1S, 2S, 3S and 4S LiPo Battery Packs Explained

LiPo battery packs are often described using labels such as 1S, 2S, 3S and 4S. These labels appear on battery packs used in portable electronics, robotics, RC equipment, drones, medical devices and other rechargeable products.

The “S” rating describes the number of LiPo cells connected in series:

• 1S means one cell group in series;

• 2S means two cell groups in series;

• 3S means three cell groups in series;

• 4S means four cell groups in series.

As the number of cells in series increases, the pack voltage increases. The capacity in mAh does not automatically increase simply because the S-rating is higher.

Using common LiPo cells with a nominal voltage of approximately 3.7 V:

• 1S = 3.7 V nominal;

• 2S = 7.4 V nominal;

• 3S = 11.1 V nominal;

• 4S = 14.8 V nominal.

The appropriate configuration depends on the host device, charger, current demand, required energy, BMS and mechanical design.

Quick Answer: What Do 1S, 2S, 3S and 4S Mean?

These values are common references for standard rechargeable LiPo cells. The exact voltage must follow the selected cell specification.

A higher S-rating means a higher battery voltage. It does not automatically mean:

• Higher capacity;

• Longer runtime;

• Better performance;

• Faster charging;

• Higher safety;

• Greater energy density.

The S-rating must match the electrical system of the device.

1. What Does “S” Mean on a LiPo Battery?

The letter S stands for series.

When cells are connected in series, the positive terminal of one cell is connected to the negative terminal of the next cell. The voltage of each cell adds together.

For a standard 3.7 V nominal LiPo cell:

Pack voltage = 3.7 V × Number of cells in series

Examples:

• 1S: 3.7 V × 1 = 3.7 V;

• 2S: 3.7 V × 2 = 7.4 V;

• 3S: 3.7 V × 3 = 11.1 V;

• 4S: 3.7 V × 4 = 14.8 V.

The S-rating describes the series count only. A pack may also include parallel cell groups, such as:

• 2S1P;

• 2S2P;

• 3S2P;

• 4S2P.

For more information about how series and parallel connections affect voltage and capacity, see Series vs. Parallel Battery Packs.

2. What Is a 1S LiPo Battery Pack?

A 1S LiPo battery pack contains one LiPo cell or one parallel group of cells.

Typical electrical values are:

• Nominal voltage: approximately 3.7 V;

• Full-charge voltage: approximately 4.2 V;

• Minimum operating voltage: application-dependent;

• Capacity: determined by the cell or parallel group.

Example: 1S1P

A single 1000 mAh LiPo cell produces approximately:

3.7 V, 1000 mAh

Its nominal energy is:

3.7 V × 1 Ah = 3.7 Wh

Example: 1S2P

Two 1000 mAh cells connected in parallel produce approximately:

3.7 V, 2000 mAh

The voltage remains approximately 3.7 V, while the capacity increases.

Typical 1S Applications

1S packs may be suitable for:

• Compact wearable devices;

• Small GPS trackers;

• Wireless accessories;

• Small IoT products;

• Portable sensors;

• Compact consumer electronics;

• Low-voltage embedded systems.

A 1S pack may use a PCM or simple protection circuit, depending on the application. The charger must be designed for a single-cell LiPo pack.

3. What Is a 2S LiPo Battery Pack?

A 2S LiPo battery pack contains two cell groups connected in series.

Typical values are:

• Nominal voltage: approximately 7.4 V;

• Full-charge voltage: approximately 8.4 V;

• Capacity: determined by the capacity of each parallel group.

Example: 2S1P

Using two 1000 mAh cells in series:

7.4 V, 1000 mAh

Nominal energy:

7.4 V × 1 Ah = 7.4 Wh

Example: 2S2P

Using four 1000 mAh cells in a 2S2P arrangement:

7.4 V, 2000 mAh

Nominal energy:

7.4 V × 2 Ah = 14.8 Wh

Typical 2S Applications

2S LiPo packs may be considered for:

• Portable equipment;

• Industrial handheld devices;

• Medical devices;

• Two-way communication equipment;

• Small robotic systems;

• Heated products;

• Medium-voltage electronics;

• Some RC and drone systems.

