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[raywilb]

do modern cars such as a new bmw go into a lock down mode if for some reason the battery goes flat & is then attempted to be started with jump leads from a donor battery ??

[henryd]

It wouldn't surprise  me if they do

[Andy B]

The Merc forum seem terrified at the mere mention of jump leads ....

when a local MB dealer managed to flatten my battery enough that it wouldn't turn over, their tech came out armed with a jumper pack 

[Lazydocker]

There was an advisory notice not to apply external power to BMW over a few years but AFAIK that was revoked

[Nick W]

The Merc forum seem terrified at the mere mention of jump leads ....

when a local MB dealer managed to flatten my battery enough that it wouldn't turn over, their tech came out armed with a jumper pack 

when we did warranty recoveries, we often got some fancy toy that wasn't used enough and had a flat battery. These were always recovered to the dealer with instruction not to start them. So I spent god knows how long easing £150k cars out of garages and drives and onto the truck, then unloading them in cramped yards stuffed with expensive and delicate cars. Then the yardman would wheel out a couple of Transit batteries strapped to a trolley, jump start the car and park it. A total waste of everybody's time.


Jump starting an early A-class always put the EML on for some reason.

[raywilb]

There was an advisory notice not to apply external power to BMW over a few years but AFAIK that was revoked

  i thought that i was doing a lady a good turn. she had been in a hospital car park for a long time leaving lights i presume on as her battery had no life in it . i told her that i would connect some jump leads but when i did everything stopped working.  i probably cost her a packet.

[Marks DTM Calib]

IF the vehicle has been correctly tested and approved then jump starting should not be an issue, part of the CI tests model significant voltage spikes and step changes which are the equivalent of jump starting, boost starting etc

[Andy H]

Maybe related to the stop/start charging system?

[Doctor Gollum]

You must use the jump points under the bonnet. Jumping straight to the battery fries various bits... 

I forget it's name, but there's a circuit board in the rear fuse box which fries.

Surrey Plod were banned from jump starting anything as they kept frying said part. Costs about £400 iirc, but kills the car dead

[iansoutham]

You must use the jump points under the bonnet. Jumping straight to the battery fries various bits... 

I forget it's name, but there's a circuit board in the rear fuse box which fries.

Surrey Plod were banned from jump starting anything as they kept frying said part. Costs about £400 iirc, but kills the car dead

SBK is the system on BMW models and the big bit is the rear distribution box that goes above the battery.

If it is an Exx model 1-3 series, probably got a faulty battery cable to the front fuse box behind glovebox.