Those Uniden battery packs are the worst. I have a pair of 245XLTs and have been thru 4 battery packs. You're not alone in your suffering.
I modded mine to accept regular AA batteries. I use alkaline but rechargeables should work as well. I don't plug in the AC adapter while running on AA batts for fear that Something Bad might happen.
The modification is fairly simple. You just need an Altoids tin (or something similar, to cut conductive strips of metal from), a couple small bits of cardboard, a sacrificial battery pack to cut the wire leads and connector from, and minimal soldering skill. You can probably Google the instructions.