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is it really serious what I have done?

3K views 30 replies 13 participants last post by  Tomvw 
#1 · (Edited)
Dear all,

Greetings with a great respect to you all,

What will happen to the car if you did car jumping to another dead car with your car BUT you did it wrong?
You connected the +donor to +recipient and then connected the -donor to -recipient?
Sequence of events:
1) After connection the way I just described, I went to the dead car, and tried to start it, but all what i got was fading engine sound, then nothing.
2) Went back to my car, (the key was in the contact) tried to start it, to give a kick to the other car, I noticed the engine sound is fading until stopped giving noise at all.

Of course the intentions was good, but consequences wasn't good at all.

Now the tow cars are parked next to each others (dead)!!!

The donor car is passat b5 1.8 and it was working great before the jumping!
Symptoms after:
Doesn't want to start, sluggish engine sounds then disappear, with more trials the engine stops giving any noise at all. All the internal lights and external lights are working fine.
The gauge has the battery light on.
Checked fuses (engine electricity) F#29 + F#32 + F#34 and all were intact.

What is the extent of damage that I made to my car by this?

What is the next step to revive the car?

Thanks in advance
 
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#2 ·
What you say you did, shouldn't cause a problem except maybe discharge the battery.
You should have had the donor car running while attempting to start the other car.

Clean battery posts and terminals and tighten.
Check/clean battery to body ground connection.
Check/clean engine to body ground cable connections.
Get the battery fully charged and load tested.
 
#3 ·
Tom, I have to disagree. It is Ok to let the dead battery charge with the running car, however I would shut the donor car off before attempting to start the dead car. A starter pulls 1 Amp per cubic inch, and there is a possibility you can kill the alternator/regulator by doing it while running. They just cant give 150 plus amps.
 
#4 ·
You are entitled to hold any view that you wish,
but you should not suggest others are wrong when you have no idea of what you are talking about.

The donor engine should always be running while attempting to start the other car.
The alternator/regulator have inbuilt controls that would prevent any damage to them.
There is no such unit as "Amp per cubic inch" or anything like it.
 
#5 ·
If he saying the draw is 1amp per cubic inch of engine displacement, that would be 110 amps required to crank a 1.8T. Which is stupidly low, especially on a higher compression engine. Never heard of that before, but ok.

You always shut the donor car off while attaching for obvious reason like, you don't want to get something caught in a running motor while draped over it. Once hooked up, you ALWAYS start and run the donor car for a minute or so to charge the dead battery a little. Then start the dead car.. To prevent possible damage to either one, you remove the cables asap.

Sounds like you fully depleted the donor battery as well. Charge one, reinstall and start. Then hook them up and start the donor to charge the other battery like my above method which is the accepted method of jump starting the world over.
 
#6 ·
Tom, I meant no disrespect, I have a degree in electronics. and since I was a kid my father (an RF design engineer) had told me this. Perhaps things have changed. (mostly the engines have gotten smaller, my 73 Thunderbird is powered by a 7.5l V8) I only said I disagreed with you, I did not accuse you of not knowing what you are talking about. I have always appreciated your help with the questions I have asked. Your knowledge of VW's is amazing. Personally I'd rather error on the side of not destroying my alternator no matter how remote the possibility might be.
 
#22 ·
Tom, I meant no disrespect, ............. I only said I disagreed with you, I did not accuse you of not knowing what you are talking about. I have always appreciated your help with the questions I have asked. Your knowledge of VW's is amazing. Personally I'd rather error on the side of not destroying my alternator no matter how remote the possibility might be.
Disagreeing with someone is a suggestion that they don't know what they are talking about, and is fine if the info is questionable.
I don't care about that, but I do feel some responsibility to set the record straight.

There is no possibility of overloading the alternator while the engine is idling (there is not enough energy available),
and there is electronic control to prevent damage at higher revs.



