A standard-issue rechargeable battery affords 11 hours of play time, and an optional 20-hour rechargeable battery will be available.

Both accept optional five-hour batteries.

An optional rechargeable battery is available for £40, which should last for about 100 sheets, and takes 6 hours to charge using the standard power supply.

Sharp offers an optional add-on battery that raises the operating life to five hours but also raises the weight to six pounds.

You must either plug them into electric outlets or buy RCA's optional rechargeable battery packs.

An optional high-capacity battery doubles these durations.

And it's so portable, you can even power it from an optional battery.

Battery life between charges is estimated at 2.6 hours with a standard four-cell battery, but an optional eight-cell battery offers 8.5 hours of operation.

The new calculators that were shipped with touchpad keypads supported an optional rechargeable battery.

An optional extended battery sticks out the bottom like a bar and props up the back of the laptop.