Charging and Discharging

   DISCHARGING AND CHARGING OF BATTERIES

            A.        Discharging

Fully discharging a battery, once or twice, would not necessarily damage the battery, but by repeating this, permanent damage would result.  The rating given by battery manufacturers is 20 hours of up to an 80 % discharge.  A fully charged 96 amp hour battery, will thus deliver 4.8 amps at ambient emperature for 20 hours, before it is 80 % discharged (11.2 volt). When using the battery at 10 amps instead, your battery life reduces to approximately 8.5 hours, instead of the calculated 9.6 hours.  This graph will get worse as the required current increases.

            B.        Recharging

What applies for discharging goes for charging.  If you repeatedly overcharge your battery, it will be damaged.  The recommended battery charge rate is - Capacity / 10 for 15 hours.  A normal vehicle battery can be charged up to a value of 2.35 volt per cell (14.1volt) and a leisure battery up to 2.4 volt per ; cell, which is 14.46 volt. Automotive batteries can be subjected to ‘boost’ charging whereas deep cycle batteries do not lend themselves to this type of charging. Suggested batteries to use with specific power requirements.  (This rating is given on the continuous power rating).

With the exception of sealed, gel cell batteries, lead-acid batteries emit hydrogen oxygen gases as well as sulphuric acid fumes when recharging.  It is advisable to vent the battery compartment to prevent accumulation of such gases and advisable not install electronic or electrical equipment in the battery compartment.

WARNING:

• Do not smoke or carry an open flame when working around batteries.

The capacity of lead-acid batteries is temperature-sensitive.  Battery capacity is rated at 25 ° C (77 ° F) .  At -20 ° C (0 ° F) the ampere-hour capacity will be about half the rated capacity.

• Do not leave batteries in a discharged state for more than a day or two. They will undergo a chemical process called sulphation which can permanently damage the battery.  In addition, the batteries will tend to self-discharge over a period of 3 to 6 months, so they should be periodically recharged-even if they are not being used,

• If your batteries are not the "maintenance-free" type, check the electrolyte fluid level at least once a month.  Use only distilled water to replenish the electrolyte fluid. Excessive fluid loss is a sign of over- Charging
• Connections to battery terminals 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 an insulating spray coating or Vaseline lubricant.
• Battery state of charge can be measured with a hydrometer or, more easily, with a voltmeter.  Use a digital voltmeter that can display tenths or hundredths of a volt when measuring 10 to 30 volts.

Take your measurements after the (12 volt) battery has not been charged or   discharged for several hours.  For a deep-cycle battery at 25 ° C (77 ° F), the following table may be used:

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