A LiPo battery may meet the basic specification but still create problems during product integration. You may already have the enclosure fixed, but the required capacity no longer fits. High peak current can also cause voltage drop or device resets. At low temperatures, usable capacity and voltage stability may decrease further.
These issues often happen when battery requirements are defined too late in the product development process. To avoid costly redesigns, engineers should define the battery space, voltage, runtime, current profile, temperature, protection, and connector requirements early.
This guide explains how to design and specify a lithium polymer battery for an OEM product, from battery space and electrical load to PCM/BMS selection, prototype validation, and certification.
What Information Is Needed to Design a LiPo Battery?
Before designing a custom lithium polymer battery, engineers should define the following electrical, mechanical, environmental, and safety requirements.
These requirements determine the battery size, capacity, current capability, protection design, and validation plan. Missing information can increase the risk of performance issues and redesign.
| LiPo Battery Design Requirements | |||
| Requirement Area | Design Parameter | Information Required | Why It Matters |
| Electrical Requirements | Voltage | Nominal and operating voltage range | Determines the cell configuration and system compatibility |
| Capacity / Runtime | Required mAh/Ah or operating time | Determines the energy requirement and affects battery size | |
| Continuous Current | Normal operating current | Affects cell selection and normal discharge performance | |
| Peak Current | Maximum current and peak duration | Affects voltage drop, cell selection, and protection circuit design | |
| Charging | Charging voltage, current, and charging conditions | Determines charging compatibility and safe charging requirements | |
| Mechanical Limitations | Battery Space | Maximum T × W × L | Determines the possible cell dimensions and whether the finished battery can fit the product |
| Wiring | AWG, wire length, and pinout | Affects voltage drop and electrical integration | |
| Connector | Manufacturer, model, and polarity | Ensures correct mechanical and electrical connection with the device | |
| Mechanical Design | Swelling allowance, mounting, enclosure, vibration, or IP requirements | Helps prevent mechanical stress and integration problems | |
| Environmental Conditions | Temperature | Charging, discharging, and storage temperature range | Affects cell selection, usable capacity, voltage stability, and battery life |
| Safety & Compliance Requirements | Protection | PCM/BMS, NTC, and protection thresholds | Defines the required protection, monitoring, and safety functions |
| Compliance | UN38.3, IEC 62133, UL, or regional requirements | Influences cell selection, testing, documentation, and project approval | |
Lithium Polymer Battery Design Process
Step 1: Define the Available Battery Space
First, define the maximum battery space available in the product. The finished LiPo battery may be larger than the bare cell because it may also include a PCM, NTC, wires, connector, insulation, and other assembly materials.
Design the battery compartment around the finished battery dimensions, not only the bare-cell size.
| LiPo Battery Space Design Checklist | ||
| Design Item | What to Provide | Why It Matters |
| Maximum Size | Thickness × Width × Length | Defines the available cell space |
| Installation Direction | Battery orientation in the product | Affects wiring and assembly |
| Wire Exit | Exit direction and cable length | Prevents routing conflicts |
| Connector Position | Connector location and orientation | Ensures correct integration |
| PCM Space | Available space for protection PCB | Affects finished battery thickness and layout |
| Mechanical Limits | Housing, mounting, vibration, clearance | Prevents fit and reliability problems |
| Product Drawing | 2D or 3D drawing | Helps engineers review the real installation space |
Key point: confirm the finished battery space before the enclosure design is frozen.
Step 2: Determine the Required Voltage
Start with the operating voltage required by your device.
A standard LiPo cell has a nominal voltage of about 3.7V and is typically charged to 4.2V. High-voltage LiPo cells typically charge to 4.35 V or 4.40 V and can provide an additional 10%-15% more energy in the same battery space. If you use a high-voltage LiPo cell, the charger, PCM/BMS, and device electronics must support the higher voltage.
