This is a 24 Volt Linak Battery replacement for the Pentair Paragon AquaTram battery powered pool lifts. The Linak brand batteries are identifiable by the metal tabs on the bottom of the battery.
You should always keep a second battery on-hand fully charged. To maintain the battery properly, the lift battery must be fully charged monthly. If the battery goes for longer than three months without a charge, the battery will have significantly reduced capacity.