How can I make a 6v external battery pack for Olympus E10 I'm thinking of using a UB645 6v 4.5 Ah battery connected to my external power jack.?

Sounds like it's possible, but without more information on the specific camera battery and the UB645 battery, there's a chance things might go wrong. But if you're wondering if it can be done, yes it's possible, but it might take some support electronics to be able to make it happen safely for the camera.