Crazy electrical/battery issue

[Onefast96svt]

I installed my tow tune to tow boat to the beach Friday. I left programmer tuning while I went and showered after work. Came back out about 20 min later, programming was done , time to go. The truck turned over good but kinda fell off at the end before cranking like the battery was gonna die. Truck drove fine and the volts were up. We stopped one time on the way 2 mon from the house to fill the boat up. Cranked fine then, cranked fine the next morning to go put boat in but would not even turn over to get boat out. Jumped it and went home about 5 min away. Cut it off and ate dinner, then it cranked fine to go get batteries checked. Test came back and said main was good, secondary to charge and test and alt had a 6v drain with everything off. So...came home...the next morning it cranked fine. Stopped by to top off boat, cut the truck off, it wouldn't crank. Jumped it, and took off cables while on the boat, and of course it cranked good. I haven't had time to look at anything but I'm hoping its just a bad battery. What y'all think?

 

[ghohouston]

Bad batts, or alternator not charging properly, which in turn will kill your batts...

 

[Onefast96svt]

Alt is charging good. 12+ idle 13.5+ cruising. It's a chance it's a batt. Another forum mentioned checking ground on block too.

 

[ghohouston]

Okay. Yes checking all connections for tightness and corrosion is always a good idea

 

[Onefast96svt]

Checked battery's of course when it first happened. One Negative was snug and others were fine. I'll get it checked tomorrow before the trip home. Thanks!

 

[ghohouston]

Its funny how electrical gremlins are. Hell, I drove around with my pass. Side ground loose on the terminal because the bolt was stripped for like 2 years and never even had a problem

 

[loboost]

Sounds like bat batteries.

I had 1 bad out of a pair that were bought at the same time and less than a year old.

A few days on a low charge then a desulfator fixed it.