Battery - Drain Testing

BATTERY - DRAIN TESTING

WARNING: Do not attempt this test on a lead-acid battery that has recently been recharged. Explosive gases can cause personal injury. Failure to follow these instructions may result in personal injury.

CAUTION: To prevent damage to the meter, do not crank the engine or operate accessories that draw more than 10A.

NOTE:
- No factory-equipped vehicle should have more than a 50 milliamp (mA) (0.050 amp) draw.
- Many electronic modules draw 10 mA or more continuously.
- Use an in-line ammeter between the positive battery or negative post and its respective cable.
- Typically, a drain of approximately 1 amp can be attributed to an engine compartment lamp, glove compartment lamp, or interior lamp staying on continuously. Other component failures or wiring shorts may be located by selectively pulling fuses to pinpoint the location of the current drain. When the current drain is found, the meter reading falls to an acceptable level. If the drain is still not located after checking all the fuses, it may be due to the generator.
- To accurately test the drain on a battery, an in-line digital ammeter must be used. Using a test lamp or voltmeter is not an accurate method due to the number of electronic modules.

Check for current drains on the battery in excess of 50 mA (0.050 amp) with all of the electrical accessories off and the vehicle at rest. Current drains can be tested with the following procedure.

1. Make sure engine compartment and interior fuse panels are accessible without turning on the interior and underhood lights.
2. Drive the vehicle at least 5 minutes and over 30 mph to turn on and activate the vehicle systems.
3. Allow the vehicle to sit with the key off for at least 45 minutes to allow the modules to time out/power down.
4. Connect a fused (15A) jumper wire between the negative battery cable and negative battery post to prevent modules from resetting and to catch capacitive drains.
5. Disconnect the negative battery cable from the post without breaking the connection of the jumper wire.

6. NOTE: It is very important continuity is not broken between the battery and the negative cable when connecting the meter. If this happens, the entire procedure must be repeated.

Connect the tester between the negative battery cable and post. The meter must be capable of reading milliamps and should have a 10 amp capability.

7. NOTE: If the meter settings need to be switched or the test leads need to be moved to another jack, the jumper wire must be reinstalled to avoid breaking continuity.

Remove the jumper wire.

8. NOTE: Amperage draw varies from vehicle to vehicle depending on the equipment package. Compare to a similar vehicle for reference.

No production vehicle should have more than a 50 mA draw.

9. If the draw is found to be excessive, pull the fuses from the central junction box (CJB) one at a time and note the current drop. Do not reinstall the fuses until you are finished testing.
10. If the draw is still excessive, remove fuses from the battery junction box (BJB) one at a time and note the current drop. Do not reinstall the fuses until you are finished testing.
11. Check the wiring schematic in the wiring diagram for any circuits that run from the battery without passing through the BJB. Disconnect these circuits if the draw is still excessive.