Here's what Lifeline says about thermal runaway in their technical manual - my link three posts above understandably
indicates that Lifeline does not, and cannot, know all user problems that their customers have run into to - like with any
company:
6.4 Thermal Runaway
Thermal runaway is a condition in which the battery temperature increases rapidly resulting in
extreme overheating of the battery. Under rare conditions, the battery can melt, catch on fire, or
even explode. Thermal runaway can only occur if the battery is at high ambient temperature and/or
the charging voltage is set too high. As the battery accepts current, its internal temperature rises.
The rise in temperature reduces the battery impedance, causing it to accept more current. The
higher current further heats the battery, and so on, causing the battery temperature to "runaway".
An upper limit will eventually be reached when the electrolyte starts to boil, but once the electrolyte
has boiled away, the temperature can climb even further to the point of plastic meltdown and
possible fire.
As of this writing, Concorde does not know of any Lifeline® AGM batteries that have failed due to
thermal runaway. To preclude the possibility of thermal runway, the charging instructions in
Chapter 5 should be carefully followed, especially if the battery will be subjected to high
ambient temperatures.
Batteries should not be installed near heat sources or in direct
sunlight that may artificially elevate their temperature. Also, there should be adequate air
circulation around the batteries to prevent heat build-up.