I was recently experiencing terrible performance of the handset battery for my cordless Panasonic KX-TG2730S (or KX-TG2730) telephone. I searched the user manuals and the Panasonic website for a solution but could not find one. So I called Panasonic at 1-800-211-7262 to see if there was anything I could do to fix the problem. They told me to follow this process to reset the NiCad battery memory:

Press the 2, 5, 8, and 0 buttons on the handset simultaneously.
Remove the handset battery.
Replace the handset battery.

After that they said the battery charge indicator should show only one bar, but mine showed three. I think it may be fixed anyway. If it doesn't keep its charge longer they said I will have to replace the battery, which isn't covered by their warranty.

Just thought you'd like to know. :)