HP TD06 (Series HSTNN-UB85) 11.1V 62Wh battery pack teardown

I picked this HP TD06 (Series HSTNN-UB85) 11.1V 62Wh battery pack up at RePC for $1 at the same time I got the ASUS AL32-1005 pack I posted about earlier. Based on the nameplate pack voltage, it was one of only a handful that used newer 3.7v lithium ion cells out of the hundred or more packs they had.

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It was also the only of TD06 pack using newer cells; there were 3-4 labeled with a 10.8v voltage.

Peeling the label back gave a tiny peak at the cells. I was able to separate the two halves of the pack case with a thin bade, pliers and a bit of elbow grease.

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The lavender-wrapped cells are clearly made by Samsung (not a big surprised, given that the pack label indicated that the cells were made in Korea. The remaining marking is ICR18650-28A. These cells are rated for 2800 mAh of charge capacity, which isn’t a surprise given the 62Wh claim. Unfortunately, they must be charged to 4.3V to achieve that capacity. When charged to the more common 4.2V, they have about 7.5% less capacity.

The battery management seems to be divided between two chips with a lot of pins.  One is labeled M37512, FC024, J2C5D. The other is 20020 ??05. The first chip appears to be an 8-bit M37512-FC MCU from Renesas intended for…battery pack applications. I’m not sure what the second chip appears to be a RS20020. This is a companion chip for battery pack applications. I can’t find information on what it does, exactly, but it seems to have connections to each cell, and to the MOSFETs that can switch the flow of current to or from the pack on and off.

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