What went wrong when I tried to replace my car battery?
August 19, 2009 11:28 AM   Subscribe

I just changed my car's old dead battery with a new, just purchased one following the directions here. Even though I clamped the connectors down hard enough that I can't move either of them, the car seems to be completely dead --- it doesn't appear to be getting any power whatsoever. Any ideas what could be wrong?

Long extended explanation, just in case people are interested / think there's a larger problem:

We have two cars, and one of them hardly ever gets used. Last time I used it was in May, after it had been sitting unused for probably several months. When I left home, it had trouble starting up (but ran fine once it started); and I needed a jump to get it started coming back. I tried to start it again the next day, and it wouldn't start.

So I ignored the problem until today. Tried to start it up again, and got some lights to turn on, but the engine wouldn't go. I jumped it with the good car, and it ran fine; I let it run for about 40 minutes (with the engine running above idle for at least 15 minutes that time). Then I turned the car off and immediately on again, but it still didn't start --- if anything, it seemed more dead than before.

I concluded the battery couldn't hold a charge, so I went and bought a new one. I followed the directions, but the car is now completely unresponsive; I see no evidence that it's drawing any power whatsoever.

I'm assuming I installed the battery incorrectly. Does that sound plausible, and if so what should I do about it? If not, what should I try instead?
posted by jacobm to Travel & Transportation (23 answers total)
It could be that the cable from the battery to ground is bad. When you jumped it, did you attach the negative wire to the engine block? With a good positive wire to the battery and a bad ground wire, the car would start then, but the battery wouldn't charge. And even with a new battery not enough current would get to the starter.
posted by Killick at 11:35 AM on August 19, 2009

Response by poster: I did attach the negative wire to the engine block, yes. But if that's what's going on, why would I be getting no current from the new battery when I was getting a least a little current from the old battery?
posted by jacobm at 11:38 AM on August 19, 2009

Tighten the nut holding the negative battery wire to the car body. But another thought: Did you hammer the battery connectors down on the battery posts? Because you shouldn't do that. It can damage the plates inside the new battery and short it out.

It is also possible someone sold you a new battery that wasn't charged.
posted by weapons-grade pandemonium at 11:45 AM on August 19, 2009

Are you 100% sure that you connected the new battery correctly?
posted by Brockles at 11:56 AM on August 19, 2009

You have an open circuit somewhere. It is possible that the jiggling of the cables during the battery switch caused the final bit of connectivity they had to be lost. If the battery is known to be good (you can always hook it up to the other car and see if it starts that one-or put a voltage meter across it-it should read at least 13v on a new battery) then completely inspect the cables. Check the connections at the terminal ends of the battery than check at both the ground location and the starter. They can corrode just like a battery does. If you have a multimeter check the resistance of the cables-they should be 0 or very low. If all of this is good you probably have blown a fuse somewhere. Get the manual to locate the fuses and check the fusible links first than start working your way through the big fuses that are usually in the engine compartment near the battery. Once again use the multimeter to test the resistance, should be 0 or very low. I have blown a fusible link when jumping a car and managed to buy another one really cheap when that was all that was wrong with it(well all that kept it froms starting...). If you don't have some idea about how car electrical system work you might want to get a professional on it-you can damage some very expensive parts by shorting out electrical systems.
posted by bartonlong at 11:57 AM on August 19, 2009 [1 favorite]

To clarify, if you connected it + to + and - to - and it was the correct battery for the vehicle, then something (like a loose earth lead) is fundamentally wrong.

The only way the car can be totally non-responsive is for there to be no electrical circuit - even a badly connected battery should give s ome sign of life (smoking, clicking or some other dim bulb glow) and a completely 100% flat battery from a store would be more than unusual.
posted by Brockles at 11:59 AM on August 19, 2009 [1 favorite]

hmm maybe the aleternator is dead.
posted by majortom1981 at 12:04 PM on August 19, 2009

Did you clean the terminals thoroughly before installing the new battery? It's possible to totally drain a battery if your terminals are rusty - speaking from experience unfortunately - if that's the case you'll need to clean them with a wire brush, re-attach the battery, charge it and try again.
posted by leslies at 12:19 PM on August 19, 2009 [1 favorite]

Was there corrosion on the old battery posts? If so, did you clean the contacts before installing the new battery? They might just be cruddy and not getting a charge.
posted by The Light Fantastic at 12:20 PM on August 19, 2009

wow...jinx, leslies! And "terminals" was the word I was looking for...
posted by The Light Fantastic at 12:22 PM on August 19, 2009

Did you have the auto parts store actually test the battery to confirm it was the problem?
posted by COD at 12:30 PM on August 19, 2009

Best answer: hmm maybe the aleternator is dead.

