The "floorpan-mounted" high-voltage battery of the Mitsubuishi i-MiEV weighs approximately 500 pounds. The entire vehicle weighs approximately 2,500 pounds so it is apparent that the vehicle is "bottom heavy." This is important to consider when stabilizing this vehicle. The floorpan battery is visible below the vehicle in this image.
Photo credit: Photos by Ron Moore
This look beneath the passenger's side of the i-MiEV shows that the high-voltage battery compartment is lower than the bottom of the blue rocker of the vehicle. This location affects stabilization procedures as well as any task that would work with the floor or rocker of the electric vehicle. A floorpan battery vehicle should not be lifted with tools against the underside area.
Basic stabilization of any electric plug-in vehicle requires blocking of wheels to prevent movement. In addition, with a floorpan-mounted high-voltage battery, rescue personnel must assure that stepchocks are placed so to avoid contacting or crushing the high-voltage battery beneath the car.
Note how the stepchock has been inverted on this electric plug-in vehicle to avoid contact with the high-voltage battery positioned beneath the floorpan. Individual cribbing blocks could also be used as long as they do not contact or crush the battery box.
The i-MiEV is approximately 12 feet long and 5 feet wide. With the i-MiEV on its side, the floorpan-mounted battery enclosure is clearly visible. The black casing running from the front to the rear of the vehicle contains all the modules that make up the 330-volt lithium-ion battery.
When an electric plug-in vehicle is roof-resting, responders must realize that a significant portion of the vehicle's weight is actually above the passenger compartment when the battery is floorpan-mounted. This situation does not occur with conventional-fueled vehicles and should require special considerations at entrapment incidents.
Stabilization of a roof-resting, electric plug-in vehicle requires rescue personnel to adapt to the unique design of the vehicle. In this case, the i-MiEV has been initially stabilized with stepchocks and wedges. Effective strut deployment will be an issue due to lack of good contact points and the desire to not block door access.
SUBJECT: Electric Plug-In Vehicles
TOPIC: Challenges of Floorpan-mounted High-voltage Batteries
OBJECTIVE: Understand procedures necessary for dealing with an electric plug-in vehicle with a
floorpan-mounted high-voltage battery
TASK: Given an electric plug-in vehicle with a floorpan-mounted high-voltage battery to review and inspect, the rescue team shall revise their existing procedures for dealing with the vehicle including unique vehicle stabilization considerations
Our series of columns on electric plug-in vehicle rescue and extrication continues with a focus on the unique challenges presented by floorpan-mounted high-voltage batteries. The vehicle featured in this series is the Mitsubishi i-MiEV, which has its high-voltage battery mounted completely beneath the metal floor of the vehicle. Electric cars such as the Tesla Model S and the Nissan LEAF also mount their large high-voltage battery under the floor. This “floorpan” location requires that emergency responders make some adjustments to several routine rescue and extrication tasks that may be necessary at an incident.
With the 330-volt, 16 kWh lithium-ion battery of the i-MiEV positioned in this floorpan location, the weight distribution of the electric vehicle changes from that which responders have become accustomed. The i-MiEV is a rear-wheel-drive electric vehicle that has 45% of its total weight in front of the firewall area with 55% toward the rear of the vehicle.
An electric plug-in vehicle’s center of gravity is also different from that of a conventional vehicle when the high-voltage battery is underneath the floorpan. Rescue personnel should consider electric plug-in vehicles with floorpan batteries as being “bottom heavy.” The weight and location of the high-voltage battery influences the way we accomplish vehicle stabilization; especially when the vehicle is side- or roof-resting. It also limits any tasks that involve cutting into the floorpan or pushing against an interior component that would crush the floor of the vehicle.
TASK: Given an electric plug-in vehicle with a floorpan-mounted high-voltage battery to review and inspect, the rescue team shall revise their existing procedures for dealing with the vehicle including unique vehicle stabilization considerations.
Ron Moore, a Firehouse® contributing editor, retired as training chief for the McKinney, TX, Fire Department. He also authors a monthly online article in the Firehouse.com “MembersZone” and serves as the Forum Moderator for the extrication section of the Firehouse.com website. Moore can be contacted directly at Rmoore@firehouse.com.