- - AGRICULTURE CORE CURRICULUM - - (CLF2000) Advanced Core Cluster: AGRICULTURAL MECHANICS (CLF2800) Unit Title: EQUIPMENT OPERATION AND MAINTENANCE ___________________________________________________________________________ (CLF2805) Topic: BATTERY MAINTENANCE Time Year(s) 1 hour 1 / 2 / 3 / 4 ___________________________________________________________________________ Topic Objectives: Upon completion of this lesson, the students will be able to: Learning Outcome #: (Q-2) - Maintain battery water levels. (Q-3) - Use safe work habits while servicing, maintaining, and adjusting agricultural equipment. Special Material and Equipment: Tractor battery, battery hydrometer, clean rags, soft or distilled water References: Jacobs, C. O., & Harrell, W. R. (1983). AGRICULTURAL POWER AND MACHINERY. New York: McGraw-Hill. Cooper, Elmer L. (1987). AGRICULTURAL MECHANICS: FUNDAMENTALS AND APPLICATIONS. Albany, NY: Delmar Publishers. Resources: Deere & Company. (1984). PREVENTIVE MAINTENANCE (Fundamentals of Machine Operation (FMO) Series). Available from: John Deere Technical Services Evaluation: Quiz by instructor. TOPIC PRESENTATION: BATTERY MAINTENANCE A. Checking Electrolyte Level in a Battery 1. The lead-acid battery stores energy in chemical form in order to release electricity when needed, and its reliability depends on maintaining the proper electrolyte (water and sulfuric acid) level. 2. To check the electrolyte level, first clean the top of the battery off with a clean rag. a. Dirt or foreign matter on top of the battery can absorb moisture and cause excessive battery drain or voltage loss between the terminals by conducting small electrical charges across the battery top. b. Cleaning the battery top before removing the battery caps keeps dirt out of the battery cells. c. If the battery and terminals are covered with acid, clean them with a base solution of 1/4 pound baking soda to one quart of water. 2. Remove battery caps and check electrolyte level. a. Some batteries are transparent which allows the electrolyte level to be inspected without removing the caps. b. The electrolyte level should reach to the bottom of the vent plug's split ring. 3. If the electrolyte level is low, add clean, soft water. a. Distilled water is often recommended by manufacturers. b. Hard water contains minerals and impurities which can build up on the plates in the battery and reduce its life and performance. 4. If water is added in cold weather, run the engine for thirty minutes so that water will completely mix with the electrolyte to prevent freezing. a. Keep open flames and sparks away from batteries while charging because they give off an explosive gas, hydrogen. b. Use caution to prevent sparks when disconnecting and connecting battery cables by always disconnecting the grounding (negative) cable first and reconnecting it last. The black cable is negative (smaller post), and the red cable is positive (larger post). B. Checking the Level of Charge in a Battery 1. The level of charge in a battery can be found by measuring the specific gravity of the electrolyte in each battery cell. a. The specific gravity of pure water is 1.000. b. The specific gravity of sulfuric acid is 1.835. c. The specific gravity of fresh electrolyte is 1.270. d. A fully charged battery will have all the sulfates in the electrolyte and a specific gravity of 1.265. e. A discharged battery will have a reading of 1.120 because all the sulfates will have been deposited on the battery plates. 2. To take a hydrometer reading, first remove the battery caps. 3. If electrolyte level is too low, fill with soft or distilled water and run engine a few minutes to mix electrolyte. 4. Insert the hydrometer into one of the battery cell openings. 5. Squeeze the bulb and slowly draw electrolyte into the hydrometer barrel. 6. Hold the hydrometer vertically so the float does not touch the side of the barrel. Keep the hydrometer nozzle in the battery cell to keep from spilling acid on the battery or yourself. 7. Read the level of liquid in the hydrometer with your eye at the same height as the liquid. 8. Repeat the procedure for each cell. Record your results. Flush the hydrometer with clean water before storing it. 9. Correct the reading for electrolyte temperature. a. Add to the hydrometer reading .004 specific gravity per 10 degrees above 80 degrees Fahrenheit. b. Subtract from the hydrometer reading .004 specific gravity per 10 degrees below 80 degrees. 10. Record the corrected readings and identify the level of charge. a. 1.265 specific gravity = 100% charged. b. 1.225 specific gravity = 75% charged. c. 1.190 specific gravity = 50% charged. d. 1.155 specific gravity = 25% charged. e. 1.120 specific gravity = Discharged. _________________________________________________________ ACTIVITY: 1. Check the electrolyte level of a battery. 2. Take a hydrometer reading and determine a battery's charge. _________________________________________________________ 6/28/91 OLR/tf #%&C