I am using rechargeable batteries with my Celestron GoTo mount, and the mount will not power up even though the batteries are new and fully charged. What’s the problem?

Most likely it’s because the NiMH (nickel metal hydride) or Ni-cad (nickel cadmium) batteries are not providing enough voltage because of their chemistry.

Celestron go-to mounts need 12V (direct current) power to work at their best. Voltages that are too low may turn on the hand control but will either not run the motors or lead to erratic behavior. Voltages that are too high can damage the electronics or even cause burning of the circuit boards.

The voltage delivered by a single cell (often the same as the battery) is determined by the chemical reaction in the battery. Lead-acid cells (used in cars, boats and motorcycles, as well as in Celestron PowerTanks) deliver about 2.1V each. To deliver 12V, they are hooked up in series or series parallel arrangements of six or more individual cells. Alkaline batteries are single cell and deliver 1.5V. Rechargeable NiMH and Ni-cad batteries only provide 1.2V per battery.

Eight AA alkaline batteries give 12V, while 8 AA NiMH or Ni-cad batteries only give 9.6V. This may simply not be enough to turn on the hand control electronics or power up the motors in your mount. You need to switch to alkalines, a PowerTank or use an AC adapter.

Updated 12/14/13