Power supply system

A power supply system includes three sets of batteries for supplying direct current to a load. Three sets of switches connect mutually respective sets of batteries to the load. A controller operates the switching means so that at any time at least two of the sets of batteries are connected in parallel to the load. The controller alternates each set of switches in open and closed positions with the switches being operated in a predetermined, cyclic manner, so that during the cycle, each of the sets of batteries provides current to the load for a portion of the cycle and is disconnected from the load for the other portion of the cycle. Utilizing the sets of batteries in pairs so that each set of batteries provides only about half the current requirement and of repeatedly disconnecting each set of batteries for a short period of time while the other two sets of batteries supply the current which maximizes the life and performance of the batteries.

BACKGROUND OF THE INVENTION 
1. Field 
This invention relates to an electrical power supply system utilizing three 
sets of batteries and switching means for successively switching a load 
among the sets of batteries. 
2. Prior Art 
There has been considerable interest in developing alternatives to gasoline 
powered vehicles for reasons both of reducing air pollution and of concern 
for the dwindling sources of oil. Some had thought that electrical power 
might be developed into an attractive alternative to the gasoline engine 
but thus far the lack of suitable long-lived batteries has inhibited 
progress in this direction. Any progress in improving electrical power 
supplies would, of course, be beneficial in a variety of situations 
besides that of powering vehicles. 
In my earlier U.S. Pat. No. 4,101,787, issued July 18, 1978, a power system 
is disclosed having a plurality of batteries for supplying direct current 
to a load and switching means for alternatively opening and closing the 
respective circuits between the load and each of the batteries to cause 
intermittent current flow between each of the batteries and the load 
serially. Successively switching the load between a plurality of batteries 
greatly improves the overall life of the batteries. 
Objectives 
It is a principal objective of the invention to provide a highly efficient 
electrical power supply utilizing three sets of batteries. A further 
objective is to provide a system in which current is drawn from the sets 
of batteries in recurring cyclic fashion so that each set of batteries 
provides current for about 2/3 of the cycle time and is then disconnected 
from the load for the other 1/3 of the cycle time. An additional objective 
is to provide for cyclic operation in which at least two sets of batteries 
are always connected in parallel with the load so that when connected, 
each set of batteries supplies only about 1/2 the total current draw of 
the load. It is still a further objective of the invention to provide a 
system for successively switching a load between three sets of batteries 
to maximize the overall life and performance of the batteries. It is still 
a further objective of this invention to provide a system wherein the 
voltage of the three battery banks will be equalized thereby extending the 
usable lifetime of the batteries. 
SUMMARY OF THE INVENTION 
The above and other objectives of the present invention are realized in an 
embodiment of an electrical power supply which includes three batteries or 
three sets or banks of batteries and three sets of switching means 
connecting mutually respective sets of batteries to the load. A controller 
is provided for operating the switching means so that current is drawn 
from the sets of batteries in recurring cyclic fashion, with each set of 
batteries providing current for 2/3 of the cycle time while being 
disconnected from the load for the other 1/3 of the cycle time. The 
control system is programmed so that are activated serially and in cyclic 
sequence, with a typical cycle comprising the following three steps which 
occur serially at equal time intervals: (1) closing the first switch and 
at about the same time opening the second switch; (2) closing the second 
switch and at about the same time opening the third switch; and (3) 
closing the third switch and at about the same time opening the first 
switch. The cycle is repeated with a time interval between steps (3) and 
step (1) being equivalent to the time interval between steps (1) and (2) 
and steps (2) and (3). By switching between the sets of batteries in such 
fashion, it has been found that the useful life and performance 
characteristics can be maximized. 
Additional objects and features of the invention will become apparent from 
the following detailed description taken together with the accompanying 
drawings.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
In accordance with the invention, three banks of batteries, labeled bank 
No. 1, bank No. 2, and bank No. 3 are provided for supplying current to a 
load 10. Each bank may include one or more batteries depending upon the 
voltage required from each bank to operate the load 10. Each of the banks 
of batteries is coupled by way of a respective relay switch 11, 12, and 13 
and a common on/off switch 14 and a speed controller 20 to the load 10. 
Thus, with the on/off switch 14 in its on position, bank number 1 of 
batteries will be in connection with the load 10 when the relay 13 is 
activated so as to complete the connection thereto. Similarly bank number 
2 will be in connection with the load 10 when relay 12 is activated, and 
bank number 3 will be in connection with the load 10 when relay 11 is 
activated. When any of the relays 11, 12, and 13 are activated 
simultaneously, the respective banks of batteries are then connected in 
parallel to the load 10. 
The relays 11, 12, and 13 are coupled to mutually respective relay drivers 
15, 16, and 17, and, in turn, each of the relay drivers 15, 16, and 17 are 
coupled to separate outputs of a control logic 18. For purposes of 
explanation, relay driver 15 will be considered to be connected to logic 
output 1, with relay drivers 16 and 17 being connected to logic outputs 2 
and 3, respectively. The control logic is connected to an oscillator 19. 
The oscillator 19, control logic 18 and relay drivers 11, 12, and 13 can 
be powered by controlled voltages from any of the banks of batteries. 
