S-Pack Batteries

Therm-ic S-Pack Batteries are the rechargeable power packs for Therm-ic Powersocks heated socks. Each set is a pair, one battery for each sock, with a single USB cable that charges both together, and each battery gives you three heat levels so you can keep your toes warm without cooking them.

Who it's for

Skiers and boarders who feel the cold in their feet, and anyone heading out in winter for long, still hours: first chair at Perisher on a minus-something morning, a night ski at Mt Buller, a ski trip to Japan, or a frosty dawn on a winter hike in Tasmania. If you already own Powersocks and want a spare set so one pair is always charged, or a bigger battery for longer days, this is where you start.

Choosing a capacity

There are four S-Packs in this listing, and the choice comes down to capacity and whether you want to adjust the heat from your phone:

• S-Pack 700: slim and compact, 1400 mAh per battery, button control.
• S-Pack 700B: the same slim size with Bluetooth app control.
• S-Pack 1200: 2400 mAh per battery, button control. Therm-ic's most popular battery.
• S-Pack 1400B: 2800 mAh per battery with Bluetooth, the most powerful in the range, and the one Therm-ic recommends for its Ultra Warm S.E.T. socks.

More capacity means more heat for longer, so we would point anyone doing full days on the hill towards the 1200 or 1400B, and the 700 or 700B towards shorter sessions or anyone who wants the smallest pack on the leg.

Fitting it

S-Pack batteries fit Therm-ic's current Powersocks: Heat Men ND, Heat Women ND, Heat Uni ND, the Heat Fusion Uni, Men, Women and Uni ND, the Ultra Warm Comfort and Performance S.E.T., and the outdoor Heat Multi, Heat Multi ND and Heat Fusion Outdoor. Each battery pushes onto the snap fasteners on the sock cuff until it clicks home. Sock batteries do not work with Therm-ic heated insoles or gloves, and older Therm-ic batteries with a 4-pin plug do not fit these socks.

Heat levels and control

Press the button to step through level 1 (one flash), level 2 (two flashes) and level 3 (steady light). The two batteries run independently, so if one foot runs colder you can set it higher. After 10 seconds the battery locks itself so a bump in your boot cannot change the setting; the light flashes every 3 seconds while it is locked, and a press unlocks it. On the 700B and 1400B you can also set the heat from the Therm-ic Heat Control app on a phone with Bluetooth 4.0 or later. Use levels 1 and 2 for most of the day and level 3 for a few minutes at a time only, because long spells on the top setting can burn.

Charging

Both batteries charge together on the supplied USB cable, with a red light while charging and green when full. Charge them fully before first use, then top them up whenever you like, as the lithium-ion cells do not need to be run flat first. Use a USB adapter of no more than 5 V.

Looking after it

The batteries are water resistant, not waterproof, so never submerge them, and take them off before the socks go in the wash. Over summer, store them switched off and disconnected, half charged, somewhere cool between 5 and 20 °C, and recharge them to half at least every six months. Wipe them clean with a soft cloth and a little mild detergent. Never wear heated socks and heated insoles together.