07 A6 flat battery

**sholdowa** · 01-01-2014, 08:58

Background: had the car for 3 years now, and it's pretty much run perfectly all that time.

I've left it for about 5 days, and the battery is completely flat. I thought to put the car on charge for a few hours and see whether it's any better. However, when I plugged in my trusty Halfords 4 amp charger the dial went off the scale, bouncing off the stop, and it started making pained whining noises.

I'm a bit worried about the next step... I really don't want to jump it if there's a major short.

Advice please...

Cheers,

Steve

**rallysunbeam** · 01-01-2014, 09:54

On a completely flat battery the dial will give a full scale deflection and make a slight noise from the transformer. Within a few minutes it should settle down. Obviously this is on the bench not attached to the car. Worrying thing is it went flat in 5 days. Did you leave the lights on or. The door slightly open? Take the battery off and put a meter across the battery cables. There should be minimal drain, interior lights, clock etc but hardly anything. If the battery voltage on the bench is below 10v before you connect the charger, there is a good chance the battery has died... And you will need a new one. Batteries deteriorate over time as the seperaters between the plates brake up. This happens quicker if the battery is le ft flat for long periods of time. Hope this helps. Happy new year.

**alladdin** · 01-01-2014, 10:24

These days batteries have a habit of just dieing like that. I think I would take it off to charge or just replace as precaution.

**sholdowa** · 01-01-2014, 10:46

Good to hear that it's not abnormal! I'll report back tomorrow... I take it it's ok to just disconnect the +ve and leave in the car? It's a big old bugger!

**rallyrob** · 01-01-2014, 10:49

As an example I had a battery that was admittedly about 5 or 6 years old but still seemed good, I used it to run a 12V lead light, it had lasted ages in the garage. I charged it once every few months. It eventually went completely flat an I charged for 24 hours, plugged the lead light back into it an not a bloody dicky bird. It was as dead as a dodo..

**jimmy2006** · 01-01-2014, 11:35

word of warning not jump start on a flat battery if the battery will not take a charge from your battery charger try putting a set of jump leads from the flat battery to a charged battery for about 1hour and the good battery will drain into the flat battery to start it cycling then when you put your battery charger on it will since there is a battery and start to charge the flat one up if it flat and you have a 4amp charger it may take about 48 hour to charger fully

**rallysunbeam** · 01-01-2014, 12:06

The thing with lead acid batteries is once they die they will never recover. Basically the insulation between the plates falls apart and their not replaceable. If it's that bad replacement is your only choice.

One word of warning. Always connect the negative last and disconnect it first. (Neg earth cars) Just think if you leave the negative connected and accidentally touch the spanner on the body as you are tightening/loosening the positive. Basically you would be shorting out the battery. Expect a very big spark and change of underwear.

**dangerousdave** · 01-01-2014, 13:39

If it's anything like the a6 I fixed the other day it kept randomly draining the battery every couple of weeks. Turned out there was a load of leaves under the plastic cover at the back of the bay by the windscreen. They had blocked the bulkhead drains and were also generally holding water which got through one of the fixtures and had filled the lighting ecu with water and was causing one of the side repeaters to stay on solid! Ecu lives up under the dash next to the steering column, just take the lower dash panel off and you'll see it next to the fuse box, worth checking to rule it out especially if its been raining/been jet washed recently and the battery checks out as ok with a charge!

**sholdowa** · 02-01-2014, 07:57

Thanks all. I disconnected the battery and got it charging. Initially was reading 4V, last time I checked it was reading 11.5V, so I think the battery is ok. Was still charging at an indicated 6/10 ( whatever that means ) after 10 hours on charge, although the computer tells me the batter is now 100%.

I'll have a good look Dave, as yes, it has been raining for the last week or so - well, it was Christmas after all! Sounds very like you've hit the nail on the head there. I did jetwash all the crap out from under the top of the bonnet eound the wipers a couple of weeks ago too.

**rallysunbeam** · 03-01-2014, 01:04

On charge voltage should be around 16v for a good battery.

**dangerousdave** · 03-01-2014, 01:44

Did you take off the plastic cover when you jet washed around there or was it still in? If it was out that may be how some water got in, if you didn't take it out then there may be some leaves in there. There's also 2 drain bung things you can pop out to stop them trapping leaves as much, the passenger side one is easier to see if rhd