18. Figure 39–4 Chemical reaction for a lead-acid battery that is fully charged being discharged by the attached electrical load. Continued
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20. Figure 39–5 Chemical reaction for a lead-acid battery that is fully discharged being charged by the attached generator. Continued
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23. Figure 39–6 As the battery becomes discharged, the specific gravity of the battery acid decreases.
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30. All batteries should be stored in a cool, dry place when not in use. Many technicians have been warned to not store or place a battery on concrete. According to battery experts, it is the temperature difference between the top and the bottom of the battery that causes a difference in the voltage potential between the top (warmer section) and the bottom (colder section). It is this difference in temperature that causes self-discharge to occur. In fact, submarines cycle seawater around their batteries to keep all sections of the battery at the same temperature to help prevent self-discharge. Always store or place batteries up off the floor and in a location where the entire battery can be kept at the same temperature, avoiding extreme heat and freezing temperatures. Concrete cannot drain the battery directly, because the case of the battery is a very good electrical insulator. Should Batteries Be Kept Off Concrete Floors?
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34. Every automotive battery has a limited service life of approximately three to seven years. During the life of a battery, the active material sheds from the surface of the positive plates. This gradually limits the power of the battery. This cycling also can cause the negative plates to become sulfated, which will also cause eventual battery failure. Excessive parasitic drains also can cause a battery to fail prematurely due to constant deep cycling of the battery. What Causes a Battery to Wear Out? NOTE: A battery becomes sulfated when lead sulfate ( SO 4 ) remains on the plates and does not return to electrolyte when the battery is charged.
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37. The capacity of any battery is determined by the amount of active material in the battery. A battery with a large number of thin plates can produce high current for a short period. If a few thick plates are used, the battery can produce low current for a long period. A trolling motor battery used for fishing must supply a low current for a long period of time. An automotive battery is required to produce a high current for a short period for cranking. Therefore, every battery is designed for a specific application. What Determines Battery Capacity?
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40. Figure 39-11 (b) Because battery acid was spilled and sprayed around the battery, the entire area was rinsed with water after unplugging the battery charger. What Can Cause a Battery to Explode? - Part 2
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49. Open circuit voltage is the voltage (usually of a battery) that exists without a load being applied. Dynamic voltage is the voltage of the power source (battery) with the circuit in operation. A vehicle battery, for example, may indicate it has 12.6 volts or more, but voltage may drop when the battery is put under a load such as cranking the engine. If battery voltage drops too much, the starter motor will rotate more slowly and the engine may not start. If dynamic voltage is lower than specified, the battery may be weak or defective or the circuit may be defective, resulting in too much current being drawn from the battery. Dynamic versus Open Circuit Voltage
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51. Figure 39–14 (a) A battery voltage of 12.28 volts is definitely not fully charged and should be charged before testing. (b) A battery that measures 12.60 volts or higher after the surface charge has been removed is 100% charged. (a) (b) Continued
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58. Figure 39–17 An alternator regulator battery starter tester (ARBST) automatically loads the battery with a fixed load for 15 seconds to remove the surface charge, then removes the load for 30 seconds to allow the battery to recover, and then reapplies the load for another 15 seconds. The results of the test are then displayed. Continued
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60. Many vehicles equipped with a diesel engine use two batteries. Usually these batteries are electrically connected in parallel to provide additional current (amperes) at the same voltage. How Should You Test a Vehicle Equipped With Two Batteries? - Part 1 Figure 39–19 Most light-duty vehicles equipped with two batteries are connected in parallel as shown. Two 500-A, 12-volt batteries are capable of supplying 1,000 amperes at 12 volts, which is needed to start many diesel engines. To successfully test the batteries, they should be disconnected and tested separately. If just one battery is found to be defective, most experts recommend that both batteries be replaced to help prevent future problems.
61. How Should You Test a Vehicle Equipped With Two Batteries? - Part 2 Figure 39–20 Many heavy-duty trucks and buses use two 12-volt batteries connected in series to provide 24 volts. Because the two batteries are electrically connected, a fault in one battery can cause the good battery to discharge into the defective battery, affecting both batteries even if just one battery is at fault.
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63. Figure 39-21 A conductance-type battery tester. (a) The up-and-down arrow keys are used to answer questions about the battery before it is tested. (b) This battery shows a calculated CCA of 729 amperes and a voltage of 12.37 volts. The display indicates that the battery is good, but should be charged before returning the vehicle to service. (c) A test code is displayed for warranty record-keeping purposes. (a) (b) (c)
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65. CAUTION: Always use a battery charger designed for absorbed glass mat (AGM) batteries because that type of battery can be damaged if charged above 15.5 volts. While AGM batteries can be charged at a high average rate (about 75% amp hour rating) the voltage must be lower than the conventional charger. Most batteries should be charged at a rate equal to 1% of the battery’s CCA rating . Continued CAUTION: Test results can be incorrectly reported on the display if improper, unclean connections to the battery are made. Also be sure the ignition switch and all accessories are in the off position.
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67. Always Use Adapters on Side-Post Batteries Figure 39–24 Adapters should be used on side-terminal batteries when charging. Side-post batteries require an adapter to be used whenever charging the battery if it is removed from the vehicle. If a bolt is threaded into the terminal, only the parts of the threads that contact the battery terminal will be conducting all of the charging current. An adapter or a bolt with a nut attached is needed to achieve full contact with the battery terminals.
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71. After the owner of a Toyota replaced the battery, the owner noted the amber “airbag” warning lamp was lit and the radio was locked out. It Could Happen To You! - Part 1 of 3 The owner had purchased the vehicle used from a dealer and did not know the four-digit security code needed to unlock the radio. Determined to fix the problem, the owner tried three four-digit numbers, hoping one of them would work. After three tries, the radio became permanently disabled. Frustrated, the owner went to a dealer. It cost over $300 to fix the problem. A special tool was required to easily reset the airbag lamp. The radio had to be removed and sent out of state to an authorized radio service center and then reinstalled into the vehicle. Before disconnecting the battery, please check with the owner to be certain that the owner has the security code for a security-type radio. A “memory saver” may be needed to keep the radio powered up when the battery is being disconnected.
72. Figure 39–27 (a) Memory saver. The part numbers represent components from Radio Shack. It Could Happen To You! - Part 2 of 3
73. Figure 39–27(b) A schematic drawing of the same memory saver. Some experts recommend using a 12-volt lantern battery instead of a small 9-volt battery to help ensure that there will be enough voltage in the event that a door is opened while the vehicle battery is disconnected. Interior lights could quickly drain a small 9-volt battery. It Could Happen To You! - Part 3 of 3
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83. A discharged or defective battery has lower voltage potential than a good battery that is at least 75% charged. A weak battery could prevent the charging voltage from reaching the voltage regulator cutoff point. This lower voltage could be interpreted as indicating a defective generator (alternator) and/or voltage regulator. If the vehicle continues to operate with low system voltage, the stator winding in the generator (alternator) can be overheated, causing alternator failure. Why Should a Discharged Battery Be Recharged or Replaced Before Further Testing?
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