The present invention is a methodology for efficiently regulating the voltage coming out of a battery pack, specifically when a series of cells (‘pack’) are connected together to produce an increased voltage, which is in turn used to power an electrical device, such as a motor. A real world example would be a battery pack in an electrical vehicle (‘EV’), which in turn is connected to an electrical motor.
DC electric motors which utilize brushes (‘brushed motor’) are proportionally controlled by the inclusion of a variable voltage regulator, placed in series with the battery pack, usually on the positive supply lead. The variable voltage regulator reduces the voltage as required by the vehicle operator, thus allowing a proportional response to throttle requirements for various speed levels from the brushed motor. A multiplicity of design methodologies exist for these variable voltage regulators; for example, but not limited to: regulators which operate utilizing a switching inductive energy storage device.
Brushless DC electric motors (‘BLDC motor’) are regulated through the timed switching of a multiplicity of magnetic coils, which are included within the design of the BLDC motor. The controllers thereto regulate power in proportional response to throttle requirements by varying the length and phasing of the electrical pulses applied to each coil within the BLDC motor. The controllers are also placed in series to the battery pack, usually on the positive supply lead.
The battery packs obviously must be recharged after usage causes depletion of storage. Invariably, individual batteries vary slightly in their ability to carry a constant charge (or a constant amount of energy). As overcharging may cause catastrophic destruction of the battery, it is critical to battery system designers to implement a methodology which prevents such destruction by stopping the charging of batteries which are already full, while allowing other batteries with greater capacity to continue charging. The impact of this design criteria may also be exacerbated by a similar problem, which is over-discharge. The individual cells within the battery pack must not be over-discharged. Therefore, electronic battery monitoring (‘battery monitoring’) exists which monitors the state of each individual cell while charging, and while discharging. The battery monitoring circuitry is usually a part of battery pack design, and is also usually a part of the EV design.
In one embodiment of the present invention, a controller is created that works by interspersing electronic switches throughout the series construction of the battery pack, thus allowing the following features:
1) Batteries which are depleting their total charge more rapidly (due to variance in manufacturing) may be switched out of circuit, so that all batteries are depleted at the same time. In the absence of this feature, the usage of the battery pack must be discontinued when the first cell (whichever cell, of all cells in series in the battery pack) is depleted.
2) If a brushed motor is used, the interspersed electronic switches allow coarse regulation of the motor speed and power by allowing any set of quantity n batteries contained within the battery pack to be dynamically connected in series. For example, a battery pack with a final voltage of 72 volts (obtained by 20 batteries of 3.6 volts, connected in series) may produce any voltage from 3.6 to 72 volts, as batteries are removed and rewired utilizing the interspersed electronic switches.
3) As individual voltages within individual cells start to reduce, as is typical for all battery cells experiencing discharge, the interspersed electronic switches allow dynamic rewiring to add in cells and increasing the total voltage of the battery pack. For example, if 12 cells (out of a series pack of 20 cells) are actively engaged via switching to produce 43.2 volts (12×3.6 volts), then as individual voltages within cells sag, a 13th cell might be added at the calculated moment via the interspersed switches. An example of this sag condition would be when the voltages of the average cell are at 3.32 volts. 13×3.32 volts=43.2 volts, so the dynamic reprovisioning allows the battery pack to be delivering the approximate required voltage without the need for an additional regulator.
The present invention provides a method to regulate voltage while ensuring that the total capacity of each battery is utilized.
10) BATTERIES: may be any rechargeable chemistry, including lead acid, nickel cadmium, lithium polymer, etc.
12) ELECTRONIC SWITCHES: although they may be thought of as a simple metal switch, they are optimally constructed from semiconductors, such as MOSFET or other similar or superior switching devices. The MOSFETs receive on/off control from a central control unit. The switching of the MOSFET allows any pair of batteries (as shown in
14) CONTROL: The control module accepts commanded input (from a throttle, for instance) and directs the series of switches present within the interspersed switch arrays to produce an output voltage which is equivalent or similar to the required output power. For instance, if the throttle commands 60% power, the switches will be set up so that 60% of the available power is routed to the output load, typically a DC or BLDC motor. Additionally, the control module analyzes the voltage of each cell and readjusts the switch matrix to remove cells which are more rapidly losing power, and also to adjust the total number of cells so that power may remain approximately constant, even as each individual cell loses voltage potential.
16) THROTTLE: In embodiments of the present invention where the application is for an electric vehicle, such as a car, golf cart, or airplane, this is an input to the control module, which instructs the control module to provide a requested amount of power to the output load.
18) ALARM OUTPUT: an input to the control module, which instructs the control module that an error condition occurs (such as motor over temperature or overspeed)
20) CHARGE INPUT: an input to the control module, which instructs the control module to configure the battery matrix for charging, and also instructs the control module to monitor individual cells for overcharge conditions and switch them out of circuit, as necessary, in order to ensure a balanced charge on each cell.
22) POWER SWITCH: An ON/OFF key, which is an input to the control module, which instructs the control module that the battery matrix may be allowed to provide power to an external load. In an electric vehicle, this would usually be a keyed electronic input, such as from an ignition switch. It may take other forms, such as provided by keyless start systems, or by simple toggle switches. It increases security and safety, by requiring, in one embodiment, a ‘zero’ or ‘idle’ condition on the throttle before the throttle may be advanced further.
24) TOTAL VOLTAGE OUTPUT: Is provided by the control module to inform the operator of the voltage which is maximally available.
26) CURRENT VOLTAGE OUTPUT: Is provided by the control module to inform the operator of the amount of voltage being delivered to the external load. on the outer surface of the foam, such as foam-compatible paint; adhesive vinyl; shrinkable Dacron (or other) fabric; or layer(s) of fiberglass or other surface composite coverings
28) TOTAL POWER OUTPUT: Is provided by the control module to inform the operator of the amount of wattage (power; horsepower) being delivered to the external load.
30) PERCENT REMAINING POWER: Is provided by the control module to inform the operator of the amount of power still remaining in the battery system
32) INDIVIDUAL CELL INFORMATION: Is provided by the control module to inform the operator critical information related to individual cells; for instance: low capacity
34) ALARMS: Are provided by the control module to inform the operator that critical levels of power remain, or that critical conditions exist.
Referring to
The present invention provides a way to build a battery controller for a series of cells, allowing interspersed switches to switch cells in and out of circuits to match power demands, as prompted by an external throttle. The present invention is sufficient to directly control a DC motor without additional circuitry, and will not suffer switching losses as are incurred in conventional voltage controllers which must rely on series voltage regulation techniques. As a result, it is more efficient. Because this improved battery controller also allows all cells within a battery pack to be fully utilized, it will show more total power available to the load per charge cycle, thus increasing cycle power longevity and efficiency.
Number | Date | Country | |
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61909253 | Nov 2013 | US |