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Anyone know roughly how many amp hours this puts out? Or more simply, how long do you have to drive it for once you have started it to put back the charge and a bit extra? Aircon and stereo were on as normal. I'd guess they would take 2 amps or so between them.

Started it today and it was barely turning over. It did start after a bit of a churn. I had used it at the weekend but it was the same then...After a short journey today it was again struggling to be bothered to turn over but at the weekend it wasn't. I then unfortunately had to drive around for about 90 minutes aimlessly in the hope that is enough to give it a decent charge. Dashboard voltage display is reading just under 14v when it is running so I'm assuming that is ok?

Battery is a few months old as it had a bad current drain and flattened the old one repeatedly so I changed the battery. Current drain was fixed so it can't be that.

I don't always need to use the car so it would be useful to know what's the minimum amount of time I'd need to take it out for if I didn't need it for a week or so.

We need to do some simplistic Arthur.

Assume that the max output of the alternator is 150A.

Assume that under normal driving conditions you're getting about 60A on average.

The RS6 is very greedy. Let's say it's using about 10A all the time, even with big consumers turned off.

That leaves 50A.

If your battery is completely discharged then you'll need to put enough charge in it to get back to 110Ah of juice.

Assuming 80% efficiency and that the battery can be charged at whatever current the alternator can supply then you will need to drive for 2 hours and 45 minutes.

I don't know if the alternator rams that much current into the battery, though. I'd be surprised if it did.

You lost me at 150amps,

That's why I use a hammer at work and not a calculator!

If it's 150 amp hour then it should realistically charge the battery within 2 hours I would have thought. In the warmer weather a 20-30 minute pootle twice a week seemed more than enough to keep it ok.

It all began because I didn't realise the cigarette lighter socket remained live when the engine was off (very stupid design) so the battery was flattened by leaving the dash cam plugged in. Previously I've only ever owned sensible cars which turned all the electrical stuff off when you turned the ignition off or when the key was out. Even the socket by the gear lever isn't switched out.

Really irritates me when cars that turn off the cigarette lighter socket. If you want power that comes on with the ignition, get your feed from the 75X terminal behind the dash.

Headlights don't go off with the ignition either. Italians realise everyone has more important things to worry about than whether they've left lights on so theirs go off

srichards wrote:Headlights don't go off with the ignition either. Italians realise everyone has more important things to worry about than whether they've left lights on so theirs go off

You do realize how old the C5 platform is don't you?

Every car I've ever owned had lights that went off with the ignition unless you deliberately turned the key to the P position for parking lights... 1989, 1990 & 2001 Italians. 1990 Japanese. I guess the Audi is too modern with its new fangled ways.