Portable propane-fueled battery charger

1. A battery charger comprising:

a housing that supports a battery connector configured to receive and support a battery pack, the battery connector including:

electrical terminals configured to engage electrical terminals of the battery pack, and

a mechanical coupling configured to engage a mechanical interface of the battery pack;

an engine including an output shaft, the engine configured to receive propane and drive the output shaft;

an alternator including a rotor and stator coils, wherein the output shaft is mechanically coupled to the rotor, and an electrical current is induced in the stator coils by rotation of the rotor; and

an electrical circuit that receives the electrical current and is configured to:

determine when the battery pack is coupled to the battery connector,

charge the battery pack based on the determination,

determine a state of charge of the battery pack coupled to the battery charger,

select, based on the state of charge, the battery pack from a plurality of battery packs, and

electrically connect the battery pack to a motor drive circuit to power the alternator and start the engine.

2. The battery charger of claim 1 , wherein the electrical circuit increases a speed of the engine responsive to a magnitude of a charging current provided to the battery pack being greater than a first threshold.

3. The battery charger of claim 2 , wherein the electrical circuit decreases a speed of the engine responsive to the magnitude of the charging current provided to the battery pack being less than a second threshold.

4. The battery charger of claim 1 , wherein the battery pack is a first battery pack and the electrical circuit is configured to simultaneously charge a second battery pack.

5. The battery charger of claim 4 , further comprising a first set of battery connectors including the battery connector and a second set of battery connectors, wherein the electrical circuit is configured to simultaneously charge the first battery pack coupled to one of the first set of battery connectors and the second battery pack coupled to one of the second set of battery connectors.

6. The battery charger of claim 5 , wherein the electrical circuit is configured to charge a third battery pack coupled to the first set of battery connectors when the electrical circuit determines that the first battery pack is fully charged.

7. The battery charger of claim 4 , further comprising:

a first sequence switch configured to selectively control the electrical circuit to provide a first charging current through one of the first set of battery connectors; and

a second sequence switch configured to selectively control the electrical circuit to provide a second charging current through one of the second set of battery connectors.

8. The battery charger of claim 1 , further comprising:

a toggle switch, wherein the engine is configured to start when the toggle switch is in a first position.

9. The battery charger of claim 1 , further comprising a second battery connector coupled to the electrical circuit, wherein:

the housing encloses the electrical circuit and includes a first side face and a second side face,

the electrical circuit is positioned between the first side face and the second side face,

the battery connector is positioned on the first side face of the housing, and

the second battery connector is positioned on the second side face of the housing.

10. The battery charger of claim 1 , wherein the electric circuit is configured to:

receive the electrical current that is induced in the stator coils by rotation of the rotor;

charge the battery pack with the electrical current; and

power the alternator with electrical current supplied by the battery pack coupled to the battery connector to start the engine.

11. A method of charging a battery pack, the method comprising:

receiving and supporting, by a battery connector of a housing, the battery pack, the battery connector including electrical terminals that engage electrical terminals of the battery pack, and a mechanical coupling that engages a mechanical interface of the battery pack;

receiving, by an engine, propane;

powering an alternator with electrical current supplied by the battery pack coupled to the battery connector to start the engine;

inhibiting generation of a spark by the engine while the alternator is powered by the battery pack until a speed of the alternator is greater than a threshold;

driving an output shaft of the engine;

inducing an electrical current in stator coils of the alternator by the driving of the output shaft;

providing the electrical current to an electrical circuit in the housing;

determining, with the electrical circuit, that the battery pack is coupled to the battery connector; and

charging, with the electrical circuit, the battery pack.

12. The method of claim 11 , wherein the battery pack is a first battery pack, the method further comprising charging, with the electrical circuit, a second battery pack.

13. The method of claim 12 , wherein charging, with the electrical circuit, the first battery pack includes charging, with the electrical circuit, the first battery pack when the first battery pack is coupled to a first set of battery connectors, and wherein charging, with the electrical circuit, the second battery pack includes charging, with the electrical circuit, the second battery pack when the second battery pack is coupled to a second set of battery connectors.

14. The method of claim 12 , further comprising:

charging, with the electrical circuit, a third battery pack coupled to the first set of battery connectors when the electrical circuit determines that the first battery pack is fully charged.

15. The method of claim 12 , further comprising:

selectively controlling, with a first sequence switch, the electrical circuit to provide a first charging current through one of the first set of battery connectors; and

selectively controlling, with a second sequence switch, the electrical circuit to provide a second charging current through one of the second set of battery connectors.

16. The method of claim 12 , further comprising:

determining a state of charge of each of a plurality of battery packs coupled to the battery connectors;

selecting, based on the state of charge, a selected battery pack from the plurality of battery packs;

electrically connecting, with the electrical circuit, the selected battery pack to a motor drive circuit; and

powering, via the motor drive circuit, the alternator with the selected battery pack to start the engine.

17. The method of claim 12 , wherein starting the engine includes:

receiving, from a toggle switch, a toggle switch signal indicative of a position of the toggle switch; and

when the toggle switch signal indicates that the toggle switch is in a first position, starting the engine.

18. The method of claim 11 , further comprising adjusting a speed of the engine based on a magnitude of a charging current being provided to the battery pack.

19. A battery charger comprising:

a housing that supports a battery connector configured to receive and support a battery pack, the battery connector including:

electrical terminals configured to engage electrical terminals of the battery pack, and

a mechanical coupling configured to engage a mechanical interface of the battery pack;

an engine including an output shaft, the engine configured to receive propane and drive the output shaft;

an alternator including a rotor and stator coils, wherein the output shaft is mechanically coupled to the rotor, and an electrical current is induced in the stator coils by rotation of the rotor; and

an electrical circuit that receives the electrical current and is configured to:

determine when the battery pack is coupled to the battery connector, and

charge the battery pack based on the determination,

wherein the electrical circuit operates the engine based on a charging current being provided to the battery pack.