New MacBook Pro battery has only 13 mAh to give

Short version: After a few weeks of usage this new battry has a Full Charge Capacity of only 13 mAh. A shutdown is a matter of seconds. Resetting SMC and nvram/pram doesn’t seem to change anything. Old battery is working well.

Long version: Bought this new battery a month ago and it worked beautiful the first two weeks. I don’t have the exact data anymore, but it was a little above the design capacity after first charge-recharge (~ 7000 mAh). Did the thermal paste replacement at the same time. When the laptop already open and that iFixit pro toolkit is begging for more. It’s hard to resist, sorry.

Everything worked well for the first two weeks. Not sure if it has anything to do with the current problem, but I decided to open this MacBook Pro for a second time to replace the thermal paste with graphite pads (advice: don’t do that. It’s a little worse than thermal paste). Everything went well, again, and as I forgot the first time to clear pram and SMC reset, did it this time in combination with a new ‘calibration’. Left it after a full charge drain the battery. Plugged the charger in after two days and the led changed to green within minutes and shows a 100% charge.

Research after a really, really quick low battery shutdown showed the Full Charge Capacity is 13mAh. No key combination, drainage or resting outside the laptop does it change to any higher value afterward.

Thinking the fiddling with the logic board had something to do with this I put the old battery back which is working great for the last week.

Today I tried the new battery again and nope, still like Friday the thirteenth.

Is this some calibration issue or a textbook example of a dead battery?

Note: Battery was outside laptop when repairing. No chance of shortcut or anything I believe.