Yes!... Replace that battery!
Lithium batteries are available through many catalogs and online sites.
They can be bought at your local Radio Shack store for under $20!
Radio Shack does not offer much anymore for hobbyists but they have
those batteries and there is usually a Radio Shack close by. Some of us
here (Including myself) replaced the original battery with a "AA" size
lithium cell and installed a double "AA" battery holder. The holder
has its lead wires soldered to the main board and the double holder
allows simple battery replacement in the future. There are threads
here that have all the details but I cannot find them.