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Haven't seen/heard of any auto batteries here, yet, that are not lead- acid in some form. (e.g. saturated glass mat). Agree it's possible that the multiplicity of 'gadgets' (To the minds of some 'Unnecessary' ones) on modern vehicles that use very small amounts of 'juice' while standing by, 'might' drain down a battery. But seems unlikely! Our 2002 Nissan, with a number of unecessary (and unwanted, but they come from the factory that way, features) with a then 5 year old (original) battery, was left standing during the winter of 2007-2008 for over 3 months. Upon returning, in March (still winter here until at least mid May), it started instantly as soon as I got back from the airport and went for groceries. Same battery still working this winter. Vehicle is moderately driven; 95,000+ Kilometres (about 8000 miles per year). Obviously our 2002 Nissan is 'listening' all the time because the key fob can activate the door locks, from a considerable distance any time day or night. Come to think of it, haven't replaced the batteries in either of the two key fobs since vehicle purchase in 2002 either.