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I opened before some laptop batteries. But this is the first time I see it. This is an IBM ThinkPad cell battery.

See picture below, the two pins to the left are connected, resistance between left-right pins is around 46 ohm (45.9 & 45.3).

What could be? What it does? What the main benefit of using it here?

  • The way it was mounted on the top of transistor, may be indicate something.
  • As requested by PlasmaHH. Resistance raise with temperature, I used a cigarette lighter, 45.9 → 46.6 & 45.3 → 45.9 . Not much change in the freezer, 45.9 → 45.8 & 45.3 → 45.2 .

enter image description here

Closeup:

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Russell McMahon
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user.dz
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1 Answers1

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This is likely what is called "logic fuse" -- a fuse which is activated by one of the two conditions:

  • overcurrent (just like regular fuse)
  • electronic control from battery management circuit

You can see how this works on page 9 of the following datasheet (from a different li-ion battery pack): http://inspired-energy.com/standard_products/NH2054/NH2054HD24%20spec%20v3.1.pdf

I am not sure why they are mounted on top of MOSFETs. Maybe they are also activated by overtemperature?

In any case, if you do not care about the battery, you can verify this theory by applying small current (1-2 amps) between left and right side of the part -- the connection between two lef pins should open.

theamk
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