i ordered one on Ebay said it is new, but it wasn't. the unit powered on but can't charge with the internal tray. So i opened it up and found out the spring post circuit was broken, then i repaired the it and glue the post with CA on the board. Now it works.
second is a trinity dpd. it worked for a while, but it just can't discharge one day. i opened it and found out a broken solder join on the battery contact.
so double check it then.