A few months back, awoke to what appeared to be a "dead battery" on my OPO.
Everything I tried failed to awake it. The phone had been fully charged that evening and removed from charger. My conclusion, dead battery and a $100 repair bill in my future.
A few days later, I decided to try one last time to reawaken it. After 10 minutes of pushing/holding various buttons, I held down both DOWN VOLUME and POWER/LOCK-KEY buttons for 60-90 seconds. BOOM! All of a sudden screen lit up displaying rough diagram of a battery & statement something like 'insufficient battery power to awake phone, connect charger". I immediately connected charger, and about 30 minutes later checked and saw battery being recharged, and was now at 30% of capacity.
Since that time, my OPO has worked flawlessly. No repeat of "dead battery" problem.
(NOTE: My OPO is currently running CM12.1.1-YOG7DAS2K1 [Android L v5.1.1] and has never been modified, except as may have been initiated in official OTA updates released by CyanogenMod.)
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