Why This Bundle
High-drain batteries perform best with a charger built to match their charging profile. This bundle pairs genuine Samsung 25R Flat Top cells with the NITECORE UI2 — a compact, USB-C powered charger that automatically selects the right charging mode and includes trickle charging and over-discharge protection. Everything you need to charge and maintain your cells, ready out of the box.
This listing is for Flat Top. Looking for Button Top? Click here to buy: Samsung INR18650-25R Button Top + NITECORE UI2 Bundle.
Samsung INR18650-25R (Flat Top) Specifications
| Item |
Spec |
| Model |
Samsung INR18650-25R (Flat Top) |
| Rated Capacity |
2500mAh |
| Nominal Voltage |
3.6V |
| Max Continuous Discharge |
20A |
| Charge Cutoff Voltage |
4.2V |
| Chemistry |
NMC (Lithium Nickel Manganese Cobalt Oxide) |
| Cell Size |
18650 (approx. Φ18.3mm × 65.0mm) |
| Terminal Type |
Flat Top — level positive terminal, suited for devices requiring full-surface contact |
| Typical Use |
Battery packs, power banks, flashlights, power tools, e-bikes, and other devices designed for flat-top cells |
Note: High-drain cells demand careful handling — avoid mixing with batteries of a different brand, model, or charge state, and inspect the wrap for damage before every use to prevent short circuits.
The Charger: NITECORE UI2
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USB-C input: charge from any 5V power bank, solar panel, or USB adapter — great for travel and outdoor use
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Automatic CC/CV Charging: intelligently selects the most suitable charging mode for each cell
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Independent Dual-Bay Control: each of the 2 bays charges independently without affecting the other
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Trickle Charging: automatically switches to 100mA trickle mode for batteries below 2.9V, then up to 1000mA standard charging above 2.9V
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Over-Discharge Activation: automatically detects and reactivates over-discharged protected Li-ion cells
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Multiple Safety Protections: reverse-polarity/short-circuit protection, intelligent temperature control, and overcharge protection
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Ultra-Compact & Lightweight: just 79.5g, 125.5 × 59.5 × 32.1mm
NITECORE UI2 – Supported Battery Types & Voltage
Charges 3.6V/3.7V Li-ion/IMR batteries, including the Samsung 25R (18650) in this bundle:
10340, 10350, 10440, 10500, 12340, 12500, 12650, 13450, 13500, 13650, 14430, 14500, 14650, 16500, 16340 (RCR123), 16650, 17350, 17500, 17650, 17670, 18350, 18490, 18500, 18650, 20700, 21700, 22500, 22650, 25500, 26500, 26650
Output voltage: 4.2V±1% Output current: up to 1000mA per bay (max 2 bays simultaneously)
Compatibility Notes
The UI2's charging bays are open-ended, allowing Flat Top batteries to seat securely without any adapter. Samsung 25R Flat Top cells measure about 65.0mm, well within the UI2's compatible battery range.
What's Included
- Samsung INR18650-25R Flat Top Battery × 2
- NITECORE UI2 Charger × 1
- USB-C Charging Cable × 1
- User Manual × 1
This listing is for Flat Top. For Button Top click here
Safety Tips
- Store batteries in a proper case, keeping them away from loose metal objects to prevent short circuits
- Never disassemble, puncture, burn, or submerge the batteries
- Charge only with a genuine, compatible charger such as the NITECORE UI2
- These are high-drain cells intended for compatible, purpose-built devices — do not use them in unauthorized or modified equipment
- Flat Top batteries are commonly used in devices with spring or flat-contact battery holders (e.g., battery packs and power tools) — check your device's terminal requirements before use
FAQ
Q: Can the NITECORE UI2 charge Samsung 25R Flat Top batteries safely? A: Yes. The UI2 automatically selects the optimal CC/CV charging mode for Li-ion cells like the 25R, with a 4.2V±1% output voltage and up to 1000mA per bay.
Q: What's the difference between Flat Top and Button Top batteries? A: The only difference is the shape of the positive terminal — Flat Top is level for full-surface contact, while Button Top has a raised nub. Capacity, voltage, and discharge rate are identical.
Q: Will Flat Top batteries sit properly in the UI2 charger bays? A: Yes. The UI2's open charging bays are designed to accommodate both Flat Top and Button Top cells without any adapter or modification.
Q: Can I charge both batteries at the same time? A: Yes. The UI2 has 2 independent bays, each capable of up to 1000mA, and one battery's charging status does not affect the other.
Q: Can I power the UI2 with a power bank while traveling? A: Yes. The UI2 has a USB-C input and works with any 5V power source, including power banks, solar panels, and USB wall adapters.
Q: What happens if a battery has over-discharged? A: The UI2 includes an over-discharge activation feature that automatically detects and reactivates protected Li-ion cells that have dropped too low from storage or improper use.
Q: Is 20A continuous discharge safe for everyday devices? A: These are high-drain cells built for devices that specifically call for high continuous discharge, such as certain power tools, flashlights, and DIY battery packs. Always check your device's battery requirements before use.
Q: What's in the box? A: 2 Samsung INR18650-25R Flat Top batteries, 1 NITECORE UI2 charger, a USB-C charging cable, and a user manual.
