I have been using AXIM X5 for last 2 months and had no problems, recently i did not use it for 2-3 consecutive days, main battery drained from 100% to 0%, resulting in back up battery going dead.
I was told by the Dell Tech Support that the main battery should not be allowed to go below 50% charge, I ended up with losing all data and replacing a new back up battery (CR 2032). I have had to change back up batteries 3 times and they are covered under warranty only for 30 days.