How to Design a Custom Lithium Battery Pack

Designing a custom lithium battery pack requires more than selecting cells and connecting them together. A properly designed battery must match the required voltage, capacity, current, chemistry, BMS, charger, dimensions, thermal requirements and application.

This guide explains the major steps involved in designing a custom lithium battery pack for EVs, e-bikes, drones, solar systems, ESS, UPS, robotics and industrial equipment.

What Is a Custom Lithium Battery Pack?

A custom lithium battery pack is designed specifically for a particular application rather than using a standard off-the-shelf battery.

The design can be customized for:

• Voltage
• Capacity
• Energy
• Maximum current
• Battery dimensions
• Weight
• Cell chemistry
• BMS
• Connector
• Communication
• Enclosure
• Mounting
• Charger

Step 1: Define the Application

Start by identifying exactly what the battery will power.

Examples include:

• Electric Scooter
• Electric Bike
• Electric Three-Wheeler
• EV
• Agricultural Drone
• Robotics
• Medical Equipment
• Solar System
• UPS
• Energy Storage System
• Industrial Equipment
• Defence Equipment

The application determines the battery’s voltage, current, energy, size and safety requirements.

Step 2: Determine the Required Voltage

The required voltage is normally determined by the equipment, motor controller, inverter or electronic system.

Common lithium battery configurations include:

The exact nominal and full-charge voltage depends on the cell chemistry.

Step 3: Calculate Battery Capacity

Battery capacity is usually expressed in Ah.

For example:

48V × 20Ah = 960Wh

Therefore, a 48V 20Ah battery has approximately 960Wh nominal energy.

For a custom battery, determine the required Ah based on:

• Operating time
• Required range
• Load
• Power consumption
• Duty cycle

Step 4: Calculate Required Energy

Energy can be calculated using:

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

For example:

51.2V × 100Ah = 5,120Wh

or approximately:

5.12kWh

For solar and ESS applications, energy is often specified in kWh.

Step 5: Determine the Current Requirement

This is one of the most important parts of battery design.

Determine:

• Continuous current
• Peak current
• Startup current
• Regenerative current, where applicable
• Charging current

For example, if equipment requires:

40A continuous and 60A peak

the cells, BMS, busbars, wiring, connectors and protection devices must all be designed to handle the required current.

Step 6: Select the Cell Chemistry

The most suitable chemistry depends on the application.

NMC / Lithium-Ion

NMC can be suitable when:

• High energy density is important
• Low weight is desirable
• Compact dimensions are required
• Higher power is needed

Common applications include:

• EVs
• E-bikes
• Drones
• Robotics
• Portable equipment

LiFePO₄ / LFP

LFP is commonly considered for:

• Solar
• ESS
• UPS
• Inverters
• Backup power
• Some EV applications

It offers different performance characteristics from NMC, including strong cycle-life potential and good thermal characteristics.

LiPo

LiPo can be considered for applications requiring high discharge capability and low weight, such as certain UAV and RC applications.

Step 7: Select the Battery Cells

Once the chemistry is selected, choose the appropriate cell type.

Common options include:

18650

Compact cylindrical cells used in many battery-pack designs.

21700

Larger cylindrical cells that can provide higher capacity per cell and can be useful for higher-capacity packs.

Prismatic Cells

Often used for:

• LiFePO₄ batteries
• ESS
• Solar storage
• Industrial battery packs

When selecting cells, evaluate:

• Capacity
• Nominal voltage
• Maximum continuous current
• Peak current
• Internal resistance
• Dimensions
• Weight
• Manufacturer specifications
• Availability

Step 8: Calculate Series and Parallel Configuration

A battery pack is normally described using S and P.

S = Series

Series connections increase voltage.

P = Parallel

Parallel connections increase capacity and current capability.

For example:

13S4P

means:

• 13 cell groups in series
• 4 cells in parallel in each group
• 52 cells total

If each cell is 5Ah:

4P × 5Ah = 20Ah

Therefore, the pack would be approximately:

13S4P 20Ah

Step 9: Calculate Battery Energy

For a 13S4P pack using 3.6V nominal, 5Ah cells:

Nominal voltage ≈ 13 × 3.6 = 46.8V

Capacity = 4 × 5Ah = 20Ah

Energy ≈ 46.8 × 20 = 936Wh

This is a simplified nominal-energy calculation.

Step 10: Select the BMS

A Battery Management System (BMS) is an important part of a lithium battery pack.

The BMS may provide:

• Cell voltage monitoring
• Overcharge protection
• Over-discharge protection
• Overcurrent protection
• Short-circuit protection
• Temperature monitoring
• Cell balancing
• State-of-charge monitoring

For a custom battery, the BMS should match:

• Series count
• Chemistry
• Continuous current
• Peak current
• Charging requirements
• Temperature sensors
• Communication requirements

Step 11: Consider Smart BMS Communication

Some applications require a smart BMS.

Possible interfaces include:

• CAN
• RS485
• UART
• Bluetooth

Smart communication can be useful for:

• EVs
• ESS
• Solar inverters
• Robotics
• Industrial equipment

If the battery needs to communicate with an inverter or controller, protocol compatibility must be confirmed before selecting the BMS.

