Critical factors in the design of ebike batteries
The key factors to consider when designing and building an ebike battery. So, to find out the aspects we consider when creating a high-quality ebike battery, please keep reading.
Testing and Selection of Lithium-Ion Cells for E-Bike Batteries
Lithium-ion cells serve as the cornerstone of every e-bike battery pack. These cells come in diverse configurations, encompassing various shapes, sizes, capacities, voltages, and discharge rates. The choice of battery for your e-bike hinges on your particular needs and preferences, which encompass factors such as power output, energy density, cycle life, safety, and cost considerations.
Presently, the market offers several types of lithium-ion cells, but the most prevalent choices for e-bikes are typically cylindrical cells, specifically the 18650 and 21700 varieties, often equipped with NMC or NCA chemistry. These selections are favored for their exceptional energy density.
When it comes to testing and selecting lithium-ion cells, we take into account several critical factors:
Capacity/Energy: This pertains to the amount of charge a cell can store and deliver at a given voltage. Capacity is usually expressed in either amp-hours (Ah) or watt-hours (Wh). A higher energy capacity translates to an extended e-bike range.
Discharge Rate: The discharge rate signifies how quickly a cell can supply current at a specific voltage. It is quantified in amps (A) or C-rate, which is the ratio of current to capacity. Higher discharge rates not only contribute to quicker acceleration but also enhance hill-climbing capabilities, assuming the motor’s power is sufficient.
Energy Density: This refers to the quantity of energy a cell can store per unit of volume or mass. Energy density is measured in watt-hours per liter (Wh/L) or watt-hours per kilogram (Wh/kg). Greater energy density results in a more compact and lighter battery.
Cycle Life: Cycle life represents the number of complete charge and discharge cycles a cell can endure before its capacity diminishes below a designated threshold, typically set at 80% of its initial value. A longer cycle life equates to a lengthier battery lifespan.
Safety: Safety concerns the cell’s ability to withstand physical stress or damage without posing a risk of fire or explosion. Safety largely hinges on the chemistry and structural design of the cell, as well as the inclusion of protective mechanisms. Certain chemistries and structures exhibit greater stability and durability.
Given the multitude of considerations, e-bike battery manufacturers cannot solely rely on data from cell suppliers. Instead, rigorous testing and performance validation are imperative for specific applications. At EcoRun Battery, we employ a comprehensive cell testing program, conducted in both our in-house laboratory and in collaboration with external laboratories and universities.
Custom Battery Management Systems (BMS) and Electronics
A Battery Management System (BMS) serves as a critical component for monitoring and controlling various aspects of an e-bike battery pack. These aspects include voltage, current, temperature, state of charge (SoC), state of health (SoH), and cell balancing. A BMS plays a pivotal role in safeguarding the battery from overcharging, overdischarging, overcurrent, overtemperature, and short circuits. Additionally, it can establish communication with other e-bike components such as the controller, display, or charger, making it an integral part of the system. Ensuring the protection of the BMS against moisture and damage is essential.
The advantages of a custom-made BMS over a generic or off-the-shelf system are manifold:
Tailored Configuration: A custom BMS can be specifically designed to suit the cell type, configuration, and performance requirements of your e-bike battery.
Enhanced Features: It can incorporate a broader range of features and functions, including data logging, diagnostics, and intelligent charging capabilities.
Integration: A custom BMS can seamlessly integrate with other electronic components on your e-bike, such as sensors, switches, LEDs, and connectors.
Quick Modifications: Any customizations requested by the customer can be promptly implemented by the battery manufacturer, ensuring adaptability to evolving needs.
Developing a custom BMS necessitates a deep understanding of electronic engineering, programming, and PCB design. Therefore, it is imperative to collaborate with an experienced battery manufacturer with the expertise to design and build a BMS that aligns perfectly with your unique requirements.
Achieving Optimal Mechanical Design
The mechanical design of an e-bike battery pack encompasses the shape, size, structure, and arrangement of cells and other components within the casing or enclosure. This design profoundly impacts the battery’s performance, safety, durability, and aesthetics. Several factors must be considered when striving for an optimal mechanical design:
Space Considerations: The available space on the e-bike frame or rack dictates the dimensions and configuration of the battery pack. Innovative solutions, such as flexible printed boards, may be necessary to optimize space utilization.
Weight Optimization: By selecting appropriate materials and an optimal shape, the battery’s weight can be significantly reduced without compromising robustness.
