Compensation for parasitic resistance in battery monitoring
View Patent ↗A system for balancing charge between a plurality of storage battery cells within a storage battery. The battery balancing system may sense changes, possibly caused by environmental influences, in the overall resonant frequency of charge balancing circuits contained within the battery balancing system and compensate for the change in resonant frequency. Further, the system may correct battery cell voltages monitored by a controller that may include errors due to intrinsic circuit problems, such as parasitic voltage, to reflect an actual voltage of a battery cell.
1. A device for correcting a monitored battery cell voltage read from a battery balancing circuit to an actual battery cell voltage, comprising:
a plurality of balancing circuits, coupled to each of a plurality of coupled battery cells, the plurality of balancing circuits enabled to conduct current to and from the battery cells;
a share bus, coupled to at least each of the plurality of balancing circuits; and
a monitoring circuit, coupled to the battery balancing circuit, the monitoring circuit configured to:
monitor a battery cell voltage;
monitor a share bus voltage; and
adjust the monitored battery cell voltage to reflect an actual battery cell voltage based on the share bus voltage, a share bus resistance and a balancing circuit parasitic resistance.
2. The device of claim 1 , wherein the plurality of coupled battery cells are serially connected battery banks, each battery bank being made up of one or more battery cells connected in parallel.
3. The device of claim 1 , wherein the balancing circuits conduct current from overcharged cells to undercharged cells.
4. The device of claim 1 , wherein the monitoring circuits are coupled to a multiplexer.
5. The device of claim 4 , wherein the multiplexer is coupled to an analog to digital (A/D) converter which converts the monitored battery cell voltage into a digital value.
6. The device of claim 1 , wherein the adjusting of the monitored battery cell voltage is performed by a processing device.
7. The device of claim 1 , wherein the adjusting of the monitored battery cell voltage for a total of i cells is governed by the equation:
V_cell
i
=
V_mon
i
+
(
R_p
R_share
)
(
V_mon
i
-
V_avg
)
Wherein V_cell i is the actual cell voltage for each cell from 1 to i, V_mon i is monitored cell voltage for each cell from 1 to i, R is the parasitic resistance, R_share is the share bus resistance and V_avg is the share bus voltage.
8. The device of claim 7 , wherein the share bus voltage is monitored by at least one of computing an average cell voltage or measuring the actual voltage level of the share bus.
9. A method for correcting a monitored battery cell voltage read from a battery balancing circuit to an actual battery cell voltage, comprising:
monitoring a battery cell voltage from a plurality of balancing circuits each coupled to at least a monitoring circuit, a share bus and a battery cell;
monitoring the share bus voltage; and
adjusting the monitored battery cell voltage to reflect an actual battery cell voltage based on the share bus voltage, a share bus resistance and a balancing circuit parasitic resistance.
10. The method of claim 9 , wherein the balancing circuits conduct current from overcharged cells to undercharged cells.
11. The method of claim 9 , wherein the adjusting of the monitored battery cell voltage is performed by a processing device.
12. The method of claim 9 , wherein the adjusting of the monitored battery cell voltage for a total of i cells is governed by the equation:
V_cell
i
=
V_mon
i
+
(
R_p
R_share
)
(
V_mon
i
-
V_avg
)
Wherein V_cell i is the actual cell voltage for each cell from 1 to i, V_mon i is monitored cell voltage for each cell from 1 to i, R_p is the parasitic resistance, R_share is the share bus resistance and V_avg is the share bus voltage.
13. The method of claim 12 , wherein the share bus voltage is monitored by at least one of computing an average cell voltage or measuring the actual voltage level of the share bus.
14. A system for balancing the energy level of a plurality of coupled battery cells, comprising:
a battery balancing system including a plurality of balancing circuits;
the plurality of balancing circuits, coupled to each of a plurality of coupled battery cells, the plurality of balancing circuits enabled to conduct current to and from the battery cells;
a share bus, coupled to at least each of the plurality of balancing circuits; and
a monitoring circuit, coupled to the battery balancing circuit, the monitoring circuit configured to:
monitor a battery cell voltage;
monitor a share bus voltage; and
adjust the monitored battery cell voltage to reflect an actual battery cell voltage based on the share bus voltage, a share bus resistance and a balancing circuit parasitic resistance.
15. The system of claim 14 , wherein the plurality of coupled battery cells are serially connected battery banks, each battery bank being made up of one or more battery cells connected in parallel.
16. The system of claim 14 , wherein the balancing circuits conduct current from overcharged cells to undercharged cells.
17. The system of claim 14 , wherein the monitoring circuits are coupled to a multiplexer.
18. The system of claim 17 , wherein the multiplexer is coupled to an analog to digital (A/D) converter which converts the monitored battery cell voltage into a digital value.
19. The system of claim 14 , wherein the adjusting of the monitored battery cell voltage is performed by a processing device.
20. The system of claim 14 , wherein the adjusting of the monitored battery cell voltage for a total of i cells is governed by the equation:
V_cell
i
=
V_mon
i
+
(
R_p
R_share
)
(
V_mon
i
-
V_avg
)
Wherein V_cell i is the actual cell voltage for each cell from 1 to i, V_mon i is monitored cell voltage for each cell from 1 to i, R_p is the parasitic resistance, R_share is the share bus resistance and V_avg is the share bus voltage.
21. The system of claim 20 , wherein the share bus voltage is monitored by at least one of computing an average cell voltage or measuring the actual voltage level of the share bus.
22. A computer program product embodied on a computer-readable medium and configured to cause a processing device to execute method steps, comprising:
monitoring a battery cell voltage from a plurality of balancing circuits each coupled to at least a monitoring circuit, a share bus and a battery cell;
monitoring the share bus voltage; and
adjusting the monitored battery cell voltage to reflect an actual battery cell voltage based on the share bus voltage, a share bus resistance and a balancing circuit parasitic resistance.
23. The computer program product of claim 22 , wherein the adjusting of the monitored battery cell voltage for a total of i cells is governed by the equation:
V_cell
i
=
V_mon
i
+
(
R_p
R_share
)
(
V_mon
i
-
V_avg
)
Wherein V_cell i is the actual cell voltage for each cell from 1 to i, V_mon i is monitored cell voltage for each cell from 1 to i, R_p is the parasitic resistance, R_share is the share bus resistance and V_avg is the share bus voltage.
24. The computer program product of claim 23 , wherein the share bus voltage is monitored by at least one of computing an average cell voltage or measuring the actual voltage level of the share bus.