Batteries - Explosive gasses and
Battery Rooms, Ventilation, Installations
Please see Appendix A 1of GelHandbookPart2.pdf ( Rev 5. Dec '03 posted here Mar '04)
Basic principles and design overview - GelHandbookPart1.pdf (Rev 1. Dec '03 posted here June 04)
While the art of low-gas production type batteries is well advanced, using Low Gassing Lead/Calcium plates and gas recombination techniques with well regulated charging devices, we CANNOT assume that the charging devices will always regulate voltage properly at all temperatures; Nor can we assume that necessary and routine maintenance of the cabling connections has been performed in a series/parallel battery set for mobile or Marine application. Given these variables, we must always design a suitably ventilated system in the event of charging induced gassing. For this reason it is strictly forbidden to use any battery technology in a sealed box or un-ventilated room. Ventilation to outside air- whether active (forced air) or passive (air slots or limber holes)- is compulsory.
ANY rechargeable battery can and will produce gas. Ventilate to outside air!
Caveat.The production of Hydrogen gas is not the sole reason for an explosion. There is a much greater need for a spark. The greatest danger of generating a detonating spark, arises from improperly secured battery terminal clamps, and from inflexible battery cables which come loose from the battery and so cause an electric spark. Batteries must be secured against motion, and the cables supported properly. Use of solid bar connectors in any motive or mobile battery application is prohibited. Well supported, good quality flexible cable or wire of suitable size will help absorb any minor motion or vibration and remove strain from the terminal connections where a spark is most likely to occur. NEVER use or mount any spark producing device in the battery chamber or box. ( Don't even think about it and if you've done it, change it before your friends are comforting your widow in certain ways not acceptable to thee..)
Gassing in open or flooded lead acid batteries.
Theoretically, Hydrogen is only caused by an over-load current. So long as a rechargeable battery is close to full charged, the fed-in current (i.e., the charging current) will be converted into electrochemical energy. In fact, however, certain quantities of hydrogen and oxygen are generated in a rechargeable battery at any time, and that means both when charging and discharging - even when inoperative!
Even when the so-called water decomposition voltage of 1.55 V per cell has not been reached (e.g., in open nickel-cadmium batteries) a certain amount of hydrogen and oxygen is nevertheless released. For this reason it is strictly forbidden to locate any kind of rechargeable battery whatsoever - even gastight nickel-cadmium batteries - in hermetically sealed spaces. Potting them in resin is likewise strictly forbidden.
Most tactical vehicles are designed so that they can operate under battened-down NBC conditions. This battened-down condition entails supplying air through filters to the crew compartment and battle station. If batteries are accommodated in the crew compartment or battle station, the battery compartment ventilation air must also be supplied via the filter.
The amount of fresh air to be fed to the battery compartments is calculated using the following formula:
Q = V . q . s . n . I in liters/hours (1/h)
(for open or flooded lead acid batteries)
s = Safety factor = 5 for
land-based equipment and land vehicles. For water vessels and boats
s = 10.
For land-based equipment and land vehicles to
For water vessels and boats to
For tactical land vehicles and military/naval vessels the current I, to be taken into account for ventilation measures equals 2 A per 100 ah of the installed battery capacity. This assumes that the charging devices are restricted so that the so-called gassing voltage of the batteries, i.e., of lead-acid batteries, does not exceed 2.4 V/cell. In the case of 24 V battery sets this figure is 28.8 V.
According to the above ventilation equation and quantity of
fresh air equivalent to
Gassing in Sonnenschein gelled electrolyte lead acid batteries, is far lower.
Dryfit battery gassing is extremely low.The
required maximum gas volume of 30mL per 1Ah per cell in 30 days
We only recommend that the Sonnenschein or
Deka Gel Cells batteries not be charged in a sealed container or environment.
In normal usage these Manufacturers sealed, gelled Lead Acid batteries have
no need to for special ventilation precautions. Ensuring that the air surrounding the
battery bank e.g. via air slots (or Limber Holes) is in contact with the outside air, is
sufficient. This opinion applies solely to Sonnenschein dryfit and Deka gel-tech.
In contrast to open lead-acid batteries
with liquid sulfuric acid electrolyte, sealed lead-acid batteries complying with VG 96 924
have a gelled electrolyte.
After 2 years of use the above values reduce by a factor of
Therefore, when using these sealed, gelled
Lead Acid batteries there is no need to take special ventilation precautions. Ensuring
that the air surrounding the battery bank e.g. via air slots (or Limber Holes) is in
contact with the outside air, is sufficient. Careful voltage regulation is compulsory for
safe use and long life of the product!
Most data above are
from the Sonnenschein Batteries for Miltary Applications (NATO)-Circa1986 - or
earlier Sonnenschein technical papers updated as gassing data are made
available. Information is believed current and dated 1st May 2002.