My Macbook Pro had the A1321 battery and I acquired the A1382 battery by mistake. I noticed the connector was different (and also wondered if the firmware could be different). First I have tried to cut and join/solder the nine wires exactly in the same order, just to find it does not work (battery is not detected).
Then, I have found jozefvaclavik’s post saying the pins were also reordered in the new model. I have cut them again and rejoined/soldered in the new order. Works like a charm and I’m sending this message from a happy Mac Book Pro.
All I have done was to invert wires 1, 2, 3 with 7, 8, 9 (leaving 4, 5, 6 as they were before).
If you are doing this, do it one cable at a time (your battery probably came charged, and if you touch the wires you will get a short circuit) and put a some insulating tape around each cable. I have used tiny pieces of insulating tape, carefully covering the joined wires, because I wanted to ensure I would still be able to fit the battery back in the same location.
Took me more time than expected, but I’m happy that I do not need to throw this one away and buy another one.
This whole thing left me wondering why Apple would release a new battery, with the same form factor, same voltage, same amperage, an apparently compatible firmware, but a different connector. I wish someone from Apple could explain the rationale behind this (there must be a good one), other than just making the batteries incompatible.