Battery sudden death? Safe to jump?

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Sep 1, 2014
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denver, co
I think my battery just died: started up just fine, drove to the sandwich shop, came out 5 min later---a couple solenoid clicks then nothing. Not even enough power to roll up the electric windows without me manually helping each one. Reading another thread on BITOG, it seems like something has shorted inside the battery. If this is in fact the case, should I bother trying to jump start it? Or is that ill advised? Applying voltage across a short is something I want to avoid.
 
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The short will be lead dendrites or sludge. I've jumped successfully in similar cases when it's the first time. Usually gets you home, then fails completely just when you start thinking "maybe it's alright"
 
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I just had a battery die at the shopping center and leave me stranded. I jumped it to get home and charged it over night. The next day it was still dead. Autozone tested it and replaced it with a new one, no charge. It was about 6 months old when it died. I made no changes and the new one has been working fine for about a month. In other words the alternator and connections were all okay. I have no idea what the exact cause was but I'm watching the new one very carefully.
 

JHZR2

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Yes you can jump it. It may or may not jump depending upon the impedance of the short inside (how much energy dissipates via the short). If a cell is in reversal, you may not even ovecome. I had a shorted cell once that wouldnt jump via the solenoid, but when I manually jumpered the starter solenoid, it started up. Shorted cells will dissipate alternator energy too, so youre risking a battery thermal runaway situation. Lead acid battery fires are not pleasant. Id swap the battery asap regardless.
 
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I've had batteries die suddenly with little prior warning. The OEM battery in our '99 Accord got margianl one day, so my wife and I set out for a replacement. The battery started the car in the driveway, and after driving about nine miles and the shutting the car off, I had to push start it to get it running. Good thing it was a stick. On another occassion, the BMW started just fine in the driveway. I pulled it out into the street to move another car. It would then not restart. Fortunately the street is a slight downgrade and as long as you have a hill to work with, you're never really stuck with a stick.
 
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Your battery could have had a catastrophic failure called a Bad-cell. A car battery has 6 cells, each developing 2.1 volts, and are connected in series to make a "12" volt battery. The technical cause of a bad-cell is......bad luck. You can safely jump it, but because a cell had become non-operational, the battery can never be more than 5/6th of its' capacity. If its' still under warranty, they'll test it and make sure. If you are a AAA member, your club may offer mobile battery service. They can give you a definitive answer on the health of the battery.
 
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My only caution would be that if you DO decide to jump-start it, be extra careful to make your last connection far, far away from the dead battery so that if there's a spark its well away from any venting hydrogen. Making the last of the 4 jumpstart connections to the engine block (or unpainted bolt on the chassis, or remote ground lug) on the vehicle with a GOOD battery is generally the safest thing to do. I really like the fact that so many modern vehicles have jumper cable lugs located well away from the battery.
 

grumpyoldman

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Sep 1, 2014
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denver, co
Thanks for the great advice, everyone. I didn't smell any sulfur, but I'll check again before the jump attempt. The connections are the first thing I checked. I could only do it visually & shaking them with my hand; they seemed pretty solid. I understand making the last connection to ground on the good car being the safest; thanks for the reminder.
 
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But what are you expecting? Your alternator will be forced to put out full power to try and charge a dead battery. That is not a great thing for an alternator. Best is to try and charge it with a AC charger or get a new battery rather than trying to jump it.
 
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Flatlands of Indiana
I suffered a sudden batery death last winter in my Tacoma. Satrted fine at work, drove home, parked at the end of the drive so I could clear the snow we got that day. Went to pull it forward, it wouldn't even drive the dome light.
 

grumpyoldman

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denver, co
Epilogue: I jumped it (started right up), drove it 0.5 miles home (during that two minute drive, a little electrical screwiness: the airbag light came on briefly), put a voltmeter on while the car was running (a pretty steady 14.2 V), turned the car off, measured the battery voltage (12.8), started it up again, no problem. Took another car to buy a new battery--was gone about 30 min. Came back, got in the car, noticed the radio station presets were all screwy, the clock was way wrong (but not 1:00, which it resets to when I remove the battery), tried to start again & got a few weak solenoid clicks. Measured the voltage again (12.7V). Measured the voltage on the new battery sitting on the garage floor (12.6). Put the new battery in. Vrroom, started right up. I'll try a longish test drive tomorrow during the light of day. Old battery (Walmart Everstart) was almost 8 years old. I certainly can't complain about it giving up before its time. Hopefully my alternator is fine & everything else is still OK. I'll certainly post back if it isn't. Thanks again, all!
 
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Its harder to kill an alternator than most people think. If the alternator is healthy, it should be able to put out its full rated current indefinitely, that's WAY more than any dead battery can absorb (usually a battery will take a big inrush current for a few seconds, and then settle down to a high, but not >100 amp, charging current). When an alternator fails recharging a dead battery, its because it was on its last legs anyway. 8 years on a battery? Just dang. I think my all-time record is about 5 years. Cooler climates sure do help with battery life!
 
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