Hello.

Typical 12V lead-acid batteries eventually die because one of the six 2Volt cells becomes short-circuited and so far, there is no way to repair that.

Happened to me last month on -20C days.  The then-healthy battery was under trickle charge and when attempted to start, 10volts!, barely cranking.    One shorted cell... garbage...   replace with new.  Question is, the short circuit dissipates a considerable amount of energy internally, damaging (or thawing!) something.  But never heard of that happening.  Why ?  Where that one-sixth of the energy stored in the battery go ?

Just now, Externet said:

Hello.

Typical 12V lead-acid batteries eventually die because one of the six 2Volt cells becomes short-circuited and so far, there is no way to repair that.

Happened to me last month on -20C days.  The then-healthy battery was under trickle charge and when attempted to start, 10volts!, barely cranking.    One shorted cell... garbage...   replace with new.  Question is, the short circuit dissipates a considerable amount of energy internally, damaging (or thawing!) something.  But never heard of that happening.  Why ?  Where that one-sixth of the energy stored in the battery go ?

Are you sure it was a short circuit failure ?

https://academy.gs-yuasa.eu/wp-content/uploads/2019/03/Battery-Failure-Modes.pdf

Thank you. 

From the symptoms listed in your link;  the 10V and the slow cranking behaviors tells there is no open circuit, checked all cells at uniform acid level, there was no lack of charging, there was no overdischarging nor overcharging nor abuse on a <2 year old battery.  After reading; am more inclined to confirm it is a shorted cell.