Abstract: A method and apparatus are provided for monitoring and adjusting angular speed or rotational frequency of a fan as well as wear. As a result of being able to monitor the angular speed or rotational frequency of a fan, a prediction of both wear and failure can be made. Due largely to increasing internal friction related to the amount of wear, the energy required to operate a fan at a given angular speed or rotational frequency varies. Hence, an algorithm and certain devices can be employed to make wear and failure predictions of either an mechanical or electrical fan based on energy consumption relative to an angular speed or rotational frequency.

Abstract: A battery cover for a battery casing has a plurality of electrolyte containing cells, a primary cover and a secondary cover. The primary cover has a plurality of barrels arranged along a longitudinal axis and the secondary cover has a plurality of tubular elements extending downwardly and insertable in the barrels of the primary cover. Each of the tubular elements has an inner tubular member and an outer tubular member. The outer tubular member has an axially extending cutout portion which runs from its tip to the surface of the secondary cover. The battery cover also has a plurality of baffles defining a circuitous passageway for gases which are evolved in the cells of the battery to be released to an external port located on the secondary cover.