LiPo Voltage Type Comparison
| LiPo Type | Typical Full-Charge Voltage | Design Consideration |
| Standard LiPo | 4.2V | Compatible with standard LiPo charging systems |
| High-Voltage LiPo | 4.35V / 4.40V | Requires a compatible charger, protection circuit, and device voltage range |
If the device requires a higher operating voltage, multiple cells can be connected in series.
| Config. | Cell Count | Nominal Voltage | Full-Charge Voltage | Rec. System Cut-Off | Lower Cut-Off Reference | Design Note |
|---|---|---|---|---|---|---|
| 1S LiPo Battery | 1 | 3.7V | 4.2V | 3.0V | 2.7V | Typical for single-cell portable electronics; the system should shut down before deep discharge. |
| 2S LiPo Battery | 2 | 7.4V | 8.4V | 6.0V | 5.4V | Check the charger, PCM/BMS, and device minimum voltage across the full 2S range. |
| 3S LiPo Battery | 3 | 11.1V | 12.6V | 9.0V | 8.1V | Common in higher-voltage portable systems; monitor cell balance in multi-cell packs. |
| 4S LiPo Battery | 4 | 14.8V | 16.8V | 12.0V | 10.8V | Ensure the device can tolerate both the 16.8V full-charge voltage and the selected low-voltage cut-off. |
| 5S LiPo Battery | 5 | 18.5V | 21.0V | 15.0V | 13.5V | Use a suitable multi-cell BMS/PCM and verify per-cell low-voltage protection. |
| 6S LiPo Battery | 6 | 22.2V | 25.2V | 18.0V | 16.2V | For 6S packs, the system-level cut-off should still protect each cell from over-discharge. |
The battery voltage must match the device operating range, charger, and protection circuit. Do not select the battery configuration from nominal voltage alone. The system must also support the battery’s full-charge and low-voltage conditions.
Key point: define the device operating voltage first, then select the LiPo cell type and series configuration.
For more details about standard and high-voltage LiPo cells, nominal voltage, charging voltage, cut-off voltage, and 1S–6S configurations, see our Lithium Polymer Battery Voltage Guide.
Step 3: Define Capacity and Runtime
Start with the required runtime and the device’s actual power consumption. Battery capacity should be estimated from the average current, standby current, duty cycle, operating temperature, and available battery space.
Estimate the Required Capacity
For a simple continuous-load device:
Required Capacity (mAh) ≈ Average Current (mA) × Runtime (h)
For devices with active and standby modes, use the actual average current over one operating cycle.
Actual runtime may vary with temperature, battery aging, device cut-off voltage, and system efficiency.
LiPo Battery Runtime Design Checklist
| Design Item | What to Provide | Why It Matters |
| Required Runtime | Hours, days, or operating cycles | Defines the energy target |
| Average Current | Typical operating current | Main input for capacity estimation |
| Standby Current | Current during sleep or idle mode | Important for low-power and long-life devices |
| Duty Cycle | Percentage of time spent active and standby | Determines the real average current |
| Operating Temperature | Expected operating range | Affects usable battery capacity |
| Available Battery Space | Maximum finished battery dimensions | Limits the achievable battery capacity |
| Device Cut-Off Voltage | Minimum operating voltage | Determines how much stored energy can actually be used |
LiPo Battery Runtime Calculator
Use the calculator below to estimate the required battery capacity or expected runtime based on your device load.
Average Current = Active Current × Duty Cycle + Standby Current × (1 − Duty Cycle)
Runtime ≈ Usable Battery Capacity ÷ Average Current
Step 4: Check Peak and Pulse Current
Runtime is mainly determined by average current, but battery performance can also be limited by short high-current loads.
Engineers should confirm:
- Peak current
- Peak duration
- Pulse current
- Inrush current
These loads are common in wireless communication, motor startup, alarms, and other short power bursts.
If the battery cannot supply the required peak current, the voltage may drop and cause device resets or early low-battery warnings.
Key point: runtime depends on average current, but stable operation depends on peak-load capability.
Step 5: Confirm the Operating Temperature Range
Charging and discharging temperature limits should be defined separately.
A typical LiPo battery may operate approximately within:
- Charging: 0°C to +45°C
- Discharging: -20°C to +60°C
Actual limits depend on the selected cell.
