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Abstract

A self-contained electronic device instantaneously assesses the stored energy capacity of single, two-volt, lead-acid cells; or of batteries comprised of such cells. The testing device is electrically connected to the terminals of a cell or battery and measures its dynamic conductance with a small, time-varying signal. An internal conductance standard permits initial calibration of the device to assure accuracy of the cell/battery measurements. Means are provided for entering a 'reference conductance', defined to be the dynamic conductance of an identically rated and constructed cell or battery having 100% energy capacity. The device displays either the test cell/battery's measured conductance in Siemens (mhos), or its 'percent capacity' determined by appropriately scaling its measured conductance in accordance with the 'reference conductance'. When determining 'percent capacity', an LED lights if the result is less than a preset threshold value. For single-cell operation, special design features permit energizing the higher current elements of the measuring circuit directly from two-volt cell undergoing test while energizing the lower current, but higher voltage, elements from a separate, low-power, dc source such as a small 9-volt transistor battery or an integral dc/dc converter powered by the cell undergoing test. This novel circuit arrangement results in the realization of a portable, self-contained, electronic instrument that provides an accurate, instantaneous, assessment of the 'percent capacity' of a two-voltage cell, or a battery comprised of such cells, without requiring any connection to external power.

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First Claim