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Battery School

General Battery Care Procedures

General deep cycle battery care procedures

Reasons Why Batteries Fail

General Difference Between Gel and Wet Batteries

State of Charge and Sulfation

Connect Your Batteries for Optimum Efficiency

Just A Little Corrosion Causes Big Voltage Drops

Don't Be Misled By Battery Ratings

Which Deep Cycle Battery Do I Choose?

Daily Amphere-Hour Consumption For Your RV

Safety Tips on Charging Batteries

Determining When A Battery is Fully Charged

Why Are My Batteries Discharged

What is the difference between series battery connections and parallel battery connections and how do they increase battery capacity and voltage?

Jump start procedures
  1. Before attempting to jump start the car, it is important to use safety glasses. Measure battery terminal post voltage with a volt meter to determine if battery has a shorted cell. A car should not be jump started if the battery has a shorted cell. The voltage at the shorted battery remains about two volts low even with the jumper cables connected. Attempts to jump start the car could result in damaged computer memories or alternator damage from voltage spikes from the source battery. Using jumper cables and jump starting should be the last resort.

    Background:  A reading of 11.89 volts(0% charge) indicates the battery state of charge and a shorted cell may not exist in the battery. Compare the actual reading obtained to the BATTERY VOLTAGE vs. STATE OF CHARGE CHART to determine the battery’s state of charge shown below. Readings below 12.45 volts indicate low state of charge and might be the reason the battery cannot crank the engine. A reading of about 10.55 volts(4.22 for six volt batteries), indicates the battery may have a shorted cell and should be replaced.

    12.66 VOLTS   100% CHARGED
    12.45   75
    12.18   50
    11.97   25
    11.76   0

  2. Place the source car (good battery) close enough to the dead car so that jumper cables can reach between the batteries without stretching too tight.  The jumper cables should be long enough and the cars close enough so the jumper cables have plenty of slack.  Do not let car bumpers touch each other. Wear protective eye glasses. Do not attempt to jump start a car if gasoline fumes are present around either the source car or the car with the dead battery.

  3. Turn the source car off before making any jumper cable connections between the two batteries. Having the source car OFF lowers the voltage on the source battery voltage. The lower voltage helps reduce the amplitude of voltage spikes generated when jumper cables are connected to the dead battery. Make your last connection be the ground on the car being jumped and maximize the distance of this connection from the positive terminal.

    Background:  Avoid voltage spikes at the battery terminals. Voltage spikes are generated when jumper cables or battery charger cables are connected to the battery terminals of a weak or dead battery.  These voltage spikes can shock computers memories and alter information stored in sensitive memory chips inside computers.  The most sensitive memory chips are called EEPROMs (Electrically-Erasable PROMs) or NVM chips (Non-Volatile Memory).

Preparing your batteries for winter

Advantages and Disadvantages of using two 12 volt batteries connected in parallel or two 6 volt batteries connected in series.

Testing the battery