Battery with integrated power management system and scalable battery cutoff

1. A battery system comprising:

a battery housing with first and second voltage output terminals;

a plurality of rechargeable battery cells within the battery housing and having first and second voltage terminals;

a power management system for generating an external control signal and an internal control signal based upon monitored operating parameters of the plurality of rechargeable battery cells, said external control signal for controlling an external power source and/or an external load, said power management system forming an integral part of the battery system;

a cutoff switch circuit within the battery housing and for making and breaking a conductive path between the first voltage terminal of the plurality of battery cells and the first voltage output terminal of the battery housing in response to the internal control signal from the power management system, where the cutoff switch circuit comprises temperature sensing devices and a plurality of metal-oxide semiconductor field effect transistors (MOSFETs) arranged as parallel groups of MOSFETs and operating as a single switch; and

a controller including executable instructions stored in non-transitory memory to measure a voltage across the MOSFETs, determine a drain-source resistance of one MOSFET in the plurality of MOSFETs from a temperature of the one MOSFET sensed via one of the temperature sensing devices, and determine current flow through the one MOSFET based on the voltage across the MOSFETs and the drain-source resistance of the one MOSFET.

2. The battery system of claim 1 , further comprising two busbars electrically coupling the plurality of rechargeable battery cells to the first and second voltage output terminals, wherein the battery cells are lithium ion cells, and wherein the MOSFETs are integrated into one of the busbars between the first and second voltage output terminals and a battery cell stack comprising the plurality of rechargeable battery cells.

3. The battery system of claim 1 , wherein the power management system includes additional instructions to selectively activate the cutoff switch circuit in response to current flow through the one MOSFET determined based on the voltage across the MOSFETs and the drain-source resistance of the one MOSFET.

4. The battery system of claim 3 , wherein the power management system includes additional instructions to determine current flow through the one MOSFET via dividing the voltage across the MOSFETs by the drain-source resistance of the one MOSFET.

5. The battery system of claim 1 , wherein the plurality of MOSFETs is a first group of MOSFETs, and where the first group of MOSFETs is connected in parallel with a second group of MOSFETs connected in parallel with each other and wherein the first group is connected in series with the second group.

6. The battery system of claim 1 , further comprising a busbar in electrical communication with the plurality of rechargeable battery cells and the plurality of MOSFETs.

7. The battery system of claim 1 , further comprising a shunt resistor in electrical communication with the plurality of MOSFETs.

8. The battery system of claim 4 , further comprising additional instructions to determine the drain-source resistance based on an initial resistance of the one MOSFET and a change in resistance of the one MOSFET due to temperature.

9. The battery system of claim 8 , wherein a battery is an automotive battery, and further comprising additional instructions to determine the change in resistance of the one MOSFET due to temperature based on power dissipation within the one MOSFET.

10. The battery system of claim 9 , wherein the external power source comprises an alternator.

11. The battery system of claim 1 , wherein a battery is a telecommunications battery.