Jump starting.....

[E39 Ian]

Due to bit of back luck, etc the E39 has been standing for a couple of weeks.

Anycase I go out to do a small maintenence job this morning with the wife's car. She phones me a while later to say she needs to go and fetch the litlle one from creche. So I say, great grab the BMW...it needs a run anyway. Well 2 minutes later, I get another call, her again, car just click, click - will not start

Ok no worries, I know the neighbour is home next door and he has a VW Polo he can jump start it. But she says the cars turned the wrong way, I say dont worry, battery is in the boot.

Ok, not funny, trying to work and the phone ringings again, its her, the does next door reckons he cannot jump start the BMW as it will mess up his electronics....WTF

So does he have a valid point or is he an a..hole?

 

[Coisman]

Jumpstarting needs to be done infront by the engine bay I think

---

Starting with a flat battery If the car's own battery is flat, the engine of your BMW can be started by
using two jump leads from another vehicle's battery. Conversely, you can also jump-start another vehicle with
your BMW. Use only jump leads with fully insulated battery-post clips.
Do not touch any electrically live parts when the engine is running, or a fatal accident may occur. Do not
depart from the procedure described below, otherwise personal injury could
result or one or both vehicles be damaged.<
1. Check that the other vehicle's battery has a voltage of 12 V. This information is on the battery label
2. Switch off the engine of the donor vehicle and all consumers in both vehicles – with the exception of the
hazard warning lights of the donor vehicle
3. Make sure that the bodies of the two vehicles do not touch – risk of shortcircuit 4. Your BMW's jump-starting connection
in the engine compartment acts as the positive terminal of the battery.
The protective cap on your BMW's jump-starting connection is marked "+". Open the cap by pulling the tab,
Begin by connecting the clip on one end of the jump lead to the positive terminal of the discharged battery,
then connect the other end to the positive terminal of the donor battery
5. Use the second jump lead to connect the negative terminals of the batteries in the two vehicles. Make the first
connection to the negative terminal of the donor battery or to earth, i.e.
ground, on the engine or body of the donor vehicle, and then to the negative
terminal or earth on the engine or body of the vehicle which you wish to start.
On your BMW a special nut is provided for this purpose,

---

Go google your model, you will find the right way

 

[Skwinty]

I think he was just too lazy to help out.

If you wanted to arc weld on his car without disconnecting the battery, then he had a point, otherwise he is just a miserable doos...fft:

 

[zaleonardz]

Just create some current draw... light, blower motor and jump away....

 

[E39 Ian]

I think he was just too lazy to help out.

If you wanted to arc weld on his car without disconnecting the battery, then he had a point, otherwise he is just a miserable doos...fft:

+1

 

[Gerhardm32]

A few months back I had endless problems with my BMW and also did some posts here about it, Jandre and LZ gave the suggestions of switching on headlights and the heater when disconnecting and I went through the manual and it said the same.

I bought a jump start pack then to stop asking everybody for a jump if I wanted to go some where, so that I don't get the story of screwing up electronics and I am busy now but will be able to assist in 2 hours or so.

The jump start pack is so easy to use that my wife can do it without phoning me all the time.

 

[Sankekur]

Just create some current draw... light, blower motor and jump away....

+1

I think it also says in the bently service manual to turn on the rear window demister, when jumping the car

 

[Gerhardm32]

Just create some current draw... light, blower motor and jump away....

+1

I think it also says in the bently service manual to turn on the rear window demister, when jumping the car

just checked the service manual on the E34 and that's correct, "lights, blower motor to full speed and the rear window demister to avoid an overvoltage between the governor and consumer equipment

 

[rick540]

Apart from working full time I also study Electrical Engineering, and I personally will not jump start any modern car.... finished klaar. I go get another battery, or charge the one in the car, but I don't risk it.

I stand firm on this one, I know what I am talking about and have worked with all the technologies involved for about 20 years from CMOS to lead acid, capacitance, inductance etc there is so much that jumping does that can blow electronics it's not funny.

