What happened to my car battery?
May 26, 2010 7:26 PM   Subscribe

Yesterday my car started fine, but today the engine wouldn't crank even once. What caused my car battery to fail so suddenly and without warning?

I have a 5+ year old Toyota Camry, and until today I used the original factory battery with no problems whatsoever. This morning it wouldn't start (the dash got some power, but the engine wouldn't crank), so I had to get a jump. I let the car run for an hour and a half to charge, but that did no good, and I had to get another jump to take it to the shop to get the battery replaced.

When my car was in the shop, they ran a battery test on my old battery. Here are the results:

Replace Battery
Rated CCA: 582
Measured CCA: 366
Measured Volts: 12.78
Degrees F: 121
State of charge: (a gauge reading ~87%)
State of health: (a gauge with the needle towards low, at about 25%)

I'm curious about how my battery might have failed. I've had batteries fail on me before, but it was always during cold weather, and they always managed to crank the engine even though they couldn't start it. I was expecting some warning sign, like noticeable difficulty turning over the engine, not a sudden and near complete failure. The service rep I spoke to said he couldn't really offer an explanation, besides saying the battery needed to be replaced.

Automotive geniuses, what could have caused my car battery to fail so suddenly and without warning?
posted by cosmic.osmo to Travel & Transportation (18 answers total)
Left your lights on or door open last night.
posted by Xurando at 7:27 PM on May 26, 2010

Response by poster: According to the dealer's test, the battery was close to fully charged, and it still wouldn't crank my car's engine. The CD Player/accessories were powered, but the only things that would happen when I tried to start it would be a single quiet click and my dash and indicator lights would dim and flicker.
posted by cosmic.osmo at 7:32 PM on May 26, 2010

Yeah, this has happened to me when the light in the boot (it was a rental, I didn't even know there was one there) stayed on as the door had shut but not all the way. A friend also had a car with a faulty latch for the passenger door light, so it stayed on permanently. Maybe check those to see if any are on when the car's shut? If so, just disconnect the battery until you can fix the light.
posted by twirlypen at 7:33 PM on May 26, 2010

Response by poster: I should also call out that I already got the battery replaced. When it was charged it still wouldn't start the car.
posted by cosmic.osmo at 7:36 PM on May 26, 2010

If the CD player works and the other electrics work (lights? horn?) I'd be looking at the starter motor or the connections to it, rather than the battery.
posted by Fiasco da Gama at 7:45 PM on May 26, 2010

Best answer: Usually it's due to a cracked plate or grouping bar; probably a cracked plate since the (presumably open-circuit) voltage read a near-normal 12.78V, but the "state of health" (presumably voltage under load) was low.

Modern batteries tend to fail in this fashion (and fairly quickly - I once had one that started the car, drove me home for lunch, locked the doors, but didn't have enough grunt to unlock the doors 30 minutes later) because they use much purer lead than they used to. Once upon a time, lead-acid batteries used in situations where vibration was an issue (e.g. moving vehicles) used lead alloyed with a small amount of other metals (e.g. antimony) to add strength; stationary batteries used pure lead. Car batteries like that 'wore out' quicker chemically, but were physically stronger than the pure-lead batteries. Modern batteries use purer lead without the strengthening alloy (primarily to aid manufacture and recycling), so tend to fail physically & quickly rather than chemically & slowly.
posted by Pinback at 7:55 PM on May 26, 2010 [1 favorite]

It isn't the battery, it's the starter. More specifically, probably the solenoid in the starter that is refusing to actuate. How a shop could have missed this is beyond me because 2 out of 2 tow truck drivers correctly identified the starter as the problem on my car when I had the same set of problems you do.
posted by 517 at 7:56 PM on May 26, 2010

Best answer: It isn't the battery, it's the starter.

If getting a jump start allowed the engine to crank then the solenoid is working fine. He even says he can hear the click of the solenoid.

What has happened is that the battery's internal resistance has gone up due to a cracked plate, which means it still puts out the correct voltage under minimal load, but once a serious current is required by the starter motor the voltage drops way down.
posted by Rhomboid at 8:09 PM on May 26, 2010 [1 favorite]

Best answer: If the CD player works and the other electrics work (lights? horn?) I'd be looking at the starter motor or the connections to it, rather than the battery.

It takes a lot less energy to run a stereo than it does to crank an engine. Symptoms described are classic dead battery symptoms.
posted by knave at 8:11 PM on May 26, 2010

I know that technology has improved since the 80s, but my father always taught me a battery had 3 good years in it, and after that it's a gamble every time you turn the key. (Which reminds me my car is a 2006 with the original battery and I should probably do something about that.)
posted by Lyn Never at 8:16 PM on May 26, 2010

Just to add a few more ideas:

1) If the jump worked then the starter / solenoid is ok. However, that does not mean HIS car's ground is ok. Corroded / broken main ground / transmission to frame ground are real possibilities;

2) nth the dead battery - bridged plates due to corrosion, cracked plate, boiled out electrolyte all can result in 12+ volts at minimal load but far less at full CCA load.

I'm voting for a bad ground. Let's enough current through to run the auxiliaries but not enough to handle full starting amperage. Remember - when you are running the starter it's nearly the same amount of current as used to weld metal, i.e., the correct nomenclature for it is "a F@#$@# shitload" of current.

