Has anyone ever heard of this

[Smeeagain]

So I get a call from the mrs today so car wont start (2004 E53 3.0D) - thinks its a flat battery.S i get a neighbour to take me to where she is as I have jump leads in the car and if it is the battery we'll be up and running in five mins. Sure enough it is the battery.
So while matey is getting the cover off his battery (2014 plate Audi A4) I get the leads out and connect them up - usual protocol, positive on donor car to positive on dead battery and so on

Let it charge for five mins and try to turn it over but nothing. Give it another ten mins and its still not picking up a charge. Another ten mins same thing. I know the battery isn't 100% flat as we still have dash lights (albeit various error messages) central locking working etc.

I decide that I will probably have to call the AA. I disconnect the leads and notice a message on his battery cover saying not to use the negative terminal but a metal tip next to the battery . Now I know the X5 has charging points under the bonnet because the battery is not accessible but what is this all about? Connected it up and two mins later the jump start works fine

Why wont it work connected directly to the battery ???????

Smee

[X5Sport]

According to Audi Forums connecting directly to the battery runs a serious risk of frying the ECU.....

Richard

[pvr]

There is indeed no protection directly on the battery, so there is a risk of spiking.

[Smeeagain]

But whats the issue (apart from spiking)?? For years - and in fact even still today on the AA website - the procedure is to jump straight off a battery - don't understand why it is suddenly a problem - my X5 was jumped off the battery by the AA man last time I had to call them out and I must have similar electronics to a measly A4

[X5Sport]

Perhaps Audi have 'weak' electronics, and with the negative body effectively being an extension of the metal ground strap it doesn't make a lot of sense to me either - unless VAG are using a 'special' master ground strap to the battery?

I know with BMW you have to be careful, but that is in case you accidentally trigger the cutter charge (normally fires in the event of airbag deployment or a rollover) on the battery positive terminal - a good reason to only use the under bonnet points.

Richard

[Smeeagain]

[quote="X5Sport"]
Perhaps Audi have 'weak' electronics, and with the negative body effectively being an extension of the metal ground strap it doesn't make a lot of sense to me either - unless VAG are using a 'special' master ground strap to the battery?

I know with BMW you have to be careful, but that is in case you accidentally trigger the cutter charge (normally fires in the event of airbag deployment or a rollover) on the battery positive terminal - a good reason to only use the under bonnet points.

Richard
[/quote]
Slightly off topic but as I started the post I'm happy to permit the high jacking of my own thread. I was told a couple of years ago by an AA man that every car has a cut off switch under the bonnet to disable electrics fuel pump etc etc - is that true and where is it on a 2004 diesel x5 ?

[AVI-8]

You can get a battery isolation switch, usually fitted as an aftermarket device on track cars, never heard of a factory fitted under bonnet cut off switch

[Jackstrath]

[quote="AVI-8"]
You can get a battery isolation switch, usually fitted as an aftermarket device on track cars, never heard of a factory fitted under bonnet cut off switch
[/quote]

its normally mainly for fuel , not the batter cut off like race cars , most cars do have it that fires automatically and what you have is a button to reset it , fords normally have this button on the bottom of A pillers

[Smeeagain]

[quote="Smeeagain"]
So I get a call from the mrs today so car wont start (2004 E53 3.0D) - thinks its a flat battery.S i get a neighbour to take me to where she is as I have jump leads in the car and if it is the battery we'll be up and running in five mins. Sure enough it is the battery.
So while matey is getting the cover off his battery (2014 plate Audi A4) I get the leads out and connect them up - usual protocol, positive on donor car to positive on dead battery and so on

Let it charge for five mins and try to turn it over but nothing. Give it another ten mins and its still not picking up a charge. Another ten mins same thing. I know the battery isn't 100% flat as we still have dash lights (albeit various error messages) central locking working etc.

I decide that I will probably have to call the AA. I disconnect the leads and notice a message on his battery cover saying not to use the negative terminal but a metal tip next to the battery . Now I know the X5 has charging points under the bonnet because the battery is not accessible but what is this all about? Connected it up and two mins later the jump start works fine

Why wont it work connected directly to the battery ???????

Smee
[/quote]

Just going back to this - I understand about the electronics on the Audi and protection from spiking etc, but why wouldnt it take a charge directly off the terminal post ??????

[X5Sport]

Not summat daft like the outer part of the actual connector being made of something other than metal?  Might be metal lined plastic/composite etc.  No conductivity on the outside faces?

Still puzzled over this myself......where's 535dboy when we need him.  He could check his own battery (assuming he knows what one is of course  >:D ) and tell us.

Richard

[Smeeagain]

it certainly looked like it was made of metal and I had the jump around the clamp and the post and the clamp was metal bolt.
Weird