Ok. First could you tell us which device you're working on. After that, since you already tested the battery, and have ruled that out. You'll want to test the charging port, is it getting electricity? After that you'll need to find the chip, on the board, that is responsible for charging. That last part is no easy task. I've currently put $800 into my microsoldering equipment, and find half of it lacking, and waiting to reinvest