Types Of Charger.
There are many battery chargers available. You should be sure to use a battery charger which is designed for motorcycles, a car charger will deliver too much charge.
Trickle chargers charge the battery continually at a fixed rate. However, they require a watchful eye as they do not have a way of responding when a battery is fully charged. Leaving them to charge excessively can damage the battery.
Taper chargers decrease the amount of current delivered through the battery as the voltage rises. As with trickle chargers they require a watchful eye to avoid overcharging. Both taper and trickle chargers are slow.
Pulse or intelligent chargers monitor and collect feedback from the battery's voltage during the charging process and drop into a standby mode once the battery is fully charged. When the battery naturally discharges to a certain level the charger will go into charging mode and restore the battery to its normal charge. A pulse charger can be left unattended for long periods of time, but you should still carry out periodic fluid level checks.
Charging
Never user a normal car battery charger to charge a motorcycle battery, even for a short time. Car chargers supply far more current than a motorcycle battery can cope with and can very quickly damage the battery plates beyond repair.
Charging is best done with the battery removed from the bike. Conventional and Yumicron batteries should have the plugs carefully removed from top of each cell. When you have removed the battery from the bike and placed it on a level surface it's probably worth giving it a clean, paying particular attention to the terminals and the area between them as any build up of of conductive material between the terminals could lead to current leakage. Bicarbonate of soda and water applied with a toothbrush can be quite effective, but make sure you leave the battery perfectly dry when you're finished cleaning.
When charging the battery you should make sure the area is well ventilated to prevent the buildup of explosive gases. When connecting the battery and charger make sure the charger is turned off to reduce the chance of any sparks. Connect the battery positive-to-positive and negative-to-negative. Charge the battery according to the manufacturers recommendations. Practice caution if the battery becomes hot to the touch, as hot batteries can explode. If the battery does become hot, disconnect the charger and let the battery cool down before recharging.
Always wear safety goggles when working with batteries. Clean away any electrolyte on the outside of the battery. If you come to contact with the electrolyte, wash the effected areas for several minutes. If you get any in your eyes wash them immediately and contact a doctor.
The absolute maximum charge you should use on a motorcycle battery is about 1 amp. Use a voltmeter to test if a battery is fully charged by connecting the positive-to-positive and negative-to-negative, putting a low load (turning on the light and ignition) and taking a reading at the battery. With a 12 volt battery you should expect at least 11.5 volts DC, a 6 volt system at least 5.75 volts.