Sometime the fuse blow, replace the thermal fuse with working one. This is sometime very troublesome, if not done properly, the fuse will blow again! Especially if one not solder it fast, the heat from soldering iron can melt the conductor inside the fuse also, because it is a thermal fuse.
The primary purpose of this thermal fuse is to prevent battery keep operating if the MOSFET(the black chip below the fuse) is overheat. MOSFET can overheat if the main protection chip fail to detect an over current condition. MOSFET can also overheat if over current occur but the MOSFET itself shorted(not working).
Those fuse can also be intentianally blown by the controller circuit if the battery controller have a sense of cells over-heating or over-charged, that is why it have three leg, one is for control, connect it to ground will blow the fuse. But if the overheating occur due to short circuit inside the cells itself, cut off the supply of current to notebook won't prevent it from continously treat by overheat or even catch fire when reach a certain temperature treshhold.
Replace the cell with new one.
Connect the new cells to the circuit board and apply some silicone glue to the temperature sensor. The reason using silicone glue is it can withstand up to 400 degree Celsius. If using normal glue, it will melt when cell overheating occurring.
Great workmanship cause housing are open nicely.
This is first time I see QFN chip pakaging for the bq chip, normally is TSSOP.
TSSOP is long IC. QFN is smaller in size by around 20%.
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