I work on a wearable, battery powered device. When it is connected to an external power source it's supposed to charge the battery and switch load to that source.
I use LiPos 1000-2500 mAh. I've experimented with two different new ones, with the same result.
But actually, it doesn't charge battery (not completely). Voltage on mcp's vbat pin is 3.9-4.01V (or even less). Not 4-4.2V as must be according to the datasheet. Also D1 is flickering.
I've tried to connect battery (2500mAh) though an amperemeter and it showed 300mA at max, instead of 500, and after several hours battery was even discharged up to 1 Volt! Without ampermeter (quantum effects? :) battery charges up to 3.8-3.9V after more then 8 hours.
I don't have special precise power source, and tried macbook's USB port and iphone's power adapter. I've tried with and without load.
UPDATE I checked 2.1A power source - nothing changes.