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Battery fire while towing


de3ug
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So I had an incident last Sunday that could have been real bad.  Actually, scratch that, it involved a fire so it was real bad, but it could have been much worse.  I'm going to share some of the details with the chump community so hopefully this does not happen to anyone else, especially since the specific issue did not seem to come up in the previous few threads about battery containers and hold down straps.

 

So what happened?
At our last race (Laguna Seca in July) we had a CV joint bushing explode on Saturday, which smothered our alternator to death in axle grease, which lead to us swapping the battery in and out of the car a few times during the race on Sunday (we didn't have a spare alternator, but we did have a bunch of vehicles in the paddock with perfectly good batteries...).  After the race, we put the original battery back in the car, but in the rush to get everything packed up and get home it seems that we did not attach both ends of the metal battery tie down strip.  I towed the car home (2 hours) that night and put the car in the garage, no issue with the battery.  I spent the last two months going through our todo list for the car (alternator replacement, led trailer lights, new dashboard, etc.), no issue with the battery.  I towed the car one hour to one of my teammates house last Sunday, I get out to unload the car from the trailer and everything on the car is fine except... there is a pile of burnt and melted plastic sitting in a pool of acid where the battery used to be.  Everything else was fine, didn't melt or even darken the lexan rear hatch.

 

What (do I think) was the root cause? 
So I'm posting before and after photos.  The before is from a few years ago when we first built our box.  You can see we have two long bolts which are connected to a metal plate below the box and attached to a metal plate with wingnuts.  It's not shown here, but we also had rubber battery terminal covers over both posts, and a lid that snapped in place.  As you can see in the after photo, the metal plate (which is grounded, since it's attached to the frame) slid to the right, under the rubber terminal cover, and shorted the battery.  Search for "car battery short fire" on youtube if you want to know what happened after that.

 

What should we all do about it?
Never leave your battery unattached, especially when moving the car, especially if you are securing your battery with a system like we were using here.  Don't assume those rubber or plastic terminal covers will protect you from a short.  We tend to focus on safety during the race and relax afterwards, but this is something that can happen at anytime if you make a mistake like this.  I'm going to add this to my checklist whenever I move the car now.  Now that we have to rebuild our battery box, I'm thinking of ways we can design a mount where this can't happen.  Maybe a hinge secured with multiple bolts on one side so the strap can't rotate, or covering the strap completely with an insulator.  Looking for thoughts or ideas, preferably with photos of everyone else's much more secure unburnt battery boxes.

after.jpg

before.jpg

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Wing nuts are not graded fasteners, at least these aren't. Use a graded bolt and nut. Like grade 5. You could also go next larger size, like 5/16"

 

In addition to being unknown strength you can't get much torque on a wing nut unless you grab it with pliers, and then you've defeated the purpose of a non tool fastener.

 

And is there anything holding in the transverse direction? Might not matter with a properly torqued 5/16" fastener but it couldn't hurt.

 

This probably should not have passed tech.

Edited by Dimsun Racing
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Either make the studs longer (maybe 1 or 2 inches), or bend the metal piece so it has a step down on either side of the battery (two 90 degree bends at each end).  It will require you to thread the bolt on further but will also make it harder for that piece to come off and slide to the side. 

 

Mine has long studs with sleeves to accommodate the Odyssey battery. This box will also support a full size battery (say when the league makes you run their battery), or a tractor battery.

 

IMG_1459.JPG

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I like the bent metal bar idea.  Are those posts rigid when the bar is not there?  I think that was another flaw in our previous design (in addition to the diameter of the posts), is that they would flop about when not tightened.  We had a metal plate under the battery box, but the posts were attached like upside down tent stakes.

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14 minutes ago, de3ug said:

I like the bent metal bar idea.  Are those posts rigid when the bar is not there?  I think that was another flaw in our previous design (in addition to the diameter of the posts), is that they would flop about when not tightened.  We had a metal plate under the battery box, but the posts were attached like upside down tent stakes.

Those studs are secured to the floor with a washer and nut on both sides of the floorboard so they are rigid.  https://www.summitracing.com/parts/sum-g1231 Can't recall if I used the studs that came in the kit or made my own.  The green sleeves I custom made from some metal tubing I had so I did not have to thread the nuts down beyond the length of a socket.

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