Hardware short circuit protection in a large battery pack
Systems and methods are described for managing charging and discharging of battery packs. In one or more aspects, a system and method are provided to minimize overcharging of battery cells of specific battery chemistries while still enabling fast charging cycles. In other aspects, a buck converter may be used to reduce a voltage of power used to charge the cells. In further aspects, a fast overcurrent protection circuit is described to address situations involving internal short circuits of a battery cell or battery pack. In yet further aspects, a bypass circuit is provided in series-connected battery packs to improve the charging of undercharged battery packs while also increasing the efficiency of the overall charging process. In other aspects, a circuit is provided that permits a controller to determine a configuration of battery packs. In yet further aspects, a system may determine a discharge current for a collection of battery packs based on each battery pack's state of health (SOH) and forward that determination to an external device.
1. A device comprising:
a plurality of battery packs connected in parallel to a power source;
a shut-off switch connected between the plurality of battery packs and the power source;
a current detector configured to determine whether a current, from the power source to the plurality of battery packs, is greater than a threshold current;
an over-current protection circuit configured to disconnect, via the shut-off switch and based on the current detector determining that the current is greater than the threshold current, the power source from the plurality of battery packs;
a controller configured to maintain the disconnection, via the over-current protection circuit, of the power source from the plurality of battery packs after the current drops below the current threshold.
2. The device of claim 1 , wherein the current detector comprises:
a resistor between the shut-off switch and one of the power source or the plurality of battery packs, wherein the current flows through the resistor; and
a comparator configured to compare a voltage across the resistor with a threshold voltage,
wherein the over-current protection circuit is further configured to disconnect the power source from the plurality of battery packs based on an output of the comparator.
3. The device of claim 1 , wherein the over-current protection circuit comprises:
a second switch controlled by the current detector,
wherein a conduction path of the second switch is connected between a gate of the shut-off switch and a voltage level,
wherein, based on the current detector turning on the second switch, the second switch connects the gate of the shut-off switch to the voltage level, and
wherein, based on the gate of the shut-off switch being pulled to the voltage level, the shut-off switch disconnects the power source from the plurality of battery packs.
4. The device of claim 3 ,
wherein the voltage level is a low voltage level, and
wherein the shut-off switch is an n-type MOSFET.
5. The device of claim 3 ,
wherein the voltage level is a high voltage level, and
wherein the shut-off switch is a p-type MOSFET.
6. The device of claim 1 , wherein the current detector comprises:
battery-pack resistors; and
comparators,
wherein, for each battery pack, a battery pack resistor of the battery-pack resistors is in series with each battery pack, wherein a portion of the current flows through each resistor; and
wherein, for each battery pack, a comparator of the comparators is configured to compare a voltage across a respective battery pack resistor with a threshold voltage,
wherein the over-current protection circuit is further configured to disconnect, based on an output of at least one comparator of the comparators being above a threshold voltage and via the shut-off switch, the power source from all battery packs of the plurality of battery packs.
7. The device of claim 6 ,
wherein each battery pack resistor is located between a positive voltage potential and a respective battery pack.
8. The device of claim 6 ,
wherein the controller is configured to detect whether at least one comparator indicates the voltage across the respective battery pack resistor is greater than the threshold voltage, and
wherein the controller is configured to, based on the detection of at least one comparator of the comparators indicating the voltage across the respective battery pack resistor being greater than the threshold voltage, maintain the shut-off switch in a state disconnecting the power source from all battery packs.
9. The device of claim 1 , wherein the shut-off switch is an n-type MOSFET.
10. The device of claim 3 , wherein the second switch is an n-type MOSFET.
11. A method comprising:
receiving power from power source, the power comprising a voltage and current;
conveying, via a shut-off switch, the power to a plurality of battery packs arranged in parallel;
determining, via a current detector, whether the current is greater than a current threshold;
based on a determination that the current is greater than the current threshold, triggering an over-current protection circuit, wherein the triggered over-current protection circuit is configured to prevent the power from being conveyed, via the shut-off switch, to the plurality of battery packs; and
a controller configured to maintain the shut-off switch in a non-conveying state after the voltage drop decreases below the threshold voltage.
12. The method of claim 11 ,
wherein the determining via the current detector comprises:
determining a voltage drop across a resistor, wherein the current flows through the resistor; and
determining whether the voltage drop is greater than a threshold voltage, wherein the threshold voltage represents the current threshold multiplied by a resistance value of the resistor,
the method further comprising:
based on determining that the voltage drop is greater than the threshold voltage, controlling the shut-off switch, via an over-current protection circuit, to prevent the power from being supplied to all plurality of battery packs; and
maintaining, via a controller, a state of the shut-off switch to prevent the power from being supplied to all of the battery packs after the voltage drop decreases below the threshold voltage.
13. The method of claim 11 , wherein controlling the shut-off switch further comprises:
selectively connecting, via a second switch, a gate of the shut-off switch, wherein a conduction path of the second switch is connected between a gate of the shut-off switch and a voltage level,
wherein, based on the current detector turning on the second switch, the second switch connects the gate of the shut-off switch to the voltage level, and
wherein, based on the gate of the shut-off switch being pulled to the voltage level, the shut-off switch disconnects the power source from the plurality of battery packs.
14. The method of claim 13 ,
wherein the voltage level is a low voltage level, and
wherein the shut-off switch is an n-type MOSFET.
15. The method of claim 13 ,
wherein the voltage level is a high voltage level, and
wherein the shut-off switch is a p-type MOSFET.
16. The method of claim 11 ,
wherein the determining via the current detector comprises comparing, for each battery-pack resistor, a voltage drop with a threshold voltage, wherein each battery-pack resistor is in series with a battery pack of the plurality of battery packs connected in parallel,
wherein a portion of the current flows through each resistor, and
wherein the triggering the over-current protection circuit further comprises disconnecting, based on an output of at least one comparator of the comparators being above a threshold voltage and via the shut-off switch, the power source from all battery packs of the plurality of battery packs.
17. The method of claim 16 ,
wherein a controller configured to maintain the shut-off switch in a non-conveying state after the voltage drop, of the at least one comparator of the comparators being above a threshold voltage, decreases below the threshold voltage.
18. The method of claim 16 ,
wherein triggering the over-current protection circuit further comprises increasing a gate voltage of a switch to permit the switch to pull down a gate of the shut-off switch.
19. The method of claim 18 ,
wherein a resistor connects the gate of the switch to ground.
20. The method of claim 18 ,
wherein the gate of the shut-off switch is pulled to a high voltage by a pull-up resistor.