What Does 4S2P Mean?
A 4S2P configuration means 4 cells in series (4S) and 2 cells in parallel (2P). For standard 18650 Li-ion cells (nominal 3.7V), the pack nominal voltage becomes 14.8V (3.7V × 4). Two parallel cells double the capacity compared to a single cell string, making 4S2P (8 total cells) ideal for mid-power applications.
Technical Specifications of a 4S2P 18650 14.8V Pack
The following table presents typical specifications used by OEMs for design and procurement. Values vary by chosen 18650 cell model (energy-focused or high-drain). For manufacturing, always request datasheets and sample tests.
Key Electrical Specifications (Typical Range)
| Specification | Typical Value | Notes |
|---|---|---|
| Cell type | 18650 Li-ion | Choose NCM/NCA for energy, INR for power, LFP for safety |
| Configuration | 4S2P (8 cells) | Nominal 14.8V |
| Nominal voltage | 14.8V | 3.7V × 4 |
| Max charge voltage | 16.8V | CC/CV charging |
| Nominal capacity | 5,200mAh – 7,000mAh | Depends on cells used (e.g., 2600–3500mAh cells) |
| Energy | ~76Wh – 103Wh | Nominal voltage × capacity |
| Standard discharge | 1C (~5–7A) | Continuous rating |
| Max continuous discharge | 10A–20A | With high-drain 18650 cells |
| Peak current | 20A–35A | Short bursts for motors, pumps |
| Operating temp (discharge) | -20°C to 60°C | Follow cell manufacturer limits |
| Cycle life | 500–1,000 cycles | Depends on C-rate and temperature |
Data sources: cell manufacturer datasheets, OEM test reports, and field experience (A&S Power testing lab).
Runtime & Performance Calculations
Example Runtime Calculation
Assume a 4S2P pack with 6,000mAh (6Ah) nominal capacity.
Battery energy (Wh) = Voltage (V) × Capacity (Ah)
= 14.8V × 6Ah = 88.8Wh
Runtime (hours) = Battery energy (Wh) ÷ Device power (W)
Example: Device = 25W → Runtime = 88.8 ÷ 25 = 3.55 hours
Discharge Curve & Voltage Window
Typical 4S voltage behavior:
- Full charge: ~16.8V
- Nominal plateau: ~14.0–15.0V
- Cut-off (recommended): 11.0–12.0V (varies by BMS and application)
Internal Structure & Mechanical Components
A 4S2P pack is more than cells — mechanical and electrical integration matters for safety and reliability.
- 18650 cylindrical cells (matched by capacity and internal resistance)
- Nickel strips for spot-welded connections
- PCM or BMS board (recommended: 4S BMS with balancing)
- NTC thermistor for temperature protection
- Insulation rings, fishpaper, shrink wrap or ABS/Aluminum enclosure
- Connectors: JST/SM/XT60/Molex depending on current and customer preference
4S2P vs Other Pack Configurations
| Pack | Nominal Voltage | Typical Cells | Use Case |
|---|---|---|---|
| 2S | 7.4V | 4 cells | Small wearables, small motors |
| 3S | 11.1V | 6 cells | Hand tools, light drones |
| 4S | 14.8V | 8 cells | Medical pumps, robotics, UAVs |
| 4S3P | 14.8V | 12 cells | Higher capacity, long-run tools |
Applications & Industry Examples
4S2P 18650 packs are widely used across industries.
Medical & Healthcare
- Hospital-grade breast pumps (continuous duty, requires SOC accuracy)
- Portable patient monitors and infusion pumps
- Handheld diagnostic instruments
Robotics & Automation
- Warehouse AGVs and service robots
- Actuators and small manipulators
Drones, UAVs & Consumer Electronics
- Mapping drones with mid-duration flight times
- Portable communication radios and lighting systems
BMS & Protection: Why 4S Needs Active Management
A 4S pack should use a proper 4S BMS for balancing, temperature monitoring, and overcurrent protection. A basic PCM is often not sufficient for multi-series packs because cells can drift over time and cause imbalance.
