Most heated jackets, vests and gloves run on a 7.4 V (2S) lithium pack or a 5 V USB power bank. Heavier workwear often uses 12 V. The right battery depends on the heater’s power, the runtime you want, and the fact that the battery sits next to the body in freezing weather. Charging lithium cells below 0 °C damages them, so the pack’s protection and charging design matter as much as its capacity.
Key Takeaways
- Runtime ≈ battery watt-hours ÷ heater watts. A 37 Wh pack runs a 10 W heating zone for about 3.3 hours after losses.
- Most Li-ion cells can discharge in the cold but must not be charged below 0 °C. The P45B datasheet, for example, allows charging only from 0–60 °C (Molicel).
- Low-temperature charging causes lithium plating, which cuts capacity and can create safety problems (NREL).
- Heated clothing battery packs have been recalled for fire hazards before, so cell quality and protection circuits are essential (CPSC).
5 V vs 7.4 V vs 12 V: Which Voltage?
| Voltage | Typical use | Pros | Cons |
|---|---|---|---|
| 5 V (USB) | Entry-level vests, scarves, insoles | Works with ordinary power banks | Lower heat output, and more current needed for the same power |
| 7.4 V (2S Li-ion) | Most jackets, vests and gloves | Good balance of heat, weight and size | Needs a dedicated charger or USB-PD input |
| 12 V (3S Li-ion) | Workwear, motorcycle gear, multi-zone jackets | High heat output, lower current | Heavier, bulkier packs |
Higher voltage delivers the same power at lower current, so the wires stay thinner and cooler. For an overview of pack voltages, see which lithium battery voltage to choose.
How Much Capacity Do You Need?
Use watt-hours, not mAh, because packs have different voltages:
- Battery energy (Wh) = nominal voltage × capacity (Ah). A 7.4 V, 5,000 mAh pack = 37 Wh.
- Heater power (W): add up all heating zones at the chosen heat setting.
- Runtime (h) ≈ Wh × 0.9 ÷ W. The 0.9 allows for conversion losses and the low-voltage cut-off.
Example: 37 Wh × 0.9 ÷ 10 W ≈ 3.3 hours on a medium setting. In the cold the cells lose some usable capacity, so size with a margin. More detail is in watts and watt-hours explained.
Which Cells Work Best?
- 18650 / 21700 cylindrical cells: the highest energy for the cost. They suit jackets and vests with a pocket for the battery.
- LiPo pouch cells: thin and flexible in shape. They suit gloves, insoles and slim designs, but need a sturdy enclosure to protect them from bending and puncture.
Pick cells with a good low-temperature discharge rating, and check the charge temperature range on the datasheet separately. See choosing 21700 cells.
Cold-Weather Safety Design
Block charging below 0 °C
Users often plug in a cold battery straight after coming indoors. The BMS or charger should read the cell temperature from an NTC sensor and refuse to charge until the cells reach about 0–5 °C. This prevents lithium plating, which reduces capacity and increases the risk of internal short circuits. See our BMS guide.
Protect the wearer from heat
- Overcurrent and short-circuit protection on every heater output
- A thermal cut-off or temperature-controlled PWM on the heating elements
- Strain-relieved connectors that survive bending, washing (with the battery removed) and repeated plugging
Mechanical protection
Packs get sat on, dropped and crushed in pockets. Use a hard enclosure or a well-reinforced soft pack, and cover exposed terminals.
Certification and Regulations
- UN38.3 to ship (see how to ship lithium batteries)
- IEC 62133-2 or UL 2054 for the battery, depending on the market (see battery certification guide)
- EU: from 18 February 2027, portable batteries must be removable and replaceable by the end user under Regulation (EU) 2023/1542. Most heated clothing already uses removable packs, but check the design.
Storage Between Seasons
Heated clothing batteries sit unused for months. Tell users to store them at partial charge (around 40–60%) in a cool, dry place and top them up every few months. Our guide on storing lithium-ion batteries has the details.
Frequently Asked Questions
Can I use a regular power bank for a heated jacket?
Only if the jacket is designed for 5 V USB. A 7.4 V or 12 V garment needs its matching battery.
Why does my heated jacket battery die faster in the cold?
Low temperature raises the cells’ internal resistance, so the voltage drops sooner under load and the pack reaches its cut-off earlier. Keeping the battery in an inner pocket helps.
Can I take a heated jacket battery on a plane?
Spare lithium batteries usually have to go in carry-on baggage and are subject to watt-hour limits. Check your airline’s rules before you travel.
Custom Heated Clothing Batteries
Jetray designs 5 V, 7.4 V and 12 V packs for heated apparel, with low-temperature charge protection, custom enclosures and connectors. See our heated clothing battery solutions or start a custom project.
