The Molicel P45B (INR21700-P45B) is a high-drain 21700 lithium-ion cell built for e-bike, e-scooter and electric motorcycle battery packs. It delivers a typical capacity of 4500 mAh at a nominal voltage of 3.6 V. Continuous discharge current reaches up to ≈45 A, which places this cell firmly in the power category.
The chemistry is Li-ion INR, and the format is a cylindrical cell measuring 21 mm in diameter and 70 mm in length. Because of that combination, the P45B suits builds where energy density and sustained current both matter at the same time. Pack designers therefore select it for power upgrades and for any 3.6 V nominal solution.
Cells are wired in series and parallel according to the voltage and capacity your project requires. Note that this is an unprotected cell without an integrated protection board (PCB). For that reason, it belongs only in packs managed by a BMS. The contact type is flat top, which makes spot welding straightforward.
Key Benefits
- 4500 mAh typical capacity – a substantial energy reserve inside a single 21700 cell.
- Up to ≈45 A continuous discharge – the cell sustains heavy current for demanding packs.
- Li-ion INR chemistry – a balanced ratio of energy density, safety and cycle life.
- 21700 format – greater energy density than solutions built around 18650 cells.
- 3.6 V nominal voltage – a clear calculation basis for series-connected packs.
- 4.20 V maximum charge and 2.50 V cut-off – a precisely defined operating window.
- Flat top contact – convenient for spot welding with nickel or copper strip.
- Molicel manufacturing – E-One Moli Energy cylindrical Li-ion cells developed for high-current applications.
Who Is This Cell For?
The Molicel P45B is intended for electric bicycle, electric scooter and electric motorcycle battery packs. In addition, it fits other 3.6 V nominal solutions whenever the finished pack runs under BMS control. Above all, it is a choice for power modifications that demand high sustained current.
This product is aimed at pack manufacturers and experienced builders. The cell is not a finished product, so you need to join it into a pack, connect a BMS and fit an enclosure. Consequently, it is not used on its own inside devices that expect a protected cell.
A single cell can be used separately only with a suitable control and charging module plus proper safeguards. Furthermore, every pack must include protection against overvoltage, deep discharge, overcurrent and short circuit. Plan those protections before you weld the first strip.
Technical Specifications
| Manufacturer | Molicel |
| Model | INR21700-P45B (P45B) |
| Format | 21700 (unprotected cell) |
| Capacity (typical) | 4500 mAh |
| Chemistry | Li-ion INR |
| Type | Rechargeable (battery cell) |
| Nominal voltage | 3.6 V |
| Maximum charge voltage | 4.20 V |
| Discharge cut-off voltage | 2.50 V |
| Continuous discharge current | up to ≈45 A* |
| Discharge and overload protection | Unprotected (no PCB) |
| Contact type | Flat top |
| Diameter | 21.00 mm |
| Height | 70.00 mm |
* The exact permissible current depends on your BMS, cooling and overall system design.
Usage Notes
- A BMS is required, with protection against overvoltage, undervoltage, overcurrent and short circuit.
- Spot welding with nickel or copper strip is the recommended joining method.
- Avoid overheating cells during soldering, since excess heat damages the cell.
- Charge only with Li-ion chargers that follow the stated specification.
- Never use damaged, deformed or deeply discharged cells.
Why Choose the Molicel P45B?
The P45B belongs to the Molicel Power series, and the model abbreviation itself points to the ≈45 A current class. It therefore differs from ordinary high-capacity cells, which cannot hold that level of continuous current. If your build draws hard under load, that distinction matters more than raw capacity alone.
The 21700 format is physically larger than the 18650 at 21 mm × 70 mm, so it will not fit 18650 holders. However, the extra volume is exactly what delivers higher capacity and better energy density per cell. Builders moving up from 18650 packs gain both range and headroom.
INR chemistry allows the cell to combine heavy discharge with solid cycle longevity. As a result, the P45B works well in packs that see repeated hard use rather than gentle cycling. Pair it with a properly rated BMS and quality strip, and the pack performs to its design figures.
Frequently Asked Questions
Is the Molicel P45B suitable for e-bike and e-scooter battery packs?
- Yes, it is designed for electric bicycle, electric scooter and electric motorcycle packs.
- The ≈45 A continuous discharge covers demanding drive systems.
Can I use the P45B in an electric motorcycle pack without a BMS?
- No, this is an unprotected cell with no PCB.
- Every pack needs a BMS with overvoltage, deep discharge, overcurrent and short-circuit protection.
Will the 21700 cell fit 18650 holders?
- No, the P45B measures 21.00 mm in diameter and 70.00 mm in height.
- An 18650 holder is physically too small for this format.
How should the cells be connected into a pack?
- Cells are joined in series and parallel to reach the required voltage and capacity.
- Spot welding with nickel or copper strip is recommended over soldering.
What are the charge and discharge limits?
- Maximum charge voltage is 4.20 V per cell.
- Discharge cut-off is 2.50 V, and nominal voltage is 3.6 V.
Can a single P45B cell be used on its own?
- Only with a suitable control and charging module plus proper safeguards.
- It should not go into devices that expect a protected cell.
What does the flat top contact mean in practice?
- The positive terminal is flat rather than raised.
- This shape suits spot welding and tight pack layouts.
The Molicel P45B gives pack builders 4500 mAh and ≈45 A continuous discharge in a single 21700 cell. Combine it with a correctly specified BMS, clean welded joints and a protective enclosure, and you have a solid foundation for e-bike, e-scooter and electric motorcycle power builds.
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