ZERNE’s 7.4V lithium battery pack page provides product-level examples of 2S battery packs with different capacities and dimensions.

4. What Is a 3S LiPo Battery Pack?

A 3S LiPo battery pack contains three cell groups connected in series.

Typical values are:

• Nominal voltage: approximately 11.1 V;

• Full-charge voltage: approximately 12.6 V;

• Capacity: determined by the capacity of each parallel group.

Example: 3S1P

Using three 1000 mAh cells in series:

11.1 V, 1000 mAh

Nominal energy:

11.1 V × 1 Ah = 11.1 Wh

Example: 3S2P

Using six 1000 mAh cells in a 3S2P arrangement:

11.1 V, 2000 mAh

Nominal energy:

11.1 V × 2 Ah = 22.2 Wh

Typical 3S Applications

3S packs may be used in:

• Portable industrial equipment;

• Robotics;

• Higher-voltage handheld devices;

• Compact power systems;

• Certain medical or monitoring products;

• RC equipment;

• Some drone platforms.

A 3S pack requires a charger and protection system designed for the 3S voltage range. It should not be charged using a single-cell or 2S charger.

ZERNE’s 11.1V lithium battery pack page provides examples of 3S LiPo battery pack configurations.

5. What Is a 4S LiPo Battery Pack?

A 4S LiPo battery pack contains four cell groups connected in series.

Typical values are:

• Nominal voltage: approximately 14.8 V;

• Full-charge voltage: approximately 16.8 V;

• Capacity: determined by the capacity of each parallel group.

Example: 4S1P

Using four 1000 mAh cells in series:

14.8 V, 1000 mAh

Nominal energy:

14.8 V × 1 Ah = 14.8 Wh

Example: 4S2P

Using eight 1000 mAh cells in a 4S2P arrangement:

14.8 V, 2000 mAh

Nominal energy:

14.8 V × 2 Ah = 29.6 Wh

Typical 4S Applications

4S packs may be considered for:

• Higher-voltage portable equipment;

• Robotics;

• Industrial tools;

• Professional electronics;

• Power-intensive RC systems;

• Some drone platforms;

• Compact energy systems.

ZERNE’s 14.8V lithium battery pack page provides product examples for 4S LiPo battery packs.

6. 1S vs. 2S vs. 3S vs. 4S Voltage Comparison

The device must be compatible with both nominal and full-charge voltage.

For example, a device designed for a 7.4 V nominal battery may need to tolerate a fully charged voltage of approximately 8.4 V. The input circuit, motor controller, charger and voltage regulator must all be evaluated.

For a practical comparison of 7.4 V, 11.1 V and 14.8 V packs, see 7.4V vs. 11.1V vs. 14.8V Battery Packs.

7. Does a Higher S-Rating Mean Higher Capacity?

No.

The S-rating indicates the number of cell groups connected in series. It primarily affects voltage.

Capacity depends on the number of cells or cell groups connected in parallel.

Using 1000 mAh cells:

A higher S-rating may increase total energy because energy equals voltage multiplied by amp-hour capacity. However, it does not automatically increase the mAh rating.

8. How Does the S-Rating Affect Runtime?

Runtime depends on total usable energy and device power, not on the S-rating alone.

The basic energy formula is:

Energy (Wh) = Voltage (V) × Capacity (Ah)

For example:

• 2S1P: 7.4 V, 1000 mAh = 7.4 Wh;

• 1S2P: 3.7 V, 2000 mAh = 7.4 Wh.

These two configurations have approximately the same nominal energy when they use the same number of identical cells. However, they are not interchangeable because their voltages are different.

