The USAlert NiMH Rechargeable Batteries are the primary power source for both the WatchDog and WatchDog LT Voice Pagers. Three individual “AAA” sized NiMH (Nickel Metal Hydride) rechargeable batteries, rated at 1100 mA/hr, come standard with the WatchDog pagers. The NiMH battery type is designed to be used in small electronic devices that are used frequently and require a strong energy source. Replacement battery pricing is for a pack of three "AAA" cells.

Battery life may be reduced after 12-18 months of use as any rechargeable battery won’t last forever. To maintain optimum pager performance, replace batteries at regular intervals with new ones having the same 1100 mA/hr capacity. Inferior or lower capacity batteries have been found to create a number of performance issues. Normal charging should take approximately 2 hours and you can charge a spare set of batteries in the charger while also charging the pager.

On fully recharged batteries, the WatchDog pager with the latest firmware will operate in Selective Call mode (or standby mode) for 48 hours or 6 days at 8 hours per day, based on the industry standard of (5) thirty second calls per 8 hour day. When listening to a channel in Monitor mode, battery life is 39 hours based on a 10% carrier active / 90% carrier inactive duty cycle. When in Scan mode, battery life can range from 46 hours in Selective Call Scan, 31 hours in 2 Channel Scan, and 28 hours in 5 Channel Scan, again all based on the 10 / 90% duty cycle. Battery life will obviously vary, depending heavily upon the activity of the monitored channel(s).