The oxygen cycle and saturation effects

The important design difference between VRLA and flooded lead-acid batteries is the partially saturated condition of the plates and separator in VRLA products. As noted earlier, the diffusion rates for oxygen and hydrogen are lO times greater 

In the more common case when a VRLA cell starts out at 95% saturation, it behaves electrochemically very much like a flooded lead-acid cell. As the cell ages, however, the saturation level of the separator drops significantly due to the following 

Clearly, this is unacceptable. This is what must be dealt with, however, in properly charging VRLA products. If this thermodynamic fact is not addressed, VRLA products will fail prematurely, not due to dry-out or grid corrosion, but due to insufficient recharge of the negative plate. 

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