![]() Poking around with a scope, we can see activity on pins 3 and 4. Voltage on the pins is now 12.6V, meaning the charger is trying to do its job but no current is actually making it in. With the laptop powered by a bench power supply, we can see a notable surrent spike when battery is inserted, so something does happen. Plan B- put the battery back in laptop and observe signals on the pin. We apply normal for it voltage (in the range of 3-4.2V per cell) and see if it “takes”any current. Next step is to try waking the battery up. Pins 6 and 7 remain mystery for now and pins 8 and 9 are the battery positive. That most likely means we have SMbus (a typical comm channel for notebook batteries) on pins 3 and 4, and a battery temperature on pin 5. Pin 5 has a single channel TVS/Diode looking thing. The next two pins (3,4) are routed through a SOT23 device that measures as a dual diode- most likely a dual Zener/TVS for ESD protection of comm lines. It is pretty obvious that the larger blades are power and ground, and by measuring resistance to case ground we can tell that the leftmost two pins are ground.
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