I need suggestion and somebody who is capable to build Lithium-Ion Battery Pack for E-foil.
Electrical Specifications and Chemistry
The assembly must strictly utilize top-of-the-range cylindrical cells with high capacity and high continuous discharge rates to guarantee minimal voltage sag under load.
• Required Cell Model: Lithium-Ion – Molicel INR 21700 P45B 4500 mAh
• Electrical Configuration: 14S 13P (14 Series, 13 Parallel)
• Total Number of Cells: 182 cells
• Nominal Voltage: 50.4V – 52V
• End-of-Charge Voltage (Max): 58.8V
• Total Nominal Capacity: 58 Ah
• Total Energy Capacity: ~3.53 kWh / 3.64 kWh
3. Geometric and Mechanical Constraints (Mandatory)
The battery pack must be housed inside an existing watertight enclosure. The spatial layout must maximize the footprint area.
• Internal Usable Dimensions of the Enclosure: 290 mm (Width) x 340 mm (Length) x 80 mm (Height). The sides ((290 \times 340\text{ mm})) of the enclosure will be aluminum, while the rest will be ABS.
• Cell Layout: A honeycomb (staggered/nested) configuration is mandatory to optimize space.
• Component Orientation:
o 290 mm Axis: Stacking of 14 cells in width (theoretical bare cell clearance ~289.3 mm). The use of plastic inter-cell spacers is forbidden on this axis due to near-zero tolerances ((\leq 0.7\text{ mm})).
o 340 mm Axis: Stacking of 13 rows in depth (theoretical clearance ~257.5 mm).
• Clearance Space for Electronics (BMS Compartment): Approximately 82.5 mm of free space remains along the length axis ((340 - 257.5\text{ mm})). This header compartment must house the BMS, structural wiring, and safety systems.
• Maximum Allowed Height: The cells (70.6 mm) leave a vertical margin of ~9.4 mm. This space must accommodate busbars, upper dielectric insulation, and anti-vibration compression material.
4. Interconnection Architecture and Busbars
The cross-section and geometry of the connections are critical to prevent localized thermal stress.
• Busbar Material: Shaped pure copper plates, laser-cut or CNC-machined (Recommended thickness: 2.0 mm, minimum equivalent width to ensure a current density (\leq 4\text{-}5\text{ A/mm}^2)).
• Load Distribution (Take-off Points): The main power terminal plates (B+ and B-) must not use a single connection point.
• A minimum of 3 symmetrical welding/take-off points along the plate is required to uniformly distribute current flow and prevent thermal imbalance between core and peripheral cells.
5. Insulation System and Mechanical Safety (Anti-Shock)
• Structural Fixing: Cell bonding using NEUTRAL (Alkoxy) thixotropic structural silicone with high thermal conductivity. The assembly must form a single monolithic block, eliminating any wrap-on-wrap friction.
• Electrical Insulation:
o Fish paper (Barley Paper) rings are mandatory on the positive terminal of every single cell.
o Vertical dividers and horizontal covers made of FR4 / G10 fiberglass sheets (minimum thickness 0.5 mm) to prevent mechanical punctures or accidental contact between adjacent busbars under vibration.
o Outer wrapping of the cell block using high-temperature Kapton (Polyimide) tape.
• Vibration Damping: Insertion of a closed-cell foam layer (Neoprene or EVA) at the top and sides to ensure constant pressure under the enclosure lid.
6. Control Electronics (BMS) and Wiring
• BMS Specifications: Integration of a Smart BMS (with Bluetooth/App and/or CAN/RS485 communication protocols) rated for 100A continuous discharge and equipped with accurate active or passive balancing.
• BMS Spatial Dimensioning: The BMS must fit within the 82.5 mm usable header compartment, thermally and mechanically isolated from the cell block by a rigid FR4 bulkhead.
• Required Safeguards: Overvoltage, undervoltage, overcurrent (charge/discharge), and short circuit protection.
• Temperature Probes: Configuration with at least 2 NTC probes embedded in the most thermally critical areas (center of the battery pack).
• Signal Wiring: Balance wires (sense wires) must be neatly organized, protected by an anti-chafing braided sleeve, and securely fastened to prevent dynamic movement.
7. Testing and Delivery Requirements
In the proposal, please specify the end-of-line tests included, such as:
• Dielectric insulation test (Hi-Pot test).
• Verification of total internal resistance of the pack (IR test).
• Testing cycle and charge/discharge report under real load (at least 1 full cycle at 50A).