Discrete voltage level controller
In an electrically powered vehicle, a computer-controlled switching system activates relays to switch additional discrete batteries into a circuit in response to throttle level, where a processor is configured to decide what specific batteries should be present in the circuit at any given time, in response to both throttle level and a battery load balancing optimization scheme.
1. A computer implemented apparatus, comprising:
a switching circuit comprising a plurality of relays that are operable to independently switch any of one or more of a plurality of batteries into and out of a motor power circuit; and
a processor configured to balance the use of the plurality of batteries;
wherein the processor is configured to:
receive a throttle position;
determine a particular number that indicates how many batteries to switch into the motor power circuit based at least on the throttle position;
determine a battery state of charge for each battery of the plurality of batteries;
select a number of batteries from the plurality of batteries based on the battery state of charge for said each battery, wherein the number of batteries selected is equal to the particular number of batteries; and
switch the selected number of batteries into the motor power circuit;
wherein the processor is further configured to:
compare the battery state of charge determined for said each battery with the battery state of charge for every other battery of the plurality of batteries;
based on comparing the battery state of charge for said each battery, identify a particular battery that has a greatest battery state of charge among the plurality of batteries; and
add the particular battery into the motor power circuit by closing a relay associated with the particular battery.
2. The apparatus of claim 1 , wherein said relays comprise any of electromechanical relays and solid state relays, and wherein said relays further comprise any of normally open relays, normally closed relays, and latching relays.
3. The apparatus of claim 1 ,
where a battery comprises:
an individual battery; or
an array of batteries, wherein the array of batteries is connected in series or in parallel.
4. The apparatus of claim 1 , wherein said switching circuit comprises a motor controller for an electric vehicle.
5. The apparatus of claim 4 , wherein said processor is configured to determine in real time how many batteries should be switched into said switching circuit to automatically maintain a commanded vehicle speed, as represented by said throttle level signal.
6. The apparatus of claim 1 , wherein said processor is configured to determine current delivered by each battery in response to a signal from a sensor, said sensor comprising any of a shunt, a Hall effect sensor, and a voltmeter that estimates battery discharge state from battery voltage.
7. The apparatus of claim 1 , wherein each of said plurality of batteries, whether connected in series, parallel, or in series and parallel, is controlled by a single relay.
8. The apparatus of claim 1 , further comprising:
a pulse width modulation controller configured to provide power up to a given voltage level;
wherein said switching circuit switches in additional batteries as needed to supply higher voltages to said pulse width modulation controller.
9. The apparatus of claim 1 , further comprising:
a traction control system for determining wheel slippage information and for supplying said information to said processor, wherein said processor is configured to receive said information from said traction control system and to operate said switching circuit to switch in a maximum number of batteries for which wheel spin does not occur.
10. The apparatus of claim 1 , wherein said processor is configured to operate said switching circuit to switch a battery or plurality of batteries in and out of said motor power circuit at high frequency to provide pulse width modulated output voltage levels between those offered by any integral multiples of battery voltages.
11. The apparatus of claim 1 , wherein said processor is configured to enforce a time latency in response to an increase in said throttle level signal to avoid generating large currents when driving in motor loads at zero or low RPMs.
12. The apparatus of claim 1 , said switching circuit further comprising:
a plurality of solid state switching devices, comprising any of MOSFETs and IGBTs, that are connected in parallel to switch said batteries in and out of said motor power circuit for high current applications.
13. The apparatus of claim 1 , said switching circuit further comprising:
a single additional high power relay of adequate current capacity to break the motor power circuit under load temporarily when the relays that switched are of an inadequate current capacity to switch the load at full power.
14. The apparatus of claim 1 , wherein said processor is configured to perform continuous integration of current delivered by each battery to determine a state of charge of each battery.
15. The apparatus of claim 1 , wherein said processor is configured to calculate an instantaneous voltage of each battery to determine a state of charge of each battery.
16. The apparatus of claim 1 , wherein each of said plurality of batteries may be alternatively switched into said motor power circuit either in series with one or more of said other batteries or in parallel with one or more of said other batteries.
17. A computer implemented method, comprising the steps of:
providing a switching circuit comprising a plurality of relays that are operable to independently switch any of one or more of a plurality of discrete batteries into and out of a motor power circuit; and
providing a processor configured to balance the use of the plurality of batteries by:
receiving a throttle position;
determining a particular number that indicates how many batteries to switch into the motor power circuit based at least on the throttle position;
determining a battery state of charge for each battery of the plurality of batteries;
selecting a number of batteries from the plurality of batteries based on the battery state of charge for said each battery, wherein the number of batteries selected is equal to the particular number of batteries; and
switching the selected number of batteries into the motor power circuit;
wherein the processor is further configured to:
compare the battery state of charge determined for said each battery with the battery state of charge for every other battery of the plurality of batteries;
based on comparing the battery state of charge for said each battery, identify a particular battery that has a greatest battery state of charge among the plurality of batteries; and
add the particular battery into the motor power circuit by closing a relay associated with the particular battery.
18. The apparatus of claim 1 , wherein the battery state of charge of said each battery is determined based on an indication of the integrated total energy output since pack recharge.
19. The apparatus of claim 1 , wherein determining the particular number of batteries to switch into the motor power circuit is further based on the battery state of charge for said each battery.