Additional Battery Packs extend total foot warming duration throughout extremely cold days.

With four (4) cells in each Battery Pack, the Power Plus e4 is Hotronic's most powerful, longest lasting Battery Pack Ever!

WARNING: The Power Plus e4 Batteries can only be recharged using the Hotronic Recharger Power Plus for e and m Series, with the white plugs.

LOST A BATTERY? We Highly Recommend:

• Slide Strap Brackets, Mounting Brackets, or Velcro® Attachment Straps to secure your batteries to your ski boots.
• OR Extension Cords

Temperature and Duration Settings Setting Approximate Average Temperature Duration Range °F °C 1 84 -95 29 - 35 16.5 - 19.5 hrs 2* 107 - 118 42 - 48 7 - 9.25 hrs 3 122 - 132 50 - 56 5 - 6.5 hrs 4 158 - 168 70 - 76 2.5 - 4 hrs Based on Battery Packs at average -22°C to -15°C (-9 to +4°F) ambient temperatures. * Setting 2 is the most common setting.

Note: If you are purchasing the the Hotronic Battery Pack Power Plus "e" series batteries (e4 / e3) to replace a Hotronic Battery Pack Power Plus "m" series batteries (m4/m3), we recommend replacing both batteries. The "e" series batteries are warmer than the "m" series batteries on the same settings.
See our >> Comparison of e Series to m Series Temperature & Duration Chart