I bought it used off of Craigslist. Replaced the battery and charger. It has worked flawlessly for over 2 years. It now shuts off unexpectedly at unpredictable times. It will power back up with no problem, only to shut off again. Any advice?
An addendum to this issue:
When I have the charger plugged in it does not have the shutoff issue present. I will check all of the battery connectors to make sure none of the wires have worked loose. Thanks to all for your suggestions.