At low temperatures, internal resistance increases and usable capacity may decrease. This can lead to greater voltage drop and shorter operating time.
For applications below the normal temperature range, the battery should be evaluated under the actual operating conditions rather than by temperature alone.
Key point: low-temperature suitability should be confirmed through application-specific testing when necessary.
Real Engineering Example: 603450HT LiPo Low-Temperature Validation for a GPS Device
In Q1 2026, a GPS customer in Israel, Yan, contacted us about a 603450 3.7V 1100mAh high-temperature LiPo battery.
The battery was mainly selected for high-temperature use, but the device could also be exposed to -30°C to -40°C.
The customer told us that the operating current was only 1.5–2mA. Because this temperature range is below the normal discharge range of a conventional LiPo cell, our engineers arranged a low-temperature discharge test under the same 1.5–2mA load.
The test results are shown below.
| Test Temperature | Battery Model | Discharge Current | Capacity Recorded in Test | Voltage During Test | Test Observation |
| 20°C | 603450HT 3.7V 1100mAh | 550mA | 1100mAh rated capacity* | — | Rated capacity reference only; no room-temperature discharge curve was provided. |
| ‘-30°C | 603450HT 3.7V 1100mAh | 2mA | Approx. 32mAh | Approx. 4.18V → 4.13V | Battery maintained stable voltage under the 2mA ultra-low-current load during the recorded test period. |
| -40°C | 603450HT 3.7V 1100mAh | 2mA | Approx. 11mAh | Approx. 4.13V → 4.10V | Battery continued to supply the 2mA load at -40°C during the recorded test period. |
| Test Note: The -30°C and -40°C values show only the capacity recorded during the test, not the full discharge capacity. The battery voltage remained above about 4.1V when the tests ended. The test confirmed whether the 603450HT 1100mAh LiPo battery could maintain stable output under a 2mA load at low temperatures. | |||||
Step 6: Select the Appropriate PCM or BMS
The protection circuit should match the battery configuration and device load.
A simple single-cell LiPo battery may use a PCB, while multi-cell or smart battery packs may require a BMS with monitoring, balancing, or communication functions.
PCB vs BMS Function Comparison
| Function / Requirement | PCB | BMS | Why It Matters |
| Overcharge Protection | Yes | Yes | Prevents excessive charging voltage |
| Over-Discharge Protection | Yes | Yes | Prevents excessive cell discharge |
| Overcurrent Protection | Yes | Yes | Protects the battery under high load |
| Short-Circuit Protection | Yes | Yes | Protects against abnormal current |
| Temperature Protection | Optional / Common | Yes | Helps protect charging and discharging at unsafe temperatures |
| Cell Balancing | Usually No | Yes | Important for multi-cell packs |
| Fuel Gauging | Usually No | Optional | Estimates remaining capacity |
| Voltage / Current Monitoring | Basic | Advanced | Supports battery status monitoring |
| Cycle Count | Usually No | Optional | Useful for smart battery management |
| Communication | Usually No | CAN / RS485 / SMBus / I²C / UART / Bluetooth | Allows data exchange with the host device |
| Typical Use | Simple single-cell packs | Multi-cell or smart battery packs | Helps select the appropriate protection solution |
Key point: select the PCB or BMS based on battery configuration, peak load, charging requirements, and monitoring needs.
Step 7: Define the NTC, Wiring, and Connector
The battery interface should match the device electronics and mechanical layout.
Engineers should confirm the temperature sensor, wire specification, connector, pinout, polarity, and cable length before the battery drawing is finalized.Common NTC values may include 10kΩ, ±1%, Beta 3435 or 3379, but the exact specification should match the device or charger.
JST, Molex, and other standard connectors can be used when appropriate. Custom wiring harnesses are also possible.
A completed battery drawing should confirm the wire exit, connector position, pinout, polarity, and cable length before sample production.
