Hello brand new here! And just bought a new Ford Focus :-) 2004 plate 77.000 miles. I've just tested the battery and alternator voltage, both showing around 10 low and medium. May I have some advice what to replace first, or could it be where it's been sat and not driven for a while? Many thanks! 

13 hours ago, Jmclovin said:

I've just tested the battery and alternator voltage, both showing around 10 low and medium.

I am not sure what 10 low & medium means. 10v on the battery would indicate it is either duff or flat.

Can you start the car? (jump or using its own battery?)

When the engine is running, the battery voltage should rise to over 14v, up to 14.8v is ok. It may take some time if it is discharged. Also, at idle speed, that would be with minimum load (just ignition). At normal driving rpm (1500 for diesel, 2000 say for petrol), then it should maintain over 14v with headlights, wipers & heater fan on.

A fully charged battery should show over 12v (12.4 to 12.6v ideally) with no load (doors shut, ignition off), even after 24 hours or more. A week without use should be no problem for it.

Either charge the battery with a charger (a decent, regulated one), or jump start it & run for at least one hour before testing the battery as above. It may take a long time to charge a flat battery, (60AH at 6 amps = 10 Hours). If it has been flat for any length of time, it may never fully recover, and need replacing.