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?

 

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

 

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

 

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.

 

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.

 

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.

http://www.uuhome.de/william.darden/carfaq2.htm

See the above link.

 

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.

http://www.uuhome.de/william.darden/carfaq2.htm

See the above link.

 

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

Mike: Lightning strikes, really? Wow.

 

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

Mike: Lightning strikes, really? Wow.

 

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

 

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

 

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

 

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

 

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

 

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

 

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.

 

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.

 

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.

 

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.

 

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 in milliseconds.
Apparently you did not suffer load dump damage. But you, like many
others who replied here, should know of load dump and what automotive
electronics (properly constructed) cost more money.