I've had a Montana 600 for about 18 months now - primarily mounted on my bike. I had a Garmin brand Lithium-ion battery. It worked exactly as advertised. When I plugged it into either a usb cable or mounted into the rugged mount, it would boot (if off), put the backlight on full and begin charging. This has been routine. About 2 weeks ago, I noticed the backlight was off while the unit while in the rugged mount. I first thought it was a fuse - which it wasn't. Then I thought maybe the mount connections. However, when I plugged a usb cable into the unit, it still would not charge. The unit also no longer turns on when plugged into either a usb or powered mount. Other than not charging, the unit worked fine - that is until the battery ran out. Then I tried charging the battery in an external charger for Li-ion batteries. It wouldn't take a charge so I figured it was the battery that was the culprit. I bought a replacement non-Garmin battery (X-Longer #CS-GRM600XL) and charged it in the external battery charger and put it in the unit. Again, the unit works fine, but does not charge nor boot when plugged into a power source. I have the latest software loaded (v 6.5). At this point I believe it could be one of two things. 1) Garmin hardware doesn't recognize 3rd party batteries enough to charge them (and something very funky happened to the original Garmin battery rendering it useless). 2) There is something wrong with the hardware that handles external power in some way. I really want to avoid the wonking service charge if at all possible. I've already been there with a cracked screen. Any similar experience or suggestions?