LiPo Battery Interface Design Checklist
| Design Item | What to Provide | Why It Matters |
| NTC | Resistance, tolerance, Beta value, location | Ensures correct temperature monitoring |
| Wire Gauge | AWG requirement | Affects current capability and voltage drop |
| Cable Length | Required wire length | Affects routing and assembly |
| Wire Insulation | Material / UL requirement | Supports safety and compliance |
| Wire Exit | Exit direction from the battery | Prevents routing conflicts |
| Connector | Manufacturer and model | Ensures device compatibility |
| Pinout | Pin assignment | Prevents connection errors |
| Polarity | Positive / negative orientation | Prevents reverse connection |
Step 8: Protect the LiPo Battery in the Enclosure
Once the battery fits the available space, the enclosure should also protect the LiPo pouch during normal use.
Allow Room for Cell Expansion
Do not tightly compress the pouch cell. Leave suitable clearance for normal cell expansion over its service life.
Avoid Sharp or Hard Contact Points
Screws, metal burrs, sharp edges, and other hard parts should not press against the pouch surface.
Keep all battery contact areas smooth.
Provide Electrical Insulation
Use suitable insulation between the battery and nearby metal parts to reduce the risk of short circuits.
Control Vibration and Movement
Secure the battery so it cannot move freely inside the enclosure, especially in mobile or industrial products.
Keep the Battery Away From Heat Sources
Avoid placing the LiPo cell next to high-temperature components such as:
- Power MOSFETs
- Motors
- Heat sinks
- High-power processors
- DC/DC converters
Battery Compartment Protection Checklist
| Design Item | What to Check | Why It Matters |
| Cell Clearance | Space around the pouch cell | Reduces mechanical compression |
| Surface Contact | No sharp edges or metal burrs | Prevents pouch damage |
| Electrical Insulation | Insulation from metal parts | Reduces short-circuit risk |
| Battery Fixing | Secure mounting | Limits movement under vibration or shock |
| Heat Sources | Distance from hot components | Reduces thermal stress |
| Enclosure Material | Smooth and non-damaging contact surface | Protects the pouch during product use |
Key point: the battery compartment should not only fit the battery; it should also protect the pouch from pressure, sharp surfaces, vibration, and heat.
Step 9: Build and Validate the Prototype
The prototype should verify that the final battery design matches the requirements defined in the earlier steps.
At VTCBATT, sample validation may include:
| Validation Item | What It Confirms |
| OCV Test | Confirms battery voltage before testing |
| Internal Resistance Test | Checks cell consistency and load response |
| 3-Cycle Capacity Test | Confirms usable capacity |
| Charge / Discharge Test | Verifies basic electrical performance |
| PCM Protection Test | Confirms protection thresholds and functions |
| Connector Polarity Check | Prevents wiring and integration errors |
| Aging Test | Screens early defects |
| Mechanical Fit Check | Confirms the finished battery fits the product |
For selected projects, VTCBATT may also perform a 45°C aging test for 72 hours.
Application-specific tests should then be added according to the actual product requirements. Examples include:
- Low-temperature discharge
- High-temperature operation
- Peak-current or pulse-load testing
- Device-level runtime testing
- Vibration or shock testing
The goal is not to test every possible condition. It is to verify the conditions that matter to the final application.
Key point: prototype validation should reproduce the real operating conditions as closely as possible.
Step 10: Confirm Compliance Before Freezing the Design
Battery compliance requirements should be confirmed before the battery design is finalized.
Different markets and applications may require different tests, certifications, and documents. These requirements can affect the cell, PCM/BMS, enclosure, labeling, and validation plan.
| Requirement | Typical Purpose |
| UN38.3 | Lithium battery transportation |
| IEC 62133 | Rechargeable battery safety for applicable portable products |
| UL 1642 | Cell-level safety evaluation |
| UL 2054 | Battery pack safety evaluation |
| CB | International certification framework |
| CE / RoHS / REACH | Product and market compliance requirements |
| KC / PSE / BIS | Regional market requirements |
The exact requirements depend on the target market, final device, battery configuration, product category, and transportation method.