A few years ago I trashed a buddies 318I DME and ABS by doing it, cost me plenty to fix as afterwards it was "my fault"

It certainly can happen, and it does I personally know of an opel, a lexus and have heard of BMW's trashed from jump starting.

If it has to be done, then switching on all acessories to create a significant load makes it far safer. (The load acts as a short to any stray high voltages)

The problem usually happens if the cables make bad contact and arc during the jump stsrt bumping the voltage up quite a bit as the spark tries to jump the gap.

Also if the battery is very discharged it initially takes very little load off the alternator for the first 60 seconds or so and the alternator regulating circuitry is not really designed to opperate under these conditions and can give spikes of a lot more than the 14 or so volts required.

 

[Hellas]

To add to this topic: How do you charge the BMW battery. I have personally seen a battery explode (in a guy's face) because they did not open the caps of the battery cells.

But since the BMW battery is sealed, should one tear off the plastic sticker covering the top or is it safe to simply charge it as is?

 

[Skwinty]

To add to this topic: How do you charge the BMW battery. I have personally seen a battery explode (in a guy's face) because they did not open the caps of the battery cells.

But since the BMW battery is sealed, should one tear off the plastic sticker covering the top or is it safe to simply charge it as is?

Sealed batteries have a vent valve to prevent overpressure whilst charging..

 

[Hellas]

Is that the little pipe on the side? So I can just go ahead and hook it up?

 

[Skwinty]

That little pipe is connected to the vent valve. Plug the charger to the battery and stand back..:excited:

Valve Regulated Lead Acid (VRLA) Batteries
Also called Sealed Lead Acid (SLA) batteries.

This construction is designed to prevent electrolyte loss through evaporation, spillage and gassing and this in turn prolongs the life of the battery and eases maintenance. Instead of simple vent caps on the cells to let gas escape, VRLA have pressure valves that open only under extreme conditions. Valve-regulated batteries also need an electrolyte design that reduces gassing by impeding the release to the atmosphere of the oxygen and hydrogen generated by the galvanic action of the battery during charging. This usually involves a catalyst that causes the hydrogen and oxygen to recombine into water and is called a recombinant system. Because spillage of the acid electrolyte is eliminated the batteries are also safer.

 

[Technician]

i blew a knock sensor by trying to jump start my bmw-
i know it makes no sense, it was fine, jumped the car started fine- drove around, perfect-
next day the battery was flat again- jump started, it started then didnt- towed it in and bam my knock sensor was blown and therefore the fuel pump was not turning on.
a few people can argue its not the direct result from jump starting- but i'll rather not jump it again to be safe.

+1 to switching on the lights, fans and rear- demister.

 

[Budleigh]

I understand the original poster's frustration, but I'd also be a bit hesitant. Plus, I so rarely see people doing it "the proper way" that I'd rather be a doos with a working car than a good Samaritan with blown electrics.

It's as bad as watching someone push-start a (manual, obviously) car in first gear, or reverse.

 

[Truvalu]

Ian have you yet figured out why your car is/was dead and needed to be jumped?

 

[Hellas]

Ian have you yet figured out why your car is/was dead and needed to be jumped?

In my case it was only because she stood for 3 months without being started or without the battery being charged. The battery was disconnected though.

 

[E39 Ian]

Somewhere...somehow...someone opened the car to get something out and did not lock it again, those big interior lights chew battery.

Since then have not had a moments trouble

Ps. I still think my neighbour is a "box" for not helping

 

[Beast_Power]

Maybe the neighbour was afraid he would end up having to buy a new computer box for your car, if he makes a mistake.

Neighbour not helping because he is afraid of blowing something, is better than you shopping for a new ECU !

 

[Skwinty]

Maybe the neighbour was afraid he would end up having to buy a new computer box for your car, if he makes a mistake.

Neighbour not helping because he is afraid of blowing something, is better than you shopping for a new ECU !

Or, he could have been really helpful and taken both batteries out of the 2 cars, put his good battery into Ians car and then swopped them back once the car was running.

But, that was too much of a hassle for the box...