Buy in this order
- A spare cell — turns a dead light into a two-second swap
- A smart charger — doubles the working life of every cell you own
- A battery case — loose lithium cells in a bag are a real fire risk
- A diffuser — five dollars, turns a spotlight into a lantern
- A better pocket clip — only if the stock one annoys you
Batteries: the accessory that decides everything
The cell is not a passive component. It determines peak output, how long the light holds that output, how it behaves in cold, and how many years the light stays useful. A high-drain cell and a bargain-bin cell in the same flashlight produce visibly different lights.
Choosing a format
| Format | Typical use | Trade-off |
|---|---|---|
| AAA | Keychain lights | Available everywhere; very limited output |
| 14500 | Small EDC (AA-sized) | Big output for the size; short runtime |
| 18650 | Standard EDC / duty | The sweet spot — mature, cheap, plentiful |
| 21700 | High-output, long runtime | Best sustained output; noticeably bulkier |
The rules
- Ignore any cell claiming 6,000 mAh in 18650 format. The chemistry does not permit it. Around 3,500 mAh is the realistic ceiling. A fake capacity claim tells you the entire label is fiction, including the safety specs.
- Buy from known cell makers or reputable rewrappers. Samsung, Sony/Murata, LG, and Molicel make the actual cells. Sofirn, Wurkkos, and Convoy rewrap them honestly.
- Check protected vs. unprotected fit. Protected cells have a small circuit board at one end that adds a few millimetres — enough that they won't fit some lights. Check before ordering.
- Match button-top vs. flat-top to your light. Getting this wrong means a cell that simply doesn't make contact.
Safety, briefly: lithium-ion cells are safe when treated properly and genuinely dangerous when they aren't. Never carry loose cells where they can short against keys or coins. Don't charge unattended overnight. Retire any cell that's dented, has torn wrapping, or gets warm sitting idle. Rewrap kits are cheap and fix torn wrapping in a minute.
Quality 18650 cells
Two spares means you're never without a working light. Buy protected button-top unless your light specifically needs flat-top.
14500 cells
AA-sized lithium for pocket lights that take a 14500 or AA cell. Output depends heavily on cell quality here — don't economize.
Lithium AAA primaries
Non-rechargeable, but they don't leak and they last a decade on a shelf. Essential for any light that sits unused for months.
18650-to-21700 adapters
Plastic sleeves that let a 21700 light run an 18650 in an emergency. A few dollars, occasionally the difference between light and no light.
Chargers: stop using the one in the box
Most lights now charge over USB-C, and for a single-cell light that's genuinely sufficient. But a standalone smart charger does three things the in-light circuit can't.
It charges spares while the light stays in use. It reports capacity and internal resistance, so you can retire a fading cell before it strands you rather than after. And it lets you set a charge current appropriate to the cell instead of whatever the light's driver decided.
A four-bay analyzing charger costs about the same as a mid-range flashlight and will pay for itself in cells you don't have to replace prematurely.
4-bay smart charger
Handles 18650, 21700, 14500, AA, and AAA. Shows voltage, capacity, and internal resistance per bay. The one accessory that improves every light you own.
Magnetic charging cables
For Olight and Skilhunt lights. Buy a spare — the cable is the single point of failure in a magnetic charging system, and owning one is asking for trouble.
Battery cases: the two-dollar safety item
This one isn't optional. A loose 18650 in a bag with keys, coins, or a multitool can short across its terminals, and a shorted lithium cell doesn't fail politely — it vents, gets extremely hot, and can ignite. It's rare, it's entirely preventable, and prevention costs about two dollars.
Get a rigid plastic case per pair of cells and use it every time, including for cells you think are dead. A "dead" cell still holds enough energy to start a fire.
Diffusers: the cheapest upgrade in the hobby
A silicone or plastic cone that slides over the head and scatters the beam. Five dollars. It converts a directional spotlight into a soft, even lantern.
That matters more often than it sounds. Inside a tent, a bare hotspot on the ceiling is harsh and useless; diffused, the same light fills the space evenly. Under a car hood, a diffuser kills the hard shadows that hide exactly the fitting you're trying to see. During a power cut, it turns your EDC light into room lighting.
Buy one sized to your light's head diameter — they're not universal, and a loose one will fall off in a pocket.
Pocket clips, lanyards & holsters
Mostly a comfort category, but a few things are worth knowing.
Clips: stock clips vary enormously in tension. Too loose and the light works its way out of a pocket; too tight and it tears at fabric. Aftermarket clips are cheap and light-specific — worth replacing if yours annoys you, worth ignoring if it doesn't. Deep-carry clips sit the light lower in a pocket so almost nothing shows.
Lanyards: genuinely useful for work over water, from height, or over a storm drain. Otherwise they snag on things and add bulk.
Holsters: only make sense for larger 18650 and 21700 lights that are uncomfortable clipped in a pocket. For anything Baton-4-sized, a holster adds more bulk than it removes.
A note on headlamps
The clip-to-a-cap-brim trick on lights like the Baton 4 works, but it's a workaround. If you regularly need both hands — car work, camping, running, home repair — a dedicated headlamp with a proper strap, a red mode, and a balanced weight distribution is a different class of tool. It's the one accessory that's really a second flashlight, and it's worth owning.
What to skip
- Colored filter kits — the red and green filters are dim and rarely used. A light with a built-in red mode is better.
- Strike bezels — aggressive crenellations shred pocket linings, and the self-defense case for them is thin.
- Remote pressure switches — for weapon lights, not everyday carry.
- Branded "tactical" kits — a bundle of things you didn't choose in a nylon case you won't use.
Frequently asked questions
What accessories should I buy first for a new flashlight?
A spare cell and a decent charger, in that order. Everything else is comfort. A second battery turns a dead light into a two-second swap, and a quality charger will keep both cells healthy for years instead of months.
Are cheap 18650 batteries safe?
Unbranded cells claiming 6000 mAh are relabelled low-capacity cells and should be avoided — the capacity claim is a reliable tell that nothing else on the label is true either. Buy cells from Samsung, Sony/Murata, LG, Molicel, or reputable rewrappers, and check that protected cells fit your light before ordering.
What does a diffuser actually do?
It scatters a focused beam into soft, even light. Slide one over the head and a spotlight becomes a lantern — useful in a tent, under a car hood, or any time a hotspot creates harsh shadows instead of showing you the whole scene.