Problems after battery replacement

I swapped with battery pack I ordered through you (thinking that it would guarantee quality). All went well (using the string-method, instead of alcohol, to loosen the original battery pack) and the battery charges etc. My problem now is that the mac wont give me any warning when juice is running out and when that happens it just suddenly shuts down the machine (about 7-8% left of battery juice). Connecting the charger it restarts immediately (chime and all). I have reset power management (SMC) due to instructions for this model, i.e. disconnecting the charger, shutting down the machine and pressing Shift+Control+Option keys and the Power button at the same time for >10 sec. (To be sure I also tried the same procedure with charger connected). No go.

Any advice will be received with utter thankfulness...