UPDATE: I’ve bought two chinese batteries hoping for the best. If they turn out to be crap, I’ll go into auto mode and slap two 18650 cells in the phone. Otherwise, the screen is now cracked so I have a new challenge of finding a screen, case etc. lol.
My previous phone was a nokia lumia. When the battery started going, I slapped on an ‘extension cord’ from the original cell to the outside where I could attach a 2P 18650 pack. It looked like a turd but worked well. That frankenstein has died and now a generous friend has given me his his Note 3, which has a battery that goes from 100% to 50% in an hour doing nothing. lol. There are ‘china’ cells available on amazon or ebay for cheap (CHEAP IS GOOD) but reviews suck.
I don’t want to make the note 3 into another frankenstein… 
but it’s PITA to have a phone that spends more time charging than not. The battery compartment is approximately 77x53mm. I can technically fit 5x14500 cells in it but, they’ll obviously protrude out the back of the phone AND it’s a lot of money I prefer not to spend if I don’t have to.
Do any of you have any other suggestions?
No. I haven’t checked as yet weather the phone can work with just +ve and -ve inputs. Worst case, I remove the circuit from the stock cell and use it with whatever is attached.
Thanks BLF!
