I changed my battery a few weeks ago (also petrol, manual) without any problems. 1st i would try to disconnect again the battery, leave it for 10-15 min disconnected and then put it on again (just the + terminal). After that, try the battery reset procedure. You can find it on youtube, it's simple. There are a number of reports of Ford Fiesta and Focus models suffering from 12V battery drain issues, and it certainly isn't unique to the mild-hybrids. Owners on Ford forums recommend either investing in a battery charger (you attach this to the battery when it isn't in use and it slowly restores charge) or upgrading to the bigger battery I can not find a guide of sorts but I plan to do the following: 1)Disconnect battery Negative terminal. 2) Let car sit for 1hour to discharge all. 3) reconnect Terminals. 4) Start car allow to idle for 10 - 15 min without touching accelerator. 5) Take for a drive and drive the way I normally do. unpMh.