Why This Bundle
The Molicel P45B is the newer, refined follow-up to the P42A — a 4500mAh typical capacity (7% more than the P42A) with the same 45A continuous discharge rating, but a meaningfully lower impedance and a much stronger fast-charge capability. A set this capable deserves a charger that can handle every cell at once while keeping close watch on their health. This bundle pairs 4 genuine Molicel INR21700-P45B batteries with the NITECORE UMS4, a QC-enabled 4-slot charger with a detailed LCD display, independent bay control, and multiple layers of protection — ready to use straight out of the box.
Molicel INR21700-P45B Specifications
| Item |
Spec |
| Model |
Molicel INR21700-P45B (Flat Top) |
| Typical Capacity |
4500mAh |
| Minimum Capacity |
4300mAh |
| Nominal Voltage |
3.6V |
| Max Continuous Discharge |
45A (80°C thermal cutoff) |
| Standard Charge Current |
4.5A |
| Maximum Charge Current |
13.5A (60°C cutoff, 3C fast-charge capable) |
| Charge Cutoff Voltage |
4.20±0.05V |
| Discharge Cutoff Voltage |
2.5V |
| Typical Impedance |
~7mΩ AC (30% SOC) / ~15mΩ DC (50% SOC) |
| Chemistry |
Li-ion, ultra-high-power |
| Cell Size |
21700 (approx. Φ21.55mm × 70.15mm max, approx. weight 70g) |
| Terminal Type |
Flat Top (Button Top also available) |
| Protection Circuit |
None (unprotected cell) |
| Typical Use |
Power tools, EVs/PHEVs, high-drain battery pack builds — Molicel recommends assembly in a pack with its own protection circuit |
Important: Molicel's official documentation recommends the P45B be assembled into a pack with a proper protection circuit — it's built as a high-power cell for engineered battery systems, not as a casual standalone consumer replacement cell.
This is an unprotected cell — 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 UMS4
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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 — still below the P45B's 4.5A standard charge current, but a meaningful step up from a basic dual-slot charger
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QC Mode output: 3,000mA×1 / 2,000mA×2 / 1,000mA×4 — Standard Mode: 2,000mA×1 / 1,000mA×2 / 500mA×4
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Independent 4-bay control: charge and monitor up to 4 batteries separately, with each bay unaffected by the others
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Detailed real-time LCD display: shows battery health (Good/Poor), internal resistance, charging current, voltage, battery type, charged capacity, charging time, cut-off voltage, and charging mode
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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 and current 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
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Universal power input: works with wall adapters, power banks, and solar panels via USB-C
NITECORE UMS4 – Supported Battery Types & Voltage
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 Molicel P45B (21700) 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 current: up to 3,000mA per bay (QC mode) / 4,000mA total
Compatibility Notes
The UMS4 uses spring-loaded contacts and its bays are sized to comfortably fit 21700 cells like the P45B. Compared to a basic dual-slot travel charger, the UMS4's higher per-bay output (up to 3,000mA with a QC adapter on a single bay) narrows the gap to the P45B's 4.5A rated charge current considerably, though it still won't reach the cell's full rated charge speed.
Note: With all 4 bays occupied, each will charge more gently at up to 1,000mA (QC mode) or 500mA (standard mode) — a safe charging pace for four high-power cells at once, though full charges will still take a few hours given the current gap versus the P45B's rated 4.5A.
What's Included
- Molicel INR21700-P45B Battery × 4
- NITECORE UMS4 4-Bay Charger × 1
- USB-C Charging Cable × 1
- User Manual × 1
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 UMS4
- The P45B is an unprotected, ultra-high-power cell intended for use within a properly engineered battery pack with its own protection circuit — do not use it as a standalone replacement cell in casual consumer devices
- Never discharge below 2.5V or charge above 4.2V
FAQ
Q: Can the NITECORE UMS4 charge Molicel P45B batteries safely? A: Yes. The UMS4 automatically detects Li-ion chemistry and applies the correct charging voltage (4.2V) and current for P45B cells, with real-time monitoring on its LCD display. Its per-bay output is still below the P45B's full 4.5A rated charge current, but it charges these cells considerably faster than a basic low-current charger.
Q: How does the P45B compare to the P42A? A: The P45B is the newer generation — 7% more typical capacity (4500mAh vs. 4200mAh) at the same 45A continuous discharge rating, with meaningfully lower impedance and a much stronger fast-charge capability (up to 13.5A/3C vs. the P42A's 8.4A).
Q: Is the P45B meant for use in standalone devices like flashlights? A: Molicel's official documentation recommends assembling this cell into a pack with its own protection circuit. It's built for power tools, EVs/PHEVs, and engineered high-drain battery packs rather than as a casual standalone drop-in cell.
Q: Can I charge all 4 batteries at the same time? A: Yes. The UMS4 has 4 independent bays and can charge all 4 cells simultaneously — up to 1,000mA per bay in QC mode, or 500mA per bay in standard mode, when all 4 slots are used at once.
Q: Will 21700 batteries fit properly in the UMS4? A: Yes. The UMS4's bays and spring-loaded contacts are sized to accommodate 21700 cells like the P45B without any adapter.
Q: How do I know if a P45B 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: Can I power the UMS4 with a power bank while traveling? A: Yes. The UMS4 has a USB-C input and works with wall adapters, power banks, and solar panels.
Q: What's in the box? A: 4 Molicel INR21700-P45B batteries, 1 NITECORE UMS4 charger, a USB-C charging cable, and a user manual.
