Why not use high and low vents?
High and low vents are unreliable and therefore hazardous. One expects them to expel lighter hydrogen rich air through the high vent while fresh air flows in through the low vent. This will only take place when the hydrogen rich air is as warm or warmer than the outside air. When the hydrogen rich air is colder than the outside air, the flow is stifled and the hydrogen can easily reach explosive concentrations. High and low vents also admit hot air during hot weather and cold air during cold weather, eliminating the advantage of an insulated battery enclosure, exposing the batteries to damaging temperature extremes.
