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sweaty 11-25-2008 05:37 PM

Battery Problem
 
I got a new battery from AAA (Exide) 18 months ago for my 2001 Nissan Sentra SE 2.0. Lately, the crank got weaker and weaker and then it would not start. AAA came, tested the battery, and said it was good. They jump started it. It ran fine for a couple days, now it did the same thing today, not starting. I cleaned the terminals and cables with the right tool, no result. I tried to jump start it with my other car, but it would not even crank.

What is the problem?

slickshift 11-25-2008 06:20 PM

A battery can check out "good" with both types of tests, and still be faulty
Though it could be a short someplace, I'd replace the battery with a known good one and see what happens
Chasing down a short can be a long and laborious process, get the faulty battery possibility out of the way first

Winchester 11-25-2008 07:16 PM

Clean all connections thoroughly and replace any corroded connectors and/or wires before replacing the battery. Those battery testers will normally tell you if you have a bad cell or something shorting out. If AAA says it's good I'd take their word for it and checking the connections first. Won't take a but a little time to do this to confirm or deny.

Best of luck. :thumbsup:

Thalweg 11-26-2008 12:15 AM

I wouldn't necessarily blame the battery. I'd assume that AAA did a load test on the battery. If it passes a load test, I'd be reasonably confident that it was good. To be sure, you can take the battery to most good auto parts stores and they will retest it. Make sure it's a load test.

However, I'd be more suspicious of a charging system problem, most likely an alternator. It sounds like the battery may have gotten a quick charge when AAA jumped it. That suggests to me that your starting system must be in pretty good condition, as it started for a while with very limited charge. But I could be very wrong about that. Your starting system could be in poor shape, which can seem like a dead battery as there might not be enough battery power to overcome high resistance in the starter (or battery cables, or solenoid, etc.)

I'd start by getting your charging system checked. Some auto parts stores will do this for you free in hopes that you'll buy parts. If not, it shouldn't be too expensive. If you want to do this yourself, get yourself a book and a multi-meter. It's not necessarily easy to interpret the tests, and if you don't know what you're doing, you can fry your multi-meter. By the way, you can't test a battery with a multi-meter. At a minimum, you can check your battery cables. There should be very low resistance across the cables. I don't remember the specs, but it seems like it's supposed to be less than 10 ohms per foot of cable, but don't quote me on that, automotive school was a lot of years ago. Also, do a visual inspection on the battery cables. If you see corrosion moving up the cable, under the insulation, replace the cables. Also make sure your battery connections are good and tight with good continuity. You can make sure you've got good negetive continuity by checking resistance between the negetive battery terminal and an engine or body ground. DON'T do this on the positive side.

Good Luck,

Rehabber 11-26-2008 11:01 AM

You CAN test the state of a batterys charge with a voltmeter/multimeter. 12.45 volts or more is a fully charged battery. 12.25 v or less and the battery needs to be recharged. However this will not give you any indication of the battrys cranking capacity.

47_47 11-26-2008 01:04 PM

Quote:

Originally Posted by slickshift (Post 190117)
A battery can check out "good" with both types of tests, and still be faulty

Quote:

Originally Posted by Winchester (Post 190154)
Clean all connections thoroughly and replace any corroded connectors and/or wires before replacing the battery.

Quote:

Originally Posted by Thalweg (Post 190277)
I'd be more suspicious of a charging system problem, most likely an alternator. It sounds like the battery may have gotten a quick charge when AAA jumped it.

I'd start by getting your charging system checked.

Quote:

Originally Posted by Rehabber (Post 190411)
You CAN test the state of a batterys charge with a voltmeter/multimeter. 12.45 volts or more is a fully charged battery. 12.25 v or less and the battery needs to be recharged. However this will not give you any indication of the batterys cranking capacity.

All of the above or you may have a short. I'd have the car tested. If all test ok, replace the battery, you may have a weak cell, not being picked up on the load test. If the battery has removable vent/fill caps and you have a DVOM, you can test for a weak or shorted cell.

slickshift 11-26-2008 06:52 PM

All good advice

However, in response to some of the replies, I'd like to say that I've personally had more than one battery test good (voltage and load) by myself, AAA, Autozone, and trusted local auto service personnel who all shrugged and said "tests good", and then the problem never appeared again after (in desperation) I switched to a new or known good battery

I'm not saying this is the problem
I'm just saying it may be easier to swap out the battery than to try and find a loose starter connection, or short in the trunk light on a modern Japanese engine ('71 Olds Cutlass would be a different story)

At the very least, it will eliminate that scenario and one can begin trying to find the starter and other "short list" potential problem wires on that thing

Sammy 11-27-2008 07:30 AM

I agree with Slickshift...

