How does this happen

[Michael9]

I go out to start the car just now, it's ***** freezing, engine turns slowly but catches, scrape ice off the windows i have it running for a good 5 minutes, stop it to go the house as i forgot something (stupid thing to do), come back out....wont start battery's flat, wtf . Is it the cold/freezing that did it?

[jmurray01]

That doesn't surprise me one bit!  If it was almost flat to begin with, then only running the motor for 5 minutes won't have put enough (if any) charge back into the battery, so turning it off was the worst thing you could have done.  But of course, in hindsight I'm sure you now realise that.

Batteries usually suffer the most during the warm weather, but it is only in the cold when they are put under extra strain that the "damage" shows. 

[stef123]

If it's running with heated front and rear screens, lights, fan etc there will likely be no juice left from the alternator to put back into the battery. 

Sounds like it was already near enough flat. 

[Michael9]

Yep...stupid ***** that i am 

Ive been driving a long time and should have known it was stupid thing to do so double 

New battery in order....not only that, i thought i was going to have to crawl through the back pass window (windy) to get out as both front ones and the door were still frozen after a run (neighbour gave me a jump)...got a bit panicky thinking i was going to be locked in