NHTSA says Chevrolet Volt at no greater fire risk than gasoline powered vehicles

by Ernie Hernandez on January 21, 2012

Chevrolet Volt“No discernible defect trend exists”

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.

{ 2 comments… read them below or add one }

Sasparilla January 22, 2012 at 1:32 pm

The powers that want plug in vehicles to die (oil companies and their lackies be-it politicians of a certain bent or Fox News) have definitely been at work in all the phony press of this.

As to the Volt, Tesla, Ford Focus Electric having liquid coolant issue. Guessing that it basically comes down to protecting and getting the best performance from the batteries over the long term. The Li batteries work best (best performance and least long term harm to pack capacity during use) when kept in a narrow range of temperatures. GM, like Ford with its Focus Electric (and Tesla as mentioned), decided to use a liquid coolant system to keep the pack temps (both on the high end and the low end) in a more narrow range than would have been possible with just air cooling – presumably this justified the extra cost to them. GM also had previous experience with a liquid thermal cooling system on the EV1 NiMH, so they probably had a good handle on how expensive it would be for them.

My personal guess is that the next generation Volt will have air cooling like the Leaf because its cheaper, but we’ll have to wait and see on that.

The other thing with the Volt pack is that it is significantly smaller than the Leaf pack and all the juice has to flow out quickly (compared to the drain being spread on more cells on the Leaf) generating heat, this may have tipped the needle to the liquid thermal management system as well.

Hopefully GM and Nissan can just get back to selling plug in vehicles, I want to see some good numbers this year. 😉

Reply

Ernie Hernandez (LEAFguy) January 22, 2012 at 8:20 pm

With any luck, Oppama production will actually get close to 50,000 this year, which would mean 20-25,000 sent to the US, perhaps more. Also, Smyrna, Tennessee production is due to come on line near year end. As more positive news actually bubbles to the surface (regarding viability of electric cars), and wider distribution is made available, we feel that EV sales will improve. Other manufacturers coming on line will also help.

Reply

Leave a Comment

Previous post:

Next post: