Here is the recent thread where this exact subject was discussed:
http://forum.ppcgeeks.com/showthread.php?t=35777
If you don't want to read through it, here's the summary: using wmwifirouter makes your battery
HOT. Like, really hot. And when your battery gets hot, it stops charging.
My solution: I take off the battery cover, slide the phone open, and place the phone HORIZONTALLY UPRIGHT in a little custom holder I made. This keeps the battery cool 99% of the time. In addition, you can set up a little fan that blows directly on the battery to keep it cool. This should solve your problem.