I feel bad for starting this, everyone is entitled to do any procedure how they see fit. Me personally, I am going to buy a couple of the Li-ion battery jumpers. I wont have to worry about it any longer. Once again, I apologize to Tom, I did not mean to offend.
Mike
I am not offended, but it is annoying when someone incorrectly suggests that I was wrong.
If not challenged other users don't know who to believe.


Those pocket size Li-ion batteries are not nearly as good as they appear in the adds.
I suggest before buying them, you check the specs and do some electrical theory revision.
 
#7 ·
as an electrical engineer, I'll jump in here and add my 2 cents, for whatever that's worth. assuming the donor battery is fully charged, it is a parallel source to the alternator. therefore, the voltage is constant and both the alternator and the battery are current sources. run the donor, or don't run the donor - doesn't matter - but I'd run the donor.
 
#12 ·
Hi Jay, I've read many of your posts. I am guessing my statement goes back to when we were all driving big V8's. If this is the case, and my Thunderbird has a dead battery I have only my B5 to jump it (90 amp alternator). worse case I am going to be drawing nearly 450 amps through the alternator and battery in parallel. I am saying that the diodes in the rectifier may not live through this. Do I have any valid point here?
 
#9 ·
Ok, there is an argument here, but you agreed on (no damage to the car has occurred) and that's really good for me.

I have a question to add, the temperature yesterday was like -12, would this low temperature affect the whole process in any way?
I am asking this because before I did the car jump, the temperature indicator was blinking after few beeping



Thank you for the valuable information
 
#11 ·
That is your low coolant level warning light, but it should not prevent a start. Check your coolant level ASAP.

When the engine is that cold, it can take more effort for the starter to spin it over and also the batteries will have less cranking amps available.
 
#13 ·
Non-electrical Engineer here, but the alternator output is kept safe by the how strong the magnetic field of the rotor is (limited by the slip ring current), and stator winding impedance, both factors must be considered when alternator designers do their job. So I doubt that a big current draw at the battery can hurt the alt.
 
#15 ·
Away from the in depth details that you are talking about :rolleyes: , I would like to ask a superficial question to you

What is the difference between wiring the cables in the 2 following orders:
1) -ve donor to -ve recipient
2) -ve donor to ground recipient

and why is it recommended to do the grounding instead of attaching -ve to -ve?

Thank you
 
#16 ·
and why is it recommended to do the grounding instead of attaching -ve to -ve?
Safety. A charging battery emits hydrogen gas, and a spark can be very, very bad in that environment.
By making the final connection to a ground point away from the battery, the spark (if it happens) occurs out of the (potential) H2 cloud around the battery.

You never, ever want to see lead-acid battery explode. That's a lot of energy stored in there - plus the metal (mmmm, shrapnel!) and acid (ouch!)
 
#17 ·
I was next to a 80's era Cadillac at a gas station, and right as he began to start the engine, there was a fairly loud thud from under the hood, and then electrolyte splashed out from under the car, so it can happen. However, most batteries are now "maintenance free" and don't emit much Hydrogen gas at all, plus many have that vent hose.

But speaking of jump-starting, usually the "dead" battery is within a couple of volts of the fresh battery, which is why the spark you get from making that last connection, with engines off, isn't that big. Running the donor car's engine or not doesn't make any difference to me either, unless you are trying to actually charge the weak battery. I just connect the cables, start the engine of the weak-battery car, then disconnect the cables and let the alternator charge the thing up again.
 
#19 ·
If good car isn't running and you try to jump the dead car. You will drain the good cars battery. Especially if the good car has a weak battery. It would most likely completely drain the battery when it wouldn't even try to turn over. I have gotten lucky that I have never gotten blown up from a leaking battery from sparking as I have jumped thousand upon thousand of cars. Can it happen? Yup. Is it likely? not really.

I rarely even ground the - cable to the car and have never had an issue. The only time I do ground it to the car is if I see it's an old battery. Albeit that isn't the correct nor safest way but again. I have never had an issue doing it this way.
 
