Originally Posted by HangFire
There is an explanation if you understand wet battery design.
The particulate in the bottom shifts in the impact an accident, and shorts out the plates on one end of the battery. Normally you have to wait for it to build up a little higher until it gets that far.
Usually by the time a battery shorts, the electrolyte is exhausted anyway, and the plates are depleted as well. Modern battery designers are pretty good at balancing those design features, as it allows them to use the minimal amount of each component (lead, acid, plastic) and still avoid early in-warranty death.
Yes this is a common phenomena. Battery plates shed material, and can get hard (low impedance) shorts, that result in a cell showing no voltage (10v battery), or high impedance shorts, that slowly deplete the energy in a cell, but contribute to the battery weakening.
Originally Posted by Trav
I read about this somewhere, the main difference between say a 60mo and 24 mo battery is the distance of the plates to the bottom of the battery case.
I have no idea but I found it interesting that by just manipulating the height of the plates in the case they can set the batteries life expectancy. You may know more about this than I do, what do you think about that?
That's an interesting theory. Managing shed materials from the plates is a consideration, but the BCI group numbers have to be maintained dimensionally. If the higher end batteries offer more cca, more rc, AND have effectively shorter plates, something has to give. So beyond a mm or two (which perhaps is all that is necessary), it's hard to see how this would be viable. That said, some higher end batteries offer higher cca (thinner plates, more surface), but also less rc (energy). Separators, current collectors, etc take up some of it, but perhaps cell dimensions do play in as well.
Only a cut apart would tell the truth.