The fully charged voltage of a battery drops as the temperature drops - and the engine is harder to crank as the oil is thicker - so a failing battery can be fine all summer and then let you down in the first cold spell.

My Vauxhalls had batteries that outlasted the cars, 14 years in one case, but my Subaru's Panasonic battery started failing during its 2nd winter.

NO, the cold does not, of itself, remove any of the energy stored in the battery. In physics, temperature is a measure of energy, so as the temperature drops, the chemical energy available to be converted to energy is reduced. That and the fact a very cold engine is much harder to crank and start provides a triple whammy which a poor battery simply might not be able to overcome.

Also note that as temperature drops a battery’s ability to be charged is reduced. The reduction is progressive below 5C and below -5C most batteries will not accept charge. Another reason batteries die suddenly in the winter even if they were fine in the summer)

I would recommend that everyone should test their battery and charging system once a year, before it starts getting cold.

Being in the boot, yours has some protection from the cold and receives some warmth from the cabin during driving. The main reason it’s there though is packaging space and shifting weight to the rear.

I show you how to test your battery and charging system here:

www.youtube.com/watch?v=AT_XmlwMVz4

All you need is a multimeter and some basic knowledge.