SunXtender Technical Manual

Document No. 6-0100 Rev. H
Page 27 of 43
CHAPTER 7 - SAFETY INFORMATION
There are four main safety hazards associated with the use of any valve regulated lead acid (VRLA)
battery. These hazards are as follows: a) Release of ignitable gas, b) Exposure to acid, c) Shorting
of terminals, d) Thermal runaway. This chapter provides a description of each of these hazards and
means to mitigate them.
7.1 Release of Ignitable Gasses
All lead-acid batteries, including VRLA batteries, produce hydrogen and oxygen gases during normal
charging. Even though VRLA 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 Sun Xtender® AGM battery in a sealed or an airtight container.
7.2 Exposure to Acid
All lead-acid batteries contain sulfuric acid in the electrolyte, which can cause chemical burns to
body tissue. Although Sun Xtender® 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.
7.3 Shorting of Terminals
Sun Xtender® 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 belt
buckles, 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.
7.4 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 Sun Xtender® 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.