Battery Testing Procedures
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BATTERY TESTING PROCEDURES
Batteries give off hydrogen gas constantly. Hydrogen gas is highly explosive.
Always wear safety glasses or goggles and use caution when working with batteries.
OPEN CIRCUIT VOLTAGE TEST
Before you can properly test any battery it must be at FULL CHARGE.
You can verify the state of charge with the use of a digital multimeter.
Connect the digital multimeter to the battery terminals. A fully charged 12 volt battery will read at least 12.6 volts (2.1 volts
per cell) on the multimeter. If your reading is 12.4 OR BELOW you must recharge the battery before testing.
Before you can properly test any battery it must be at FULL CHARGE.
The only way you can thoroughly test a battery is to place a high amperage load across the battery terminals.
Starter motors have very high amperage requirements which can exceed 300 amps on certain engine applications. If the
battery has to be recharged you must first remove the surface charge. This can be done by using the starter. Disable the ignition
spark (consult manufacturer’s method to avoid electronic ignition) and crank the engine for 10-15 seconds. Once you have
removed the surface charge, disconnect the battery cables and connect the battery load tester to the battery posts.
Adjust current draw on the load tester to 50% of the CCA rating. Continue this for 15 seconds while viewing the voltage reading
on the battery tester. The voltage should stay above the specified reading (see chart below) without falling off. If the voltage
remains at the specified level or above, the battery would be considered good. If the voltage reading drops below the specified
level, replace the battery.
LOAD TESTING THE BATTERY
Determine the cold cranking amperage rating of the battery you are testing.
If the cold cranking amp rating (CCA) is not known, use 450 CCA for four cylinder engines,
550 CCA for six cylinder engines and 650 CCA for V-8 engines.
Open Circuit Volts Percent of Charge
11.7 volts or less 0%
12.0 25%
12.2 50%
12.4 75%
12.6 or more 100%
Minimum Voltage Temperature (degrees)
9.6 70 F 21C and above
9.5 60F 16C
9.4 50F 10C
9.3 40F -1C
9.1 30F -7C
8.9 20F -12C
8.7 10F -18C
8.5 0F -18C
Load Test Chart
12 volt battery
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