Panasonic has created prototype flexible lithium ion batteries for use in wearable devices that maintains its electrical characteristics even after repeated bending.

The battery means more freedom for designers of wearable devices.

Three prototypes showcased at CES were sized at 40mm by 65mm, 35mm by 55mm, and a smaller one at 28.5mm by 39mm.

All three are just 0.45mm thick, considerably thinner than a credit card. They can be bent up to a radius of 25mm or twisted to an angle of 25 degrees.

The batteries weigh just a gram or two and output 3.8 volts.

The batteries are small enough to be embedded inside credit cards or similar sized card systems.