Battery state-of-charge estimation
A battery pack management system adjusts the relative state-of-charge of respective battery blocks in a battery pack to equalize (i.e., align, balance or otherwise make similar) the peak battery block voltages (i.e., maximum or “upper peak” battery block voltages when the battery pack is being charged and/or minimum or “lower peak” battery block voltages when the battery is being discharged). Upon detecting an anomalous battery block that exhibits outlier upper and lower peak voltages, the battery pack management system adjusts the relative state of charge of respective battery blocks to center their respective upper and lower peak voltages between operating limits, thus maximizing the operating margin of the battery pack as a whole.
1. A method of operation within a battery system having a plurality of battery blocks coupled in series between terminals of a battery pack, the method comprising:
measuring respective charging and discharging voltages of the battery blocks while charging and discharging the battery blocks;
determining a state-of-charge of the battery pack based, at least in part, on the charging and discharging voltages of the battery blocks;
detecting an anomalous battery block exhibiting outlier upper and lower peak voltages with both upper peak voltage, during charging, and lower peak voltage, during discharging, exceeding statistical thresholds;
adjusting a state-of-charge of one or more of the battery blocks downward, responsive to determining that an upper peak battery block voltage of each of the one or more of the battery blocks during the charging reaches a predetermined proximity to a high operating limit that prevents damage during the charging, wherein the adjusting downward comprises discharging the one or more of the battery blocks into one or more other battery blocks;
adjusting a state-of-charge of a further one or more of the battery blocks upward, responsive to determining that a lower peak battery block voltage of each of the further one or more battery blocks during the discharging reaches a further predetermined proximity to a low operating limit that prevents damage during the discharging; and
adjusting a state-of-charge of the anomalous battery block to center the outlier upper peak voltage and the outlier lower peak voltage, relative to the high operating limit and the low operating limit.
2. The method of claim 1 wherein charging the battery blocks comprises supplying a current pulse to the battery pack via the battery pack terminals.
3. The method of claim 1 wherein charging the battery blocks comprises supplying current from a regenerative braking system within a hybrid electric vehicle or an electric vehicle to the battery pack via the battery pack terminals.
4. The method of claim 1 wherein measuring respective charging voltages of the battery blocks during the first interval comprises measuring each of the battery block voltages concurrently.
5. The method of claim 1 wherein determining a state-of-charge comprises identifying a first battery block of the battery blocks that has a charging voltage higher than at least a second battery block of the battery blocks and discharging the first battery block to reduce the difference between the charging voltages of the first and second battery blocks.
6. The method of claim 5 wherein discharging the first battery block comprises switchably coupling balance resistors to the battery block.
7. The method of claim 1 further comprising displaying the state-of-charge of the battery pack to the operator of a hybrid electric vehicle or an electric vehicle.
8. The method of claim 1 further comprising determining a driving range of a hybrid electric vehicle or an electric vehicle based, at least in part, on the state-of-charge of the battery pack.
9. The method of claim 8 further comprising displaying the driving range to the operator of the hybrid electric vehicle or the electric vehicle.
10. The method of claim 1 wherein determining the state-of-charge of the battery pack based, at least in part, on the charging voltages of the battery blocks comprises:
measuring respective open-circuit voltages of the battery blocks;
generating an initial estimate of the state-of-charge of the battery pack based on the open-circuit voltages of the battery blocks; and
adjusting the initial estimate of the state-of-charge of the battery pack based, at least in part, on the charging voltages of the battery blocks.
11. A method of operation within a battery system having a plurality of battery blocks coupled in series between terminals of a battery pack, the method comprising:
measuring respective charging and discharging voltages of the battery blocks while charging and discharging the battery blocks;
determining a state-of-charge of the battery pack based, at least in part, on the charging and discharging voltages of the battery blocks;
adjusting a state-of-charge of one or more of the battery blocks, responsive to determining that an upper peak battery block voltage of each of the one or more of the battery blocks during the charging is within a predetermined proximity to a high operating limit preventing damage during the charging, or determining that a lower peak battery block voltage of each of the one or more battery blocks during the discharging is within a further predetermined proximity to a low operating limit preventing damage during the discharging, so as to center the upper peak battery block voltage and the lower peak battery block voltage of each of the one or more of the battery blocks relative to the high operating limit and the low operating limit;
detecting an anomalous battery block exhibiting outlier upper and lower peak voltages with both upper peak voltage, during charging, and lower peak voltage, during discharging, exceeding statistical thresholds; and
adjusting a state-of-charge of the anomalous battery block to center the outlier upper peak voltage and the outlier lower peak voltage, relative to the high operating limit and the low operating limit, wherein the adjusting comprises discharging the one or more of the battery blocks into one or more other battery blocks.
