What is the 3v lithium battery for

aaron, I think there are a few things that are mixed up. The 3V battery is your RTC battery. This battery powers a chip called the Real Time Clock (RTC) chip. The RTC is like a watch that runs all the time powered by that battery, whether or not the computer has power. When the computer boots up, it queries the RTC to get the correct time and date. RTC batteries normally last from 3 to 5 years. That is what keeps your system date/time,setup and other things alive when your computer is off etc., it is not a 6cell battery. The only 6 cell battery that you may have is the laptop battery itself, but that one is not 3V. No, the RTC battery is not responsible for your mouse not working.