Following on from my GPS battery exercise, I have been educating myself on LI phone type batteries. I dissected the duff GPS battery and found out that all Li phone type batteries have charge control built into them. The circuitry is very compact, fits across the top of the battery and features both charge rate/discharge rate and charge control, via a disconnect function. I found a breakdown of the Iphone6? battery and this uses the identical construction to my GPS battery. There are 3 and
5 wire configurations. It would appear that 3 wire batteries provide fast charging via temperature control(or battery size indication in Nokia units) and 4 wire provide data to the phone logic chips. A Li battery without these features seem to need about a 12 hour charge time.I have also found out the hard way, that all charge cables are not equal, some have better connectivity in a mini USB socket than others! I expected it to be a series resistance problem, but it was a contact resistance problem