21700 cells: Molicel P45B, Samsung 50S, P42A, or 40T for a powerful battery

For a powerful electric scooter battery, the choice of the 21700 cell comes down to a trade-off between capacity and current. The Samsung 50S stores the most energy per cell; the Molicel P45B offers almost the same capacity with a significantly higher discharge current; the Molicel P42A and Samsung 40T are proven high-performance cells, with slightly less capacity. There is no single "best" cell; the right cell depends on the intended use, the number of cells used, and the required current.

The 21700 format

The name indicates the dimensions: 21 mm in diameter and 70 mm in length. Larger than the 18650 (18 mm by 65 mm), the 21700 contains more active material and dissipates heat more effectively. It has become a standard in high-performance batteries. All the cells in this comparison are lithium-ion batteries with a nominal voltage of 3.6V, charged to 4.2V and dischargeable down to 2.5V, according to their specifications.

The four cells, described individually

The values below are those declared by the manufacturers and reported by specialized distributors. The continuous currents are given under specific conditions, sometimes with a cutoff at a cell temperature of 80°C: these are laboratory maximums, not comfort values.

Samsung 50S

This is the most high-capacity option, with a typical capacity of 5,000 mAh. Its advertised continuous current of 25 A is very respectable for a cell of this capacity. It is suitable for batteries where range is a priority, or for those with many cells in parallel, which divides the current demand for each individual cell. We use it, for example, in our 67 V 40 Ah 18S8P battery for Weped Coupe.

Molicel P45B

It combines 4,500 mAh and a stated continuous current of 45 A. This rare combination makes it the current benchmark for performance batteries: with the same number of cells, it provides both good range and high current output. It equips our most advanced batteries, such as the Performance 80 V 40.5 Ah for Nami Burn-E or the Performance 80 V 40.5 Ah for Slack Core 920R, as well as the RM-X.

Molicel P42A

This very common power cell boasts a capacity of 4,200 mAh. Its continuous current is often stated to be 45A; however, independent tests suggest it performs better with lower currents during prolonged use. It remains a reliable option for sports batteries.

Samsung 40T

Another powerhouse option, boasting 4,000 mAh and a continuous output of 35A. Its performance is similar to the P42A, and the two are often interchangeable in the same application. That's why our Performance batteries, such as the Performance 72V 40Ah battery for Dualtron Thunder and Thunder 2, are equipped with Samsung 40T or Molicel P42A cells, depending on availability, without any change in capacity or current.

From the cell to the battery

The current that a battery can provide is, at first approximation, the current of a single cell multiplied by the number of cells connected in parallel. A 20S10P battery using cells rated at 45A can theoretically deliver significantly more current than a 20S10P battery using cells rated at 25A, for a similar capacity. However, this calculation represents an upper limit: the BMS (Battery Management System), the nickel or copper connections, the connectors, and the overall heat generation all impose a real-world limit.

It's also important to consider the internal resistance: this determines the voltage drop and heat generation at high current levels. Two cells with the same "maximum" current rating can heat up very differently at the same current. Our guide read the technical specifications of a lithium cell details these figures, and explains why the voltage drops when you accelerate, outlining their effects on performance.

Which one to choose?

• Original controller, prioritizing range: Use a high-capacity cell, such as the 50S, in sufficient quantity.
• Rebuilt controller, for sports use: A power cell (P42A, 40T) or, preferably, the P45B.
• Circuit, high current demands, limited space: The P45B offers the best compromise within a given volume.

The choice also depends on the available space in the deck: more cells in parallel mean more current and longer range, but they need to fit. The difference between our product lines is explained in Performance vs. Range Battery.