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"Why is my golf car battery dead?" The answer may be a bad voltage regulator or its remotely possible its a bad starter generator. 99.9% of the time its a failed voltage regulator. This guide pertains to 12V SLI battery found in gas powered golf cars. This guide does not pertain to 36V or 48V electric golf cars or dead batteries in electric golf cars. The difference between electric and gas golf car batteries will be the topic of future guides. Each golf car is different so the exact details of remove and replace are best described in a factory service manual. Since gas golf car battery charging systems are principally the same this guide works best as a diagnostic tool.
Gas golf cars have one 12V battery that is recharged with a starter generator. A typical starter generator looks like this.
The starter generator produces electricity to recharge the golf car battery. The starter generator produces too much power for recharging the battery so a voltage regulator is put in between the generator and the battery. Voltage regulators limit the voltage to around 14.0V so the battery recharges properly. Voltage regulators fail in two ways. Failure number one: voltage regulator cuts off all voltage and the battery dies. Failure number two the voltage regulator allows all current to pass and the battery overcharges and suffers damage. Voltage regulators come in many different configurations and look differently in various golf cars. Here are just a few examples.
Prepare the car for testing.
The following tests require some vocational skills including how to use and read a 12VDC multimeter. Multimeter use goes beyond the scope of this guide.
Test #1: Scenario - bad battery, good starter generator, good voltage regulator.
Test #2: Scenario - good battery, good starter generator, bad voltage regulator
Test #3: Scenario - good battery, good starter generator, bad voltage regulator
Gas golf cars have one 12V battery that is recharged with a starter generator. A typical starter generator looks like this.
The starter generator produces electricity to recharge the golf car battery. The starter generator produces too much power for recharging the battery so a voltage regulator is put in between the generator and the battery. Voltage regulators limit the voltage to around 14.0V so the battery recharges properly. Voltage regulators fail in two ways. Failure number one: voltage regulator cuts off all voltage and the battery dies. Failure number two the voltage regulator allows all current to pass and the battery overcharges and suffers damage. Voltage regulators come in many different configurations and look differently in various golf cars. Here are just a few examples.
Prepare the car for testing.
Park and lock the parking brake. Block the front wheels from movement with chocks. Jack up the rear end of the cart so the drive wheel spins freely, the car will not run away when the go pedal is depressed. Recharge the 12V battery with a 12V automotive car charger.
The following tests require some vocational skills including how to use and read a 12VDC multimeter. Multimeter use goes beyond the scope of this guide.
Test #1: Scenario - bad battery, good starter generator, good voltage regulator.
Car parked, blocked, locked and rear end jacked up depress the go pedal completely to the floor. Test the voltage at the battery. The voltage should be around 14.0V to 16.0V Let off the go pedal so the car is at rest. Test the voltage at the battery. The voltage should be slightly higher than 12.0V If all of these voltages are in these ranges the battery may have simply drained down or the battery bad and in need of replacement. The voltage regulator is functioning properly and the starter generator is producing electricity. Solution: replace the battery.
Test #2: Scenario - good battery, good starter generator, bad voltage regulator
Car parked, blocked, locked and rear end jacked up depress the go pedal
completely to the floor. Test the voltage at the battery. Let off the go
pedal so the car is at rest. Test the voltage at the battery. When the car is running at full speed and at rest the voltage is virtually the same, slightly higher than 12.0V, the voltage regulator is bad. The voltage regulator has failed and is cutting off all power coming from the starter generator. Solution: replace the voltage regulator.
Test #3: Scenario - good battery, good starter generator, bad voltage regulator
Car parked, blocked, locked and rear end jacked up depress the go pedal
completely to the floor. Test the voltage at the battery. The voltage will be very high. Higher than 16V something like 19V or 20V. Let off the
go
pedal so the car is at rest. Test the voltage at the battery. The voltage is slightly higher than 12V. When
the car is running at full speed the starter generator is overcharging the battery. The voltage regulator is allowing all of the power to pass. The voltage regulator is bad.
The voltage regulator has failed and is allowing all power coming
from the starter generator to overcharge the battery. Solution: replace the voltage regulator.
Guide created: 07/18/08 (updated 08/18/08)
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