Runtime also depends on:

• Device power;

• Converter efficiency;

• BMS cutoff;

• Temperature;

• Current demand;

• Battery aging;

• Operating profile.

For a detailed calculation method, see How to Calculate Runtime for a Lithium Battery Pack.

9. Charging 1S, 2S, 3S and 4S LiPo Battery Packs

Each S-rating requires a charger designed for the corresponding series count.

A charger with an incorrect voltage can result in:

• Incomplete charging;

• Overcharging;

• Excessive heat;

• Battery damage;

• Protection cutoff;

• Safety risks.

Multi-series packs may also require balancing. The charger and BMS should be selected together with the cell configuration.

The exact charging current depends on the cell specification and application. It should not be selected solely according to the S-rating.

10. BMS and Protection Requirements

The S-rating also affects the protection system.

1S Packs

A 1S pack may use:

• PCM;

• Protection IC;

• Overcharge protection;

• Over-discharge protection;

• Overcurrent protection;

• Temperature sensing where required.

2S, 3S and 4S Packs

Multi-series packs may require:

• Individual series-group voltage monitoring;

• Cell balancing;

• Overcharge protection;

• Over-discharge protection;

• Overcurrent protection;

• Short-circuit protection;

• Temperature monitoring;

• Communication functions where required.

As the series count increases, the BMS must be designed for the corresponding number of cell groups.

The BMS should also match:

• Pack current;

• Charger;

• Connector;

• Host-device interface;

• Mechanical space;

• Required testing.

Detailed BMS design is outside the scope of this article. The broader design relationship between BMS, voltage, capacity and runtime is covered in Lithium-Ion Battery Pack Design: Voltage, Capacity, BMS and Runtime.

11. Capacity and Parallel Groups

The S-rating does not determine the complete battery capacity.

For a pack with parallel groups:

Pack capacity = Cell capacity × Number of cells in parallel

For example, using 2500 mAh cells:

This is why an OEM requirement should specify both:

• Series count;

• Parallel count or target capacity.

Saying only “4S battery” does not define the complete pack.

12. How to Choose the Right S-Rating for an OEM Device

The selection process should begin with the device’s voltage requirements.

Step 1: Identify the Device Voltage

Confirm:

• Nominal input voltage;

• Minimum input voltage;

• Maximum input voltage;

• Full-charge tolerance;

• Motor or controller voltage range;

• Converter input range.

Step 2: Select the Series Count

Match the required nominal voltage with the appropriate cell count.

For common 3.7 V LiPo cells:

• Approximately 3.7 V system → 1S;

• Approximately 7.4 V system → 2S;

• Approximately 11.1 V system → 3S;

• Approximately 14.8 V system → 4S.

Step 3: Confirm Capacity

After selecting the series count, determine the required parallel count or individual cell capacity to achieve the target runtime.

Step 4: Check Current

Confirm that the selected cells, BMS, wiring and connector can support continuous and peak current.

Step 5: Check the Charger and BMS

The charger and protection system must match the selected S-rating.

Step 6: Check Mechanical Integration

Confirm that the selected cell count and layout fit the device enclosure.

13. 1S–4S LiPo Packs in Drone Applications

1S, 2S, 3S and 4S LiPo packs are also used in different drone and RC applications. However, drone selection depends on more than voltage.

Relevant factors include:

• Motor and ESC compatibility;

• Propeller configuration;

• Current demand;

• Battery weight;

• C-rating;

• Flight profile;

• Connector;

• Required flight time.

For a drone-specific comparison involving 3S, 4S and 6S configurations, see 3S vs. 4S vs. 6S LiPo Battery: Which Drone Configuration Fits?.

This article focuses on the general meaning of 1S–4S configurations for rechargeable LiPo battery pack design rather than drone performance selection.