Step 12: Design the Battery Pack Layout

The cells need to physically fit within the available enclosure.

Consider:

• Cell arrangement
• Cell holders
• Busbars
• Nickel strips
• Insulation
• BMS position
• Temperature sensors
• Wiring
• Connector position
• Cooling
• Mounting points

The layout should also allow appropriate electrical isolation and mechanical protection.

Step 13: Design Current Paths

High-current battery packs require carefully designed current paths.

Consider:

• Nickel strip thickness
• Copper busbars
• Wires
• Connectors
• Fuse
• BMS current path
• Weld quality

The current-carrying components should be appropriately rated for the intended continuous and peak current.

Step 14: Thermal Management

Battery temperature can affect performance, safety and service life.

Depending on the application, consider:

• Cell spacing
• Thermal sensors
• Ventilation
• Heat dissipation
• Enclosure design
• Cooling system

High-power EV, drone and industrial batteries may require more detailed thermal analysis.

Step 15: Select the Charger

The charger must match:

• Battery chemistry
• Series configuration
• Full-charge voltage
• Charging current
• BMS requirements

For example, an NMC battery and an LFP battery with similar nominal voltage do not necessarily use the same charging profile.

Never select a charger simply because the connector fits.

Step 16: Select the Connector

The connector should be suitable for the required:

• Voltage
• Continuous current
• Peak current
• Charging current
• Mechanical environment

Common battery connectors include:

• XT30
• XT60
• XT90
• Anderson-type connectors
• Custom high-current connectors

The connector must be appropriate for the actual application.

Step 17: Battery Enclosure

A custom enclosure can be made from materials appropriate to the application.

The enclosure should provide:

• Mechanical protection
• Electrical insulation
• Protection against appropriate environmental exposure
• Secure mounting
• Access to connectors
• BMS protection

For outdoor applications, enclosure design should consider the required level of dust and moisture protection.

Step 18: Cell Matching

Before assembly, cells can be tested and grouped based on suitable characteristics.

Testing can include:

• Voltage
• Capacity
• Internal resistance
• Cell grading

Proper cell selection and matching can improve consistency between parallel groups.

Step 19: Battery Pack Assembly

A professional battery assembly process may include:

Cell Inspection → Cell Testing → Cell Matching → Configuration → Welding/Busbar Assembly → Insulation → BMS Installation → Wiring → Enclosure Assembly → Testing

The exact assembly method depends on cell type and pack design.

Step 20: Test the Finished Battery

A custom battery should be tested before deployment.

Possible tests include:

Electrical Testing

• Pack voltage
• Cell-group voltage
• Capacity
• Charge
• Discharge
• Internal resistance

BMS Testing

• Overvoltage protection
• Undervoltage protection
• Overcurrent protection
• Temperature protection
• Cell balancing

Mechanical Inspection

• Insulation
• Connections
• Weld quality
• Enclosure
• Connectors

Example: Custom 48V Lithium Battery

Suppose an electric vehicle requires approximately:

• 48V nominal system
• 20Ah capacity
• 40A continuous current
• 60A peak current

A possible design could be:

13S4P

using suitable NMC cells.

If each cell is:

3.6V, 5Ah

then:

13S = approximately 46.8V nominal

4P = 20Ah

Total cells:

13 × 4 = 52 cells

The actual configuration should then be validated against the controller’s voltage and current requirements, the selected cell’s discharge rating and the BMS specifications.

Custom Battery Pack Design Checklist

Before requesting a battery quotation, prepare:

Common Battery Design Mistakes

Avoid these common mistakes:

❌ Selecting cells only by capacity
❌ Ignoring peak current
❌ Using an undersized BMS
❌ Mixing incompatible cells
❌ Using an incompatible charger
❌ Ignoring battery dimensions
❌ Ignoring thermal requirements
❌ Using poor-quality cells
❌ Not testing the completed pack
❌ Choosing the cheapest battery without checking specifications

Custom Lithium Battery Pack Design for Different Applications

EV Battery

Focus on:

Voltage + Current + Range + Weight + BMS + Thermal Management

Solar / ESS Battery

Focus on:

kWh + Cycle Life + BMS + Inverter Communication + Safety

Drone Battery

Focus on:

Weight + Energy Density + Discharge Current + Connector + Flight Time

E-Bike Battery

Focus on:

Voltage + Ah + Range + Controller Current + Size + Weight

Industrial Battery

Focus on:

Reliability + Current + Operating Environment + Communication + Enclosure

Why Choose Lion Battery?

Lion Battery provides custom lithium battery pack design and manufacturing for customers in Gujarat and across India.

Our capabilities include:

• Custom Lithium Battery Packs
• LiFePO₄ Battery Packs
• NMC Battery Packs
• EV Battery Packs
• E-Bike Batteries
• Agricultural Drone Batteries
• Solar Batteries
• ESS Batteries
• Industrial Battery Packs
• Battery Pack Assembly
• Cell Matching
• BMS Installation
• Battery Testing
• Battery Repair
• Battery Refurbishment
• OEM Battery Manufacturing
• Private Label Battery Manufacturing

Contact Lion Battery

Lion Battery

📞 Phone / WhatsApp: +91-9724991737
📧 Email: info@lionbattery.in
🌐 Website: lionbattery.in