Guide
Why mAh Alone Does Not Tell a Heated Vest’s Runtime
A battery labeled 20,000mAh does not tell you how many hours a heated vest will run. It gives one piece of electrical information. To reason about runtime, you also need the relevant voltage, usable energy and the garment’s power use under the selected settings.
Three labels that answer different questions
Swipe across the table to compare all columns.
| Label | What it describes | What it cannot settle alone |
|---|---|---|
| mAh | Milliamp-hours: a measure of electrical charge capacity. | Hours of heating across different systems. |
| Wh | Watt-hours: a measure of energy. | Actual runtime without knowing power use and usable energy. |
| W | Watts: the rate of energy use or delivery. | Total available energy in the battery. |
The U.S. Energy Information Administration distinguishes power in watts from energy used over time in watt-hours. One watt-hour corresponds to one watt used for one hour.
Source: U.S. EIA — measuring electricity.
Why voltage belongs in the comparison
For a stated nominal battery rating, watt-hours can be expressed as amp-hours multiplied by the corresponding nominal voltage. Convert mAh to Ah by dividing by 1,000. The important word is corresponding: the voltage must belong to the capacity rating you are using.
Do not multiply a power bank’s advertised mAh by whichever output voltage looks convenient. A label may express capacity at an internal cell voltage while listing different external output modes. Use the manufacturer’s stated Wh rating where available, or ask for clarification.
A mathematical example, not a ThermStride runtime claim
Suppose a hypothetical battery is rated at 10Ah at 3.7V. That rating corresponds to 37Wh. If a hypothetical load used a constant 10W and all that energy were usable, the arithmetic would give 3.7 hours.
Those numbers are an illustration only. They are not specifications for a ThermStride battery, do not include conversion losses and do not establish how a heated vest changes power use during operation.
The garment changes the question
Selected heat level and operating conditions affect runtime. ThermStride’s vest page identifies battery capacity, heating level, outside temperature and conditions of use as relevant factors.
Source: ThermStride — vest details and operating instructions.
That means even a correct energy calculation is not a substitute for the model’s documented runtime conditions. A headline maximum is especially easy to misread if you do not know which battery and setting it describes.
Compare batteries in this order
- Confirm that each battery is compatible with the exact vest.
- Check the complete model and rating information, including Wh where provided.
- Compare the manufacturer’s runtime conditions on an equivalent basis.
- Consider the practical fit of the battery in its intended pocket.
- Plan for your full outing rather than relying on capacity arithmetic alone.
A larger capacity option can be useful within a supported product system. The mistake is treating one number as a universal promise across batteries, garments and settings.
Frequently asked questions
Does twice the mAh always mean twice the runtime?
No. The comparison requires equivalent voltage and operating conditions, and actual usable energy and system behavior also matter.
What is the difference between mAh and Wh?
mAh measures electrical charge capacity; Wh measures energy. Relating them requires the corresponding voltage.
Can I use the output voltage to calculate Wh?
Only when it is the voltage corresponding to the stated capacity rating. Do not assume an external output mode is the basis of the advertised mAh.
Does a Wh rating guarantee heating hours?
No. You also need the actual power use and usable energy under the operating conditions.
What should I check before choosing a larger battery?
Compatibility first, then exact ratings, published runtime conditions and pocket fit. A larger mAh label alone is not enough.