(s). On some fuel injected bikes you can remove the ignition or ECU fuse. NOTE: Removing the ignition fuse on some motorcycles may also disable the starter motor and preventing you from performing the battery test.

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3. CRANK BIKE OVER AND RECORD LOWEST VOLTAGE READING: While watching the DMM, press the start button as if starting the engine for 4 seconds and before letting go of the start button press the “hold” button at the top right corner of the DMM, this will pause the meter’s reading.  This test will place an electrical load on the battery;  you’ll want to see a minimum voltage reading of 9.5 volts while the starter is operating. A reading of 9.5 volts indicates that the battery passes the test but is probably in the last few months of its useful life. Higher readings (usually 10.5 volts) indicate that the battery is in good condition. If the battery is bad (fails the test) the voltage will drop below 9 volts (usually around 2 or 3 volts), and the battery should be replaced, as no amount of charging will bring it back from the dead.

Note: If you are testing during winter months in a cold garage (40 degrees F or lower) the battery may not pass the test. The voltage numbers work for temperatures around 60F or above.

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Summary

1. Connect DMM to battery.

2. Disable ignition system.

3. Crank bike over and record lowest voltage reading; Should test higher than 9.5 Volts.

This simple procedure will give you the information you need to determine if your battery is in good condition and whether or not you need to replace it before doing any further testing of your motorcycle’s electrical system.

Below are two suggestions for digital multimeters to use for testing your motorcycle battery. The first is the Craftsman digital multimeter we use in our videos, the second is the more advanced Fluke multimeter that Tracy Martin uses in his books.

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