Cordless tool battery chargers replenish the power of depleted tool batteries so that the batteries can be reused. They work with batteries of the same brand and a compatible voltage and battery chemistry/type (Li-Ion, NiCd, or NiMH). They have one or more ports for connecting batteries to the charger. An indicator on the charger confirms that a battery is charging. Charging at room temperature helps batteries get an optimal charge. Charge times differ based on the charging rate in amps (A) of the charger, with higher amps delivering a faster charge. They also differ based on the amp-hour (Ah) rating of the battery, with higher Ah batteries taking longer to charge. For example, it takes a 6A charger about one hour to charge a 6Ah battery and about half an hour to charge a 3Ah battery.