Why This Bundle
Six high-drain cells need a charging setup that can keep up — at home and on the go. This bundle pairs 6 genuine Samsung 25R Flat Top batteries with the NITECORE UMS4 (a 4-bay smart LCD charger for fast, monitored charging at your desk) and the NITECORE UI1 (an ultra-compact single-slot charger for travel or topping off a spare cell). Together, all 6 batteries can be charged at once — 4 in the UMS4, 2 more with a second UI1 or staggered through the UI1 — with full visibility into every cell's health.
This listing is for Flat Top. Looking for Button Top? Click here to buy: Samsung INR18650-25R Button Top + NITECORE UMS4 + NITECORE UI1 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 Chargers: NITECORE UMS4 + NITECORE UI1
NITECORE UMS4 — 4-Bay Smart LCD Charger
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USB-C input with QC support: up to 4,000mA total output, up to 3,000mA on a single bay with a QC adapter
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Independent 4-bay control: charge and monitor each battery separately
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Real-time LCD display: shows battery health (Good/Poor), internal resistance, charging current, voltage, charged capacity, and charging time
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3 automatic charging modes: CC, CV, and -dV/dt, selected automatically based on battery type and charge level
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Manual adjustment: set charging voltage (3.7V/4.2V/4.3V) and current (300mA–3000mA) for specialized battery types
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Safety features: automatic internal resistance detection, reverse-polarity and short-circuit protection, overtime charging protection, and over-discharged battery activation/restoration
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Fire-retardant PC/ABS housing with built-in temperature regulation
NITECORE UI1 — Compact Single-Slot Charger
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Type-C input: automatically adapts to the optimal charging mode, works with power banks, solar panels, and USB adapters
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Up to 1000mA output with automatic CC/CV mode selection
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Trickle charging protects over-discharged cells and extends battery lifespan
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Over-discharge activation for protected Li-ion batteries
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Ultra-lightweight: just 40.5g — ideal for travel, a backup charge, or topping off the 6th cell while the UMS4 handles the other 4
Supported Battery Types & Voltage
NITECORE UMS4 — compatible with 3.6V/3.7V Li-ion, 3.8V Li-ion, 3.2V LiFePO4, and 1.2V Ni-MH/Ni-Cd batteries, including the Samsung 25R (18650) in this bundle: IMR/Li-ion/LiFePO4: 10440, 14500, 14650, 16500, 16340(RCR123), 16650, 17350, 17500, 17650, 17670, 17700, 18350, 18490, 18500, 18650, 18700, 20700, 21700, 22500, 22650, 25500, 26500, 26650, 26700 Ni-MH/Ni-Cd: AA, AAA, AAAA, C, D Output: up to 3,000mA per bay (QC mode) / 4,000mA total
NITECORE UI1 — compatible with 3.6V/3.7V Li-ion/IMR batteries, including the Samsung 25R (18650): 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
Compatibility Notes
Both the UMS4 and UI1 use spring-loaded contacts that accommodate Flat Top and Button Top batteries without any adapter. Samsung 25R Flat Top cells measure about 65.0mm, well within the compatible battery range of both chargers.
What's Included
- Samsung INR18650-25R Flat Top Battery × 6
- NITECORE UMS4 4-Bay Charger × 1
- NITECORE UI1 Single-Slot Charger × 1
- USB-C Charging Cables × 2
- User Manuals × 2
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 genuine, compatible chargers such as the NITECORE UMS4 and UI1
- 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 I charge all 6 batteries at the same time? A: Yes. The UMS4 charges 4 batteries independently and simultaneously, while the UI1 can charge a 5th or 6th battery alongside it — or you can stagger charging through the UI1 if only one is used at a time.
Q: Are Samsung 25R Flat Top batteries safe to charge in both chargers? A: Yes. Both the UMS4 and UI1 automatically recognize Li-ion chemistry and apply the correct charging voltage (4.2V) and current for 25R cells.
Q: What's the difference between the UMS4 and UI1 in this bundle? A: The UMS4 is a 4-bay charger with an LCD screen showing detailed real-time data (battery health, internal resistance, voltage, capacity) and faster QC charging up to 3,000mA per bay. The UI1 is a single-slot, ultra-compact charger (40.5g) best suited for travel or charging one battery at a time.
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 both charger slots? A: Yes. Both the UMS4 and UI1 have spring-loaded contacts designed to accommodate Flat Top and Button Top cells without any adapter.
Q: How do I check if a battery is degraded? A: The UMS4's LCD display shows battery health as "Good" or "Poor" along with internal resistance readings, making it easy to spot cells that have aged or lost performance.
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: 6 Samsung INR18650-25R Flat Top batteries, 1 NITECORE UMS4 charger, 1 NITECORE UI1 charger, 2 USB-C charging cables, and user manuals for both chargers.
