THE WORD OF GOD SPEAKS:
OUKITEL K10000 4G Phablet - 2GB RAM 16GB ROM BLACK
With a rooted, optimized system and that mega-bigass battery, it is very unlikely that you'll ever starve for power… 
Cheers ^:)
i know its sacrilege to the op but i had one of these with a different name that i dremeled out the battery holder and put in an 18650 holder and a tp4056 board.
i was about to suggest some of these older design units but was beat to it.better buy spares if you like it since this is a 8 year old design at least.its one obsolete part away from a redesign.