How It’s Made
Each part is separately made, then all the sub-assembly are joined together to engineering a battery pack. CMIUTA Electric Company uses original techniques in manufacturing to ensure maximum quality and performances.
Adding matching cells and to engineer the battery packs. To minimize the variability inside a battery pack and to ensure maximum quality, all the cells need to have the same weight (margins of 0.001 grams), identical voltage rated, same rank and initial charging date, from the same manufacturing batch.
For a more compact design, translated into more energy density per unit volume and to improve mechanical and thermal performance, the battery cells are joined in “honeycomb form”.
An active cooling system based on air flux or liquid pipelines is more efficient but adds weight to the drone battery, that can reduce performances and operating time of this.
In the case of our battery pack, cell joining and a passive thermoregulation system described below is an optimal solution to keeps the weight of this as low as possible.
Between rows of cells, it inserted a thin thermally conductive strip, insulated and connected to the outer shell-layer reinforcement which contains aluminum layer. Its main purpose of the interstitial material it is to help absorbs and disperses /spreads heat accumulated in battery pack core, generated during high-discharge rate, prolong in this way the lifespan of the battery. This passive cooling technology relies on the thermodynamics of conduction.
Using TECBOND, a hot-melt adhesive based on high-thermally conductive polyamide (PA) copolymer with great bond strength, the empty space between cells is filled and the battery pack is fully sealed.
Welding cells in serial and parallel.
The cells terminals are connected by thin nickel busbar (with 99,97% purity) through RSW (Resistance Spot Welding), according to the configuration needed.
Wiring, safety elements and covering.
Spending attention to detail and safety elements, the harnesses for PCB/BMS, polarized gold-plated connectors and shielded discharge cables are applied using Silver-Copper-tin alloy.
The entire cell block is surrounded by a multi-layers shield with mechanical strength and dielectric insulated, outside-reinforced with an aluminized film used in the spacecraft industry. All the covering materials are lightweight and provide a high sealing, improve thermal performance and contribute to the robustness of the battery pack.
To reduce manufacturing costs, the pack is wrapped with a hard (Black & Blue) PVC film. With this kind of covering the aesthetic appearance isn’t charming, but looks very compact and solid. However, we work hard to develop a tough and lightweight battery housing, from composite materials.
Upcoming in 2018
IBHS (Integrated Battery Heating System)
Because of the cold temperatures in high-altitude flight or polar climate applications, the UAV battery performance can be greatly reduced, we have found a technical solution to combat this issue by integrating a 20°C heating system, that is using a light and thin 6W element managed by a PTC thermistor. It is completely safe – has no a direct contact with cells because this is achieved through the use (in the reverse) of interstitial strips for thermal transfer. The hardware requires 6V power source connection from PDB/BEC of the aircraft.
CMIUTA Electric Company will use 3D printing technology to manufacture a honeycomb-type battery cell holder from composite materials, for ultimate cooling efficiency, safeties and reliability. 8 hours it is average print time to mold a complete battery cell holder, including the covering parts
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. Engineering Technologist: Cristian Miuta.