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[terry paget]

Friend of mine has a small Kia, with a battery labelled DO NOT JUMP START. He reckons his car cannot be jump started, I reckon it means his battery is too small to jump start another car. Who is right?

[Lazydocker]

Read the manual 

For about 18 months there was a directive to “Apply no exterior power” to all new BMW diesels. Not sure why, believe it was because of the risk of a power spike.

[Andy B]

Read the manual 

For about 18 months there was a directive to “Apply no exterior power” to all new BMW diesels. Not sure why, believe it was because of the risk of a power spike.

The Mercedes forum seem petrified of jump starting a Merc, often quoting 'power spikes'. The expert indies though are apparently exempt when using their jumper/booster packs 
Won't the very presence of a battery on the 'jumpee' prevent a 'power spike'? 

[Nick W]

The Mercedes forum seem petrified of jump starting a Merc, often quoting 'power spikes'. The expert indies though are apparently exempt when using their jumper/booster packs 
Won't the very presence of a battery on the 'jumpee' prevent a 'power spike'? 

Ferraris were the same, with customers frightened into having their shiny underused toy recovered back to the dealer just because the battery was flat again. So you'd struggle for ages getting it out of the garage and onto the truck, and the same unloading it. Once the paperwork was done, the yardman would the start it with same booster you have and park it normally. A complete waste of everyone's time, which could normally be solved with regular use of a £50 smart charger.

[Doctor Gollum]

With BMWs they should be jumped via the engine bay terminals or risk blowing a relay pack in the rear fusebox

Most vehicles with remote mounted batteries have this requirement and the appropriate terminals clearly identified in the engine bay

[Viral_Jim]

Read the manual 

For about 18 months there was a directive to “Apply no exterior power” to all new BMW diesels. Not sure why, believe it was because of the risk of a power spike.

"Accepted online wisdom" (whatever you consider that to be worth) is that you need to put a decent load on the battery before disconnecting the car that's providing the jump. So turn on heated read/front screens, blower motor and headlights.

I see the logic, not sure how effective it will be though. I also remember reading that batteries have to be coded to the car so that they charge correctly. Really don't under that one 

[2boxerdogs]

With BMWs they should be jumped via the engine bay terminals or risk blowing a relay pack in the rear fusebox

Most vehicles with remote mounted batteries have this requirement and the appropriate terminals clearly identified in the engine bay

. 



Merc ones are easily identifiable under the bonnet, the battery is located under the rear seat. Manual gives all instructions.

[Andy B]

With BMWs they should be jumped via the engine bay terminals or risk blowing a relay pack in the rear fusebox

Most vehicles with remote mounted batteries have this requirement and the appropriate terminals clearly identified in the engine bay

. 



Merc ones are easily identifiable under the bonnet, the battery is located under the rear seat. Manual gives all instructions.

Or in my case, under the driver's seat 

[Andy B]

With BMWs they should be jumped via the engine bay terminals or risk blowing a relay pack in the rear fusebox

 ......

Not doubting you ... just asking. Why? Surely if the donor car is switched off before connecting jump leads, it's the same as connecting a new battery to the dead car 

[Bigron]

here's my guess, Andy: donor car's battery would be fully charged after a run and has a high terminal voltage, donee car's battery flat and high internal impedance, so it won't pull down the (high) terminal voltage of the donor battery - hence a large voltage spike that has potential to upset the electronics/micriprocessors of rhe donee vehicle?

Ron.

[JasonH]

I know exactly why the BMW's can't be jump started, particularly diesels, the reason is voltage spikes. The alternators are typically capable of putting out 170A and are electronically controlled. When the jump start battery is disconnected the change in load can cause a very short voltage spike in excess of 18V. There are two modules, the Bluetooth MULF and the Glow plug Controller (all electronic, no relays here) that basically go pop the moment their supply exceeds something like 18V....

An "expert" would, if doing it properly, pull the fuses for at least the Glow Plug Controller before jump starting.

[Doctor Gollum]

When I did a volunteer stint with Surrey Police, jump starting was one of the potential jobs... The fried electronic unit is about the same size as a 16gb ram board and melts quite spectacularly costs ££££ too...

[YZ250]

Just had a look at my bmw hand book out of curiosity. With reference to jump starting there is nothing unusual mentioned, with the exception of allowing a diesel to run for ten minutes prior to using it as a donor car.
As mentioned, they do have a +live post clearly marked with a big red cover under the bonnet but the starting procedure is pretty standard. It does say not to have the donor car running until the jump lead connections are complete but apart from that nothing any different.

[Bigron]

As jump-starting is a fact of life with cars of whatever vintage, surely the designers of modern car electronics should have incorporated a simple over-voltage protection to their sensitive circuitry? It IS easyto do!

Ron.

[Doctor Gollum]

When I did a volunteer stint with Surrey Police, jump starting was one of the potential jobs... The fried electronic unit is about the same size as a 16gb ram board and melts quite spectacularly costs ££££ too...

Should add, that I was shown a frazzled one as a practical demonstration of what happens if done wrongly, ie by connecting directly to the battery

[JasonH]

Just had a look at my bmw hand book out of curiosity. With reference to jump starting there is nothing unusual mentioned, with the exception of allowing a diesel to run for ten minutes prior to using it as a donor car.
As mentioned, they do have a +live post clearly marked with a big red cover under the bonnet but the starting procedure is pretty standard. It does say not to have the donor car running until the jump lead connections are complete but apart from that nothing any different.

I think that the by the time the F series came out all the modules are robust enough to survive a jump start. The service bulletin was issued for E series cars.

