For quite awhile now I have been having a problem with my batteries dyng or not working at all. It seems the problem is that the posts corrode and the batteries won't take a charge. The other part of the problem is that when they corrode the cables tend to loosen and the engine starts and stops.It was rather embarrassing the day it felt as if the reverse gear went out and the rig was jumping when backing. I had it towed in and the dealer cleaned the posts and it worked great,for awhile.I have a battery brush and clean the posts when they start to look bad and have tried the goop,monkey s**t and the red goop,but nothing seems to work.The other day as we were getting ready to hook up and leave the campground with the trailer,it wouldn't start,dead battery,so I got a jumpand no way... Called the road service and waited for them and ,again,no way..I had cleaned all the terminals before the help arrived..Pulled them apart and put them back and another guy brought his 25AMP Wal-mart special charger over and in 15 minutes,it started(I now own one of those)
Any suggestions on making sure this doesn't happen again or why it's happening every several months.. It also happened in Moab this summer in 105 degree heat,so I don't think living in the dry (?) corner of the US specifically causes it..

 

Have you tried a corrosion preventer? I just spray the terminals every once and a while and it helps keep the corrosion at bay. Its a cheap thing to try.

Amazon.com: Permatex 80370 Battery Protector, 6 oz Aerosol can: Automotive

best of luck

 

In my years of experience, I am gonna say that you have corroded battery cables and/or corroded contacts at the starter + post or ground point from the main ground cables...... clean all the contact points of the main battery cables I could tell you in a heartbeat if I was looking at you truck myself. you can also measure the resistance between the two ends of the cable... if its anything other than 0 or almost 0 ohms cables have corrosion in them and need to be replaced. any swelling of the cables near where they attach to the battery also means they need to be replaced....
this is also assuming you have recently had both batteries load tested and they passed ... see the special tools thread and my post about Carbon Pile Load tester.. you would be wise to buy one... also get a DC amps multimeter...