We got a SIKER battery replacement for a 2012 MacBook Pro, but one cell swelled up and the battery wouldn't hold a charge. One Amazon reviewer for one of the replacement MacBook battery packs says that they might be building replacement battery packs out of old worn damaged, or mismatched cells. I don't know if that's the case.
In any case I bought a second battery pack from TECHOWL and it seems to be working for a few weeks so far. Fingers crossed...