The Rapid Optimum Charger offers key advantages for Makita 18V Lithium-Ion cordless tool users. The exclusive built-in fan cools the battery (sold separately) by forcing air through the batterys air vents during the charging process for faster charging. The charger communicates with the batterys built-in chip throughout the charging process to optimize battery life by actively controlling current, voltage and temperature. The result is category-leading battery charge times, which means the battery spends more time working and less time sitting on the charger. (note: also charges 14.4V Lithium-Ion batteries)