Pre-compressed glass fiber separators for batteries

Abstract

A substantially binder-free glass fiber separator, especially for valve regulated ('sealed') lead acid batteries is disclosed. The separator has a reduced thickness and temporarily inhibited resiliency. A substantially binder-free glass fiber web having a given thickness is wetted with a controlled amount of liquid and compressed to a substantially reduced thickness and the liquid suppresses the natural resiliency of the glass fiber separator so that it will have a substantially reduced thickness when the compression is released. The amount of liquid required to suppress the resiliency of the glass fiber separator is substantially less than the minimum amount of the portion of electrolyte which would be carried in the separator in a finished cell. When sufficient electrolyte is added to the moistened, reduced thickness separator, its resiliency is substantially restored and it will expand or, if confined within a cell stack within a case, it will try to expand, thereby placing the confined cell stack components under compression. The separator can be wetted and compressed in a battery manufacturing line or a glass fiber web can be compressed, before all of the liquid is removed from the web. The reduced thickness of the separator makes it easier to insert a cell stack containing the separator into a battery case and the restoration of the resiliency when electrolyte is put into the case ensures that there will be the degree of compression needed for good performance of a VRLA battery.