Mine had been doing that for a while too. Now that we've got our first sub-freezing day of the year, it won't start at all. I'm almost sure it's not the battery; all of my accessories come on. The engine clicks when I try to start it though. Alternator??
Take your battery somewhere and have it tested. It is mostly a bad battery.
01 gtp-big cam e85 dd 78dodge- guzzling fuel 05 cummins- rollin coal
SMGPFC Two Nipple General