Low voltage cutoff circuit for an electrochemical cell
View Patent ↗The present invention is an electrical circuit that disconnects an electrochemical cell from a load when the cell's voltage descends to a predetermined value. The present invention is also applicable to a battery configuration and its corresponding electrochemical cells. The predetermined value is designed to decrease the chance that the cell or battery will become unstable while connected to the load.
1. A low voltage cutoff circuitry comprising:
a) at least one primary electrochemical cell generating an electrical current powering a load;
b) a first switch in a closed position between the load and the at least one primary electrochemical cell so that the primary cell powers the load;
c) a sensing device that measures the at least one primary cell's voltage, transmits a close signal to the first switch in order to maintain the connection between the at least one primary cell and the load when the at least one cell's voltage is above a predetermined minimum threshold, and transmits an open signal to the first switch to disconnect the at least one primary cell from the load when the voltage is below the predetermined minimum threshold; and
d) a manually operable reset switch that prevents re-connection of the at least one primary cell through the first switch to the load even if the at least one primary cell's open circuit voltage recovers to a value above the predetermined minimum threshold until the reset switch is manually reset.
2. The circuitry of claim 1 wherein the at least one primary cell is a lithium based electrochemical cell.
3. The circuitry of claim 1 wherein the at least one primary cell is of a moderate rate size D.
4. The circuitry of claim 3 wherein the predetermined minimum cell voltage threshold is about 2.0 volts.
5. The circuitry of claim 1 wherein the predetermined minimum threshold cell voltage is the voltage output when the at least one primary cell initiates a significant drop in voltage output or capacity.
6. The circuitry of claim 1 wherein the predetermined minimum threshold cell voltage is a voltage output between when the at least one primary cell initiates a significant drop in voltage output or capacity, but prior to the at least one primary cell becoming unstable.
7. The circuitry of claim 1 wherein the at least one primary electrochemical cell is selected from group consisting of a magnesium based electrochemical cell, a zinc manganese based electrochemical cell, a nickel-metal hydride based electrochemical cell, or a lithium based electrochemical cell.
8. The circuitry of claim 1 further comprising a delay mechanism to ensure that measurement of the at least one cell's voltage is accurate prior to transmitting the close signal or the open signal.
9. A low voltage cutoff circuitry comprising:
a) a battery comprised of at least a first primary electrochemical cell and a second primary electrochemical cell;
b) the first electrochemical cell generating an electrical current having a first cell voltage;
c) the second primary electrochemical cell generating an electrical current having a second cell voltage;
d) the first electrical current and the second electrical current forming a battery electrical current having a battery voltage powering a load;
e) a first switch positioned between the load and the primary battery so that the battery powers the load;
f) a first sensing device that measures the battery voltage and transmits a first close signal to the first switch to maintain connection between the primary battery and the load when the battery's voltage is above a predetermined minimum threshold voltage, and transmits an open signal to the first switch to disconnect the primary battery from the load when the battery's voltage falls below the predetermined minimum threshold; and
g) a manually operable reset switch that prevents re-connection of the battery to the load even if the battery's voltage recovers to a value above the predetermined minimum threshold until the reset switch is manually reset.
10. The circuitry of claim 9 wherein the first primary cell and the second primary cell are either in a series or a parallel configuration.
11. The circuitry of claim 9 wherein the first and second cell voltages are independently measured.
12. The circuitry of claim 9 wherein the first and second primary cells are lithium based.
13. The circuitry of claim 9 wherein the first and second primary cells are of a moderate rate size D.
14. The circuitry of claim 9 wherein the fixed rate cell voltage is about 2.0 volts.
15. The circuitry of claim 9 wherein the fixed rate cell voltage is a voltage output between when at least one of the first and second cells initiates a significant drop in voltage output or capacity and prior to when the first or second cell becomes unstable.
16. The circuitry of claim 9 wherein the predetermined minimum threshold battery voltage is the voltage output when the primary battery initiates a significant drop in voltage output or capacity.
17. The circuitry of claim 9 wherein the predetermined minimum threshold battery voltage is a voltage output between when the primary battery initiates a significant drop in voltage output or capacity and prior to when the primary battery becomes unstable.
18. The circuitry of claim 10 wherein the first and second primary electrochemical cells are selected from the group consisting of a magnesium based electrochemical cell, a zinc manganese based electrochemical cell, a nickel-metal hydride based electrochemical cell, and a lithium based electrochemical cell.
19. The circuitry of claim 9 further comprising a delay mechanism to ensure that measurement of the battery voltage is accurate prior to transmitting the first close signal or the first open signal.