[YZ250]

Just had a look at my bmw hand book out of curiosity. With reference to jump starting there is nothing unusual mentioned, with the exception of allowing a diesel to run for ten minutes prior to using it as a donor car.
As mentioned, they do have a +live post clearly marked with a big red cover under the bonnet but the starting procedure is pretty standard. It does say not to have the donor car running until the jump lead connections are complete but apart from that nothing any different.

I think that the by the time the F series came out all the modules are robust enough to survive a jump start. The service bulletin was issued for E series cars.

 

I had several E92's (330d/335d's) but never bothered looking at the hand book/supplements so I wouldn't have noticed that. 

[biggriffin]

When i was a boy in tut war, we was told on the car with the flat battery, make sure headlights are switched on, to eliminate voltage surge.

[Doctor Gollum]

X5s were particularly fragile* for inappropriate jump starting...

Not exactly robust elsewhere either

[Nick W]

As jump-starting is a fact of life with cars of whatever vintage, surely the designers of modern car electronics should have incorporated a simple over-voltage protection to their sensitive circuitry? It IS easyto do!

Ron.

you've forgotten that German engineers don't expect their products to break down, so such measures are unnecessary.


There are worse problems though: Mercedes are particularly good at them. Many of the bigger cars won't shift out of park unless the engine is running. So how are you supposed to move it if it  won't start? The FWD ones have a different issue, in that they automatically move back into park after a few seconds. Winching one onto a truck is a tedious business.

[Lazydocker]

The instructions came Direct from BMW Assist. It has now been rescinded 

[BazaJT]

At one time[not long ago] if you tried a booster pack on some Fords-C-Max for one-it would blow the radio/head unit at least.

[TD]

As jump-starting is a fact of life with cars of whatever vintage, surely the designers of modern car electronics should have incorporated a simple over-voltage protection to their sensitive circuitry? It IS easyto do!

Ron.

you've forgotten that German engineers don't expect their products to break down, so such measures are unnecessary.


There are worse problems though: Mercedes are particularly good at them. Many of the bigger cars won't shift out of park unless the engine is running. So how are you supposed to move it if it  won't start? The FWD ones have a different issue, in that they automatically move back into park after a few seconds. Winching one onto a truck is a tedious business.

Have a look around the shift, theres probably a small flappy bit of plastic which you can poke a screwdriver down and move a plastic lock lever, that then enables you move the auto shift out of park. There was on my c220 

[Andy B]

As jump-starting is a fact of life with cars of whatever vintage, surely the designers of modern car electronics should have incorporated a simple over-voltage protection to their sensitive circuitry? It IS easyto do!

Ron.

you've forgotten that German engineers don't expect their products to break down, so such measures are unnecessary.


There are worse problems though: Mercedes are particularly good at them. Many of the bigger cars won't shift out of park unless the engine is running. So how are you supposed to move it if it  won't start? The FWD ones have a different issue, in that they automatically move back into park after a few seconds. Winching one onto a truck is a tedious business.

Have a look around the shift, theres probably a small flappy bit of plastic which you can poke a screwdriver down and move a plastic lock lever, that then enables you move the auto shift out of park. There was on my c220 

But more & more models have an electrically operated column change .... like mine. I believe free wheeling hubs are available for these cars 

[Nick W]

As jump-starting is a fact of life with cars of whatever vintage, surely the designers of modern car electronics should have incorporated a simple over-voltage protection to their sensitive circuitry? It IS easyto do!

Ron.

you've forgotten that German engineers don't expect their products to break down, so such measures are unnecessary.


There are worse problems though: Mercedes are particularly good at them. Many of the bigger cars won't shift out of park unless the engine is running. So how are you supposed to move it if it  won't start? The FWD ones have a different issue, in that they automatically move back into park after a few seconds. Winching one onto a truck is a tedious business.

Have a look around the shift, theres probably a small flappy bit of plastic which you can poke a screwdriver down and move a plastic lock lever, that then enables you move the auto shift out of park. There was on my c220 

That doesn't apply to the ones with electronic shift levers on the steering column. Certain BMWs are the same. The original X5 had a manual release(the toolkit had a plastic thing supplied by Ann Summers to do this) which was deleted on later models.

JLR get electronic shifters and handbrakes right; they DO have a manual release. the

[Kevin Wood]

Can't believe Panzerwankywagens have such fragile electrics as this while everyone else has managed to make electronics in cars pretty much bomb proof. ..   

Hang on though.. Yes, perhaps I can.

[Mister Rog]

This is all news to me. My Volvo has battery right in the back. Never even looked at it, maybe I should.

So the risk is to your car if you are being jump started, not if you are jump starting another vehicle ?

Sorry for being so thick . . .

[Doctor Gollum]

This is all news to me. My Volvo has battery right in the back. Never even looked at it, maybe I should.

So the risk is to your car if you are being jump started, not if you are jump starting another vehicle ?

Sorry for being so thick . . .

Read the handbook, but only ever use the engine bay terminals for jump starting purposes

[Marks DTM Calib]

Can't believe Panzerwankywagens have such fragile electrics as this while everyone else has managed to make electronics in cars pretty much bomb proof. ..   

Hang on though.. Yes, perhaps I can.

'It woz not in zee spec!'

[Nick W]

This is all news to me. My Volvo has battery right in the back. Never even looked at it, maybe I should.

So the risk is to your car if you are being jump started, not if you are jump starting another vehicle ?

Sorry for being so thick . . .

Read the handbook, but only ever use the engine bay terminals for jump starting purposes

But not on an XJ Jag! Those are done off the battery in the boot and the earth stud in the wheel well provided for the job.

[Marks DTM Calib]

Under the bonnet on the XF 

[TheBoy]

Under the bonnet on the XF 

Jump links under bonnet on X351 XJ as well