14. Common 1S–4S LiPo Battery Pack Mistakes

Mistake 1: Treating Nominal Voltage as Full-Charge Voltage

A 3.7 V pack may reach approximately 4.2 V when fully charged. The device must tolerate the complete voltage range.

Mistake 2: Assuming 4S Is Always Better Than 2S

A higher S-rating is suitable only when the device is designed for the higher voltage.

Mistake 3: Using the Wrong Charger

The charger must match the series count and charging voltage.

Mistake 4: Ignoring Capacity

The S-rating does not define mAh capacity. Parallel count and cell capacity must also be specified.

Mistake 5: Omitting Balancing

Multi-series LiPo packs may require cell balancing and appropriate BMS protection.

Mistake 6: Comparing Packs Only by Voltage

A 2S1P and a 2S2P pack may both be 7.4 V but have different capacity, runtime, current capability, dimensions and weight.

Mistake 7: Copying a Drone Battery Configuration Into Another Device

A configuration suitable for a drone may not be suitable for a medical device, IoT product or industrial tool. The host device must determine the final battery design.

15. 1S, 2S, 3S and 4S Selection Checklist

Before approving a LiPo battery pack, confirm:

• Required nominal voltage;

• Minimum device input voltage;

• Maximum device input voltage;

• Full-charge voltage compatibility;

• S-rating;

• Parallel count;

• Target capacity;

• Continuous current;

• Peak current;

• Charger voltage;

• Charging current;

• PCM or BMS requirements;

• Cell balancing requirements;

• Connector and cable;

• Available installation space;

• Weight limit;

• Operating temperature;

• Runtime target;

• Testing requirements.

FAQ

What does 1S mean on a LiPo battery?

1S means that the pack contains one LiPo cell group connected in series. A typical 1S LiPo battery has approximately 3.7 V nominal voltage and 4.2 V full-charge voltage.

What is the voltage of a 2S LiPo battery?

A typical 2S LiPo battery has approximately 7.4 V nominal voltage and 8.4 V full-charge voltage.

What is the voltage of a 3S LiPo battery?

A typical 3S LiPo battery has approximately 11.1 V nominal voltage and 12.6 V full-charge voltage.

What is the voltage of a 4S LiPo battery?

A typical 4S LiPo battery has approximately 14.8 V nominal voltage and 16.8 V full-charge voltage.

Does 4S mean the battery has four times the capacity of 1S?

No. 4S indicates four cell groups in series and primarily describes voltage. Capacity depends on the cell capacity and parallel configuration.

Can I use a 2S charger for a 3S LiPo battery?

No. A 3S pack requires a charger designed for the 3S charging voltage. Using the wrong charger can cause incomplete charging, damage or safety risks.

Does a 2S battery always last longer than a 1S battery?

Not necessarily. Runtime depends on total energy, device power, efficiency, capacity and operating conditions. A 1S2P pack and a 2S1P pack can have similar nominal energy while using the same number of cells.

Is a higher S-rating better for an OEM device?

Only if the host device, charger, BMS, wiring and power-management system support the higher voltage. The correct S-rating is determined by the device requirements.

Conclusion

1S, 2S, 3S and 4S describe the number of LiPo cell groups connected in series.

Using common 3.7 V nominal LiPo cells:

• 1S = 3.7 V nominal;

• 2S = 7.4 V nominal;

• 3S = 11.1 V nominal;

• 4S = 14.8 V nominal.

The typical full-charge voltages are:

• 1S = 4.2 V;

• 2S = 8.4 V;

• 3S = 12.6 V;

• 4S = 16.8 V.

The correct configuration depends on the device’s voltage range, required capacity, current demand, charging system, BMS, mechanical space and runtime target.

If you are developing a rechargeable LiPo battery pack, share the application, required voltage, capacity, current demand, available dimensions, connector requirements and expected production volume with the ZERNE technical team. ZERNE provides custom lithium battery pack solutions for OEM and ODM projects and can help determine the appropriate 1S, 2S, 3S or 4S configuration.