USE's Exposure MaXx lights already have impressive burn times which are more than adequate for most people.
However, the Piggyback battery feature allows the burn times to be extended up to a phenominal 96 hours! (depending on which light and which piggyback you use).
Simply by plugging a Piggyback lithium-ion battery into the charger port and attaching the extra battery beneath your stem you can add burn times equivalent to having a second Joystick or Enduro MaXx by adding either a 1 or 3 cell battery.

The idea of the Piggyback battery is to plug it into the light at the start of use. This will allow you to use the light on MaXx, Ride and Low settings for a greatly extended period of time.
If the battery is plugged in with the light half charged, the Ride and Low modes will be avilable.

The Piggyback batteries can be mounted either on your stem / handlebar or helmet - making your extra burn time flexible in all aspects!

This single cell version is ideal to enhance your Joystick, as the compact, light weight makes it easy to mount on your helmet.