Apparatus to control multiple parallel batteries to share load current

[0002] 1. Field of the Invention

[0003] The present invention relates to apparatus for supplying electrical power, and more particularly to a method for reducing wear on a plurality of parallel connected batteries by controlling each battery to share a load element equally.

[0004] 2. Prior Art

[0005] Prior techniques for connecting multiple parallel batteries included techniques for over-sizing the battery cell capacity to account for loss, or providing a relay and switch matrix to compensate for multiple battery cell failures. Such prior techniques are costly and inefficient.

[0006] An object of the present invention is to provide a highly efficient apparatus to reduce wear on a plurality of parallel connected batteries.

[0007] Another object of the present invention is to provide apparatus wherein each battery in a plurality of parallel connected batteries is controlled to share a load equally. Still another object of the present invention is to provide an apparatus for a plurality of parallel connected batteries that provides a high level of fault tolerance while minimizing the number of components.

[0008] Other and further features, advantages and benefits of the invention will become apparent in the following description taken in conjunction with the following drawing. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawing which is incorporated in and constitute a part of this invention and, together with the description, serves to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure.

[0009] The foregoing aspects and other features of the present invention are explained in the following description, taken in connection with the accompanying drawings, wherein:

[0010] FIG. 1 is a schematic illustration of an embodiment of a circuit for carrying out the principles of the present invention.

[0011] Referring to FIG. 1, an embodiment of the present invention is shown that includes an architecture of n parallel batteries 10-1 . . . 10-n, each of which consist of N number of series connected battery cells where n and N may or may not be the same number. FIG. 1 also shows a load current monitor 12 that monitors the current through a load element 14, a battery current monitor 16-1 . . . 16-n for each battery, and n number of DC/DC converter circuits 18-1 . . . 18n having outputs connected in series with each battery 10-1 . . . 10-n respectively. Current sharing of the batteries is accomplished as follows: The load current output signal of the load current monitor 12 is scaled by 1/n, where n is the number of batteries, by a scale down amplifier circuit 20 and distributed as a reference voltage to summing circuits 22-1 . . . 22-n where the scaled down load current is compared to the output of the battery current monitors 16-1 . . . 16m. The outputs of the summing circuits 22-1 . . . 22-n are respectively connected as control signals to each of the DC/DC converters 18-1 . . . 18-n that are connected to each battery 10-1 . . . 10-n. Each DC/DC converter 18-1 . . . 18-n adjusts it's output voltage to regulate the battery currents I1 . . . In of each of the n batteries to be equal to the reference voltage from the load current monitor 12. The DC/DC converters 18-1 . . . 18-n are typically either n+1 redundant or primary/backup. Each of the DC/DC converter circuit's 18-1 . . . 18-n output voltage will typically be the difference between the bus voltage and the battery voltage. Thus, each of the batteries 10-1 . . . 10-n share the load element 14 equally. A secondary voltage loop can also be added to use the DC/DC converters 18-1 . . . 18n to regulate the bus voltage.

[0012] It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.