The optional NiMH batteries and charger will save you money in battery replacement costs. Standard alkaline batteries will operate the caller for 18 to 24 hours, depending on the volume used, before battery replacement is necessary.
 
The NiMH batteries offer a run time of about 85% of that of the alkaline batteries. Instead of throwing the exhausted alkaline batteries away, the NiMH batteries are simply recharged in place by connecting the wall charger to the caller. The charge time is about 14 hours for totally depleted batteries.
 
The NiMH batteries can be recharged hundreds of times and do not suffer from “memory” problems, as do some NiCad batteries.

$19.95