“2S” means 2 cells connected in Series, which doubles the nominal voltage to 7.4V (from a single cell’s 3.7V). The number before “P” indicates how many of these series strings are connected in Parallel to multiply the capacity. A 2S1P pack has 2 cells total. A 2S2P pack has 4 cells total (2 series strings, each with 2 cells in parallel).

A 2S pack is necessary when your device requires more power (Watts) than a 3.7V system can efficiently deliver. Higher voltage allows you to draw the same amount of power using less current (Amps). This means less heat generated in your device’s wiring and electronics, making it ideal for devices with motors (like printers or medical pumps) or high-brightness screens.

In a series circuit, the same current flows through all cells. If one cell has slightly less capacity or higher internal resistance than the other, it will charge and discharge faster. Over time, this imbalance grows. A good BMS with a balancing function monitors the voltage of each individual cell level (node) and slowly bleeds off charge from the fuller cell, ensuring both cells stay perfectly matched and safe.

Yes, Hanery insists on integrating a high-quality BMS into every multi-cell pack we manufacture. Operating a 2S pack without a BMS is extremely dangerous, as it can easily lead to overcharging one cell and over-discharging the other.

Since a single standard lithium-ion cell charges to 4.2V, a 2S pack (two cells in series) has a maximum charge voltage of 8.4V. You must use a charger specifically designed for 2S (8.4V) lithium-ion batteries.

A safe discharge cut-off voltage for a single cell is usually around 3.0V. Therefore, the BMS for a 2S pack is typically configured to cut off power when the total pack voltage drops to around 6.0V (or when any single cell drops to 3.0V) to prevent permanent damage.

Not directly. Because a 2S pack requires 8.4V to fully charge, a standard 5V USB output is insufficient. You will need a device mainboard with a built-in step-up (boost) charging circuit, or you must use a dedicated 8.4V charger.

Yes, the cylindrical nature of 18650 cells allows for flexible pack geometry. For a 2S2P pack (4 cells), we can arrange them side-by-side (flat), in a 2×2 square block, or even end-to-end (like a long stick), depending on the physical constraints of your device’s battery compartment.

Yes. All lithium-ion battery packs, regardless of size, must pass UN38.3 testing to be legally transported by air or sea. We manage this testing and certification process for all custom packs we build.

To provide an accurate design and quote, our engineers need:

1. Target Capacity (mAh): How long does the device need to run?

2. Continuous and Peak Discharge Current (Amps): How much power does your device draw?

3. Maximum Dimensions: The exact L x W x H of the battery compartment.

4. Wiring and Connector: Required wire length, gauge (AWG), and specific connector type (e.g., JST, Molex).

5. Estimated Annual Volume.