How to Vent Your Solar Batteries
The process of charging lead acid batteries involves passing electric current through water, contained in the electrolyte inside the battery. A natural by-product of this process is the splitting of the water into its basic components, hydrogen and oxygen, which can build up to explosive levels if it is not ventilated properly.
Explosive mixtures can be prevented if the battery enclosure is designed to take advantage of the principles of natural convection and ventilation. The patented H2Vent™ systems from Zomeworks have been developed to vent batteries.
Principles of Natural Convection
The most reliable and Fail-Safe way to ventilate hydrogen from a battery shelter is by using the principles of natural convection, taking advantage of
- The natural property of light-density gas to rise upward, and
- The heavier-density gas to sink downward
Under most common conditions, Hydrogen has a lighter density than air and tends to rise upward when in contact with air. Warmer air is less dense than cooler air, and so warm air tends to push upwards when in contact with cooler air.
Just as a bowl will hold water when right side up, but will not when upside down, a hydrogen ventilation system will trap hydrogen unexpectedly if the geometry is arranged upside down or backwards.
These natural principles can be put to good use by the proper use of vents, ducts, heat exchangers and other components. But only the right combination of components will provide effective and fail-safe hydrogen ventilation.
The Presence of Hydrogen
The ideal hydrogen ventilation system should react only to the presence of hydrogen, and not provide constant ventilation air when it is not needed, so as to avoid the extra heating and cooling problems that this would create. It should not require a fan or other mechanical or electrical components that are prone to random failures. It should not react to air temperature, only the presence of hydrogen.
The following pages show five different configurations intended to ventilate hydrogen from a battery box, but only one is not fatally flawed;
Example 1 shows how a Fan can be used, but in the inevitable event of mechanical and electrical failure, ventilation would cease and the box would become a hydrogen trap.
Example 2 shows how High and Low vents can be used, but this is not very well regulated, allowing too much outside air into the battery shelter, creating extreme temperatures and creating a hydrogen trap at times when the inside is cooler than the outside.
Example 3 shows how a small chimney (called a riser tube) can be used with a low vent to trap warm air in the battery box. Unfortunately this system acts as a very effective and dangerous hydrogen trap as well.
Example 4 shows how a riser tube and a high vent can be used, but this will only ventilate effectively when the inside is warmer than the outside. At other times it, too, will become a dangerous hydrogen trap.
Example 5 shows that when the chimney is reversed (now called a dip tube), and high vents and a heat exchanger are properly arranged, that hydrogen is ventilated without any of the drawbacks or failures of the other 4 examples.
The Zomeworks patented H2Vent™ passive hydrogen ventilation systems are designed according to the principles shown in Example 5.
This system is available on all Cool Cell passive temperature regulating battery enclosures and is the only system that cannot fail and become a trap for hydrogen.
The H2Vent™ passive hydrogen ventilation systems can also be designed into other battery charging cabinets, vaults, rooms or shelters. For more information, see the H2Vent™ web page or contact Zomeworks Corporation, 1 (800) 279-6342.