The oscillator 19 is adapted to produce a square wave signal having an 
adjustable period of approximately 2 seconds to 5 seconds. The control 
logic 18 is adapted to produce three square wave output signals which 
change states serially with input pulses from the oscillator. A timing 
diagram is shown in FIG. 2 showing the three output signals from the 
control logic 18. As shown, each of the output signals has a square wave 
with the duration of the high portion being about twice the duration of 
the off or low portion. Logic output 1 turns high and logic output 2 turns 
low on one of the pulses from the oscillator 19. On a subsequent pulse 
from the oscillator 19, logic output 2 turns high and logic output 3 turns 
low. On the next subsequent pulse from the oscillator 19, logic output 3 
turns high and logic output 1 turns low. The cycle is then repeated upon 
subsequent pulses from the oscillator 19. 
The logic outputs from the control logic 18 are coupled to relay drivers 
15, 16, and 17, respectively. The relay drivers are, in turn, connected to 
the relays 11, 12, and 13, respectively, and are adapted to activate their 
respective relays when the logic output to the respective relay driver is 
on or high. In a particularly preferred embodiment, the relay drivers 15, 
16, and 17 are adapted to delay the opening of their respective relays 11, 
12, and 13 for a short period following the logic output turning low. The 
delays produced by the line drivers is shown as dashed lines imposed on 
the timing diagram of FIG. 2. The time delay is preferably about 0.25 
second to 0.5 second depending upon the period of the oscillator 19. 
As illustrated, the relay drivers 15, 16, and 17 operate the relays 11, 12, 
and 13 in such manner that the load 10 is connected sequentially to the 
banks of batteries nos. 1,2, and 3 in a particular cyclic order. In 
operation, the controller 18 and relay drivers 15, 16, and 17 alternate 
the relay switches 11, 12, and 13 in open and closed cycles wherein the 
closed position has a time duration about twice that of the open position, 
and the switches 11, 12, and 13 are switched open and closed in cyclic 
predetermined order, with the switch 11 closing at about the same time the 
switch 12 opens, the switch 12 closing about the same time the switch 13 
opens, the switch 13 closing about the same time switch 11 opens, and then 
repeating such switching cycle over and over. As can be seen from the 
timing diagram of FIG. 2, the load draws current equally from two banks of 
batteries at most instances. At the instances when the relay switches are 
opening and closing, there is a short overlap in which all three banks of 
batteries concurrently supply current to the load. The operation in 
accordance with the present invention provides a repeating rest period for 
each bank of batteries, with the rest period having a duration of about 
1/3 the total cycle. Sequencing of the banks of batteries provides for a 
fresh bank of batteries to be switched into connection with the load every 
1/3 cycle, with the bank of batteries which had previously been connected 
to the load for 2/3 cycle being disconnected for the rest period. 
With at least two banks of batteries always being connected in parallel to 
the load, the current load of any bank is only half that which would be 
drawn if each bank were connected singly to the load. The short overlap in 
the connections at the switching points in the cycle provides repeating 
short periods wherein all three banks of batteries are connected in 
parallel. Having two banks normally in connection with the load with the 
overlap occurring during switching of the banks results in reducing relay 
point arcing to a minimum. 
When Bank 1 and Bank 2 are paralleled the voltages of these banks will be 
equalized. When Bank 2 and Bank 3 are paralleled the voltages these banks 
will be equalized. When Bank 3 and Bank 1 are paralleled the voltages of 
these banks will be equalized. This equallizing effect causes all three 
banks to remain balanced in voltage during the normal operating period. 
This guarantees that the load 10 receives the same power through the speed 
controller 20 regardless of which banks of batteries are connected thereby 
extending the usable lifetime of the batteries. 
The three battery system of the present invention utilizing a switching 
cycle in which two banks of batteries are always connected in parallel, 
results in a much greater increase in performance, especially endurance, 
in comparison to systems such as disclosed in my earlier patent preferred 
to above. In tests made on an electrically powered automobile, the 
automobile was able to operate for up to 5 times as long with the three 
bank system of this invention as compared to when two banks of batteries 
were used in alternating fashion as described in my earlier referenced 
patent. The batteries in the banks all being of equal number and duty, it 
would be expected that the three bank system would have a 50% greater 
capacity than the two bank system. However, tests show that a remarkable 
increase in capacity of about 500% is achieved. 
The optimum time that any one bank of batteries is connected to the load 
per cycle can be readily determined experimentally for the particular kind 
of batteries being used. It is advantageous to select batteries having an 
ampere/hour rating of about 10 or more times the load current in amperes. 
Generally, for such batteries, it has been found advantageous for the time 
per cycle that any one bank of batteries is connected to the load to be 
from about 4 to 10 seconds, with the time per cycle that any one bank of 
batteries is disconnected being from about 2 to 5 seconds. 
It is to be understood that the above-described arrangements are only 
illustrative of the application of the principles of the present 
invention. Numerous modifications and alternative arrangements may be 
devised by those skilled in the art without departing from the spirit and 
scope of the present invention, and the appended claims are intended to 
cover such modifications and arrangements.