Tacklebox ’n Tools

Heated Gear Battery Life Calculator

Find out how many hours of heat you get from your heated jacket, vest, gloves, socks, hand warmer or seat cushion, and how many batteries to pack for a long sit in the stand or on the ice.

How to use it

  1. Pick your gear. Choose the type, then a real product. Each one uses the run times its maker publishes for its own battery.
  2. Pick the heat level you expect to run most of the day. High uses about two to four times the power of low.
  3. Tell it about your day. How many hours you'll be out, and how many batteries you carry, counting the one in the gear.
  4. Read the results. Hours of heat, a yes or no for your day, how many batteries to bring, every heat level side by side and what to buy.
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Your setup

An example is loaded to start. Change any field and the results update. Simple shows the essentials. Detailed adds more settings, a comparison table and the math.

View

Your gear

Heat level

Setting you'll use most

Your day

hours
batteries
Count the one in the gear plus your spares.
Leave it at 100% to match the maker's run times. Lower it for an older battery, or one riding in an outside pocket in hard cold.

USB power bank

mAh
%
The mAh on a power bank is counted at its 3.7 V cells. Some is lost turning that into 5 V for the USB plug. Anker puts that at about 80 to 85%.

How the numbers are worked out

Power the gear uses

Heated gear makers publish run times, not watts. So for each product we take the battery size the maker lists and its run time on each level, and work out the power: watts = battery Wh ÷ maker's hours. Put back into the run time math, each product gives back exactly the hours its maker lists.

Where a maker gives a range, like Lenz's 10 to 14 hours, we use the middle. Where it says "2+ hours", we use 2. A battery's Wh is mAh × volts ÷ 1,000.

Hours and batteries

Hours on one battery is battery Wh × share you can count on ÷ watts. With every battery you carry, it's that times the number of batteries. Batteries needed is hours out ÷ hours per battery, rounded up.

Gloves and socks have one battery in each glove or sock, each running its own heater, so they are counted in pairs.

USB power banks

Power bank mAh is counted at 3.7 V, so a 10,000 mAh bank holds about 37 Wh. Anker says about 80 to 85% of that reaches the USB plug, and we use 82%, the figure in Anker's example: hours = mAh × 3.7 ÷ 1,000 × 82% ÷ watts.

For gear that runs from a USB plug, the watts are worked out at the plug, with the same 82% taken off the maker's battery, so the maker's run times still come back exactly.

Cold weather

Lithium-ion batteries give less in hard cold, but we did not find a published figure for these packs, so the calculator does not cut the hours for you. ORORO tested its heated apparel battery at 14 °F, rates its batteries for use from 14 to 86 °F and suggests a spare for long stretches below 32 °F. Keep the battery in an inside pocket where your body keeps it warm, and use the slider in Detailed view if yours rides out in the cold.

What it leaves out

  • Gear that turns its heat down on its own as it warms up, which can stretch the hours.
  • Using the battery's USB port to charge your phone, which takes from your heat time.
  • Batteries that are getting old. They hold less each season.
  • Wind, wet layers and how well your outer layers hold the heat in.

Assumptions we made

  • Milwaukee lists its M12 CP2.0 as 12 V and 2.0 Ah, so we used 24 Wh.
  • Thaw and ActionHeat give mAh but no volts, so we used 3.7 V, the usual lithium-ion cell voltage Anker gives.
  • These only change the watts shown. The hours still match each maker.

Stay safe. Charge only with the charger your maker specifies, inside the temperatures in your manual (ORORO says 32 to 104 °F, and never below freezing). Don't use a battery that has been dropped hard, is damaged, swollen or leaking. ORORO warns that close contact with the heater can burn, at any setting, and not to run high for long stretches or wear the gear while you might fall asleep. Stop if it feels too hot, and check your skin now and then on long sits at high heat, most of all your feet in heated socks. People with poor circulation or skin that can't feel heat well should ask a doctor first. To work out charging at camp, try our battery charging time calculator.

Sources