Originally Posted By: oilpsi2high
Heat, not cold, is what apparently kills these things.
Absolutely. Batteries start ageing from the secomd they are formed. Precisely why small power equipment batteries (and most others back in the day) were shipped dry and the electrolyte is added at first use.
Chemical ageing is indeed a major degradation phenomena, increasing impedance and reducing active material to take part in the electrochemical reaction. Remember that reaction rates double for every 8-10 degrees C, so a hotter battery will have much more rapid degradation than a cooler one.
The other thing that kills lead acid batteries is being undercharged. In climate controlled float service, IPS battery warranties are going up to 15-20 years! An alternator does not do the proper charge profile, so though the energy removed by starting is miniscule, the true state of charge is not perfect, and so they degrade to the point that a 10 year battery is rare, and a 5 year battery is fairly long life even in cooler climates.
Originally Posted By: Bluestream
Originally Posted By: oldhp
Agree. I sold more batteries in the summer than winter when I worked at NAPA. Most "no starts' in winter are from poor battery care, bad cables or bad grounds.
That goes against info I have for my area, where winter is by far the busy season for battery sales. Not much strain on the battery starting an engine in the summer.
That's again because reaction rates are slower in the cold. So you have a trifecta of issues - less volatile fuel in an engine that doesn't want to crank, lower battery voltage due to Gibbs free energy, and slower chemical reactions that don't produce current as readily.
The same cold temps that prevent chemical degradation also prevent electrochemical reaction...