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SECTION 2
SAFETY
Battery Safety Information:
There are four main safety hazards associated with the use of any AGM battery. These hazards are:
a) Release of ignitable gas
b) Exposure to acid
c) Shorting of terminals
d) Thermal runaway.
This section provides a description of each of these hazards and means to mitigate them.
A. Release of Ignitable Gasses
All AGM batteries produce hydrogen and oxygen gases during normal charging. Even though these
batteries are designed to recombine these gases internally, the recombination efficiency is less than
100%. Small amounts of hydrogen and oxygen are released from the pressure relief valve during
charging. Normally, the hydrogen gas dissipates very rapidly and never reaches a concentration level
that is hazardous. However, if the battery is installed in an enclosure with minimal airflow, the
concentration of hydrogen could build up to a high enough concentration to be of concern. Hydrogen can
ignite at concentrations as low as 4% in air. For this reason, never install a AGM battery in a sealed or
an airtight container.
B. Exposure to Acid
All lead acid batteries contain sulfuric acid in the electrolyte, which can cause chemical burns to body
tissue. Although AGM batteries are classified as Nonspillable, exposure to the electrolyte is possible
under extreme conditions (e.g., if the battery is cracked open or crushed). In the event that electrolyte is
displaced from the battery, avoid contact with the skin, eyes and clothing. In the event of an accident,
flush with water and call a physician immediately.
C. Shorting of Terminals
AGM batteries have very low internal impedance and therefore are capable of delivering high currents if
the external terminals are short circuited. The resulting heat can cause severe burns and is a potential
fire hazard. Accidentally placing metal objects across the terminals can result in severe skin burns. It is a
good practice to remove all metallic items such as watches, bracelets and rings when installing or
servicing batteries. As a further precaution, insulating gloves should be worn and only insulated tools
should be used when installing or servicing batteries.
D. 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.
Currently, manufacturers are not aware of any AGM batteries that have failed due to thermal runaway.
To preclude the possibility of thermal runway, the battery charging instructions provided in the service
section 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.
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