Battery cable came off!

Hi, was checking my '95 Civic 1.6L today. It was idling, and I heard the idle sound change: it seemed higher. I stepped on the gas a bit, and I heard a soft electrical "pop" near the stereo panel. I hurriedly shut down the engine, I found that the negative battery cable had come off! (It had a quick-release connection). I connected it, restarted and found everything working fine, even checked all the stereo functions, LEDs, and the ECU.

I've read that the battery acts as a big capacitor to smooth out voltage spikes. The entire episode didn't take more that 10 seconds, but I'm worried... could there be any permanent damage?

Reply to
sharx333
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For an event like that, the damage will be clear immediately. The only electrical zaps I've seen delayed failures on were lightning strikes. I've dealt with about two dozen lightning strikes (one on a bizjet, the rest at communication sites) and have come to the conclusion that although the failure rate drops off after 6 months the equipment is often never completely right again.

Sounds like you dodged the bullet. Congratulations!

Mike

Reply to
Michael Pardee

You read wrong. The battery reacts too slowly to absorb spikes, it lives at 12V versus your alternator's typical 13.5-14.5V, your alternator wouldn't produce a spike unless it failed spectacularly, and having the terminal come off wouldn't cause a spike either.

Ultimately, cars have batteries for one purpose: starting the engine. Once the engine is running, the alternator provides for all the car's power requirements. Yes, batteries are also used to power accessories when the car is off, but the only reason they're there in the first place is to crank the starter.

Reply to
Matt Ion

Matt Ion wrote in news:ovefh.470560$R63.142904@pd7urf1no:

It absolutely would. Damage may not always occur, but there will be spikes.

The battery's secondary function IS to provide a buffer for the alternator's pulses. Connecting the cables together without the battery in between is dangerous to the car and should NOT be done. You could to that n

1976, but not now.

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See the above link.

Reply to
Tegger

I'm happy to be wrong on this one, Matt. Thanks, guys. *Whew*.

Mike: Lightning strikes, really? Wow.

Reply to
sharx333

I've taken two direct strikes to my antenna mast in the last 5 years. No damage at all. But...I ground out my feedlines when storms are in the area. The strikes hit about 15 ft from where I'm sitting at this puter. I was sitting here both times. My mast is very well grounded, with low resistance. When a strike hits that mast, it's very quiet. Sounds about like a light bulb being thrown on the ground, and then a loud sonic boom directly overhead. Pretty wild.. But I have no trouble at all. My puter doesn't even flinch. You can set the station up for full time use, even with direct strikes, "all broadcast stations are set up this way", but it takes a detailed installation using a ground bulkhead, careful single point grounding, suppressors, etc, etc.. I'm too cheap and lazy to mess with all that. :/ I just manually ground the feedlines at the bulkhead. As far as the car, yes, it's not good to unhook the alternator while running. You got lucky. Many cars would have done a toasting of the alternator in record time. You dodged the bullet this time it seems. If it did have a problem from doing that, it will usually be blown diodes I would think. MK

Reply to
nm5k

Yep - mostly mountaintop sites, two or three a year since I moved to the mountains. For some reason the storms prefer holidays and my anniversary!

Mike

Reply to
Michael Pardee

The problem is that alternators are very inductive. Without a battery, changes in current produce wild fluctuations in voltage; suddenly reducing the current draw by half should roughly double the voltage for a moment. At low current I would expect the alternator and regulator to go into oscillation without a battery to stabilize it.

Mike

Reply to
Michael Pardee

Tegger wrote in news:Xns989685880ECE2tegger@207.14.116.130:

To clarify;the alternator generates AC voltage which is rectified to pulsating DC,and the ONLY thing that smooths it to reasonably pure DC is the battery. Otherwise,your car radio would be buzzing in tune with the engine RPM.

Reply to
Jim Yanik

"Michael Pardee" wrote in news:eNidnUXxjMR6YuDYnZ2dnUVZ snipped-for-privacy@sedona.net:

Try Central Florida,the lightning capital of the US. Also,the power density of Florida strikes are on average twice that of northern lightning strikes.

I've had a pine tree about 300 ft from my apartment(tallest in the area) get struck(and killed) while I was watching. The bolt travelled right down the side,blowing a channel of bark off the tree. It took out a surge protector on my phone line and my modem,didn't harm the phones or the TeleZapper.

Reply to
Jim Yanik

The battery does as Jim said. But another condition called load dump could have created a destructive transient. Load dump is defined by the ISO to be as large as 270 volts on the 12 volt system. SGS Thompson defines it as 80 to 100 volts. But then better automobiles are designed with electronics that make load dump not destructive.

Of course when you connect a computer to the car using a discount inverter, does it have load dump protection - or did you just save some pennies?

The damage, if it occurred, would be complete > Hi, was checking my '95 Civic 1.6L today. It was idling, and I heard

Reply to
w_tom

Fair enough - a SIGNIFICANT spike.

And pray, how does it do that? It's not a voltage regulator, it's not a capacitor. Internal resistance limits how quickly it can react to voltage changes.

You mean the battery cables? Yeah, that'll fry your alternator in a hurry, since you're basically shorting its output.

I wouldn't even try it in a '76.

See the phrase "IN THE FIRST PLACE" in my above paragraph.

Of the four uses Darden lists for the battery, I've already noted the first and fourth above... for the second ("filter and stabilize") it can only do so much - there's still ripple in the voltage measured even with the battery, as the charging voltage is usually well above the battery's voltage... as for the third, if the battery is really needing to "provide extra power" while running, then the charging system is under-rated to begin with, and the battery is acting as a band-aid.

Reply to
Matt Ion

Uh, the battery is nothing more thann a large capacitor. Capacitors are the main components of voltage "smoothing." You know, like radio noise suppression etc.

JT

Reply to
Grumpy AuContraire

Actually, they're not. Capacitors /store/ electrical energy. Batteries /create/ it via a chemical reaction. Charging a battery is not storing energy; it's (to oversimplify) merely reversing the checmical reaction.

Reply to
Matt Ion

Technically yes, but both smooth voltage..

JT

Reply to
Grumpy AuContraire

Batteries do, to a degree. That's not what they're designed for though.

Reply to
Matt Ion

Matt Ion wrote in news:P8fgh.485006$R63.220768@pd7urf1no:

But it's one of the things they're *used* for.

Do you want to email Bill Darden and tell him he's wrong?

Reply to
Tegger

Batteries most definitely do have capacitance, do you have a meter?

Batteries most definitely do store energy when charged. Or are you suggesting that when it is used up that more is created out of nothing?

Reply to
jrk

Matt Ion wrote in news:Clegh.480395$5R2.401317@pd7urf3no:

The plates of a battery have capacitance. They are charged by the chemical reaction.

Reply to
Jim Yanik

Capacitors are electrostatic while batteries are electrochemical. A capacitor capable of storing the energy within a car battery and power capability needed to start a car would be the size of a double long semi.

Reply to
AZ Nomad

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