Electric vehicles, whether they are full battery-electric vehicles such as the Nissan LEAF, or hybrid electric vehicles such as the Chevrolet Volt, present new technology that has not yet been fully tested in the real world. By this we mean that computer simulations and laboratory testing will provide a large data-set of information, but there is no way that all future possibilities can be foreseen, or planned for, with such evaluations. Thus, the Volt fires developed based on unforeseen circumstances.
The National Highway Traffic Safety Administration (NHTSA) has recently released a statement containing the following information:
Today, the National Highway Traffic Safety Administration closed its safety defect investigation into the potential risk of fire in Chevy Volts that have been involved in a serious crash. Opened on November 25, the agency’s investigation has concluded that no discernible defect trend exists and that the vehicle modifications recently developed by General Motors reduce the potential for battery intrusion resulting from side impacts.
This statement is likely to make many Volt owners breathe easier. Likely many other electric vehicle (EV) owners as well.
Within the NHTSA press release is a link to the final reports, which we checked out. “Bones” – the forensic anthropologist television show – has nothing on the guys that wrote the reports of the Volt fire analysis. Fascinating reading if you’ve got some time and plenty of patience to let your brain process what the reports have to say. Two things come to light through reading the reports that make us glad that we own the LEAF.
First, the Chevrolet Volt uses a fiberglass case installed on a steel plate to encase the battery packs. The Nissan LEAF uses a steel case. There was physical intrusion through the fiberglass case which allowed damage to the Volt battery. General Motors has since made structural enhancements to the vehicle to prevent this physical intrusion in a future similar severe side impact collision. This statement is taken from the linked GM press release:
GM conducted four successful crash tests between Dec. 9 and 21 of Volts with the structural enhancement. The enhancement performed as intended. There was no intrusion into the battery pack and no coolant leakage in any of the tests.
Second, the “no coolant leakage” portion of the last sentence in the press release reference. LEAF does not use coolant which could be a contributing factor in a severe collision. The interesting part about this, that we don’t quite understand, is the necessity of having a coolant system in the Volt. Volt uses lithium ion battery pouch-type cells, as discussed in the final reports referenced above, similar in design to those used in the LEAF. Tesla, on the other hand, uses cylindrical batteries that do not have the same heat dissipation characteristics as those demonstrated by the Nissan design. The Tesla battery pack requires an active cooling system. We are not sure why the battery pack in the Volt does.
We are not writing this post to discourage Volt ownership. In fact, from a safety standpoint both the Volt and the LEAF have achieved a five star overall safety rating from NHTSA based on crash test data. We are, however, pointing out that not all manufacturers make the same choices when it comes to vehicle design. Some of these vehicle design choices don’t make their effects known immediately. In this instance, there are at least two reasons, from a safety standpoint, that the Nissan LEAF seems to be the better choice.