What's confusing is I used to be able to talk for at least 30 minutes with out any problems and that was with an older, lower capacity battery. The issue seemed to show up after the two Motorola's were programmed this last time. We added some frequencies, checked the power output to a dummy load, and also checked the frequency alignment. Everything looked good. I'm wondering if the CDM 1550 LS+ series has an internal adjustable set point for the low voltage alarm? Maybe that inadvertently got changed to a higher voltage number. Does that sound reasonable? I have also been considering what you are suggesting with a duel battery set up, more so for emergencies than just my convenience.