Walter Mundstock

Hi all. This is my first post on this forum. I am struggling with an issue on a MZ-N10 with internal battery. The device has the LIP-3WMB li-ion battery, and when I place it into the creddle, it will charge the battery as it would normally do. Displays the remaining charge time (usually around 1 hour), and keep charging until the time remaining reaches zero and then turns itself off. So far so good, but after its completely charged, I turn it on and after about 10-20 seconds battery status indicator start decreasing. It will gradually decrease until it gives me the Low Bat indication and then shut down - this takes about a minute or two. From my understanding a li-ion battery, when dead, wont charge at all. They call this a "sleeping" battery, but this doesn't seem to be the case as the battery will charge normally. I tried to completely discharge the unit by turning it on multiple times until it barely show the "Low Bat" sign. Then recharge it completely (around 70 minutes as per display). So my questions are: Can this, alone, indicate the battery is dead? Could this be some sort of resistence in the contacts? How would you recommend a cleanup (not sure a contact cleaning spray would do it). Any suggestion of other things I could try BEFORE trying to replace the battery? Thanks. Walter