tablet not charging

Hi all,
My girlfriend got me a Motorola Xoom for my birthday.

She must have gotten it second hand, as it had no box, and she ordered the charger separately.

I am a mobile app developer, and I was hoping to use the XOOM to preview apps I am making.

Anyway, the tablet doesn't seem to charge..I have tried several chargers, and what seems to happen is the device starts, the charger is not recognized, and it shuts off.

I read several posts about the charger not working, and that often it is a battery issue. As it is secondhand, I doubt Motorola would repair it for free...just wondering if it's worth it to try to repair.

Thanks so much for any advice,

Natalie