BMS Recommended Functions
- Over-charge protection (≈4.25V/cell)
- Over-discharge protection (≈2.5–3.0V/cell)
- Cell balancing (passive or active)
- Overcurrent & short-circuit protection
- Temperature sensing & thermal cutoff
- Optional communication: SMBus, CAN, UART, Bluetooth
For medical and safety-critical equipment, choose certified smart BMS modules with logging and communication capabilities so devices can record battery events and support regulatory compliance.
Safety & Certification Requirements
To ship and sell internationally, 4S2P battery packs typically require the following tests and documentation:
| Certification / Test | Purpose |
|---|---|
| UN38.3 | Air transport and shipping safety |
| IEC62133-2 | Cell and pack safety standard for portable batteries |
| UL1642 / UL2054 | Safety & flammability tests (often requested in US market) |
| MSDS | Chemical safety documentation |
| CB Scheme | Global electrical safety recognition |
Medical device OEMs may also require ISO13485, traceability, and manufacturing audits. Keep product labels, batch codes, and test reports accessible for customs and clients.
Charging Recommendations
Use a CC/CV charger configured for 4S Li-ion packs:
- Charge voltage: 16.8V (4 × 4.2V)
- Recommended charge current: 0.5C – 1.0C (e.g., for 6000mAh pack, 3A recommended max for standard charging)
- Do not charge below 0°C or above 45°C unless cells support it
- Always use certified chargers and recommend users to follow device manual
Cycle Life & Storage Best Practices
Proper usage dramatically impacts longevity. Below are practical guidelines and measured cycle-life estimates.
| Temperature | Typical Cycle Life |
|---|---|
| 25°C (room temperature) | 800–1,000 cycles |
| 40°C | 500–700 cycles |
| 60°C | <300 cycles |
Storage tips:
- Store at 40–60% state of charge for long periods
- Keep in cool, dry place away from direct sun
- Avoid continuous full charge or deep discharge when idle
OEM Customization Options
For product designers and procurement teams, 4S2P packs can be customized along:
- Cell selection (high-energy vs. high-drain vs. high-safety)
- BMS features (balancing, communications, thermal thresholds)
- Connector types and wire lengths
- Mechanical casing: shrink, ABS, or aluminum with IP rating
- Labeling, barcode/QR code for traceability, and packaging
A&S Power supports ISO9001 manufacturing, sample preproduction testing, and full compliance documentation for export markets.
Frequently Asked Questions (FAQ)
Is 4S2P the same as 14.8V?
Yes. A 4S pack of nominal 3.7V cells results in a nominal voltage of 14.8V (3.7V × 4).
Can I use a 12V charger with a 4S2P pack?
No. 4S Li-ion packs require a charger set to 16.8V (full charge) and CC/CV charging profile. Using a 12V charger will not fully charge the pack and may cause charging problems.
Do I need a BMS for a 4S2P pack?
Yes — a proper 4S BMS is recommended for balancing, over/under-voltage protection, and thermal monitoring. For safety-critical equipment (medical, industrial), choose a smart BMS with logging and communication.
How long will a 4S2P pack last?
With standard usage and proper thermal management, expect 500–1,000 cycles. Real-world calendar life often ranges from 2–4 years depending on usage patterns and environment.
Recommended Videos
How Lithium-ion Batteries Work
Good overview of Li-ion fundamentals.
Understanding 18650 Cells & Packs
Practical insights on cell selection and pack assembly.
Battery Packs Production
About Battery pack production process.
Ready to Design a Custom 4S2P Pack?
If you need a custom 4S2P 18650 14.8V pack for medical, robotics, or industrial use, our engineering team can provide cell selection, BMS integration, certifications, and manufacturing. We offer sample builds, test reports, and full documentation for export.
Request Quote / Technical Consultation
