Has anyone successfully built a working diy rechargeable battery? I ordered some aaa rechargeable ni-mh batteries, sacrificed an original pronto battery back for the diode (never saw any fuse anywhere) and a simple 4 aaa battery holder. By trimming down the battery holder slightly it all fits properly in my TSU7000 however it literally stays at 50% and doesn't last long at all. It says it's charging on the base, but I don't know that it is. I've tried charging the batteries externally on a ni-core charger and get the same results. Any suggestions?