12. A battery management system to control a battery system having a plurality of battery blocks coupled in series between terminals of a battery pack, the battery management system comprising:
one or more voltage measurement inputs to receive respective charging and discharging voltage measurements of the battery blocks while the battery blocks are being charged and discharged;
state-of-charge determination logic to determine a state-of-charge of the battery pack based, at least in part, on the charging and discharging voltage measurements received via the voltage measurement inputs;
state-of-charge adjusting logic for adjusting a state-of-charge of respective battery blocks wherein a state-of-charge of one or more of the battery blocks is adjusted downward responsive to determining that an upper peak battery block voltage of each of the one or more of the battery blocks during the charging is within a predetermined proximity of a high operating limit that acts to prevent damage during the charging, wherein the adjusting downward comprises discharging the one or more of the battery blocks into one or more other battery blocks, and wherein a state-of-charge of a further one or more of the battery blocks is adjusted upward responsive to determining that a lower peak battery block voltage of each of the further one or more of the battery blocks during the discharging is within a further predetermined proximity of a low operating limit that acts to prevent damage during the discharging; and
the state-of-charge adjusting logic further for detecting an anomalous battery block exhibiting outlier upper and lower peak voltages with both upper peak voltage, during charging, and lower peak voltage, during discharging, exceeding statistical thresholds for the battery blocks, and adjusting a state-of-charge of the anomalous battery block to center the outlier upper peak voltage and the outlier lower peak voltage, relative to the high operating limit and the low operating limit.
13. The battery management system of claim 12 wherein the state-of-charge determination logic further comprises outputs that indicate a state-of-charge of each of the respective battery blocks in the battery pack.
14. The battery management system of claim 12 wherein the battery system is disposed within an electric/hybrid-electric vehicle.
15. The battery management system of claim 12 wherein the number of charging voltage measurement inputs is equal to the number of battery blocks.
16. The battery management system of claim 12 wherein the state-of-charge determination logic is implemented at least in part by a programmed processor.
17. The battery management system of claim 12 wherein the battery system is disposed within an electric/hybrid-electric vehicle, the battery management system further comprising an output to provide a value corresponding to the state-of-charge of the battery pack to an operator display device disposed within the hybrid electric vehicle or the electric vehicle, the operator display device to display information corresponding to the state-of-charge of the battery pack to an operator of the electric/hybrid-electric vehicle.
18. The battery management system of claim 12 wherein the battery system is disposed within an electric/hybrid-electric vehicle, the battery management system further comprising driving range determination logic to determine, based at least in part on a value received from the state-of-charge determination logic that indicates the state-of-charge of the battery pack, a driving range of electric/hybrid-electric vehicle.
19. The battery management system of claim 18 further comprising an output to provide a value corresponding to the driving range of the electric/hybrid-electric vehicle to an operator display device disposed within the electric/hybrid-electric vehicle, the operator display device to display information corresponding to the value corresponding to the driving range to an operator of the electric/hybrid-electric vehicle.
20. A battery management system to control a battery system having a plurality of battery blocks coupled in series between terminals of a battery pack, each battery block having a plurality of cells in parallel, the battery management system comprising:
a plurality of voltage measurement devices corresponding to the plurality of battery blocks, each voltage measurement device across and in parallel with the plurality of cells in parallel in a corresponding one of the plurality of battery blocks;
a plurality of current measurement devices corresponding to the plurality of battery blocks, each current measurement device in series with the plurality of cells in parallel in a corresponding one of the plurality of battery blocks;
a plurality of switch and balance resistor devices corresponding to the plurality of battery blocks, each switch and balance resistor device across and in parallel with the plurality of cells in parallel in a corresponding one of the plurality of battery blocks; and
battery management circuitry coupled to the plurality of voltage measurement devices, the plurality of current measurement devices and the plurality of switch and balance resistor devices to adjust state-of-charge of each of the plurality of battery blocks and detect an anomalous battery block exhibiting outlier upper and lower peak voltages with both upper peak voltage, during charging, and lower peak voltage, during discharging, exceeding statistical thresholds and adjust state-of-charge the anomalous battery block relative to other battery blocks, wherein during the discharging, one of the plurality of battery blocks is discharged into one or more other battery blocks.