Certification should be planned early because it may affect component selection, testing, documentation, labeling, and project timing.
Key point: confirm the required certifications before the battery design is frozen.
Common LiPo Battery Design Mistakes
Even when the basic battery specification looks correct, small design decisions can cause delays during prototyping, testing, or certification. The following mistakes are common in OEM LiPo projects.
Based on our OEM battery projects, most design delays come from incomplete application requirements or decisions made too late in the development process.
| Common Mistake | Typical Result | Better Approach |
| Finalizing the enclosure before confirming the battery | Required capacity may no longer fit | Confirm finished battery dimensions and runtime early |
| Ignoring peak current | Voltage drop, resets, or early low-battery warnings | Provide peak current and peak duration |
| Evaluating low-temperature performance by temperature alone | Battery performance may be underestimated or overestimated | Test under the actual load and operating conditions |
| Leaving no room for cell expansion | Mechanical pressure on the pouch cell | Allow suitable clearance in the enclosure |
| Selecting PCM/BMS by capacity alone | Protection settings may not match the real load | Select protection based on load, charging, and monitoring needs |
| Confirming certification too late | Additional testing, redesign, or schedule delays | Define target markets and compliance requirements early |
How VTCBATT Supports LiPo Battery Design Validation
VTCBATT engineers review the battery design against the actual product requirements before pilot production.
Depending on the project, validation may include capacity, internal resistance, PCM/BMS protection, connector polarity, mechanical fit, aging, temperature, and application-specific load testing.
Typical custom samples can often be prepared in around 2 weeks. Special designs may require approximately 2–3 weeks, depending on tooling, components, and testing requirements.
The goal is to verify the battery design before moving to production.
Frequently Asked Questions
What information is needed to design a lithium polymer battery?
Provide the available battery space, voltage, required runtime, continuous current, peak current, charging conditions, operating temperature, PCM/BMS requirements, connector, wiring, and certification requirements.
Should the battery or product enclosure be designed first?
They should ideally be evaluated together.
If the enclosure is finalized before battery capacity and load requirements are understood, the remaining battery cavity may not be large enough to achieve the required runtime.
How much space should be reserved for LiPo battery expansion?
The exact amount should be confirmed according to the cell design and product application.The required clearance depends on the cell thickness, pouch construction, operating conditions, and expected service life. Confirm the finished battery dimensions and expansion allowance with the battery manufacturer before freezing the enclosure.
The enclosure should account for:
- Manufacturing tolerance
- Insulation
- PCM
- Wiring
- Mechanical assembly
- Normal cell expansion during service life
What certifications may be required for a LiPo battery?
UN38.3 is commonly required for lithium battery transportation.
Depending on the final product and target market, other requirements may include:
- IEC 62133
- UL 1642
- UL 2054
- CB
- CE
- RoHS
- REACH
- KC
- PSE
- BIS
Certification requirements should be confirmed before the battery design is finalized.
How long does LiPo battery sample development take?
For many custom projects, sample development can often be targeted at around 2 weeks.
Special customization may require approximately 2–3 weeks, depending on the battery structure, components, tooling, and testing requirements.
Request a LiPo Battery Design Review
If you are developing a new OEM product, provide the following information for an initial engineering evaluation:
Maximum battery space + voltage + required runtime + continuous current + peak current + temperature + connector + certification requirements.
A complete product drawing and load profile can help engineers evaluate:
- Suitable LiPo cell dimensions
- Achievable capacity
- PCM/BMS requirements
- Connector and wiring
- Mechanical integration
- Prototype testing requirements
Design Your Custom LiPo battery
Screen the available 3.7V ultra-thin LiPo model list by size. Results are matched against the source-listed model data.Find My Battery
Author Introduction
Dr. Kevin Yang
Lead Electrical Engineer
Dr. Kevin Yang has 16 years of R&D experience in lithium battery power management systems (BMS) and 10 years in lithium ion battery engineer. Experienced in various lithium ion battery applications,he is capable of offering customized lithium battery solutions beyond cutomer expectation .
