Battery life fix from 2,5 hours to 5,5 hours!
I bought a used folio and in the original OS it had battery life of 2,5 hours after couple of complete charges. I then installed ICS CM9 and no change in battery life, the device shut itself off after 2,5 hrs.
Well after Googling I decided to try the battery stats reset in CWM. After 100% charge I did the battery stats reset in CWM and went to ICS to test the battery. After about 2,5 hours battery meter was showing 6%. 3hrs still 6%. 4hrs still 6%. 5hrs still 6%. Only after about 5,5hrs it dropped to 5% and about 15mins after that it was 1% and my device shut itself off. What an improvement! And I was using wlan and watching videos etc practically the whole time!
To fix the battery meter showing 6% for several hours I have used the device many times from 100% to lower than 6% and then charging the folio with power on. Now it shows 6% only for 45mins or so and I bet after couple more cycles it will be perfect! Then ill run it to 0% once more to be sure to make use of the whole battery.
So before you buy a new battery this is definately worth a try.
PS. You don't want to drain the battery to 0 % very often because this too will have a negative effect on battery life. Maybe once every 20 cycles is ok.