GM cars use plastics in power storage

David Vink

Published: November 19, 2012 6:00 am ET
Updated: January 3, 2013 6:30 am ET

Related to this story

Topics Automotive, Sustainability, Materials, Injection Molding, Film & Sheet, Molds/Tooling

MANNHEIM, GERMANY (Nov. 19, 12:55 p.m. ET) — The batteries in General Motors’ Opel Ampera and Chevrolet Volt electric vehicles contain more than 40 kg. of polymers.

Matthew Carroll, engineering group manager at General Motors, revealed details of the EVs’ rechargeable energy storage system (RESS) at the 2012 VDI plastics in automotive conference in Mannheim.

The RESS is made up of nine automatically assembled lithium ion 18- and 9-cell plastic battery modules, which account for 22 percent of battery system weight. These hold the battery cells in position, transfer pressure to the cells, provide heating/cooling, electric connection, cell tension sensors and integration of temperature sensors.

In each RESS, 27 kg. of polymers is used in the end frames and 135 repeater frames (made in BASF’s nylon 6/6 grade, Ultramid 1503-2F NAT, which is 33 percent glass filled and hydrolysis stabilized), the nine interconnect boards (ICBs) and the housing. Soft alignment with pins, tabs and slots are used together with brass compression limiting inserts and EPDM seals to assemble the frames into battery blocks, in preference to full snap-fit engagement.

The total amount of glass fiber reinforced nylon 6/6 used in the frames and the ICBs is 18 kg.

Yazaki North America supplies the ICB. Its manufacture involves insert molding a metal cell connector (1.4kg nylon 6 per RESS) on a vertical 300-metric ton Nissei machine. The company uses DuPont’s Zytel 7335F grade of nylon 6 for the base plate and connector housing, as well as Zytel 70G33 HS1L (35 percent glass filled nylon 6/6) for overmolding the ICB.

Mann+Hummel uses a 420-metric ton KraussMaffei electric drive injection molding machine to mold repeater and end frames in a four-cavity mold. Each cavity contains a Kistler 6157 pressure sensor to optimise control of injection pressure. Statistical analysis of injection pressures in the range 48.5-49.7 MPa over the four cavities has shown standard deviations for individual cavities of 0.38-0.40 Mpa.

M+H monitors coordinate measurement machine (CMM) values on 35 consecutive samples from each mold cavity, ensuring a maximum 0.125mm dimensional tolerance window is respected. Some parts are made on an Engel molding machine and others on a machine from a Japanese company not named in Carroll’s presentation.

Carroll said the 9.7 kg. watertight RESS housing is the heaviest part, accounting for 17 percent of battery system weight. It is molded in lightweight BD 840V vinyl ester resin based sheet molding compound (SMC) from Ashland Chemical. This contains 7 percent hadite nanoclay filler and 40 percent glass fibers that are 25mm in length.

The housing is covered in a reflective metal foil for electromagnetic shielding. The use of nanoclay filler has reduced density from 2.0 to 1.5 g/cm3 and cut 1.13kg from the part weight reduction. The coefficient of linear thermal expansion is equivalent to that of steel.

The SMC contains a styrene-based low profile additive that is acceptable so far. However, Californian AT-PZEV (Advanced Technology Partial Zero Emission Vehicle) regulations may require a switch to a styrene-free formulation in future.

Continental Structural Plastics Inc. in Huntington, Ind., supplies the silicone-sealed watertight SMC housing. The housing, which has 73 openings, is molded in an open-to-close time of 180s and an overall cycle time of 4min, allowing for cooling and flash removal. Ashland Chemical designed the mold tooling, which was made by Century Tool & Gauge in Fenton, Mich.

Another part, a 150 µm thick pouch cell, is supplied by LG Chem. Plastics account for 10 percent of its weight, with PET on the outside, polyamide coating of the gastight aluminum enclosure, a ceramic coated polyolefin SRS (safety reinforced separator) and two tie layers. There is a polyurethane foam separator between each pouch to deflect compressive forces (around 50 percent compression at 20 kPa) and their sheet metal heat exchangers are coated with a Mylar PET film layer.


Comments

GM cars use plastics in power storage

David Vink

Published: November 19, 2012 6:00 am ET
Updated: January 3, 2013 6:30 am ET

Post Your Comments


Back to story


More stories

PE suppliers go after oxo-biodegradable technology in Mexico

July 31, 2014 1:12 pm ET

Mexican industry defends itself, calling claims 'misleading'    More

Bioplastic created using rice starch

July 31, 2014 10:40 am ET

The new transparent, biodegradable material has a high degree of mechanical strength and good thermal resistance.    More

Private equity firm buys majority share of truck accessory maker

July 31, 2014 10:30 am ET

A majority share of Ann Arbor, Mich.-based truck accessory manufacturer Tectum Holdings Inc. has been acquired by Boston-based private equity firm TA ...    More

Spain's ITC Packaging acquires Coveris rigids plant

July 31, 2014 9:59 am ET

International packaging group Coveris Holdings has sold its Spanish business Coveris Rigid Spain, including an injection molding plant, to the...    More

Image

Plastics News Now: PVC pipe used to help repel sharks from beaches

July 31, 2014 6:00 am ET

Also, we visit Nicolet Plastics which is using a unique employee structure, and Washington D.C. bans polystyrene.    More

Market Reports

Pipe, Profile & Tubing Extrusion in North America 2014

U.S. demand for extruded plastics is expected to grow by 3 percent in 2014, with PVC remaining the largest segment.

Plastic pipe will post the strongest gains through 2018, continuing to take market share from competing materials in a range of markets.

Our latest market report provides in-depth analysis of current trends and their financial impact on the pipe, profile and tubing extrusion industry in North America.

Learn more

2014 Injection Molding Industry Report

GROWTH, OPPORTUNITY IN SIGHT FOR INJECTION MOLDERS IN 2014

In the wake of the economic turbulence earlier in this decade, molders today find themselves in much better shape. Molders are gaining a competitive advantage by investing in people, equipment and seeking inroads into new markets on a global scale.

Growth in the injection molding industry is going to be driven by low financing costs and a continued move to reshore some business.

Learn more

Shale Gas Market - Analysis of North American Region

This report highlights the impact of shale-based natural gas on the North American plastics market and features an in-depth analysis of production trends in the United States during 2013 and a forecast for 2014 and beyond.

Learn more

Upcoming Plastics News Events

September 10, 2014 - September 12, 2014Plastics Caps & Closures 2014

January 14, 2015 - January 14, 2015Plastics in Automotive

February 4, 2015 - February 6, 2015Plastics News Executive Forum 2015

More Events