Here's the issue with my GO2535 ™ The unit will not boot up unless it is plugged into an external power source. Yes! you may think the battery is dead however reading from the data screen log shows battery at 85% charged. I also removed the battery and did a bench test and got a reading of 4 volts using an old analogue VOM meter - hence I concluded the battery is still good. I didn't want to purchace a new battery and have the same problem. Anyone have this issue? I invite your feedback. Any simple solution? Thanks