Curved battery-pack devices and accessories

1. A wearable battery-pack accessory comprising:

one or more curved batteries;

charging circuitry that charges the one or more curved batteries;

supplying circuitry that supplies power to a connected external computing device; and

an outer housing comprising at least:

a first curved surface oriented to face away from a user when the wearable battery-pack accessory is worn by the user; and

a second curved surface oriented to face towards the user when the wearable battery-pack accessory is worn by the user, the second curved surface having a varying radius of curvature derived by:

measuring body contours of a plurality of individuals; and

constructing a model of a body based at least in part on an averaging of the body contours of the plurality of individuals, wherein:

the model of the body comprises one or more spline curves; and

the varying radius of curvature of the second curved surface substantially matches a varying radius of curvature of the one or more spline curves of the model of the body.

2. The wearable battery-pack accessory of claim 1 , wherein the connected external computing device comprises a head-mounted display system.

3. The wearable battery-pack accessory of claim 2 , wherein the one or more curved batteries comprise:

a top battery having a first spline surface curved to conform to a top side of the user's head;

a right battery having a second spline surface curved to conform to a right side of the user's head; or

a left battery having a third spline surface curved to conform to a left side of the user's head.

4. The wearable battery-pack accessory of claim 1 , wherein:

the first curved surface of the outer housing has:

a first radius of curvature at a first point; and

a second radius of curvature at a second point;

the first radius of curvature differs from the second radius of curvature;

the second curved surface of the outer housing has:

a third radius of curvature at a third point; and

a fourth radius of curvature at a fourth point; and

the third radius of curvature differs from the fourth radius of curvature.

5. The wearable battery-pack accessory of claim 1 , wherein each of the one or more curved batteries has an inner radius between 80 millimeters and 95 millimeters.

6. The wearable battery-pack accessory of claim 1 , wherein each of the one or more curved batteries has an inner radius between 70 millimeters and 125 millimeters.

7. The wearable battery-pack accessory of claim 1 , further comprising:

an input port for receiving power from an external power source; and

an output port for transmitting power to the connected external computing device, wherein the charging circuitry charges the one or more curved batteries using power from the external power source while the supplying circuitry supplies power to the connected external computing device.

8. The wearable battery-pack accessory of claim 1 , further comprising an input/output port for receiving power from an external power source and transmitting power to the connected external computing device, wherein:

the charging circuitry charges the one or more curved batteries when the external power source is connected to the input/output port; and

the supplying circuitry supplies power to the connected external computing device when the connected external computing device is connected to the input/output port.

9. A head-mounted display system comprising:

a head-mounted display;

a strap that is coupled to the head-mounted display and wraps around the back of a user's head when the user is wearing the head-mounted display; and

a battery-pack accessory detachably coupled to the strap, the battery-pack accessory comprising:

one or more curved batteries;

charging circuitry that charges the one or more curved batteries;

supplying circuitry that supplies power to the head-mounted display; and

an outer housing comprising at least:

a first curved surface oriented to face away from the user when the battery-pack accessory is worn by the user; and

a second curved surface oriented to face towards the user when the battery-pack accessory is worn by the user, the second curved surface having a varying radius of curvature derived by:

measuring head contours of a plurality of individuals; and

constructing a model of a head based at least in part on an averaging of the head contours of the plurality of individuals, wherein:

the model of the head comprises one or more spline curves; and

the varying radius of curvature of the second curved surface substantially matches a varying radius of curvature of the one or more spline curves of the model of the head.

10. The head-mounted display system of claim 9 , wherein:

the strap comprises an adjustment mechanism for adjusting a size of the strap;

the adjustment mechanism comprises a dial;

the outer housing of the battery-pack accessory comprises a notch that exposes the dial when the battery-pack accessory is coupled to the strap.

11. The head-mounted display system of claim 9 , wherein the outer housing of the battery-pack accessory comprises an interface for coupling the battery-pack accessory, via a friction fit, to the strap of the head-mounted display system.

12. The head-mounted display system of claim 9 , wherein:

the one or more curved batteries comprise:

a top battery curved to conform to a top side of the user's head;

a right battery curved to conform to a right side of the user's head; or

a left battery curved to conform to a left side of the user's head; and

at least one of the one or more curved batteries has a varying radius of curvature.

13. The head-mounted display system of claim 9 , wherein each of the one or more curved batteries has an inner radius between 80 millimeters and 95 millimeters.

14. The head-mounted display system of claim 9 , wherein each of the one or more curved batteries has an inner radius between 70 millimeters and 125 millimeters.

15. The head-mounted display system of claim 9 , wherein the battery-pack accessory further comprises:

an input port for receiving power from an external power source; and

an output port for transmitting power to the head-mounted display, wherein the charging circuitry charges the one or more curved batteries using power from the external power source while the supplying circuitry supplies power to the head-mounted display.

16. A method comprising:

measuring body contours of a plurality of individuals;

constructing a model of a body based at least in part on an averaging of the body contours of the plurality of individuals, wherein the model of the body comprises one or more spline curves;

providing a curved battery;

coupling the curved battery to charging circuitry that charges the curved battery;

coupling the curved battery to supplying circuitry that supplies power to an external computing device; and

placing the curved battery, the charging circuitry, and the supplying circuitry within an outer housing of a battery-pack accessory, the outer housing comprising at least:

a first curved surface oriented to face away from a user when the battery-pack accessory is worn by the user; and

a second curved surface oriented to face towards the user when the battery-pack accessory is worn by the user, the second curved surface having a varying radius of curvature substantially matching a varying radius of curvature of the one or more spline curves of the model of the body.

17. The method of claim 16 , wherein providing the curved battery comprises:

placing a flat electrode assembly of the curved battery between spline surfaces of an upper jig and a lower jig;

curving the flat electrode assembly by pressing the flat electrode assembly between the spline surfaces of the upper jig and the lower jig;

separating the upper jig from the lower jig; and

removing the curved electrode assembly from the upper jig and the lower jig.

18. The wearable battery-pack accessory of claim 1 , wherein:

the one or more spline curves of the model of the body are defined by at least:

a starting point;

an ending point;

a midpoint;

a first radius at the starting point;

a second radius at the ending point; and

a third radius at the midpoint; and

the first radius, the second radius, and the third radius are different.

19. The wearable battery-pack accessory of claim 1 , wherein the one or more spline curves of the model of the body are defined by at least:

a first curve segment having a continuously varying radius of curvature; and

a second curve segment having a constant radius of curvature.

20. The wearable battery-pack accessory of claim 1 , wherein the one or more spline curves of the model of the body are defined by multiple control points.