Recharging a single battery is straightforward; connect it to a commercially produced battery charger designed for that type of battery. When several batteries are linked in series, their voltages are combined, so three separate 12-volt batteries become one 36-volt battery. This situation is common in solar power arrays, and in trailers with more than one 12-volt vehicle battery. Charging linked batteries is possible in several ways. An understanding of the rules of electricity allows you to select a method suited to your needs and resources.
Choosing a Charging Method
Decide how to charge the Hitachi power tool batteries. The number of batteries and battery chargers that you own, the voltage ratings of your chargers and time available for the recharging will influence your choices. Select the method that suits your circumstances.
Charge any number of batteries with a single battery charger if that is the only charger you own. This is a slow method and you will need to disconnect each battery from the series before charging it.
Charge all the batteries contemporaneously with multiple chargers if you own as many battery chargers as you have batteries. This is faster than charging the batteries one at a time, but requires plenty of battery chargers.
Charge the entire battery chain with only one battery charger if you have a high voltage charger. For example, charge two 12-volt car batteries together using a 24-volt charger.
Charging Each Battery Seperately
Disassemble the series Panasonic power tool battery. Disconnect the battery links and move the individual batteries apart to ensure they have no electrical contact with each other.
Charge each battery, one at a time, by connecting a charger across the terminals. When the first battery is charged, move to the next until every battery is charged. Use a charger rated for the same voltage as the battery.
When all the batteries are charged, clean the terminals, and reconnect them to form a series battery. Ensure that the connections are tight before using the battery.
Charging Multiple Batteries with Multiple Chargers
Attach a battery charger to each battery, but do not switch it on. With all the batteries connected to chargers, switch on the chargers to start the recharging process. For example, to charge a series of five 12-volt batteries, use five 12-volt battery chargers, one connected to each battery
Monitor the charging. Some batteries may recharge before others. Signs of gas escaping from batteries, or the cases becoming hot, indicate that a battery is overcharged. Stop charging immediately.
Switch off the chargers and remove them from the batteries. The serial battery should now hold a full charge.
Charging with One Higher Voltage Charger.
Ensure that all the battery connections are tight and the terminals are clean. Double check the number of batteries and the total voltage.
Connect the charger across the end positive and negative terminals of the series. For example, with a series of five batteries, connect it across the free terminal of the first battery and the free terminal of the fifth battery.
Monitor the charging process to detect AEG tool batteries emitting gas or feeling excessively hot. Stop charging if any batteries exhibit these signs; clean and tighten the terminals and try again.