Bump...

The extra pins could be several things, but I haven't seen the inside of that battery pack. Could be voltage present, could be cell bank voltage, could be thermistor input, could be other voltage outputs, etc. It would be best to try to clean up the old circuit board inside the battery pack, or duplicate the PCB and rebuild a new one. If you don't know how to do that, obtain another battery pack and hope it isn't damaged. I would really order some proper NiMH batteries to try rebuilding the pack if you still go that route.

wiretap wrote on 2021-12-21, 02:04:

The extra pins could be several things, but I haven't seen the inside of that battery pack. Could be voltage present, could be cell bank voltage, could be thermistor input, could be other voltage outputs, etc. It would be best to try to clean up the old circuit board inside the battery pack, or duplicate the PCB and rebuild a new one. If you don't know how to do that, obtain another battery pack and hope it isn't damaged. I would really order some proper NiMH batteries to try rebuilding the pack if you still go that route.

Thanks - I have no idea about rebuilding PCB so that's not an option for me. If I post a pic of the PCB and the terminals would that help at all? Can't find any details about it online (or a battery pack for that matter).

Sure, pictures are always good. Maybe someone knows the circuit and can answer.

Here's a picture from three different angles, I've annotated as much as I know.

Any chance of a high-res/less blurred/brighter lit copy of the front and back with the wires held out of the way? Ideally want to be able to see all the traces and part numbers. Looks like there's both the thermistor that I assume goes out to the middle of the pack, and I think there's also a PTC type fuse stuffed under CN4&5, opposite those two 0.1ohm (I think) power resistors, which must be a sort of current limiter. That MIC2951-03BM is a 5V regulator, but it's difficult to see what it supplies. I can't make out the part number for U1 (bq2610?), I assume it's a battery status monitor of some sort. Corrosion around R5 looks pretty bad, might be worth checking the resistance across it. Maybe there's some sort of battery status/check handshake thing that goes on between laptop and battery (that U1 chip?) which if it fails the laptop won't use the battery. Or the laptop needs 5V from U2 on CN3 (assuming U2 connects to that)?

Here's a high res pic.

Thanks. It looks like there's some corrosion damage, and that's making it hard to see where various tracks go, particularly how P1 and P2 get to any of the CN contacts. I suspect there may be a track somewhere that's been cut by corrosion.

The bq2010 (U1) is a battery status monitoring chip, which supports a one wire communication protocol. So it's possible that one of the 5 pins goes there, maybe CN2. Maybe the laptop will refuse to use the battery unless it can read a charge level from U1. CN1 looks to be the thermistor output, possibly outputs a voltage based on the temperature. Have you got a multimeter? One interesting thing to check is where pin 1 of the MIC2951 goes to. pin 8 should go to battery +ve and pin 4 to battery -ve. Pin 1 is a 5V output which I'm assuming is eventually connected to the thermistor and U1, but I can't see how.

I think to figure this out then you might need to fully work out what the circuit does, which will mean removing quite a few components to look where tracks go under the components. Particularly the 5 battery contacts and the PTC, and U1, U2 R1 and R2 on the component side. Given the corrosion that may be a good idea anyway so you can clean under the components to stop any further damage. It's a shame there seems to be no documentation about what the pins are. Hopefully someone else might have a working battery and be able to measure the voltages on each pin.

snufkin wrote on 2021-12-23, 00:42:

Thanks. It looks like there's some corrosion damage, and that's making it hard to see where various tracks go, particularly how P1 and P2 get to any of the CN contacts. I suspect there may be a track somewhere that's been cut by corrosion.

The bq2010 (U1) is a battery status monitoring chip, which supports a one wire communication protocol. So it's possible that one of the 5 pins goes there, maybe CN2. Maybe the laptop will refuse to use the battery unless it can read a charge level from U1. CN1 looks to be the thermistor output, possibly outputs a voltage based on the temperature. Have you got a multimeter? One interesting thing to check is where pin 1 of the MIC2951 goes to. pin 8 should go to battery +ve and pin 4 to battery -ve. Pin 1 is a 5V output which I'm assuming is eventually connected to the thermistor and U1, but I can't see how.

I think to figure this out then you might need to fully work out what the circuit does, which will mean removing quite a few components to look where tracks go under the components. Particularly the 5 battery contacts and the PTC, and U1, U2 R1 and R2 on the component side. Given the corrosion that may be a good idea anyway so you can clean under the components to stop any further damage. It's a shame there seems to be no documentation about what the pins are. Hopefully someone else might have a working battery and be able to measure the voltages on each pin.

Thank you for the detailed response.

I'm not sure how P1 and P2 goes to the respective CN4 and CN5 terminals, but they do because I've tested that with a multimeter while I had my makeshift battery pack wired up to it. So that part is not an issue, but what you say about the rest of the control circuitry makes sense. However I don't really have the skills/knowledge or tools to start manipulating it i.e. removing or re-soldering components etc.

I do have a second board from a different battery pack, also with some corrosion but on closer inspection I now realise that this other board is actually different - in fact might be slight simpler too. I'm going to give it a good clean and then post another pic, maybe something more can be derived from that.