# EV Conversion collision safety



## madderscience (Jun 28, 2008)

Hi All-

Sort of an info-rant here. I got rear ended in my scion xB EV conversion today. I'm fine and the car survived with minor damage but will need a couple ounces of bondo and a new rear bumper. The other guy, immediately after the accident realized he was late for something and had to speed off in the opposite direction, but this isn't about that.

I've seen a few conversions done that would likely have done very bad things if involved in the same minor collision I was just in due to where batteries were located and other such things, so I thought maybe a thread discussing basic collision safety design considerations was appropriate.

Some basic things that come to mind for me:


Pick a vehicle that will stay within GVW as much as possible after conversion. These days with lithium, its pretty easy.
When installing battery boxes, ensure that any cuts made to the chassis, for example to install a sunken battery box in the vehicle floor, do not weaken the structure of the vehicle body. Avoid cutting or removing frame rails, cross members, bulkheads, and joints where multiple sections of sheet metal bodywork come together.
Avoid altering the original crumple zones of the body (either by weakening or strengthening)
Don't remove or alter the original bumpers.
Don't attach battery boxes, high voltage wiring, or anything else to the bumpers for support. Leave as much crush space between the bumpers and battery boxes as possible; at least a few inches but ideally a foot or more.
Locate battery boxes, high voltage wiring and circuits and anything else as close to the center of the vehicle as possible, and as low as possible.
Isolate batteries and high voltage wiring from the passenger compartment as much as possible.
Ensure that there is a readily accessible high voltage disconnect in addition to fuses. Ideally this will divide the pack voltage down to safer levels when pulled.
Ensure the battery boxes are solidly attached to the car body, and the cells themselves are held down. Ensure that if cells do come loose or shift in a rollover, whatever is directly above them (the battery box lid, etc) won't short them out.
All high voltage wiring (technically, anything over 72V in the USA I believe) where exposed should be sheathed in orange conduit or otherwise colored orange to indicate high voltage danger to first responders. Its not a bad idea to include warning stickers stating the voltage and where the disconnect is as well.
Employ redundancy in your design. Multiple fuses, multiple layers of insulation between high voltage and the chassis, Multiple layers of physical protection between the batteries and the outside, etc.
I'm sure there are many other ideas. Any other experiences?


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## poprock (Apr 29, 2010)

madderscience said:


> Hi All-
> 
> Employ redundancy in your design. Multiple fuses, multiple layers of insulation between high voltage and the chassis, Multiple layers of physical protection between the batteries and the outside, etc.
> I'm sure there are many other ideas. Any other experiences?


I have 4 interrupts to the main contactor earth (12v). Filler flap open switch (plug cover), drivers seat pressure switch, hidden switch under dash, hood open switch. As well there is the panic button-disconnect. ANN400 fuses are at the + end of the 84v (48+36battery pack(FLA) and at the + of the rear pack(48v) .


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## evmetro (Apr 9, 2012)

Like poprock is saying, lotsa fuses!


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## dtbaker (Jan 5, 2008)

and don't forget the simple inertia switch interrupt on the 12v side of the main contactor.... mounted VERTICALLY. The electrical 'airbag' that should kill the motor if you are in an accident if you are rendered unconcious.


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## poprock (Apr 29, 2010)

dtbaker said:


> and don't forget the simple inertia switch interrupt on the 12v side of the main contactor.... mounted VERTICALLY. The electrical 'airbag' that should kill the motor if you are in an accident if you are rendered unconcious.


Yes, I forgot to include the inertia switch. But mine says to mount horizontally. Hopefully only a difference between brands?


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## elevatorguy (Jul 26, 2007)

madderscience said:


> Hi All-
> 
> Sort of an info-rant here. I got rear ended in my scion xB EV conversion today. I'm fine and the car survived with minor damage but will need a couple ounces of bondo and a new rear bumper. The other guy, immediately after the accident realized he was late for something and had to speed off in the opposite direction, but this isn't about that.
> 
> ...


I'm glad to hear you are ok and sorry to hear about the accident. I recently was in an accident in a standard vehicle but a Hybrid car was involved as well. I noticed that the first responders cut the battery cables on both vehicles, This is an unknown on a conversion as many of the parts have been relocated. I am going to make an effort to label the vehicle as electric and signs to indicate disconnect locations.
A manual disconnect in reach of the driver is a good idea as well in case of short, or runaway controller. Do not depend on relays for all disconnect as they can weld at the worst time.


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## dtbaker (Jan 5, 2008)

poprock1 said:


> Yes, I forgot to include the inertia switch. But mine says to mount horizontally. Hopefully only a difference between brands?



if you mount horiz, the unit is 'directional', and may trigger if you hit a hard bump. I THINK they all have to be vertical for best results from impact in any direction.

and yes, a manual choke pull to the main circuit breaker is a good backup. by drivers left knee, reachable from driver's window is a good idea although there is no official standard.


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## evmetro (Apr 9, 2012)

I often debate in my mind the merits of having high voltage warning stickers when involved in collision. Our high voltage cables are routed in roughly the same location as gasoline lines are in an ice mobile, so should we bother indicating that our vehicles are electric? Might they be afraid to saw or chop your roof off for a rescue if they don't know that it is safe to do so? I understand the dangers of EVs and the importance of responders knowing that it is an EV, but think about it for a second....


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