During the past 2 to 3 weeks my Focus Zetec 1.8 petrol has been showing some unusual starting problems when starting with cold engine. On turning the key, engine would turn over and fired up then instantly stop. Note, the engine turned over as normal and did not give the usual 'dead battery' symptom of slow or not turning over. This is what I found and the cure.

• Checked the instrument panel for DTC fault codes (Focus Dashboard Secret (Trick))
  
• Found dtc fault code 9318 fault code = 'Low Battery Voltage'
  
• Used multimeter to measure 'Battery Voltage' with engine off = 12.2 Vdc
  
• Used multimeter to measure 'Battery Voltage' with engine running = 14.9 Vdc
  
• Visual check of battery indicator window = RED (battery discharged or failing)
  

After finding these symptoms I purchased a Silver Calcium battery from local Ford dealership (25% discount made it competitive price)

Fitted the new battery and checked the voltage engine off 12.6 Vdc and engine running 14.0 Vdc

Now the car starts perfectly with cold engine.

This may have also 'reset' the Engine Management Computer as the fuel consumption appears to be improved, previously was going from full to empty in about 320 miles. My latest petrol fill up is down to 1/4 tank after 300 miles, so I'm expecting 400 + miles on this tank of petrol.

Batteries are so troublesome, they can give out some rather odd readings especially in the cold. Mine too failed this winter, and caused no end of trouble. I think the problem is with a cold engine the battery is put under more strain, plus batteries dont particularly like cold weather. After fitting a new standard (Halfords) battery to my car, the instructions said the battery should not be stored below -5 (a bit difficult when the car is on the road, and unfortunately I cant control mother nature!)

So as the battery gots hot and cold, it seems to make the acid a bit more "delicate" for lack of a better word. And although it can output theoretically the load it requires, when the battery is strained by the engine, it just cant output enough, and therefore cuts out altogether.

If you got 3 years or more out of your battery you did well, mine died ages 5 years old, so it lasted a good time! But when it comes to this sort of trouble it is always best to buy a new battery. As even if the other battery has a little health left in it, although you cant rely on it day in day out. If your car is ever stuck outside and cant start, you can pop your removed (charged) battery onto the terminals and either use it for a jump start! it doesnt cost a thing, and could save you a few hours waiting for mr Recovery to come and fixit for you!