Buy a Convoy S2+ or a C8+ and you've bought yourself a second decision: what are you actually going to charge that spare 18650 in? A lot of people run their cells in whatever charger came bundled with something else, never check the amp rating, and wonder why their "5000mAh" battery dies twice as fast as it should. Charger choice matters almost as much as battery choice. Here's how to pick one that actually fits how you use your lights.
Bay Chargers vs. USB-C Power Banks — Two Different Jobs
Chargers for loose 18650/21700 cells split into two camps. Bay chargers are dedicated charging stations you set a battery into and walk away from — think of them as a workbench tool. USB-C power bank chargers do double duty: they charge your battery, but the same unit can also push power back out to top off a phone or another USB device. Neither is objectively better; they solve different problems, and most people running more than one or two lights end up wanting one of each.
Vapcell Q4 — The Everyday Bay Charger
The Vapcell Q4 Quad Charger is the one to start with if you don't own a dedicated charger yet. Four independent bays means you can charge a mismatched set — an 18650 next to a 21700 next to a couple of 14500s — without worrying about pairing cells by capacity, which matters if you're running a mixed stable of Convoy S2+, T3, and M21A lights that each take a different cell size. Independent bays also mean one weak or dying battery doesn't drag the charge cycle for the others.
Vapcell Q8 — When Four Bays Isn't Enough
If you're past the one-or-two-lights stage and have a real battery rotation going — spares for every light plus a couple of loose cells in a pouch — the Vapcell Q8 doubles the bay count to eight. Same independent-bay logic as the Q4, just built for people who'd rather do one big charging session on a Sunday night than top off two batteries at a time throughout the week.
Yonii TC4 — A Simple Quad Alternative
The Yonii TC4 Quad Charger covers the same four-bay use case as the Q4 with Yonii's take on the display and bay design. Worth cross-shopping against the Q4 if you want to compare screen readouts and bay spacing before deciding — both are legitimate choices for a first bay charger.
Yonii PD2 and SPERAS PD21700 — Charger and Power Bank in One
This is the category that trips people up: the Yonii PD2 and the SPERAS PD21700 aren't just chargers — they're USB-C power banks that happen to take a swappable 18650 or 21700 as their power source. Drop a charged cell in, and you can use it to juice up a phone in the field. Drain it doing that, and you charge the cell back up the same way you'd charge any other USB-C device. If you're the type who carries a spare battery "just in case" anyway, one of these turns that spare into a backup phone charger too, instead of a cell that just sits in a pocket doing nothing until your light needs it.
Yonii Magnetic Travel Charger — For One Battery on the Go
The Yonii Magnetic Travel Charger is the answer to "I don't want to pack a whole bay charger for one spare battery." It's a small magnetic sled that clips onto a single cell and charges off any USB-C source — a wall brick, a laptop, a power bank. Not a replacement for a bay charger if you're charging multiple cells at home, but it's the one that actually makes sense to throw in a bag next to a single spare 18650.
Lights With Built-In Charging Don't Need Any of This
Worth saying plainly: if your light is one with a built-in rechargeable cell and USB-C port — most of the OLIGHT and Nitecore lineup, for example — you plug the light itself in and skip the external charger question entirely. This guide is for lights that take swappable cells, which is most of the Convoy lineup and any light where you keep spares in a pouch to hot-swap in the field.
Matching Charger Output to Your Battery
One thing all of the above get right that a bargain-bin charger often doesn't: current output that actually matches what a modern high-drain cell wants to see. Charging a 21700 on a charger designed for old-school 18650s at trickle speeds just means longer waits and, over time, cells that never quite balance right across a set. If you're running higher-drain cells — the kind rated for 20A+ discharge that pair well with a Convoy 3X21A or 4X18A — a charger built with 21700 in mind is worth the few extra dollars over whatever charger you already have in a drawer.
Bottom Line
One bay charger (Q4 if you're starting out, Q8 if you've got a real rotation) covers home charging for good. Add a PD2 or PD21700 if you want your spare cell to double as a phone charger, or a Magnetic Travel Charger if you just need something small for a single spare on the road. Check out the full battery charger lineup and pair it with cells from our 18650 battery collection to get your rotation set up right.