Hi guys
I have a 2013 Octavia 2.0 TDI with stop-start which hasn't been driven since Christmas eve. Apparently we left a door ajar on it so the battery is now too flat to start the car. When I turn the key, all the dash lights come on as normal but when it tries to turn over, all the lights flash with each attempted revolution but it's never succesful. Initially if I tried to turn the headlights on, the dash would light up.

I attempted to jump-start it this morning from our Seat Alhambra, also a 2.0TDI. Not by any means the first time I've ever jump started a car, but possibly the first time I've needed to do it on this one.

I connected the positive terminals on each battery, then connected the negative on the Alhambra to the earthing point on the chassis of the Octavia. Had the Seat engine running whilst connected for about 25+ mins but still no change except that the dash dials no longer light up if I turn the headlights on (though they do still come on if I turn the key). Essentially I think for whatever reason, when I had the jump cables connected, the Skoda battery wasn't taking any charge from the Seat.

I'm assuming I've done something wrong here. Can anyone advise what may be going on or what the correct technique for jump-starting is?

Edit - adding in case it's relevant: It was about -2 outside when I was trying this morning, don't know if that may be a factor?

Edited 5 January5 Jan by alessio92

Are you reading an increasing voltage on the Octavia Battery, measured with a jump lead disconnected.

Could the battery be bad, possibly a single cell, and as you say not taking any charge ?

Are your jump leads thick high current ones or the thinner core variety ?

Frustratingly I don't have a multimeter to check voltage. Will see if I can borrow one.
Im starting to suspect the cables may be the issue. Going to check the spec of them and see where our other ones have gone - I did have some chunky ones!

Edit - they're supposedly rated for vehicles up to 3000cc...

Edited 5 January5 Jan by alessio92

Many years ago, the first time that I needed to use a new "good" set of jump leads to help a neighbour out - I failed, same outcome as you had!

Crimps on the leads were very substandard, I replaced/reinforced the crimps on the crock clips with heavy duty cable clamps - and over the next 30+years have never had the need to use these leads!

With modern cars I'd only ever now use a jump pack, which also has many uses as a portable 12V DC power source.

Edited 5 January5 Jan by rum4mo
changed "will" to "with" - just a mistake!

6 hours ago, alessio92 said:

Hi guys
I have a 2013 Octavia 2.0 TDI with stop-start which hasn't been driven since Christmas eve. Apparently we left a door ajar on it so the battery is now too flat to start the car. When I turn the key, all the dash lights come on as normal but when it tries to turn over, all the lights flash with each attempted revolution but it's never succesful. Initially if I tried to turn the headlights on, the dash would light up.

I attempted to jump-start it this morning from our Seat Alhambra, also a 2.0TDI. Not by any means the first time I've ever jump started a car, but possibly the first time I've needed to do it on this one.

I connected the positive terminals on each battery, then connected the negative on the Alhambra to the earthing point on the chassis of the Octavia. Had the Seat engine running whilst connected for about 25+ mins but still no change except that the dash dials no longer light up if I turn the headlights on (though they do still come on if I turn the key). Essentially I think for whatever reason, when I had the jump cables connected, the Skoda battery wasn't taking any charge from the Seat.

I'm assuming I've done something wrong here. Can anyone advise what may be going on or what the correct technique for jump-starting is?

Edit - adding in case it's relevant: It was about -2 outside when I was trying this morning, don't know if that may be a factor?

Perhaps the negative chassis connection tag was not giving a clean connection to the jump lead?

6 hours ago, alessio92 said:

Had the Seat engine running whilst connected for about 25+ mins but still no change

Did you not try to start the Octavia whilst connected?

Never heard of a jump start being trying to charge the battery with another car.

15 hours ago, Stonekeeper said:

Did you not try to start the Octavia whilst connected?

This

When you connect to the final jumper clamp you should see a small spark and or hear the other car load up a bit.

Try earth connection to engine or even negative on the skoda battery.

Then after 2 min, try and crank the skoda with the Seat running and connected still

This is just as many have done for decades. Now with modern electrics doi not be surprised if there are Faults / Warning lights, steering etc, which may require once the car is going to turn the steering to each stop. A starter pack is by far a safer way of boosting and starting.

I have never required a jump start but have a 1.5M length of just 2.5sqmm with 4 crocodile clips and have started quite a number of cars using this bit of cable, I allways connect up the cables and then let my car running for ~ 10 minutes or so, then rev to around 2000RPM while the flat battery car is being cranked, never failed yet. I would think that the "flat" battery is doing some of the heavy lifting here because the voltage drop through my 1.5M (total 3M) cable even with a fairly low 300A crank will be ~ 6.5V if supplying that full current, so without that 10min or so charge then very doubtful IMO of working. Of course, if a proper set jump leads are used then no need for the initial charge.

Edited 6 January6 Jan by Johngerard

Ye proper Jump Cables. Not what many might have from a Super market or even Halfords that cost around a tenner maybe even less even years ago.

Do most people have their engines running when jump starting someone else? and if so, why?, even a 500A load for for say a 3 sec crank, enough to start almost any car, will only drain the donar battery by 0.42AH, the sqroot of nothing from even a 56AH battery.

Yes so the car giving the charge is not surprised!

Battery may be completely dead. Had same problem a few years ago. Left battery too long and it went flat. Jumped from a similar sized diesel and all that happened was the leads started to melt. Good contact at both ends but reckon the old battery was taking any power/shorted out. Disconnected old battery and put on charge. Showed charging for a few mins then blew fuse in charger. New battery time.

Alasdair

Well, I solved it.

Turns out that the leads are ok, they're rated for up to 3000cc. But on the Alhambra engine bay, I'd made a mistake about where to connect the black cable to earth it.

The actual earthing strip is just a thin bit of bare metal with a painted nut or something either side of it. Looks like the first time I'd connectedd to the painted bit not the unpainted bit, which is very thin and can only be clipped to one way!

15 hours ago, Johngerard said:

Do most people have their engines running when jump starting someone else? and if so, why?

Absolutely

It's about getting the voltage up a bit more than keeping the battery up.

You are pushing with 14.4V rather than say 10 (which is what a battery hooked to a flat one will go down to).

Also as someone else said, the VR on the running alternator helps smooth out the spikes when you clip leads on and off