8 Alternator (Generator) Charging system workhorse
9 Battery PurposeSupplies all electrical power when the charging system is not operatingActs as a voltage stabilizer for the charging systemProvides extra current for short periods of time while the charging system is catching up to a new load
11 Battery RatingsIn North America, the Society of Automotive Engineers established two ratings for domestic made batteries:cold cranking amps, which indicate the number of amps a battery can deliver at 0° F for 30 seconds and stay above 7.2 voltsreserve Capacity, which indicates the number of minutes a fully charged battery at 80° F can deliver 25 amps and stay above 10.5 volts.
13 Voltage A typical battery has six cells. The cells are connected in a series configuration.Each cell generates approximately 2.1 voltsThis equates to each battery having an actual voltage of 12.6 volts.
14 Battery Construction Each cell contains a series of lead plates. Some lead plates are positive (lead dioxide) in charge and some are negative (lead).The plates are kept from touching by a porous separator material, usually plastic or fiberglass.
15 Battery ConstructionA battery produces electricity during the chemical reaction between the lead plates and the electrolyte.The electrolyte is 36% water (H2O) and 64% sulfuric acid (H2SO4) when the battery is fully charged.
16 Battery ElectrolyteBattery electrolyte is measured by its specific gravity.Specific gravity is measured with a hydrometer.The specific gravity of the battery electrolyte correlates to its state of charge. Specific Gravity measurements must be temperature compensated.A fully charged battery will have a specific gravity of at 80 degrees Fahrenheit.
18 Batteries today can have a built in hydrometer to measure the specific gravity or state of charge in the battery. Built in hydrometers show colored dots that are either:Green – 65% or better chargedBlack – must charged before testingClear – low electrolyte level, discard battery
19 Maintenance Free Batteries Most batteries today are said to be maintenance freeThese batteries do NOT have removable caps on the top.These batteries have an open chamber under the lidCalled a liquid/gas separator
20 Batteries Check electrolyte specific gravity with a volt meter. 12.6 V = a fully charged battery12.4 V = 75% charged12.2 V = 50% charged
21 There are many new types of batteries on the market today One of these is the absorbent glass mat battery or AGM battery.This battery contains absorbent mat separators that prevent the electrolyte from leakingThis reduces the effects of vibration, which extends battery life.
22 Battery OperationDuring the generation of electricity the battery discharges.During discharge the positive and negative plate surfaces become sulfated causing the battery to lose voltage.
23 As the battery discharges, a chemical reaction occurs The oxygen molecules from the positive plate’s lead dioxide (PbO2) are released into the electrolyteThe electrolyte absorbs the oxygen molecules and releases it’s sulfate moleculesThis causes the positive and negative plates lead (Pb) to gain sulfate molecules (SO4 )both of the plates are changing to lead sulfate (PbSO4)the electrolyte’s acid is changing to water (H2O).As the battery is recharged the reaction is reversed.
27 Battery Discharge Conditions Starting a vehicleWhen the demand of the electrical system exceeds the output of the generator (usually at idle)Using powered accessories while the vehicle is not running.Battery or vehicle storageNormal battery drain (parasitic draw)ClocksRadio station presetsComputer memory
28 Other conditions that can result in a discharged battery include… excessive parasitic drainbattery malfunctionsstarting and charging system malfunctions
29 Battery ChargingWhen the engine is running at sufficient speed, the generator in the charging system supplies current to the battery. In this condition, the battery is said to be charging.
30 Battery ChargingWhen a battery is nearly or completely discharged, recharging is required for the battery to provide proper service.
31 Battery ChargingAlways charge a battery with the vehicles ignition OFFAlways wear safety glasses!
32 Battery ChargingWhen a charger is first connected to a completely discharged battery, the battery accepts only a small amount of current.As the battery becomes more charged, electrolytes begin to return to sulfuric acid, therefore increasing the charge rate. The charge time for a completely discharged battery may be more than twice as long as that for a half-charged battery.
33 Battery ChargingIf you must recharge a battery that’s in the vehicle, make sure that the ignition switch is in the OFF position.If the ignition is not in the OFF position, damage to the vehicles electronic equipment may occur.A battery should be charged at no more than 10% of its CCA rating.
35 Storing BatteriesWhen a battery is new the lead and acid will begin to react and it will slowly discharge.Any battery that sits unused for several months will slowly go dead and begin to sulfate.This will ruin the battery..All batteries should be periodically recharged.New batteries, awaiting sale, are given a “trickle charge” (2 - 4A) on a regular schedule
37 Battery Cables Large enough to carry all current demanded Large cable goes directly to the starterCables for 12-volt systems are usually 4 or 6 gaugeCable clamps are made of steel or lead
38 Battery Hold-downs Battery must be held in its tray Excessive vibration can harm the batteryHolddowns are made of steel or plastic
39 Reasons for Battery Failure Damaged battery case can leak electrolyteUndercharging can cause sulfationOvercharging can cause buckled/warped platesVibration can cause more material to be shed from platesShort between the plates can cause a dead cellAge (batteries are good for three to six years)
40 Hybrid and Other Battery Types Other types of batteries include:Nickel metal hydride batteriesLithium-ion batteriesHybrid battery voltages range 200 – 500 voltsThis can kill you!Be careful!Do not work on a hybrid until you have been schooled!