Some one has asked me to hard wire his forklift battery charger. Charger is 3 ph 208/240/480. His panel is providing 208. My question is do we need to open charger to change different input.

Most likely, yes.

You really need to check the manufacturer's info to be sure.

I've done a few, and yes, you should open the unit and read the paperwork. They usually come set for a given voltage, but don't assume it's still that way.

Yes open it up, I have never seen one that could adjust itself for different voltages.

You will probably have some jumpers to move and many times you need to change some fuses.

You really got to follow the directions, if you don't have them you can usually get them on line or call the company and they may fax you out a set.

Don't forget to check the control transformer as well. I was called to our warehouse to check a charger a co-worker installed. He changed the taps to have it operate on 480, but didn't change the primary on the control transformer. It was still tapped at 208. Needless to say, it didn't like that very much.