Battery Fire!

So, heading to work this morning, downtown street at 25mph, my bike suddenly stopped all electrical functions. I coasted to the side of the road and fiddled with the key in the ignition, turning it back and forth from OFF to ON, but got no electrical response.

Then I noticed the smoke.

I pulled the seat off, and the negative terminal of the battery, and the bottom of the seat were on fire. I blew it out, and took a picture:



You can't tell from the picture, but the negative post on the battery is actually detached from the body of the battery. This battery is two days old.

What do you guys think? What could have caused this, and how much of this wiring needs to be replaced? And is it possible to just replace SOME wiring, or will I need a new harness altogether?

 

holy crap, talk about a hot-seat! trust you are OK...no other...um....equipment burned! I'd be leary of the wiring and would likely swap the main harness and battery leads/terminals to be safe then have a mechanic check it out. That coulda been bad.....

 

Wait, you're in the US...shouldn't you sue someone for this? (just kidding...)

 

I was fine, thanks for the concern. The flames were pretty small, and it definitely could have been worse.

I have a theory going: the battery had a manufacturing defect, the post broke off while riding, and that's why the motorcycle stopped running. While turning the key on and off, sparks (?) or whatever caused a fire.

Does this sound reasonable to anyone? Or is there some other reason why the negative post would break off? I doubt that the fire could cause that, but don't know how to be sure.

 

Did the post break around the plastic?

It could have been damaged before you put it in. That looks like a good battery, did it come in a box? Maybe the post got smacked from another battery while on the shelf at the shop?

I broke a post off a battery once trying to get a wire off.

 

I didn't have too close a look, but I think it did break around the plastic. It came in a box, and has a one-year warranty. I'm going to try to exchange it today.

Would the post snapping while running be a possible cause for the fire? Because it certainly wasn't broken when I installed it two days ago.

 

I'm not qualified to answer this.


But a quick google search shows that sulfuric acid, which is in batteries is not flammable.

Also, a poor electrical connection around that area, perhaps from a broken battery post, will get very hot. Hot enough to burn the housing off a wire.

Sometimes the plastic connectors around a plug that has a bad connection will be melted and or crispy looking.

 

looking at the pic whats the bare wire under the positive termenel ? im gathering from what im looking at it shouldnt be the wiring there is a fuse that comes off the small positive lead that supplies power to the whole bike except the starter and alt first check the fuse make sure someone hasnt wrapped foil around it im not sure but for some reason check the starter relay it might of shorted out and went to ground the negitive wire is smaller so it would melt first . check the wire with the main fuse in it i bet it isnt shorted with a meter . it has to be something major not fused to melt the negitive cable all the rest of the wires are much smaller and would have caught long before the neg . battery cable

 

you got very lucky, when a battery is in use it "gasses" hydrogen, which is highly explosive, when you think about it, when you're riding your bike you litterally have a small hydrogen bomb between your legs, glad you're safe. my opinion is replace the entire wiring harness front to back to eliminate the chances of another fire somewhere else on the bike

 

where the black wire goes between the battery box and the red wire
the insulation failed and there was a direct short across the battery, the black wire looks fine past where it crosses the red wire
when it got hot enough the negative terminal failed as the plastic melted
just replace the black wire, tape up the red wire, make sure nothings pinched and it should be fine

 

Looks to me like the insulation burned off the ground lead. I suspect that was your fire.

The wire looks a little thin in the pic. You sure it's the correct gauge?

It might be possible that the terminal broke off the battery first. At that point the voltage regulator is going to get into trouble because it requires the battery as a damper for the system. Voltage regulator goes into overdrive, cranking up the alternator. The loose lead bounces against the battery and enough current runs to cook the wire. Just a theory......

 

I had a chance to have a closer look after work last night. It's not pretty.

The battery itself had melted solder running down the side of it. The post wasn't broken off, it was just no longer connected by the solder.

The thin black wire's insulation was melted not just where it's visible, but higher up into the wiring harness (it enters the main harness on the upper left side of the picture). I followed the harness up a few inches and the big thick insulation was also melted, exposing bare wire inside.

I'm not much at the electronic side of this, but I'm willing to learn: that thin black wire is the ground wire through the wiring harness, right? So do we think that it just shorted out across the top of the battery?

Is there a guide somewhere to replacing the entire wiring harness? Since it's melted past where thin wires are visible, I'm thinking it'll need to be replaced.

 

Something isn't right with the ground wire. There should be a heavy gauge wire (like the heavy red one) going from the (-) to a bolt on the engine case.

 

Look very carefully at anywhere the Positive Terminal Battery Connection could have vome in contact with the Frame.

If the Battery took a bounce and the Positive Terminal can into contact with the Frame ... the arc would be strong enough to weld the Terminal end to the Frame until the heat melted the Battery Post and ended the discharge.

Your Battery Box should have a Partition that prevents the Terminal from accidentally coming into contact with Frame!

If you recover from this incident without having done major damage to wiring; rig the Bike so it cannot happen again.

Cut a section of Bicycle Inner Tube and cement it to the Frame.
It's less than an ounce of prevention.

 

There is. It goes straight down from the right-hand side of the picture, but can't be seen in the picture I took.

I know the '85 700s are kind of oddballs, but I think this is the way the wiring is supposed to look, minus the melted insulation.

Excellent advice. This is what I'm hoping happened, because the only other explanation I can think of involves a short in another component PLUS a fuse not blowing when it should have.

I'll look again tonight and report.

 

If an exposed post from the starter solenoid rubs the frame it will give the same results. And that's not solder, that's actual melted lead.

 

The High-Amp Connections are all supposes to have a Rubber Protector against accidentally being Short circuited.

The Battery Cables and Solenoid Wires protective ends may have become brittle and fallen-off or pulled-off by a PO.

If your Solenoid does not have such protectors ... put some Rubber Hose on the Posts.
If the Solenoid "Falls-out" of the Mount, ... wrap the Solenoid Body with a few layers of Electrical Tape and make is snug, again.
Use a Plastic Tie-wrap to anchor a Solenoid which has its Mount in poor condition.

 

My rubber protectors, both battery and solenoid, are all a disaster. This was probably the cause.

I'll make sure that when I do the fix I get those covered up.

Meanwhile, any good tips on full-harness replacement?

 

For replacement: expose as much as possible of the harness. Take pics...LOTS of pics. Make some diagrams of routing as well. Start at one end, and as much as possible replace one for one each connection along the run.
This doesn't always work, but it'll get a good start.
You can also label the connections as you take them apart (using masking tape). Label each side of each connection. Lay out the old and new harness together side by side. Match the connectors, then make new labels for the new harness that match the old one. DO NOT remove the labels from the old harness, just in case. Once you have the new harness all labeled, lay it out on the frame and start matching labels/connections.

Either way, plan on taking your time. As with all projects, when you start getting pissed off it's time to walk away.

 

My Seca 750 came with a damaged and cut-up harness - -I found one on E-Bay for $15 that even came with the 5 relays. It worked perfect, and even solved the turn signal problem I had.