Sparking Battery/Smoking Car

I was replacing my friend’s battery and I put the new battery in, without cleaning the tray. I started with connecting the ground cable, then when I put the positive cable on, it sparked real big and then something in the other part of the car started smoking and smelled horrible. I’ve replaced batteries before and this has never happened.

Question: Do I start with the positive cable first? Her car has been sitting in the driveway for 6 months. What’s wrong?

Yes, you should always disconnect the ground first and connect it last, but this has nothing to do with the electronics that you fried. What has happened is that you have connected the battery backwards. This is likely to be an expensive mistake.

what he said X 2.

Somehow the terminals got reverseed when you hooked up the battery. While 12 volts sounds like no big deal, the reality is that a car battery can pack a lot of punch. There are a lot of amps in them 12 volts and when things are connected wrong you can have very hot wires, sparks, and fires, all from that shoe box sized 12 volt battery.

Are you sure you connected the terminals correctly?

It sounds like you reversed the polarity, which would not be good for the car or your friendship with its owner.

I don’t think the order of connection is the problem, although you did that backwards, too.

Take a closer look at the battery terminals, and see which is positive and which is negative, then tell us whether you hooked it up correctly or not.

We’ll never hear from this guy again.

Probably b/c he just got beat up by that guy who used to be his friend.

The Volvo is toast but maybe you could get something for the battery…

Thanks all, but the polarities are not mixed up. Unless they were labeled incorrectly on the battery. We’re taking it to a mech.

You could put a meter on the battery to qyickly determine if the polarity is reversed.

If the polarity is ok (the red wire ties to the positive post and black wire to negative post) then from what you say there may be a short on the main cable to the starter solenoid. I once ran into a similair problem where the stud bolt for the main cable connection to the starter solenoid got turned. The square head of the bolt inside the solenoid turned enough to contact the case ground and shorted the lead. By just turning the bolt back slightly the short to ground was cleared. The case of a simple problem that caused a lot of sparks.

Another possibility is the solenoid and starter are somehow jammed in the on position and that would basically cause the same kind of thing.

You can’t begin to count on the battery cable wire colors to tell which is positive and which is negative. Many auto makers do not follow the red/black convention, and it’s always possible that someone had to replace the cables on this car in the past. That someone may have used red for negative and black for positive because that we the cable colors they had in the right lengths.

Trace the wires. The negative will go to the metal of the car somewhere (usually near the battery), and the positive usually goes off to an electrical junction box or to the starter.

Assuming polarities were correct when the battery was hooked up, the negative/ground cable should always be connected last. If the negative cable is connected first, there is the possibility of creating a short when the positive cable is connected, i.e. if the wrench is grounded to the frame when tightening the nut on the cable.

I did this installing a battery in a 1969 Buick, I almost welded the wrench to the frame when it shorted. The amount of current flowing through the short is more than enough to fry the electronics on a newer car