If your clock uses "AA" or "AAA" batteries:

**When choosing the proper batteries for your clock, please consider the following information: There are many brands of alkaline batteries available on the market today, but there are several brands out there that just don’t perform well in clocks. We recommend using Rayovac or Duracell brand. Other brands, such as Energizer, have extra plastic coating on the negative end of the battery, which can cause clocks to malfunction or not work properly at all. Alkaline batteries are the only type of battery that should be used in clocks. Lithium powered or re-chargeable batteries will cause your clock to malfunction, or not function at all. Lithium and rechargeable batteries are meant for “high-drain” devices, such as digital cameras, etc. Alkaline batteries are best used in “low-drain” devices, which includes clock movements.

Corrosion is also an issue. Remove the battery and scrape the metal contacts inside the battery well. If you see corrosion, then clean it with a dry paste of baking soda and water and clean thoroughly.