Hooked up my charger this afternoon to "freshen" up the batteries. Trolling batteries were full, green light showed imediately. my cranking battery showed green, then nothing, then all staged lights went red, then they went to green then it repeated over and over.

any clues?

dual pro 10 amp charger - optima battery

3rd possibility: loose connections or corrosion on the terminals. they need to be tight-tight-tight and bright.

to know for certain you'd need to measure the battery voltage and maybe do a load test, but IMHO the charger is the most likely suspect.

If it is the charger, call Dual Pro. I had one go out and called them. They were cheaper than Bass Pro plus they gave me $100 trade in for the old one.

Looks like maybe a bad battery. Do you have a regular charger handy to see what it does when you hook it up?

I use a dual pro charger and My cranking battery did the same thing! It was the battery. I had it tested and it showed voltage but when loaded it crapped out. I replaced it with a dual use trolling/ cranking battery and fixed the problem. I use my boat all the time and I started using Interstate megatron deep cycle batterys and they work great. I was using the walmart specials and I would get 12 to 18 months if I was lucky. I get three to four years with the interstates and they only cost $25 buck more.

Charger works fine on my trolling batteries, I am pulling the cranking battery out to have it tested at batteries plus.

It is a 5-1/2 year old optima!

That's what I would do. What I did was swap the leads on the charger and the other bank did the same thing after I swapped so I knew it was the battery.