#20 ·
If good car isn't running and you try to jump the dead car. You will drain the good cars battery. Especially if the good car has a weak battery. It would most likely completely drain the battery when it wouldn't even try to turn over.
Given enough time, the two batteries would reach equilibrium, where no current flows, but the "good" battery would not be drained, as in out of energy.
 
#21 ·
We had a massive battery explosion at work. One of the cargo loaders lost the battery while trying to start. Sounded like a shotgun going off, luckily no one was close to the battery area.
 
#25 ·
I just purchased one of those small 'jump packs' and within the 1st few days I jumped 3 different things. A lawn mower at work, my pick up truck and the 3rd was on a car in a parking lot. All 3 jumped without issues and all 3 were deader than a door nail.

I have been looking for a portable jump box for a while as we often are having to either jump one truck from another or roll out the charger which is a PITA.

I just picked up this https://no.co/gb40

It claims to jump anything up to a 6.0L gas engine and up to a 3.0L Diesel and anything in between. This should cover anything I need to jump. It says it will not jump anything that runs duel batteries though. I still keep a pair of heavy duty jumper cables in my car but this little jump pack seems to do what I need it too.

Time will tell
 
#26 ·
I just picked up this https://no.co/gb40
It snowed here yesterday, so at the dealership we had to move all 300+ cars to plow. As usual, a couple of dozen wouldn't start - I jump a LOT of cars. The jump box linked is very fancy, but for that price I think I'd prefer a more basic type. We use THESE. Big, high capacity battery, hefty cables, never fails. Heavy, but the lead acid battery is much less fussy than the Li-Ion types.
 
#29 ·
Another factor to consider is that all batteries age and eventually fail. For lead acid batteries, 5-7 years is the average lifespan if they are treated well. If you are trying to start a car with a 'dead' battery, it matters a lot whether the battery is brand new but drained (down to ~9 volts, any less than that and the battery will never recover) or near the end of its life span and drained.

Also the starter motor takes a very high surge current to get started. So things like the resistance of the jumper cables makes a big difference. Just the incremental resistance of dirty battery/cable contacts can reduce this surge current enough to cause the dreaded 'click, click' sound when turning the key.

Plus lead acid batteries lose efficiency when cold. Often, just warming the battery up will allow a 'dead' battery to start the car, even if the engine is still cold. The engine oil is more viscous at cold so the starting effort required is higher but the major factor on cold weather non-starts is that the battery has lost power.

Remember that the body of the car is grounded to the negative terminal of the battery. Therefore, be careful to make sure the bodies of the cars are not touching or that will connect the negative terminals of the batteries. This can cause a spark when the positive terminals are connected.

I would recommend that both of you go buy new batteries. If your battery was drained by trying to jump another car, it is probably near the end of its lifespan. And unless your friend left the lights on or something over-night, that battery is obviously near end of life also. Be sure to clean the battery terminals and cable ends to shiny clean when installing the new battery and you should be good for another 5 years.

Finally, one tip when I jump cars is that I connect (+) to (+), then (-) on donor car and lightly tap a metal part under of the hood of the recipient car just to verify everything is OK, then connect the cable to the (-) of the recipient. It doesn't hurt to rock the cable end back and forth a few times just to make sure it has gotten through any superficial oxidation layer on the terminal or cable end. Usually, at this point the idle of the donor car will bump up due to the added load on the alternator. I like to rev the donor car up for a few minutes to help charge the dead battery. Then start the dead car and unhook the cables.
 
#30 ·
I've always made sure I connected the negative lead of my jumper cables to the engine block and had the donor car running before attempting to start the dead car. One caveat with this setup is that you may have difficulty starting to dead car if the negative battery cable does not have a solid ground connection. Make sure the point of contact from the battery to the car engine or chassis is clean and free of corrosion. Same goes for the battery terminals. I've found instances where the negative lead connection was either loose or badly corroded and the car would not start as a result.
 
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