Tesla Energy Group Open for Business

Ford Th!nk City


The life of the Th!nk City in the United States was short lived. Nonetheless, it has served as a model for a number of electric minicars.

Tesla Motors has announced that a new division, Tesla Energy Group. It is being led by Dr. Bernard K. Tse, a Tesla Motors board member who stepped off the board to lead the Energy Group. The establishment of the Tesla Energy Group adds a significant new dimension to the business of Tesla Motors. In an example of vertical integration, Tesla Motors is developing and marketing battery packs.

“Tesla Energy Group will provide additional sources of operating income for Tesla Motors while accelerating our competitive advantage in battery pack design and manufacturing. Both of these support our core business of developing and marketing extraordinary electric cars such as the Tesla Roadster,” said Martin Eberhard, CEO of Tesla Motors.

Along with announcement of formation of the Energy Group, Tesla Motors also announced that they have their first customer. Think of Norway signed a development and supply agreement worth $43 Million.

The supply agreement covers the development and delivery of battery packs starting in December 2007 and continuing through 2008. The supply agreement represents up to $43 million in revenues, of which approximately $3 million is expected to be realized in 2007 with the remainder in 2008.

Autoblog Green1 (does a Tesla… press release) quotes Jan-Olaf Willums, CEO of Think, as stating that “Tesla Energy Group provides Think with an advanced battery pack design with impressive performance”.

So what does Think Global get? Lithium-ion battery packs for their line of “TH!NK city” electric cars, which at present is designed, like the electric Smart fortwo, to use a Zebra battery. The high temperature, molten sodium sulfur battery can give the “TH!NK city” a 180 km (112 mile) range and a top speed of 100 kph (62 mph).

Assembly of Hybrids-Plus advanced lithium battery pack


In Colorado, Hybrids-Plus personnel assemble a traction battery pack from A123Systems cells. In the near future with improved modularity, you even may be able to hot-swap the advanced lithium cells in and out of the battery packs.

Green Car Congress2 reports that Tesla now builds its large Energy Storage System packs from small commercial cells, rather than larger-format cells. Thus, Th!nk will benefit from Tesla Motors technological development, which has focused on a high level of redundancy and multiple layers of protection in order to deliver a safe and reliable high power pack. “The 56 kWh ESS for the Roadster contains more than 6,800 18650 cells. According to Think, their new pack will contain around 3,000 cells.”

The commodity cells Tesla uses in its pack all have an internal positive temperature coefficient (PTC) current limiting device, which limits short circuit current on an individual cell level. The power electronics continually monitor voltages, currents and temperatures within the pack, as well as inertia acceleration and vehicle orientation. The microprocessors, logic circuitry and sensors also monitor smoke, humidity, and moisture. “Should any threshold be exceeded, high voltage contactors immediately disconnect the high voltage of the battery pack from the car.”

The cells also have an internal Current Interrupt Device (CID) that will break and electrically disconnect the cell in the event of excessive internal pressure caused by over-temperature or other failures resulting in over-temperature. Tesla selected cells with packaging, materials and chemical factors that further augment the safety profile.

The Roadster pack comprises 11 battery modules, a main control and logic board, and a 12V DC-DC power supply. Each of the 11 modules carries a monitoring circuit board that communicates with the rest of the vehicle microcontrollers, broadcasting the voltage and temperature measurements of its module over a standard CAN bus.

Each of the cells has two fuses (one each for the cell’s anode and cathode). This allows the cell to become electrically separated from the rest of the pack if either of its fuses blow. In addition to cell fuses, each of the 11 battery modules has its own main fuse that guards against a short circuit across the complete module.

Th!nk also will benefit from the passive safety features as well as the active protection systems built into the battery pack. In other words, Tesla Motors invested in extensive risk management before their commerical venture. But, not everyone is convinced of the safety or the desirability of battery packs from small commercial lithium ion cells. GCC commentator AES notes:

From the perspective of a technophile, this frustrates me because Tesla’s pack technology is entirely predicated on the intensive thermal and electrical management demands of conventional lithium ion batteries. Alternative battery technologies have emerged and been independently verified - ones that do not require this kind of intensive management.

Continue reading here: NiMH Powered Scooters

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