Tesla Motors — the company whose stunning electric car we just can't seem to get enough of — has taken another step towards its goal of commencing deliveries of the 2008 Tesla Roadster to customers by this fall (but don't set your sights on getting one right away). Its Energy Storage System (ESS) successfully met all of the UN Testing Protocol's safety requirements — which included altitude simulation, thermal cycling, vibration, shock and external short circuit. The vehicle's power pack consists of 11 battery modules, a 12-V DC-DC power supply and a main control and logic board.
The ESS power pack, which consists of thousands of lithium-ion cells, has multiple layers of protection and a level of redundancy that limit the potential for short circuit currents. This is because each cell has an internal positive temperature coefficient (PTC) current limiting device. Each cell is also equipped with a current interrupt device (CID) that can break and electrically disconnect it in case of an excessive internal pressure incident prompted by over-heating (the car uses a 50-50 mix of water and glycol for cooling purposes). Because each cell has two fuses (one for the anode and one for the cathode), it can also separate itself electrically from the pack if either fuse blows. As if those precautions weren't enough, the vehicle's microprocessors, circuitry and sensors — including smoke, humidity and moisture sensors — continuously monitor the pack's different voltages, temperatures and currents, and the pack's design has an array of passive and active safety features. If a particular threshold were to be exceeded, however, the battery pack's high voltage can immediately be disconnected from the car by a series of high voltage contactors.
For more information — especially about the more detailed tech/safety specifications — check out Tesla Motor's press release and accompany white papers. Here's hoping they start upping those production numbers soon.