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Visually inspect for obvious problems: loose or broken alternator belt, electrolyte levels below the top of the plates, dirty battery top, corroded or swollen cables, corroded terminal clamps, loose hold-down clamps, loose cable terminals, or a leaking or damaged battery case.
If the electrolyte levels are low in non-sealed batteries, allow the battery to cool and add distilled water to ½ inch over the separator.
Recharge the battery to 100% State-of-Charge. If the battery has a difference of 0.03 specific gravity reading between the lowest and highest cell, then you should equalise it.
To equalise, increase the charging voltage, add 5%. Heavy gassing should start occurring. Take specific gravity readings in each cell once per hour. Equalisation has occurred once the specific gravity values no longer rise during the gassing stage.
- Maintenance free batteries
If the hydro-eye is showing red, charge battery until it reaches 12.8 volts.
Surface charge is the uneven mixture of sulfuric acid and water along the surface of the plates as a result of charging or discharging. It will make a weak battery appear good or a good battery appears bad. You need to eliminate the surface charge by one of the following methods
- Allow the battery to sit for between four to twelve hours to allow for the surface charge to dissipate
- Turn the headlights on high beam for five minutes, shut them off, and wait five to ten minutes
- With a battery load tester, apply a load at one-half the battery’s Cold Cranking Amps rating for 15 seconds and then wait five to ten minutes.
Revision still waiting for June to provide on Temperature Compensation and table.
Accessible: For Non-sealed batteries
Check the specific gravity in each cell with a hydrometer and average the readings. For sealed batteries, measure the Open Circuit Voltage across the battery terminals with an accurate digital voltmeter. This is the only way you can determine the State-of-Charge. Some batteries have a built-in hydrometer, which only measures the State-of-Charge in ONE of its six cells.
Maintenance Free: For Sealed Batteries
If the State-of-Charge is BELOW 75% using either the specific gravity or voltage test or the built-in-hydrometer indicates “bad” (usually dark), then the battery needs to be recharged BEFORE proceeding.
- If there is a .050 (sometimes expressed as 50 ‘points’) or more difference in the specific gravity reading between the highest and lowest cell, of an accessible battery you have a week or dead cell(s).
- If the battery will not recharge to a 75% or more State-of-Charge level or if the built-in hydrometer still does not indicate “good” (usually green, which indicates a 65% State-of-Charge or better), buy a new one.
- If a digital voltmeter indicates 0 volts, you have an open cell.
- If the digital voltmeter indicates 10.45 to 10.65 volts, recharge first. If the battery doesn’t recover you probably have a shorted cell. A shorted cell is caused by plates touching, sediment (“mud”) build-up or “treeing” between the plates.
If the battery’s State-of-Charge is at 75% or higher or has a “good” built-in hydrometer indication, then you can load test the battery by one of the following methods:
- Turn the headlights on high beam for a few minutes.
- With a battery load tester, apply a load equal to one half of the Cold Cranking Amps rating of the battery for 15 seconds. Battery voltage should not drop below 9.8 volts during the test period.
If the battery has passed the load test and after the load is removed, wait ten minutes and measure the State-of-Charge. The battery is okay if it has retained 75% State-of-Charge.
If the battery bounces back to less than 75% State-of-charge (1.225 specific gravity or 12.45 Open-Circuit-Voltage), then recharge the battery and load test again.
If the battery fails the load test a second time or bounces back to less than 75% State-of-Charge, then you should replace it because it lacks the necessary Cold-Cranking-Ampere power.
If the battery passes the load test, you should recharge it as soon as possible to restore it to peak performance and to prevent lead sulfation.