Per the Manufacturer: The Hitachi UC18YRL Universal Battery Charger is designed to recharge the Hitachi EBM1830 HXP Battery. And for added flexibility and convenience, this charger can also recharge other compatible 7.2-18 volt, Lithium-Ion, NiCd and NiMH batteries. It is important to fully charge your battery before attempting to use it in your power tools. To use your UC18YRL charger properly, connect the charger power cord to the base and then insert the battery into the charger. Position the battery so that the nameplate faces toward the nameplate of the charger and press the battery into place until it comes into full contact with the bottom plate. Inserting the battery turns the charger on, and the pilot lamp should light up red. If the pilot lamp does not light up, pull out the power cord from the base and check the battery mounting condition. Once your battery is fully charged, the pilot lamp will slowly blink red and you're battery will be ready to use. In general, the UC18YRL should charge your battery in 20-45 minutes depending on the type of battery (the Hitachi EBM1830 charges in 45 minutes). Although the variation is minor, ambient temperature above or below room temperature may effect recharging time.

Added flexibility and convenience allows this charger to recharge other compatible 7.2-18 volt Lithium Ion NiCd and NiMH batteries.

Universal charger charges 7.2 volt to 18 volt Hitachi Lithium-Ion batteries as well as NiCd and NiMH batteries of same voltage.

HXP batteries have a low power discharge while in storage.
Recharging New Batteries: What to Expect
The internal chemical substance of new batteries and batteries that have not been used for an extended period is not activated, thus the electric discharge might be low when using them the first or second time. This is a temporary phenomenon and is not cause for alarm. The normal time required for recharging will be restored by recharging the battery 2-3 times.
How to Make Your Battery Perform Longer
The best way to take full advantage of your charger, and maximize the life of your battery, is to follow two easy steps. First, remember to recharge your battery before it becomes completely exhausted. When you feel that the power of the tool becomes weaker, stop using the tool and recharge the battery. If you continue to use the tool and exhaust the electric current, the battery may be damaged and its life will become shorter. Secondly, you should always avoid recharging your batteries at high temperatures. A rechargeable battery will be hot immediately after use. If a battery is recharged while it's still hot, its internal chemical substance will deteriorate, and the battery life will be shortened.