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High Dispensing Speeds Even with Highly Abrasive Potting Media - System Solution for Heat Management in High-Voltage Batteries

July 24, 2019
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Electric mobility is picking up speed: Vehicles with alternative drive systems are regarded as a key component in the fight against noise pollution and constantly rising emissions in densely populated areas. With a view to current environmental and climate protection targets, various European countries are already planning to abandon the combustion engine. China - currently the world's largest market for electric vehicles - reported over 1 million electric cars sold last year. According to the management consultancy McKinsey, the local market grew by 85 percent in 2018.

In addition to the electric motor and power electronics, a core element of these vehicles is the high-voltage (HV) battery. According to the current status, lithium-ion technology has emerged as the dominant technology here, as it currently exhibits the best performance in comparison. The HV battery consists of hundreds to thousands of individual cells of various shapes and performance classes, which are assembled into modules and finally into a complete battery. The design of the individual cells varies depending on the manufacturer or vehicle manufacturer. Cylindrical and prismatic shapes are used as well as pouch cells, which are also referred to as "coffee bag" cells due to their external resemblance to vacuum packaged coffee powder. The decision for a certain cell format is linked to several central factors for the vehicle manufacturer, such as manufacturing costs, energy density, weight and scalability. Also essential are the properties of the cells in terms of heat generation and the associated cooling requirement.

Up to 44 lbs of thermal conducting material in use
Thermal influences have enormous effects on the service life, capacity and in particular the operational safety of HV batteries. For normal operation of an electric vehicle, outside temperatures of 50 to 77°F and operating temperatures of approx. 68 to 104°F are ideal. Applying higher thermal loads not only causes faster degradation of the materials used in the battery cells. In the worst case, even failures or severe to irreparable damage to the HV battery and vehicle may occur.

To prevent this, every electric vehicle has a cooling system built into the battery housing. This is controlled by the battery management system (BMS), which, in addition to thermal management, is also responsible for monitoring the charging and discharging process. To ensure optimum heat dissipation, the battery modules and cooling elements are thermally coupled with heat-conducting pastes, adhesives or sealants. Several quarts of these highly viscous media enriched with heat-conducting fillers are used per vehicle. Depending on the filler density, this can correspond to a material weight of up to 44 lbs. (20 kg). These materials provide reliable heat transfer and help prevent potential defects due to overheating.

However, due to their high viscosity and the high proportion of abrasive fillers, the application of heat conducting materials poses a challenge. Since these media often only allow comparatively low dispensing speeds, this process step often proves to be a bottleneck, especially in fully automated production processes with fast cycle times, as it is the case in the automotive industry. If no special attention is payed here to fine-tuned dispensing and material feeding technology, users also risk high maintenance and repair costs.

Dispensing speeds of up to 80 ml/s
Especially for this dispensing task Scheugenpflug offers a powerful system solution consisting of a dispenser and a compatible material feeding system. The system offers dispensing speeds of up to 80 ml/s even with highly abrasive potting materials - with consistently high dispensing accuracy.

The high performance volumetric Dos HP dispenser enables fast and precise application of thermally conductive media with a viscosity of up to 1,000,000 mPa∙s. The maximum volume per dose is 370 ml. Two powerful electric motors in the dispenser ensure the required performance. An additional metal sleeve reinforces the mixing tube and ensures the necessary stability during material application. In order to ensure a sufficiently large operating range for the application, the Dos HP is usually mounted on an industrial robot.

The high performance dispensing system is based on the system technology of the proven volumetric piston dispenser Dos P. This was upscaled and optimized especially for the discharge of very large material volumes in a short time. With Dos HP, users also benefit from the well-known advantages of Scheugenpflug's volumetric dispensing systems: Their robust mechanical design principle not only enables long service lives, but also simple and fast maintenance and therefore considerably reduced maintenance costs. In addition, precisely dimensioned dispensing cylinders ensure the output of precise, reproducible material volumes.

The fast and process-reliable feeding of material to the dispensing system is carried out by the PailFeed200 Abrasive drum follower plate system, which has been specially designed for 55-gallon drums. The delivery volume of the integrated double piston pump is 480 cm3/stroke, the maximum delivery pressure is 65 bar. In addition to a continuous pumping process, the pump also offers long service lives, as the piston only comes into contact with the abrasive dispensing material on one side. A rinsing fluid on the back prevents the contained fillers from adhering to the seal and pump components. Thanks to the high-performance system technology, a high volume flow and consequently fast cycle times are guaranteed - even with thermally conductive materials that are difficult to process. As an option, two feeding systems can also be connected in parallel to the dispenser, allowing for redundant system operation without downtimes.

Summary
The application of thermally conductive media is often a bottleneck in production - especially in industries with highly automated manufacturing processes. But modern manufacturing technology can also effectively alleviate this bottleneck. Fine-tuned integrated solutions are the more economical solution here than individual systems, because material preparation, dispensing and mixing as well as control technology are optimally tailored to each other with regard to the materials used. That pays off in the end - and the quality is right.

The high-performance solution for thermal management of HV batteries in video

About Scheugenpflug:
Scheugenpflug is a leading manufacturer of precision engineered systems and machines for efficient adhesive bonding, dispensing and potting processes. The product and technology range extends from cutting-edge material preparation and feeding units and high performance manual work stations to modular in-line and automation solutions, specially tailored to customer specifications. Scheugenpflug systems are used in the automotive and electronics industries as well as the telecommunications sector, medical technology and the chemical industry. The company has four additional locations in the USA, China and Mexico as well as numerous service locations and sales partners all over the world. Due to its considerable expansion Scheugenpflug was able to double its number of employees within 5 years and now employs nearly 700 staff.

For more information, contact Scheugenpflug Inc., Tel. +1 770 218 0835 (sales.us@scheugenpflug-usa.com) or go to www.scheugenpflug-usa.com

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