2004 International 4200

I have a 2004 International 4200 box truck Automatic trans, electric hydraulic brakes. Batteries were dead the other day, so I removed them and charged them. When I re-installed them them, I hooked up both positive wires, then when I touched the ground to the terminal I heard a fast clicking noise up near engine. It stopped after 10 seconds or so. Is this normal? (It sounded like my old 2006 6.0 powerstroke when you turn the key on and it cycles the injectors...) I believe the truck does this normally when the key is turned to the ON position before starting normally. But when when batteries are connected and key is off?

Also, any ideas on known issues that could be drawing amperage on these trucks to drain batteries?

Thank you in advance!

 

Actually I believe the key was turned backwards to ACC. Still very strange.

 

If anyone has any info on this or possible fixes please let me know. From what I'm told the batteries go dead after a few days and will need jumped or charged up.