Time for some ground strap sleuthing, seems to me.
posted by BrooksCooper at 8:19 PM on May 26, 2010

I got Pinback's exact explanation from my mechanic four days ago after getting the battery replaced due to a very similar failure. My battery was going flat within two days of parking the car. I just drove it an hour ago, no issues.

I was hugely relieved; before taking it to the mechanic I attempted to self diagnose and measured a 1.5 amp draw on the battery half an hour after the car was turned off, leading me to fear that I had some sort of power-off drain due to a short. Which could possibly be very expensive. It turns out that the low voltage from the bad battery was causing the alarm circuit to stay on because other components were not getting enough voltage to power down correctly. This was, of course, exacerbating the battery drain. Also, the alarm circuit is apparently aware of the hood being opened and it is necessary to disconnect a switch sensing that before an accurate power-off reading can be taken. I'm slowly accepting that I simply cannot work on this new car like I did the old beater I used to own.
posted by Derive the Hamiltonian of... at 8:30 PM on May 26, 2010

Best answer: nthing dead battery.

A battery might look like it's healthy, putting out 12.7V with minimal load, but the starter is the real test of a battery's health - nothing a battery does during the course of its' operation is anywhere near as demanding as getting the motor started.

When you turn the key, the battery has to:

1) Provide the starter motor with enough juice to get it to rotate the camshaft at ~ 500RPM, which means moving 4-6 pistons (in the case of the Camry) through their cycles, with all the resistance caused by cold oil, compression, etc. Extremely high amps, but low voltage.

2) fire 4-6 sparkplugs in sequence. Extremely high voltage, but not a lot of amps, if I remember correctly.

3) Power your stereo, lights, engine computer, butt warmer, etc

4) Do all this until the motor turns over, at which point you still have to power #2 & #3, but at least the starter motor draw is over.

5) Keep supplying the juice until the alternator kicks in to start recharging the battery (which in cars is generally at idle, if I remember).

My motorcycle's motor is tiny compared to a car's (650cc v-twin), and its' starter motor draws something like 60 amps. If I remember correctly, automotive starter motors are drawing in the range of 150 amps. I do know you've got far more cylinders, and they're a lot larger than mine.

Rhomboid nailed it - there's enough juice to get things lit up, and to activate the starter solenoid, but the moment you put the load of the starter motor on it, not a chance. Classic dead battery.
posted by swngnmonk at 9:49 PM on May 26, 2010

Not to be pedantic but all non-essential accessories like blower fans, stereos, and butt warmers are disabled while cranking; the main force to overcome is the crankshaft not the camshaft, though they're linked so it's really the sum of both; and the alternator is active whenever the motor is turning, not just at idle.
posted by Rhomboid at 10:26 PM on May 26, 2010

the main force to overcome is the crankshaft not the camshaft, though they're linked so it's really the sum of both; and the alternator is active whenever the motor is turning, not just at idle.

While we're getting pedantic....

Yes, the crankshaft is kind of one of the main source of friction, maybe, but it's turning the engine over that's hard - you can't separate it out. The larger individual friction element will be the dry piston rings on the cylinder wall, not the crank bearings, but being as they are connected to the crankshaft, it's impossible to blame one major problem. One of the significant drags on turning a cold engine is pumping cold oil (the pump is driven by the crank) into the small gaps between the bearing shells and the crank/camshafts when heavy components have settled. Also, the oil pump needs to generate and hold a significant pressure throughout the whole engine, and flowing cold oil volume to create this pressure is hard - especially at cranking speeds.

Also, the alternator is not necessarily 'active' whenever the engine is turning. It has a very different loading (and hence power production) depending on rotation speed and doesn't produce any significant voltage at cranking speeds. Some alternators don't produce charge at all (by not energizing the coil) until a minimum RPM to help cranking loading.
posted by Brockles at 7:26 AM on May 27, 2010

Best answer: You need a battery. 336 measured amps isn't much. Using labscope testing, I've measured peak initial starter current draw at over 600 amps on a 4 cylinder engine (the battery had a 700CCA rating, if I remember correctly). Most battery testers, or even voltmeters, aren't accurate enough to catch that initial draw when the contacts close and the starter begins to spin from a dead stop. The min-max feature on my Fluke 87-V can't even pick up the extremely breif (but huge) amp surge that gets the starter turning. My scope, on the other hand, picks up the amperage spike and that testing has really proved to me how critical battery health is and how misleading those dummy testers can be.
Five years is the average life-span of an automotive lead-acid battery.
posted by Jon-o at 9:41 AM on May 27, 2010

Make that 700 total amps, not CCA
posted by Jon-o at 10:05 AM on May 27, 2010

Heh. This is funny timing. My father ALSO has a Toyota Camry, I think about 4-6 years old, and yesterday he drove about 3 miles to go pick up my kids after their after-school activity, and when he turned the car back on 5 minutes later to drive them home, the car would not start. We tried jumping it with two different cars and two different sets of jumper cables, and it would not jump. Something happened to it in just a 5 minute stretch of time to render the battery nearly dead.

I say nearly dead because roadside assistance with some sort of superduper battery was able to jump it and he could drive it home. This morning, after being on a trickle charge all night, it was still dead. So we got a new battery and he seems to be fine now.

It seems curious that it would be fine and then 5 minutes later be not at all fine! But according to the above responders... it's, um, normal.
posted by molasses at 1:00 PM on May 27, 2010

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