What is a thermal runaway?

The appropriate charge voltage depends on the battery temperature. A warmer battery requires a reduced voltage. If the voltage is not reduced the current accepted by the battery increases. When the current increases heating within the battery increases. This can continue in a loop feeding on itself with the battery temperature and charging current rising to destructive levels. This is thermal runaway. Gel batteries are much less susceptible to thermal runaway than AGM batteries. Batteries may become more susceptible with increasing age. Without a recombination reaction, flooded batteries convert most excess charging energy to gas, not heat. This makes them almost immune from the thermal runaway.

Thermal runaway can be prevented with:

    * Temperature compensation monitoring at the battery – not at the charger.
    * Limiting charging currents to appropriate levels
    * Allowing for adequate air circulation around the batteries.
    * Using timers, or Ampere-hour counters.
    * Using smart chargers that recognize the signature of a thermal runaway which will shut the charger down.