If you have been using them for a week or more, it may be time to CLEAN the batteries. Get some 99% alcohol, wet a rag, and twist it firmly around the threads until they are clean. Then use a safety pin and insert the sharp tip into the connector end of the battery and just under the rim you will get some black gunk to come out. Next, use the sharp tip to poke through the air holes in the threading until those are clear. Finally, wipe down the outside of batteries and let them sit for about 30 minutes. Charge and try it again. Will work like new.