USB rechargeable batteries are lithium-ion cells with the charging circuit built into the cell itself, so you plug a USB-C cable straight into the battery instead of using a separate bay charger. Lumen Vault stocks two: the XTAR 21700 at 5000mAh and the XTAR 18650 at 3500mAh, both with a built-in USB-C port and a 10A discharge rating. This guide is for anyone who owns a flashlight or similar device and is tired of hunting for a charger, and it will help you pick the right size and know what to check before you buy.
Actual photos of the product we stock
Actual photos of the product we stock
What makes a battery USB rechargeable?
The difference is where the charging happens. A standard lithium-ion cell needs a dedicated charger that you plug into the wall; a USB rechargeable cell has that circuitry inside it.
The XTAR 21700 and XTAR 18650 both take a USB-C cable directly. That cable can come from a phone charger, a power bank or a laptop, which means one less item in your bag on a trip or a night shift. The 18650 also has a charge level indicator built into the cell, so you can see where you stand without a charger display.
The trade-off is that you charge one cell at a time by cable. If you keep six batteries in rotation for a long patrol or a camping weekend, a bay charger still has its place.
21700 or 18650: which size does your device take?
Match the cell to the device first, because the two sizes are not interchangeable. The number is the physical size in millimetres, and a 21700 will not fit a flashlight built for an 18650.
- XTAR 21700: 5000mAh, 3.6V, 18Wh, 75.5mm long and 21.5mm across, flat top, protected.
- XTAR 18650: 3500mAh, 3.6V, 12.6Wh, protected, with a 10A maximum continuous discharge.
- Both are rated at 10A maximum continuous discharge and both are rechargeable over USB-C.
The 21700 has the larger capacity, so it runs longer between charges in a device that accepts it. The 18650 suits the many flashlights built around that size. Check the label inside your torch or the maker's specification before ordering, then look at our 21700 lithium battery cells if you need the larger size.
How long does each cell last between charges?
The 21700 holds 5000mAh and 18Wh; the 18650 holds 3500mAh and 12.6Wh. Higher capacity means more running time, but the exact hours depend on the brightness setting you use and the device itself.
On the 10A discharge rating, both cells are built to feed high-drain LED flashlights, including the kind of output that brands such as Klarus, Olight, Imalent, Sofirn and Ledlenser use on Turbo modes. The 18650 is listed for exactly that kind of heavy current draw.
The XTAR 21700 is rated for roughly 800 recharge cycles, so it is a long-term purchase rather than a disposable one. Keep a spare charged and you are never caught with a dark torch.
Which brands and devices do these cells fit?
The 21700 has a flat top and is listed as fitting flashlights from Ledlenser, Olight, Fenix and Nitecore, plus any other 21700-compatible device. The 18650 is listed for high-drain LED flashlights from Klarus, Olight, Imalent, Sofirn and Ledlenser, and other 18650-compatible devices drawing similarly heavy current.
Flat top means the positive end is flat rather than raised. It is the common shape in these torch brands, but it is still worth checking your own device before you buy. If your torch takes the smaller cell, browse our rechargeable 18650 lithium-ion batteries to see what is available.
| Feature | XTAR 21700 Battery | XTAR 18650 Battery |
|---|---|---|
| Product | ||
| Price | KSh 3,000 | KSh 2,500 |
| Battery Size | 21700 | 18650 |
| Capacity | 5000mAh (highest) | 3500mAh |
| Energy | 18Wh (highest) | 12.6Wh |
| Battery Chemistry | Li-ion | Li-ion |
| Stands out | Highest capacity, energy | |
| Suits | Flashlights from popular brands including Ledlenser, Olight, Fenix and Nitecore | High-drain LED flashlights from brands like Klarus, Olight, Imalent, Sofirn and Ledlenser |
| Link | View & Buy | View & Buy |
What should you check before buying?
Four things decide whether a cell is right for you: the size your device takes, the discharge rating it needs, whether the top shape matches, and whether protection matters to you. Both XTAR cells here are protected against overcharge, over-discharge and short circuit.
- Confirm the cell size your torch or device uses.
- Check the discharge rating your device draws, both cells here are rated 10A maximum continuous.
- Check flat top versus raised top, the 21700 here is flat top.
- Decide whether you want a charge indicator on the cell, the 18650 has one.
- Remember the 18650 carries a 1 Year Manufacturer Warranty.
Get those right and the battery simply works. Get the size wrong and no amount of capacity will help.
Where these cells earn their place
Power cuts, late patrols and camping trips are where a torch with a fresh cell matters most. A USB rechargeable cell means you can top it up from the same power bank you charge your phone with.
Other options worth a look if you want to compare further:
- XTAR 21700 RAW Battery, 5000mAh, 35-90A High-DrainKSh 2,300
- XTAR 18650 RAW Battery, 3500mAh, Flat Top, 10A DischargeKSh 1,600
- XTAR INR 18650 Battery, 2600mAh, 20A/30A High-DrainKSh 1,400
- XTAR 26650 Battery, 5200mAh, Protected Flat Top, 10AKSh 2,700
- 1Kon 26650 Battery, 3000mAh, Protected Li-ionKSh 2,000
- XTAR AA USB-C Rechargeable Battery, 2450mAh, 4-PackKSh 3,500
- XTAR AA 3960 Rechargeable Battery, 2500mAh, 4-PackKSh 3,000
- XTAR AAA Rechargeable Battery, 1000mAh, 1.5V, 4-PackKSh 2,700
So the answer is simple: pick the size your device takes, and let the built-in USB-C port do the rest. If you are ready, start with the 21700 for its larger capacity or the 18650 for the many torches built around that size.
Check the XTAR 21700KSh 3,000 · In stock
Which one should you pick?
Pick the XTAR 21700 Battery if
- Pick this for the larger capacity at 5000mAh and 18Wh.
- Choose it if your device is a 21700 with a flat top.
Pick the XTAR 18650 Battery if
- Pick this if your flashlight takes the smaller 18650 size.
- Choose it for the on-cell charge level indicator.
Where you would use it
- Night patrols Keep a charged cell in your torch for security rounds, then top it up from a power bank before the next shift.
- Camping trips Charge your torch battery from the same power bank or phone charger you already carry in your bag.
- Power cuts A spare USB-C cell means your torch stays ready when the mains goes off at home.
- Long drives Top up a battery from a car USB charger so your torch is full before you reach your stop.
Frequently asked questions
Yes. Both the XTAR 21700 and XTAR 18650 have a built-in USB-C port, so you charge them straight from a phone charger, power bank or laptop with a cable.
They are different physical sizes. The XTAR 21700 is 75.5mm long and 21.5mm across with 5000mAh, while the XTAR 18650 is the smaller cell size with 3500mAh. A device built for one size will not take the other.
About 800 cycles. The XTAR 21700 5000mAh cell is rated for roughly 800 recharge cycles, so it is a long-term buy rather than a disposable battery.
Yes. The XTAR 21700 has a flat top and is protected against overcharge, over-discharge and short circuit. It is listed as fitting flashlights from Ledlenser, Olight, Fenix and Nitecore.
High-drain LED flashlights from brands such as Klarus, Olight, Imalent, Sofirn and Ledlenser, plus other 18650-compatible devices drawing similarly heavy current. It is rated 10A maximum continuous discharge.