Protection: To shield the battery pack from external factors like impact, vibration, moisture, dust, and heat, a robust and waterproof casing, along with suitable padding and shock-absorbing materials, must be employed. Enhanced protection can be achieved by incorporating safety devices like fuses, SCP, to prevent overvoltage, overheating, and overcurrents.
Cooling: Efficient cooling is essential to dissipate heat generated during charging or discharging. Materials with high thermal conductivity, such as aluminum or copper, can be used for casings and connectors. Heat sinks can also be integrated to enhance heat dissipation from the pack or BMS.
Serviceability: An optimal mechanical design should not hinder battery servicing. Avoiding extensive potting or permanent glue is crucial to facilitate maintenance and repair as needed.
The mechanical design of your e-bike battery pack is a pivotal element in achieving an efficient, safe, and durable power source, and it demands careful consideration and expertise during the design process.
Proper Procedures for Mass Production
Achieving success in mass production of ebike batteries demands a systematic approach that ensures high quality and consistency. To this end, several vital procedures must be followed:
DFMEA/PFMEA: Implementing Design Failure Mode and Effect Analysis (DFMEA) and Process Failure Mode and Effect Analysis (PFMEA) is crucial. These methodologies help identify and address all foreseeable risks related to design and production processes.
Cell Sorting: Prior to assembly, cells should be carefully sorted based on production batches and graded according to their voltage and internal resistance. Grouping cells with similar characteristics enhances balance, performance, and overall battery lifespan.
Spot Welding: Selecting appropriate welding parameters is essential to establish robust and reliable electrical connections between cells. High-quality welds minimize resistance and heat generation. Poor welding can lead to vibration-induced issues and significantly reduce the battery’s expected lifespan.
Testing: Thorough testing is a cornerstone of quality assurance. Incoming components and each battery pack should undergo evaluation on an End of Line tester. This ensures that each pack meets specified performance standards and that defects and faults are promptly detected.
Design Validation Process
Design validation is a critical step in ensuring that an ebike battery design aligns with its intended purpose and meets all necessary requirements. It involves a series of tests and experiments conducted on prototype models or representative samples of the battery pack under realistic conditions. Experienced battery manufacturers employ a comprehensive Design Validation Plan & Report (DVP&R) to guide the entire product development process. The results of these tests are meticulously documented in corresponding reports.
Additionally, some aspects of initial pre-validation can be addressed during the early design stages through thermal and mechanical simulations. These simulations help inform design decisions, ensuring that the final product will effortlessly pass validation and certification, without necessitating costly redesigns. This approach not only accelerates project realization but also minimizes potential issues, leading to a smoother and more efficient development process.
Product Certification for Target Markets
Product certification is the essential process of securing approval or recognition from relevant authorities or organizations, allowing an ebike battery to be legally sold or utilized in a specific market or geographical region. Attaining product certification necessitates strict adherence to established standards, regulations, laws, or guidelines governing the quality, safety, performance, or environmental impact of the battery.
Product certification often entails subjecting the product to testing and inspection procedures conducted by accredited third-party laboratories or agencies. These assessments verify the product’s compliance with the requisite standards and ensure its quality.
Certification for ebike batteries is a pivotal and obligatory step in the production process. It is imperative that a battery manufacturer possesses the necessary facilities for conducting internal tests, such as UN 38.3, and has established partnerships with external certification bodies to facilitate a streamlined certification process, including CE and/or UL marking. This strategic approach minimizes delays and facilitates the efficient market entry of the battery.
Conclusion
Eebike batteries are intricate products that demand meticulous design and production to guarantee optimal performance, safety, and durability. By selecting a manufacturer committed to adhering to best practices, you can have confidence that your ebike battery will not only meet your specifications but also smoothly navigate the certification process. This process ensures the delivery of a high-quality product that complies with the requisite standards for various target markets.
About Eco Run Battery
When it comes to reliable e-bike battery OEM manufacturers, EcoRunBattery stands out as a trusted name in the industry. Based in Shenzhen, China, EcoRunBattery has established itself as a leading manufacturer of integrated intelligent BMS lithium-ion battery packs. With a rich experience spanning over several years, EcoRunBattery has earned a reputation for delivering top-notch lithium batteries solutions to businesses worldwide.
EcoRunBattery looks forward to establishing long-term partnerships with clients who value exceptional products and outstanding service. Partner with us, and together, we can power the future with reliable, innovative, and sustainable battery solutions.
Thank you for considering EcoRunBattery as your trusted partner.
