M4 Sealed Lead Acid Battery (12 VOLT 8 AH AGM) For M4 $24.99
This workhorse battery provides enough power to pump up to 200 gallons per charge. Four hours continuous use. Does not need to be charged during the average working day. No memory effect - 300% more energy per dollar than lithium or NIMH batteries. Changing batteries only takes a few seconds via M4 battery door. The latest M4 design no longer requires attaching wires. Just push the battery into the battery compartment where the J2 posts engage the built in spring plates.