ELECTRICAL 10 BATTERY TESTING Battery testing has two basic elements 1.Visual Inspection 2.State of Charge a.Specific Gravity b.Open Circuit Voltage 1. VISUAL INSPECTION Battery service should begin with a thorough visual inspection. This inspection may reveal simple, easily correctable problems. Check for cracks in the battery container and broken terminals. Either may allow electrolyte leakage and warrant battery replacement. Check for broken cable or connectors. Replace as needed. Check for corrosion on terminals and dirt or acid on the battery top. Clean the terminals – and battery top with a mixture of water and baking soda. A battery wire brush tool is required to remove hard scales if any on the terminals. Check for a loose battery hold-down or loose cable connection, clean and tighten as needed. 2.STATE OF CHARGE The state of charge of a battery can be easily checked in one of two ways a. Specific Gravity Test b. Open Circuit Voltage Test a. Specific Gravity Test Procedure Wear suitable eye protection. Remove vent plugs from the battery cells. Squeeze the hydrometer bulb and insert the pickup tube into the cell up to the plate’s top. Slowly release the bulb to draw in only enough acid to cause the float to rise. Do not remove the tube from the cell. Read the specific gravity indicated on the float. Be sure the float is drifting free, not in contact with the sides of top of the barrel. Bend down to read the hydrometer at eye level. Disregard the sight curvature of liquid on the float. Record your readings and repeat the procedure for the remaining cells. Specific gravity varies with the temperature. If the electrolyte temperature is substantially above 27OC add seven points (0.007) to the observed specific gravity reading for every 10OC by which the actual temperature is above 27OC. Deduct seven points per 10OC where the observed reading is below 27OC to obtain the temperature corrected reading at 27OC. Eg, for observed gravity 1.240 at 35OC, true gravity is 1.240 + (0.007/10 X 8) = 1.2456 at 27OC. Specific gravity should not be measured immediately after topping up a cell as the added distilled water will not have diffused enough and gives a false reading. A charge for sixty minutes or more after topping up will mix the electrolyte and allow accurate readings to be taken. NOTE If there is insufficient electrolyte in the cells to obtain a hydrometer reading, tilt the battery at 30 deg angle to one side to increase the electrolyte over the plates. If the level is still low, top up all cells with distilled water and mix by charging the battery to attain full charge. Then take specific gravity readings, applying temperature correction if the battery has become hot due to charging, and continue according to the battery testing procedure. b. Open circuit Voltage A digital multimeter must be used to check the battery’s Open-circuit voltage. Turn the headlamps high beam for 30 sec to remove any surface charge. Turn the headlamp off, and connect the digital voltmeter across the battery terminals. Read the volt in the multimeter. A fully charged battery will have an open circuit voltage of 12.60V. DE-MINERALIZED WATER TOP UP PROCEDURE: Open the vent caps and look inside the fill wells. Check electrolyte level. The minimum level is at the top of the plates. If necessary add just enough water to cover the plates at this time. Put batteries on a complete charge before adding any additional water Once charging is completed, open the vent caps and look inside the fill wells. Add water until the electrolyte level is 1/8" below the bottom of the fill well. Clean, replace and tighten all vent caps.
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