My Celestron PowerTank is taking longer to charge and to show a fully charged light. Why?

PowerTanks use a lead-acid battery technology. These batteries start out new at 100% capacity in amp-hours. PowerTanks come in 7 amp-hour and 17 amp-hour capacities. 

As they age, the full capacity of the batteries decreases due to chemical and mechanical processes inside the battery cells. The ability to take a full charge of 100 percent of the original capacity is lost. It also takes longer to charge up due to the reduced capacity.

The PowerTank battery will also age more rapidly when repeatedly deep discharged–losing its capacity in fewer cycles than if not deep discharged. It is recommended to turn off the PowerTank when the yellow "Needs Charging" light comes on and to charge the battery after every use.

Your PowerTank will continue to hold a large part of its charge when fully charged, even though the fully charged light may not come on. And it will continue to be useful, though the runtime and amp-hours of the battery will be diminished. Replacement is a good idea when the runtime is short even after prolonged charging. When properly used, your PowerTank should last for years before it needs to be replaced. Always recycle the dead battery.

Additional, specific charging recommendations to prolong the life of an idle or stored PowerTank are provided in the instructions that come with your PowerTank.


Updated 10/29/13