I have had new batteries pass the load test at the auto parts store but still fail... Including intermittent no start/start like a new battery within 20 minutes of each start attmept.

Best way I have found is to test each cell with a battery hydrometer.
Looks like an anti-freeze tester and available at the auto parts store for a few bucks. Just be careful with the acid.

Quick basic charging system check can be done once the car is running by measuring voltage between the positive battery terminal and a ground on the engine block... Should read 13 plus volts if good.

Thalweg 11-30-2008 09:25 PM

OK, I dug out my old automotive electrical textbooks to get the straight story and refresh my memory. The best information will come from specific gravity (SG) measurements with a hydrometer. This obviously requires that you can access the cells through caps on the battery. If it's one of those maintenance free batteries that are sealed, you're out of luck. If you're in a cold climate, the SG should be about 1.280 in each cell for a 100% charged battery, 75% charged should have SG of 1.230, 50% charged should have SG of 1.180, 25% charged should have SG of 1.130, discharged should have SG of 1.080.

An SG difference of 0.025 or more between individual cell readings indicates that the battery is starting to fail due to internal shorts, normal deterioration from age and use, loss of acid, etc. If the highest cell SG is below 1.190, charge the battery and retest.

You can do some tests with a voltmeter, but not across the terminals. The battery will develop a surface charge that will read on a voltmeter, but doesn't tell the real voltage of the battery. I've seen readings up to about 16 volts, but 14 is about normal. Back when I was doing this for a living, if a customers battery was in the neigborhood of 12 volts, we considered the battery pretty much dead and knew there was a problem somewhere. Anyhow, voltage measurements across the the terminals might tell you something, but they may also be very misleading. If you're making judgements based on these measurements, you might be going down the wrong road. However, if you can open your cells, measure voltage between the cells (in the electrolyte) and the battery case (don't forget to clean the probes afterward). This is called an open circuit voltage test. If the cell voltages are below 2.06 volts per cell, recharge the battery. If individual cells vary by more than 0.5 volts, the battery needs to be load tested. The open circuit test correlates directly with the SG test, and therefore may not be of great use if you've got good SG measurements.

A load test (also called a capacity test) is by far the best way to test a battery. The problems people have with them usually come from not doing it correctly. To do a load test, the SG of the battery must be over 1.220. If it is less, the battery should be trickle charged (NOT fast charged) until the battery is fully charged. Then apply a carbon pile load tester for 15 seconds and measure battery voltage. Voltage of 9.5 V or more indicates ample capacity, and if the SG was over 1.220 before testing no additional service is required. However, if the SG was below 1.220 before load testing, and the battery WAS charged, you've either got a problem with the charger or the battery is probably toast.

There are a couple more tests that you can follow past this point, but I figure that if we can't get the SG up to specs, it won't take a charge, and fails a load test, we're wasting time. The battery is gonzo.

47_47 12-01-2008 09:29 AM

Quote:

Originally Posted by Thalweg (Post 192026)
However, if you can open your cells, measure voltage between the cells (in the electrolyte) and the battery case (don't forget to clean the probes afterward). This is called an open circuit voltage test. If the cell voltages are below 2.06 volts per cell, recharge the battery. If individual cells vary by more than 0.5 volts, the battery needs to be load tested.

There are a couple more tests that you can follow past this point, but I figure that if we can't get the SG up to specs, it won't take a charge, and fails a load test, we're wasting time. The battery is gonzo.

Good expaination, a fully charged battery will read 12.6 volts or 2.1 volts per adjacent cell. Also test between the end cells and the battery posts and combine both of these readings. The voltages should not vary by more than .1 volt or the battery is junk. This test is only meaningful if you didn't just add water to the battery. Also the electrolyte should just have a faint odor. If there is excessive hydrogen sulfide gas (rotten egg) the battery is junk.

I too am leaning toward a battery, but just wanted the op to know what else could be wrong.

sweaty 12-15-2008 12:36 PM

The starter was replaced and it worked. I appreciate everyone's help.

rjordan392 12-15-2008 07:32 PM

For what its worth.

To slow down early breakdowns of the starter or charging system, replace the battery one year prior to its warranty expiration to be safe. A battery that does not accept a full charge will make the starter and charging system to work harder. Some who try to keep their batteries beyond the warranty period usually end up with these problems.


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