Understanding the Differences: 21700 vs 18650 Batteries

We frequently encounter queries on the distinctions between common battery types. Given the interest, we decided to shed some light on this subject, specifically focusing on the two most prevalent types of flashlight batteries: the 21700 and the 18650. By the end of this blog post, you should have a clear idea of which battery is better suited to your needs.

Size and Capacity: The Core Difference

At the heart of the comparison between the 21700 and the 18650 is their size. The 21700, being larger, naturally boasts a more substantial capacity. To put it in numbers, while an 18650 battery offers a maximum capacity of around 3500 mAh, its 21700 counterpart can go up to 5000 mAh. This enhanced power translates to longer burn hours, making the 21700 an excellent choice for scenarios demanding extended use without intermediate charging. Think of a traffic police officer working throughout the night – the 21700 ensures their flashlight won’t dim prematurely.

The Upside of Being Bigger: Beyond Just Capacity

The physical dimensions of the 21700 present another advantage. Its larger size provides room for better cooling and improved power characteristics. For instance, a 21700 battery can support up to 1400 watts, while the 18650 taps out at 800 watts. This disparity in capacity means devices powered by the 21700 battery are not only more robust but also enjoy extended runtime.

A Real-World Battery Showdown

To give a tangible sense of the difference, we ran a test using the Fenix HT18 hunting flashlight with a luminosity of 1500 lumens. This model was chosen for its compatibility with both battery types using mounts.

Performance of Fenix HT18 with 21700 Li-ion battery:

  • Turbo: 1500 lumens, runtime ~1:40 hours*
  • High: 500 lumens, runtime ~4:15 hours
  • Medium: 150 lumens, runtime ~20:15 hours
  • Low: 30 lumens, runtime ~61 hours
  • Strobe: 1500 lumens

Performance of Fenix HT18 with 18650 Li-ion battery:

  • Turbo: 1100 lumens, runtime ~1:40 hours*
  • High: 500 lumens, runtime ~2:15 hours
  • Medium: 150 lumens, runtime ~14:10 hours
  • Low: 30 lumens, runtime ~53 hours
  • Strobe: 1100 lumens

*Note: The highest light setting’s runtime is measured from activation. Due to temperature adjustments, the light dims to a lower mode after 2-3 minutes.

Making a Case for the 18650

While the 21700 battery may seem superior on paper, the 18650 is by no means obsolete. It has the advantage of being compact and lightweight, and from a budgetary perspective, the 18650 is more cost-effective. It still packs a significant amount of illumination power, sufficient for typical flashlight applications, and it won’t burn a hole in your pocket. So, for the average user, the 18650 remains a commendable choice.

In conclusion, your choice between the 21700 and 18650 should hinge on your specific needs. Whether you prioritize extended runtime or compactness and cost-effectiveness will guide your decision.