Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Seamas]

I nearly just cooked myself to char trying to wire these two 12v batteries together like a damned fool.

So there are these three PA's in my garage that have dead batteries in them, and it fell to me that I had to get them fixed.  Says I, "I'll just go ahead and buy replacement batteries and put them in myself!"  I could send them to the company that makes them (these are Liberty 4500's by Anchor Audio) but that would cost a lot of money and time is of the essence.  This job needs to get done ASAP.

I don't know much about electricity, which is probably why I had the foolhardiness to go ahead and try to do this on my own. 

I bought the batteries, brought them home, and proceeded to wire them up as they were wired before I started tinkering.  I take my first battery, connect the positive (+) to the negative (-) of the second battery, and all seems well.  Let me note now that in retrospect the battery terminals (little metal strips sticking out of the battery) seemed just an iota too wide for my cable that I had  taken out of the PA wiring, which had previously connected the batteries.  Using a pair of needlenose pliers I pried the metal bits at the end of the cable just a millimeter wider in order to snugly affix them to the respective terminals.  If this was stupid, let me know now please.

With my batteries wired together, and prepared to insert them back into the housing to connect the (+) and (-) cables leading into the PA system, I bent over the PA housing, starting bumbling them into place with one battery in each hand, when POW!  The freaking things just exploded in sparks and menacing electric sizzle - the cable was ejected from the batteries and dropped to the ground, glowing like molten iron.  Foul smoke erupted from the PA box wherein I had, in terror, dropped the batteries upon their unexpected explosion and ran like a little girl.

The smoke has subsided and I have sorted out the wreckage.  Now that my heart palpitations have subsided and my breathing is back to normal, I'm annoyed that I wasted $65 on two now-fecked 12v batteries, irritated that I have still not fixed my PA's and possibly destroyed one of them, and frustrated that I screwed up this seemingly straightforward technical job. 

My question to you is: what went wrong?  If I could at least understand how I fucked this up exactly I would feel much better.

[10ebbor10]

You might have short-circuited your battery. Never make a closed loop before there's something utilizing the power in there.

Though probably, you used wrong voltage batteries, hence why it was the PA system that fried, rather than the batteries, or the wire. My bad, apparently the batteries fried. Probably a short circuit then

[Pnx]

I bought the batteries, brought them home, and proceeded to wire them up as they were wired before I started tinkering.  I take my first battery, connect the positive (+) to the negative (-) of the second battery ...

I'm really not an expert on electrics, but this doesn't seem right to me, you're sure that's the way they were wired when you found them?

[10ebbor10]

I bought the batteries, brought them home, and proceeded to wire them up as they were wired before I started tinkering.  I take my first battery, connect the positive (+) to the negative (-) of the second battery ...

I'm really not an expert on electrics, but this doesn't seem right to me, you're sure that's the way they were wired when you found them?

It's serial wiring, which doubles the voltage, rather than parallel, which increases lifetime. Switching those up could result in interesting situations.

[Pnx]

I bought the batteries, brought them home, and proceeded to wire them up as they were wired before I started tinkering.  I take my first battery, connect the positive (+) to the negative (-) of the second battery ...

I'm really not an expert on electrics, but this doesn't seem right to me, you're sure that's the way they were wired when you found them?

It's serial wiring, which doubles the voltage, rather than parallel, which increases lifetime. Switching those up could result in interesting situations.

Huh, I guess I have seen batteries connected in serial before, but I really don't understand how exactly that actually works. I mean aren't you creating two seperate circuits?

[10ebbor10]

Not really. Most batteries are actually serial connected smaller batteries stuffed into a casing.

[Pnx]

Not really. Most batteries are actually serial connected smaller batteries stuffed into a casing.

That's just giving me more questions!

Which just goes to show I really don't understand how batteries work at all.

[LordSlowpoke]

Not really. Most batteries are actually serial connected smaller batteries stuffed into a casing.

That's just giving me more questions!

Which just goes to show I really don't understand how batteries work at all.

Define questions.

* LordSlowpoke dusts off a high school physics textbook

[Seamas]

You might have short-circuited your battery. Never make a closed loop before there's something utilizing the power in there.

Hmm, I see.  So connecting those two batteries was the last thing I should have done, rather than the first? 

In correct order it would have been to wire the negative of one, and the positive of the other, to the PA system and THEN gone about connecting the remaining terminals together, uniting the batteries.

BTW, in retrospect the PA is not fried, but I did incinerate the little cable that came with it to connect the batteries, so now I have to find one of those.

The batteries I bought - are they still serviceable or does this jinx them permanently?  Each terminal (that was connected with the wire) now has what looks like a big bite taken out of it.  About 30% of that part just blew off the batteries.  Once those things are screwed up, the whole battery has to be canned, right?

[10ebbor10]

You might have short-circuited your battery. Never make a closed loop before there's something utilizing the power in there.

Hmm, I see.  So connecting those two batteries was the last thing I should have done, rather than the first? 

In correct order it would have been to wire the negative of one, and the positive of the other, to the PA system and THEN gone about connecting the remaining terminals together, uniting the batteries.

BTW, in retrospect the PA is not fried, but I did incinerate the little cable that came with it to connect the batteries, so now I have to find one of those.

The batteries I bought - are they still serviceable or does this jinx them permanently?  Each terminal (that was connected with the wire) now has what looks like a big bite taken out of it.  About 30% of that part just blew off the batteries.  Once those things are screwed up, the whole battery has to be canned, right?

I assume so. However, if I'm wrong, and it's a problem with the voltage, or with parallel rather than serial connection, connecting them to the PA first will probably result in it being fried if something goes wrong. So better make sure you're using the correct voltage and configuration.

If you incinerated the cable, it's possible that you put to much power through it. Might want to look for a slightly thicker one.

And yeah, that battery's toast. Quite possibly it's entire interior has melted, and one of the cells actually exploded. Might start leaking, so watch out with it. That stuff is fairly acidic.

[Pnx]

Define questions.

* LordSlowpoke dusts off a high school physics textbook

I don't know, my understand was electricity works because at one end there's something that really wants electrons, and at the other end you've got something that really wants to get rid of electrons, and they make an exchange through an indeterminate number of intermediaries. The electrical circuit is then all about exploiting the mechanics of the intermediaries for fun and profit.

With this you're basically telling me that you can connect a whole bunch of positives and negatives together, and they'll still go through the intermediaries? How does that work?

[10ebbor10]

Because it's not the electrons that are getting exchanged, but the ions and anions. The electronics just move to reestablish the equilibrium.

[Zrk2]

Sounds like you shorted your batteries, and/or overloaded your speakers, ruining them.

[DJ]

I'm guessing your + and - cables touched directly while you were trying to connect them to the PA. Always connect the thing that's using power before connecting power.