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Battery Tips
36
Discharged Batteries
Do not leave batteries in a discharged
state for more than a day or two. They will undergo a
chemical process (sulfation) that can permanently damage the
battery. As well, batteries self-discharge over a period of
three to six months, so they should be recharged periodically
even if they are not being used.
Electrolyte Level
If your batteries are not the “maintenance-
free” type, check the electrolyte level at least once a month.
Excessive fluid loss is a sign of overcharging. Replenish the
electrolyte using distilled water only.
Battery Connections
Connections to battery posts must be
made with permanent connectors that provide a reliable, low-
resistance connection. Do not use alligator clips. Clean the
connections regularly and prevent corrosion by using a
protective spray coating or vaseline.
Battery State of Charge
You can measure battery state of
charge with a hydrometer or, more easily, with a voltmeter.
Use a digital voltmeter than can display tenths or hundredths
of a volt when measuring 10 to 30 volts. Make your
measurements when the battery has not been charged or
discharged for several hours. For a deep-cycle battery at
77º F (25º C), use the following table:
Battery Voltage State of Charge
12.7–13.0 100%
12.5–12.6 80%
12.3–12.4 60%
12.1–12.2 40%
11.9–12.0 20%