Motorola v600 won't switch on
My wife had the V600 and I had the V300. As far as I could tell, the two are the same with only some features and the look is different. I think the line goes all the way down to like V150 or something like that.
Anyway, try use a multi meter to measure the resistant between the 3 pins that touches to the battery. The number should read above 3 ohms. If lower, there might be a short inside the phone.
You could bring it back to whoever your cell provider and have them check. There shouldn't be any charge for them to check. They could also try to put new firmware for you. You could ask them if they have a battery for you to try see if it turns on also.
When I had my V300, T-mobile suggested to switch it off once in awhile. I did it weekly.
Last attemp, you could open it up and if you could find anything. I opened up my V300 a couple of times. I include a pic of the V300 when I opened it up. Maybe that'll help you open yours. But I suggest this as a last last solution. As in you are about to trash it.