Battery: Testing and Inspection
INSPECTIONInspection:
Any of the following conditions can result in abnormal battery discharging:
1. Corroded or loose battery posts and terminal clamps.
2. A loose or worn generator drive belt.
3. Electrical loads that exceed the output of the charging system. This can be due to equipment installed after manufacture or repeated short trip use.
4. Slow driving speeds (heavy traffic conditions) or prolonged idling with high-amperage draw system in use.
5. A faulty circuit or component causing excessive ignition-off draw or "parasitic" draw.
6. A faulty or incorrect charging system component.
7. A faulty or incorrect battery. Before testing, visually inspect the battery for any damage (a cracked case or cover, loose posts, etc.) that would cause the battery to be faulty.
WARNING:
- IF A BATTERY SHOWS SIGNS OF FREEZING, LEAKING, LOOSE POSTS OR LOW ELECTROLYTE LEVEL, DO NOT TEST, ASSIST-BOOST OR CHARGE. THE BATTERY MAY ARC INTERNALLY AND EXPLODE. PERSONAL INJURY OR DEATH COULD OCCUR.
- EXPLOSIVE HYDROGEN GAS FORMS IN AND AROUND THE BATTERY. DO NOT SMOKE, USE FLAME, OR CREATE SPARKS NEAR THE BATTERY. PERSONAL INJURY OR DEATH COULD OCCUR.
- THE BATTERY CONTAINS SULFURIC ACID WHICH IS POISONOUS AND CAUSTIC. AVOID CONTACT WITH THE SKIN, EYES OR CLOTHING. IN THE EVENT OF CONTACT, FLUSH WITH WATER AND CONTACT A PHYSICIAN IMMEDIATELY. KEEP OUT OF THE REACH OF CHILDREN.
- IF THE BATTERY IS EQUIPPED WITH REMOVABLE CELL CAPS, BE CERTAIN THAT EACH OF THE CELL CAPS IN IS PLACE AND TIGHT BEFORE THE BATTERY IS RETURNED TO SERVICE. PERSONAL INJURY AND/OR VEHICLE DAMAGE COULD OCCUR.
ELECTROLYTE LEVEL
1. Check whether or not the electrolyte level lies between "UPPERLEVEL" line and "LOWER LEVEL" line.
2. If low, add distilled water to "UPPER LEVEL" line. Do not overfill.
HYDROMETER (SPECIFIC-GRAVITY) TEST
The hydrometer tests battery state-of-charge by measuring the specific gravity of the electrolyte. This test cannot be performed on maintenance-free batteries with non-removable cell caps. Specific gravity is a comparison of the density of the electrolyte to the density of pure water. Pure water has a specific gravity of 1.000, and sulfuric (battery) acid makes up approximately 35% of the electrolyte by weight, or 24% of its volume. In a fully charged battery the electrolyte will have a temperature-corrected specific gravity of 1.260 to 1.290. However, a specific gravity of 1.235 or above is satisfactory for battery load testing and/or return to service.
1. Measure specific gravity with a hydrometer. Refer to the instructions supplied with the hydrometer for recommendations on the correct use of the hydrometer.
BATTERY OPEN-CIRCUIT VOLTAGE TEST
A battery open-circuit voltage (no load) test will show the state of charge of a battery. This test can be used in place of the hydrometer test. Before proceeding with this test, make sure the battery is completely charged.
1. Before measuring the open-circuit voltage, the surface charge must be removed from the battery. Turn on the headlights for fifteen seconds, then allow up to five minutes for the battery voltage to stabilize.
2. Disconnect and isolate both battery cables, negative cable first.
3. Using a DVOM(Digital Voltage and Ohm Meter) connected to the battery post, measure the open-circuit voltage. Refer to the Open-Circuit Voltage table. This voltage will indicate the battery state-of-charge, but will not reveal its cranking capacity. If the open-circuit voltage reading is 12.4 V or greater, perform the load test.
BATTERY LOAD TEST
1. Disconnect and isolate both battery cables, negative cable first. Make sure the battery top and posts are clean.
2. Connect a suitable VAT Tester to the battery posts. Check the open-circuit (no load) of the battery. Open-circuit voltage must be 12.4 V or greater.
3. Apply a 300 Amp load to the battery for fifteen seconds to remove the surface charge from the battery, then allow the battery to stabilize for five minutes.
4. Apply a load equal to 50% of the CCA rating of the battery. After approximately fifteen seconds, check the loaded voltage reading, then remove the load.
5. The voltage drop will vary with the battery temperature at the time of the load test.
BATTERY IGNITION OFF DRAW TEST
The battery draw test refers to power being drained from the battery with the ignition switch in the OFF position. A normal electrical system will draw from five to twenty-five milliamps (0.005 to 0.025 ampere) with the ignition OFF and all non-ignition controlled circuits working properly. The 0.025 ampere is needed to enable the memory functions of the vehicle to function.
1. Verify that all electrical accessories are OFF. Turn off all lamps, remove the ignition key and close all doors.
2. Disconnect the negative battery cable.
3. Set a DVOM (Digital Voltage and Ohm Meter) to its highest amperage scale and connect the DVOM between the disconnected negative battery cable and the negative battery post.
4. If the amperage reading is higher that 0.025 ampere, remove each fuse until the amperage reading becomes within specifications, this will isolate each circuit and identify the source of the draw. If the amperage reading remains high after disconnecting each fuse, unplug the connector from the generator. If the amperage reading becomes within specifications, check the charging system.
5. After appropriate repairs have been made, retest the system.
VOLTAGE DROP TEST
The voltage drop test will determine if there is excessive resistance in the battery terminal connections or the battery cables. When performing these tests, remember that the voltage drop is giving an indication of the resistance between the two points at which the DVOM probes are attached. For example, when testing the resistance of the battery positive cable, connect one of the DVOM leads to the positive battery cable clamp and the the other cable connector at the starter solenoid. If you probe the positive battery terminal post and the cable connector at the starter solenoid, you are actually reading the combined voltage drop in the positive battery cable clamp-to-terminal post connection and the positive battery cable.
1. Connect the positive lead of the DVOM to the negative battery terminal post.
2. Connect the negative lead of the DVOM to the negative battery terminal cable clamp.
3. Turn the ignition switch to the start meter and observe the DVOM. If voltage is detected, correct the poor contact between the cable clamp and the terminal post.
4. Connect the positive lead of the DVOM to the positive battery terminal post.
5. Connect the negative lead of the DVOM to the positive battery terminal cable clamp.
6. Turn the ignition switch to START and observe the DVOM. If voltage is detected, correct the poor contact between the cable clamp and the terminal post.
7. Connect the voltmeter to measure between the positive battery terminal post and the starter solenoid battery terminal stud.
8. Turn the ignition switch to START and observe the reading on the DVOM. If the reading is above 0.2 V, clean and tighten the battery cable connection at the solenoid and repeat the test. If the reading is still above 0.2 V, replace the faulty positive battery cable.
9. Connect the DVOM to measure between the negative battery terminal post and a good clean ground on the engine block.
10. Turn the ignition switch to START and observe the DVOM. If the reading is above 0.2 V, clean and tighten the battery cable connection on the engine block and repeat the test. If the reading is still above 0.2 V, correct the faulty negative battery cable.
11. Connect the DVOM positive lead to the starter housing. Connect the DVOM negative lead to the negative battery terminal post.
12. Turn the ignition switch to START and observe the DVOM. If the reading is above 0.2 V, correct the poor starter to engine block ground contact.