Samsung 25R 2500mAh 20A Button Top Battery 4-Pack with Nitecore UMS4 Smart Charger – High-Drain Power Kit with LCD Control for Flashlights & Power Tools

What's in This Bundle

• 4x Samsung INR18650-25R, 2500mAh, Button Top
• 1x Nitecore UMS4 4-slot LCD USB-C charger
• Cable and manual included with the charger

A complete kit for anyone running a 4-cell high-drain device or building a small pack — four matched, genuine 25R cells paired with a charger that reports real per-cell health, not just charge status.

This listing is for Button Top. Looking for Flat Top? Click here to buy: Samsung INR18650-25R Flat Top + Nitecore UMS4  Bundle.

Why This Pairing Makes Sense

The 25R is one of the classic high-drain 18650 cells — moderate capacity, a strong 20A continuous discharge rating, and a long track record in mods, RC applications, tools, and custom packs. Four cells bought together as a matched set means consistent capacity and internal resistance across the group, which matters more for a high-drain cell like this one, where mismatched internal resistance between cells shows up faster under load.

The Nitecore UMS4 pairs especially well here because it doesn't just charge the cells — it measures and displays internal resistance for each slot with a "Good" or "Poor" health rating. For a high-drain cell where internal resistance directly affects real-world performance, that's a genuinely useful way to confirm all four cells are actually matched, not just similarly labeled.

Samsung 25R — Battery Specs

This is a genuine high-drain cell, verified against Samsung's official datasheet — not rewrapped or relabeled stock. The 25R is often run close to its current ceiling in real devices, so heat management in your build matters more here than it would with a lower-drain cell.

This listing is for Button Top. For Flat Top click here

Nitecore UMS4 — Charger Specs

A realistic note on charge time: with all four slots occupied, the UMS4's fast charge mode delivers roughly 1000mA per slot — well within the 25R's 4A max charge rating, so there's real margin here. Expect a full charge in roughly 2.5-3 hours for all four cells at once, genuinely quick for a 4-slot charger running this many cells simultaneously.

Why the Internal Resistance Readout Matters Here

High-drain cells like the 25R are exactly where internal resistance differences between cells matter most — a cell with meaningfully higher resistance than its packmates will run hotter and sag more under load, dragging down the performance of a series or parallel pack even if its capacity looks fine on paper. The UMS4's per-slot mΩ readout and health rating let you actually check this instead of assuming four cells from the same order are automatically matched.

Where the 25R Actually Shines

• RC applications — cars, planes, and similar hobbies that need real current delivery
• Power tools and custom packs where discharge capability matters more than maximum runtime per cell
• Robotics and DIY builds needing dependable current under load, verified before assembly

Not the ideal pick if capacity or runtime matters more to you than raw discharge current — a cell like the 30Q or 35E will serve you better in that case.

Things Worth Knowing Before You Use This Kit

• The 25R is an unprotected cell. The charger enforces its own voltage and current cutoffs, but your device still needs to handle discharge-side protection.
• Don't mix these cells with older ones you already own, even if they're also 25R — the UMS4's internal resistance readout is exactly the tool for checking this before you combine batches.
• This cell runs warm at its rated ceiling. That's expected behavior for a 20A cell pushed toward that limit, not a defect — but ventilation and enclosure design in your build matter.

Frequently Asked Questions

Can this charger handle the 25R's full capacity safely? Yes. Even at the UMS4's fast charge rate of roughly 1000mA per slot with all four bays occupied, that's comfortably under the 25R's 4A max charge rating — a full charge takes roughly 2.5-3 hours for all four cells.

What does the "Poor" health rating actually tell me? It means that cell's measured internal resistance is elevated relative to what's expected for a healthy cell. For a high-drain cell like the 25R, that's worth taking seriously — a "Poor" rating suggests the cell may underperform or run hotter than its packmates under load.

Why does the 25R run hotter than lower-drain cells like the 35E? It's a direct consequence of the design trade-off — the 25R prioritizes current delivery (20A continuous) over capacity, and pushing more current through a cell generates more heat. This is expected and within the cell's rated tolerance.

Can I charge two different battery sizes at once? Yes — the UMS4's four slots operate independently, so you can mix cell sizes or even Ni-MH/Ni-Cd batteries across the slots if needed.

What does the lithium battery repair function do? When an over-discharged IMR lithium cell is detected, the display shows an "EE EE" prompt; pressing the V button attempts a controlled repair charge. It won't recover every over-discharged cell, but it gives borderline cells a real chance before writing them off.

In stock now. This bundle ships as a matched set of four genuine Samsung 25R Button Top cells with a verified Nitecore UMS4 charger — ready for mods, RC, tools, and other high-drain builds out of the box.