A car battery charger generally has an output of 4,6 or 8 amps, and can be plugged into the mains to recharge a 6 or 12 volt battery. It includes an ammeter to register the charge, and may have an overload control to prevent a blown fuse.
Unless a battery is very flat, it is normally charged after 18-24 hours. The charger shows a high reading at first, then trickles at 1-2 amps.
A battery to be charged should be clean and topped up. Remove individual cell caps, but leave a trough cover in place. Use in a dry place off the floor, and make sure the cooling vents are not obstructed.
A battery charger or recharger is a device used to put energy into a secondary cell or rechargeable battery by forcing an electric current through it.
The charging protocol depends on the size and type of the battery being charged. Some battery types have high tolerance for overcharging and can be recharged by connection to a constant voltage source or a constant current source; simple chargers of this type require manual disconnection at the end of the charge cycle, or may have a timer to cut off charging current at a fixed time. Other battery types cannot withstand long high-rate over-charging; the charger may have temperature or voltage sensing circuits and a microprocessor controller to adjust the charging current, and cut off at the end of charge. A trickle charger provides a relatively small amount of current, only enough to counteract self-discharge of a battery that is idle for a long time. Slow battery chargers may take several hours to complete a charge; high-rate chargers may restore most capacity within minutes or less than an hour, but generally require monitoring of the battery to protect it from overcharge. Electric vehicles need high-rate chargers for public access; installation of such chargers and the distribution support for them is an issue in the proposed adoption of electric cars.
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A high charging rate If the charging rate is much more that 4 amps, take off the cell caps...