Molicel P45B vs P50B: two 21700 power cells compared
Same manufacturer, same format, both high-power. The difference is where each one sits on the capacity-versus-current trade, and the charge rate that comes with it.
In short
The P50B carries 500 mAh more capacity and 15 A more continuous discharge than the P45B, and charges at 5 C against 3 C. The P45B is the lighter cell at 69 g and remains the cheaper option where 45 A per cell is already more than the duty needs. Both are 21700 power cells with manufacturer data sheets on file.
At a glance
P45B and P50B, side by side
Every figure in this table is traceable to a model page or a manufacturer document. Where a value is not published in the source we hold, the cell says so rather than carrying a plausible-looking number.
| Attribute | P45B | P50B | Note |
|---|---|---|---|
| Model | INR21700-P45B | INR21700-P50B | |
| Format | 21700 | 21700 | |
| Typical capacity | 4,500 mAh | 5,000 mAh | |
| Nominal voltage | 3.6 V | 3.6 V | |
| Continuous discharge | 45 A | 60 A | |
| Max charge (continuous) | 3 C — about 13.5 A | 5 C — about 25 A | |
| Mass | 69 g | Not published in the sheet we hold | |
| Energy density | Not published in the sheet we hold | 265 Wh/kg | |
| Cycle life | Not stated as a single figure | 1,400 cycles at 100 W discharge | |
| Data sheet on file | Yes | Yes |
The same trade, at two points
Both cells are built for current, so both give up capacity relative to an energy-grade 21700 of the same size. The P50B gives up slightly less of it while carrying more current, which is why it is the newer and more expensive part. The P45B sits one step down: still a power cell, with a lower current ceiling and a lower price.
The practical question is not which cell is better, but whether your duty is above or below 45 A per cell. Below it, the P45B is doing the same job with money left over. Above it, the P50B is the only one of the two that is rated for the load — and a design that runs a 45 A cell at 55 A has no documented margin at all.
Charge rate is the difference people overlook
The 5 C charge rating on the P50B is the part that changes product design rather than cell selection. At 5,000 mAh, 5 C is roughly 25 A per cell: a 4P pack can absorb about 100 A, which makes a 20-minute turnaround possible in principle. The same pack built on P45B tops out near 54 A at 3 C.
That has consequences downstream — charger sizing, connector rating, and the thermal path during charge rather than discharge. Charge heat is generated in the same can that has just been asked to deliver current, so a pack designed for fast turnaround needs its thermal design validated in both directions.
What both have in common
- Rated current is conditional: both figures hold while the cell stays inside the manufacturer temperature cut-off, which is a thermal design requirement, not a property of the cell alone.
- Both are unprotected industrial cells — a BMS or protection circuit is mandatory, and interconnects must be welded rather than soldered.
- Both are covered by a manufacturer data sheet on file here, so the figures above can be checked against the source rather than against a reseller table.
How to decide
- Calculate current per cell from pack current divided by parallel count (see the selection guide).
- If it is below 40 A, the P45B leaves margin and saves cost; if it is between 40 and 55 A, the choice turns on how much margin you want.
- If it is above 55 A, the P50B is the only option of the two.
- If fast charge is a product requirement rather than a convenience, start from the charge rate — that usually decides it before the discharge figure does.
Questions about this comparison
Is the P50B just a higher-capacity P45B?
Not exactly. It carries more capacity and more current at the same time, which usually means a different electrode and separator design rather than a simple formulation change. That is why the cycle-life and charge-rate figures differ as well.
Can the two be mixed in one pack?
No. Cells sharing a series string must match on capacity and impedance. Mixing models — even from the same manufacturer — guarantees a mismatch that the weakest cell will define.
Which one lasts longer?
Cycle life depends on the duty, not only the cell. The P50B publishes a cycle figure at a defined discharge power; the P45B does not publish a single number in the sheet we hold. Without comparable test conditions, "which lasts longer" cannot be answered from the data sheets alone.
Are both figures verified against the manufacturer?
Yes. Both pages link the manufacturer data sheet held on file, and the figures in this table are read from those documents.
Related
Where to go next
Settled on a cell? Send the duty profile.
Give us the continuous and peak current, the envelope and the target cycle life. We will confirm what is obtainable and which documents travel with it.