Chargers for cordless tool batteries restore the power of drained batteries, allowing them to be reused. They are compatible with batteries of the same brand, voltage, and chemistry/type (Li-Ion, NiCd, or NiMH). They have one or more ports where batteries can be connected to the charger. The charger's indicator confirms that the battery is charging. Charging batteries at normal temperature ensures that they receive the best possible charge. Charge times vary depending on the charger's charging rate in amps (A), with larger amps offering a faster charge. They also differ according to the battery's amp-hour (Ah) rating, with greater Ah batteries taking longer to charge.