Tell me how by jumping a battery you can screw up

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How does jumping a battery with these new cars cause so much damage? I remember crossing cables 30 yrs ago and nothing ever happened except sparks. Now if you do this and whatever else, you can fry bulbs, electric motors, loads of $$$$$$ damage. Does anyone know what else should not be done other than the obvious cable switch?? Thanks in advance!!
 
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I've always heard that a cousin's friend's brother's inlaw coworker gave someone a jump, and a city block burned down, so you can't be too careful. Electronic gizmos are expensive. It is unknown just how much reverse protection they put into them. I do believe the various electrical systems are design to different levels of protection: brake related sensors are designed to withstand reverse battery without damage, airbags used to (still are?) designed to work with the battery removed, etc. But electronic gizmos that draw loads of power are less likely to have reverse battery protection, by virtue that the low cost methods of protection cost too much in power--and the low power loss methods cost too much money. Also I don't think jump starting cars is as common as it used to be -- so there may be less incentive (to the manufacturer) to design for it. Beats me. I'd be interested in hearing more.
 
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Originally Posted By: supton
But electronic gizmos that draw loads of power are less likely to have reverse battery protection, by virtue that the low cost methods of protection cost too much in power--and the low power loss methods cost too much money.
I think you hit the nail on the head there.
 
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Quote:
Does anyone know what else should not be done other than the obvious cable switch??
Don't use the wrong style battery on a Dodge Stratus. LOL Had a client that stuffed a top post in there (OE is a sidepost grp 70 or maybe a 75) It was all cobbled together with all sorts of adaptors and cable ends. He came in complaining that "ever since I did the installation on his car, everything cuts off when he goes around a corner." I checked my install. All to spec. Went over it with a fine tooth comb. Everything looked good until I pulled the front left wheel and fender liner off. There it is. Scorch marks where it contacted the metal all Frankensteined together. It executed his Body Control Module. He still wants me to pay for it. Still insists that his crazy battery mod had nothing to do with the failure. duh
 
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Jumped dozens of cars in the past 10 years and never had a single issue. Even the battery in my car that i used to jump other cars with is still going strong after all these years.
 
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I was working at a place a bunch of years ago when a taxi came to pick someone up. When he went to leave his battery was dead. They sent another cab to jump it. When they went to hook up the cables the guy was leaning over the battery,and when he touched the cables it blew up right in the guys face. Now I've jumped alot of cars like everybody else has, but I tell you any time I do it now I stand to the side of it and put safety glasses on.The guy was alright after we flushed his face and eyes with water.To this day I don't know if he hooked the cables up wrong, or the battery shorted itself out.,,
 

Patman

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My original battery in my Civic died a couple of weeks ago when I was waiting in a parking lot for my fiancee for 5 minutes and was running the radio as well as having the fans on full blast. Luckily I found someone with jumper cables in their truck (a rarity these days) and got a boost and it caused no problems whatsoever. I immediately went to Walmart and bought a new battery though, as the old one definitely would have caused problems in the future.
 
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Wife had my wagon for a day, she needed the hauling capacity, and crossed the cables jumping a coworker's civic. Blew the civic's main fuse or main relay. THEN I get the phone call about what should she do. They found the part within the lunch hour and got it in, so no big deal there. And she wonders why I'm nuts about pulling the car up, shutting off the key, hooking up the cables, then restarting. She didn't do any of this and my car survived. smirk
 
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My Sears jumper cables came with safety glasses. Good idea. Also as they say but few people listen is to attach the neg. to a strong ground, not the neg. terminal.
 
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my brother got a jump and reversed the polarity- he blew the main fusible link and a few other fuses- luckily we were able to change the fuses and all was ok. I heard BMWs are sensitive to jumping.
 
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Never hook up directly to the dead battery's negative terminal. The spark may casue an explosion (hydrogen released on depleted battery). Also, the voltage surge can damage electronics if the ignition key is left on while hooking up. Connecting to a ground on the dead car acts like a "shock absorber" and the spike is lessened as it meets the ground resistance to the battery.
 
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Someone jumped my daughter's Honda backwards last week and killed the main fuel relay. It had diodes in the circuit to protect the ecu. I had one of the electrical guys at work dissect it to investigate....he replaced the diodes and all returned to normal. It took quite a bit of troubleshooting and research to get to the bottom of that one. Saved sixty bucks and learned quite a bit about the car though.
 
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Originally Posted By: Gotch
Never hook up directly to the dead battery's negative terminal. The spark may casue an explosion (hydrogen released on depleted battery). Also, the voltage surge can damage electronics if the ignition key is left on while hooking up. Connecting to a ground on the dead car acts like a "shock absorber" and the spike is lessened as it meets the ground resistance to the battery.
This
 
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Originally Posted By: AVB
You don't realize how loud it is when a battery explodes untill you experience it.
Got one in the face when young, surgery by a fantastic doctor saved my eyes. Unbelievable how much force was involved, parts of the battery were hundreds of feet away! One die hard rule (no pun intended) is do NOT have the good vehicle running when the actual start up takes place. Two competing alternators can cause issues beyond imagination.
 

ottotheclown

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Bingo we have a winner! After the car started no# 1. signal lights #2. tail lights #3. power windows #4. head lights except for high beam #5. fuses blown. I was not present when it was jumped. I believe cable screw up with dead battery car key on. Amazing frown a favor can turn out so expensive. $290 in cost added to a alternator cost.
Originally Posted By: R2d2
Originally Posted By: Gotch
Never hook up directly to the dead battery's negative terminal. The spark may casue an explosion (hydrogen released on depleted battery). Also, the voltage surge can damage electronics if the ignition key is left on while hooking up. Connecting to a ground on the dead car acts like a "shock absorber" and the spike is lessened as it meets the ground resistance to the battery.
This
 
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I keep a jumper pack now since I'm never tired of being a good Samaritan. I had jumper cables but it was too short if you want to jump someone from behind. Anyways good tip on the negative to engine block on dead car. Whenever someone asks me for a jump and brings their own jumper cables I'll hook them up properly myself.
 
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Another good rule for the paranoid is to take the dead car's keys and hold them. (If the dead car's owner has a problem with it they can wait for another jump.) This keeps meth-heads from just rapidly flicking to "start" every half second as soon as you make a connection and theoretically getting a little more surface charge on their battery. If there's a way to keep them from spastically wiggling the alligator clips for a good spark show (derpa derpa got a good connection now, cletus) I'd like to hear it! PS reason #342523 why I would hate a drive by wire car, I'm always grabbing my throttle from under the hood to give a good RPM goose when the victim goes to start. Figure it spreads the damage across all my alt diodes as well as providing more amperage.
 
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Some cars use the computer as a regulator - all sorts of expensive damage can ensue. Many sensitive electronic systems and components are now in cars. Full battery current can kill them, or a short can ruin them. I decline to jump cars now with my own vehicles unless there is a real emergency. BTW, even with CORRECT cable attachment , it can be harmful to the donor car! For real!
 
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I don't know how you can jump a car w/o the donor car running. You need that voltage to charge. At least you did, back in the day. It's also nice to hear the donor car lug down. Hook up, wait a few minutes, try cranking. The deader the battery the longer one has to wait. Still haven't gotten out of the habit of going directly to the battery though. But I hook up donor first. And I stand clear of the battery. I figure, it's gonna spark when I wiggle the cables, as it never makes good contact initially.
 
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