I have this Acer Aspire that suddenly decided not to "remeber" time and date after shut down. I've changed the battery, reinstall windows-ubuntu, bios rewrite...nothing helped. If the charger is connected, it doesen't forget the time after shutdown, but the battery holds power very well. Any clues pls?
Check the pins on the holder on the battery and make sure they are getting contact. Check the output on the battery you put in. Some of those batteries stay on the shelf for years and are dead even though they have never been opened.
CLOSING due to age... but please start another thread if you are still having problems , which I will answer promptly...