The alternator has nothing to do with this problem. A new battery should start up a car even if the alternator is completely missing.

I'd say the most likely thing is that the store neglected to charge the battery before selling it to you. They don't come charged. Do you have a voltmeter? It's the easiest way to get to the bottom of this.

(Forgive me if this sounds incredibly stupid, but is there any chance you forgot to remove the plastic caps on the posts before reattaching the clamps?)
posted by Rhomboid at 12:31 PM on August 19, 2009

(Er, "they don't come charged" was meant to imply that the store has to do it before they sell it to you, not that they should sell it to you in a dead state.)
posted by Rhomboid at 12:33 PM on August 19, 2009

So you completely pulled out the old battery, and then reattached the new battery, and there was a period of time where there was no battery or anything?

It is to some degree possible that you've locked yourself out via the onboard security system. This is why autoparts stores often either temporarily bridge the connection with a portable jump-start device or by plugging a battery into your cigarette lighter.

It does sound like a bad ground, possibly a rodent-chewed line or a crimp that's come loose and now your neg terminal isn't making good connection with your neg line, which you bypassed on the jump.

I'd grab a multimeter and see if the new battery was putting out any voltage at all. You're looking for ~14V.
posted by TomMelee at 12:40 PM on August 19, 2009

But if that's what's going on, why would I be getting no current from the new battery when I was getting a least a little current from the old battery?
Hmm, I'm not sure. If the only problem was a bad ground cable, then it does seem like if you were getting some current before (clock, lights, whatever) then I think you're right that you should still be getting some current after you installed a new battery. A bad cable is still something I would check for (actually if you don't have a multimeter then you might just want to buy new cables anyway, as they are not that expensive and they do age) but there might be something else going on here.
posted by Killick at 12:59 PM on August 19, 2009

Response by poster: I had to go to work, so I can't test the battery with a voltmeter yet. In the meantime, here are some followups:

Brockles: I'm not 100% sure I connected everything correctly, but if I did something incorrectly I don't know what it was. I'm sure I attached positive to positive and negative to negative --- I checked that several times. I also know that I attached the connections solidly enough that they won't move when I pull them.

leslies: I cleaned them, but not super-thoroughly. When I took them off, they looked like they had some corrosion on them, but they weren't giant rust-balls or anything.

COD: No.

Rhomboid: I am 99% sure that there weren't plastic caps on the posts when they gave it to me at the store, but since I don't have it in front of me right now I can't say with 100% certainty. I wouldn't put myself above missing something like that :)
posted by jacobm at 12:59 PM on August 19, 2009

a bad alternator could be causing the problem. in it's poor state, it may be causing the open circuit.
posted by lester at 1:04 PM on August 19, 2009

The alternator is wired in parallel with everything else in the car. There's no way that something in parallel can cause an open circuit to other things that are in parallel.
posted by Rhomboid at 1:11 PM on August 19, 2009

Rhomboid is correct - even if if the alternator was able to cause this issue, then jump starting the car with the aid of an additional battery would also be impossible as it would not rectify the supposed 'alternator open circuit' that people are mentioning.
posted by Brockles at 1:37 PM on August 19, 2009

Is the transmission in Park?
posted by Iron Rat at 4:09 PM on August 19, 2009 [1 favorite]

Response by poster: So, ummm .... turns out there was still a plastic cap on one of the terminals.


Let's all just pretend this little discussion never happened.
posted by jacobm at 5:37 PM on August 19, 2009 [1 favorite]

Occams Razor for the win.

also, KERPWNT.
posted by TomMelee at 6:45 PM on August 19, 2009 [1 favorite]

one terminal makes it worse--it means you remembered to remove one of them.
posted by lester at 5:22 AM on August 20, 2009

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