Method and system for determining a state of charge of a battery

1. An apparatus comprising:

a battery;

a magnetic sensor is one of located adjacent to and attached to the battery; and

a state of charge module in operable communication with the magnetic sensor, the state of charge module being configured to:

subject the battery to a predetermined magnetic field such that the battery and the state of charge module jointly create a resultant magnetic field; and

to detect an electromagnetic response to the predetermined magnetic field.

2. The apparatus of claim 1 , wherein the predetermined magnetic field is applied by a permanent magnet.

3. The apparatus of claim 1 , wherein the state of charge module comprises:

an output amplifier;

a first conductive winding configured to induce the predetermined magnetic field in the battery by conducting a first current flow;

a second conductive winding configured to conduct a second current flow induced in the second conductive winding by the resultant magnetic field; and

a control circuit configured to adjust the first current flow and the second current flow to produce a balanced input to the output amplifier.

4. The apparatus of claim 3 , wherein the first conductive winding and the second conductive winding are wound around the battery.

5. The apparatus of claim 3 , wherein the first conductive winding at least partially overlaps the second conductive winding.

6. The apparatus of claim 3 , wherein the control circuit comprises a variable inductor connected in series with the first conductive winding and the second conductive winding.

7. The apparatus of claim 6 , wherein the control circuit comprises a variable resistor connected in parallel with the second conductive winding and the variable inductor.

8. The apparatus of claim 7 , wherein the output amplifier receives an input from the variable resistors.