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 hydrogen gas venting is not done properly.
Explosive mixtures can be prevented if the battery enclosure is designed to take advantage of the principles of natural convection and ventilation for hydrogen venting. The patented H2Vent™ systems from Zomeworks have been developed to vent batteries.
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:
Hydrogen is less dense 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 ideal hydrogen ventilation system should work only when hydrogen is present and not otherwise. It should not provide constant ventilation, this avoids the extra heating and cooling problems. It should not require a fan or electrical components that are prone to failures. It should not react to air temperature, only the presence of hydrogen.
The following are five different configurations intended to ventilate hydrogen from a battery box, but only one is not fatally flawed:
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.
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.
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.
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
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.