Battery & Cell Checker

Picking the right cell is half of getting a flashlight working — the wrong format, or an unrated charger, is where people get stuck. Pick your light’s cell type and how you’ll use it, and the checker returns the typical capacity in mAh, whether it’s rechargeable, the charging notes (USB-C onboard vs an external charger), plain-English pros and cons, and which flashlight classes use that cell — plus a rough runtime estimate so the numbers mean something.

It’s usually printed on the cell, or in the light’s spec sheet.

Output drives the runtime estimate — higher lumens drain any cell faster.

Pick a cell type above to see its capacity, charging notes, pros and cons, and a rough runtime estimate.

How the runtime estimate is calculated
  • The maths. Rough runtime (hours) ≈ (capacity in mAh ÷ 1000) × cell voltage × efficiency factor ÷ power drawn at the LED (watts). Power at the LED ≈ lumens ÷ lumens-per-watt. We assume a typical modern emitter at roughly 120 lumens per watt and a driver efficiency factor of ~0.85. Li-ion cells are taken at a nominal 3.6 V, AA/AAA at 1.5 V (a single-cell light steps that up to drive the LED).
  • Why it’s a ballpark. Real runtime depends on the exact driver, emitter, thermal step-down, cell quality and temperature. A regulated light holds output flat then steps down; a direct-drive light sags the whole way. The estimate is a sanity-check on the order of magnitude, not a substitute for the maker’s published ANSI/NEMA FL-1 runtime-to-10% figure — always trust the FL-1 number on the light.
  • Capacities used are typical mid-market figures for each format from published cell specs and community-measured data — not bench measurements of a specific named cell.

Shopping for a light around a cell format? See the best 18650 flashlights guide, or decode the spec sheet in the specs hub. Not sure which light fits your use case? Try the flashlight matcher.

Affiliate note: our guides earn from qualifying Amazon purchases at no cost to you. Full disclosure. Specs are quoted from manufacturer ANSI FL-1 figures and current listings — no hands-on lux or throw testing claims.