Audi A4 2010 Battery Problem

I think the "coding" is just a hint to the battery module that it should record the date the battery was changed, and keep track of the ageing.

The stop/start system on my A5 started "disengaging", VCDS didn't show an eact reason, consensus on forums was "shagged battery does that", many suppliers online were out of stock, so ventured to Halfords, their system took reg plate and decided (wrongly what I needed) took it back and swapped it for correct physical size.

Swapped battery (jump leads to neighbour's car to prevent any loss of power/settings) recoded battery with VCDS it was about 2Ah larger capacity, the computer noticed the change, still showed stop/start disengaged, decided to let it settle a few days, after some italian tune-up runs it would sometimes stay engaged, but still isn't entirely happy ...

Car is perfectly happy to start, run headlights, heated rear screen etc, so battery itself is happy, just the stop/start.

I have a Kia Picanto, brand new a year ago. Don't use it a lot. Came out one morning to find the battery pancake flat. Voltage down to ~5 volts. I didn't know they would ever go that low. Recharged it with my battery charger OK. I now trickle charge it every Sunday for one hour. Like you, the current drain by the system when it's parked in the garage and everything is nominally OFF, is minimal, so I'm still puzzled as to why it happened, but I'm determined not to let it happen again.

I think random software glitches are probably responsible for these events that seem to hit many modern cars randomly. I’ve had it happen in my Kia for no good reason and after a recharge all seems fine.

Tim

There was a mention in the MOT testing manual of a change of proceedure for testing some models of car. Things were left powered after plugging in to the OBD socket leading to battery drain.

Grumps snipped-for-privacy@here.com wrote:

Appx 1000 hours. which is around 40 days.

Every time I took my car into a certain garage a strange fault would appear a few weeks later....

It's just a PITA having to trickle every w/e - just in case it decides to flatten the battery. Maybe I can add a solar panel to do the charging.

I guess so. Thanks for confirming it's not just me.

Have you got any further info on that? Seems like it could lead to the cause.

So there must be something draining far more than 80mA as the battery went flat in less than two days.

Care to elaborate, or was it the start of some humour?

It could be factual, if a service visit requires connection of the vehicle, to their bus tester that connects to the comms bus. If it leaves any of the car computers in a high power state, that might be sufficient to drain the battery.

I could find a report today, where the entertainment system was drawing 6 amps from the battery after the car was off. And after things where shut down in a particular order, the current drain dropped to 0.140 amps. Which is still not spectacularly good, and should be fixed. But at least that won't flatten the battery by the next morning. Just leave the battery "half-there".

Using a clamp-on ammeter, my car was somewhere around 20mA, but the ammeter did not have a sensitive enough range for the determination. Hall probe sensors can be made more sensitive than that, because I made some circuit boards for that in one of my jobs.

The reason you use a clamp on meter, is if you slide the battery cable off the terminal and insert a regular multimeter on amps into the circuit, the act of adding the meter to the circuit, causes all the computers to reset and "removes the flaky scenario". This is why you try not to disturb the "car full of computers", and measure it in a non-disturbing way. In this way, you can be an "impartial observer", and watch some computer go from full-power to snooze to sleep to "Off" (which likely is not off).

Nothing is as "Off" as an older car was. The current on those only needed to be enough to run the car clock, which is 10uA (with the display dark).

Paul

I'll probably have to wait until next year when it has its service. Then I can measure the battery current with my clamp. See if it holds at a high reading when it's supposed to be asleep.

I wouldn't have thought a clamp meter is going to tell you much down at the amp or so that you're concerned about.

I would say 10s mA would be the threshold for a clamp meter.

Is that just a typo "10s mA"? If you mean 10mA then I think it's pushing beyond the limit.

A typical DC clamp meter will have a smallest full scale range of 40 amps. Looking at one from CPC it's 40amps at ±(2.5 % + 5 digits).

The garages, might have had it sat a while, with thing left on, flattening the battery even more.

I had a discharge of around that level, eventually traced to my voltage sensing relay, clicking on and off, which would flatten my battery if parked for an extended period. After resolving it, parked up, it drops to 18mA.

Always when parked in my garage, I plug the car into a charger. The charger is switched on each day, by Alexa, for 20 minutes.

The charge cable hangs from the garage roof, with a ciggy plug, by the drivers door. To ensure it makes a good connection, I use a 555 time IC, which flashes an LED, when the lead 'sees' 12v. Basically - plug in, and check the LED is flashing and forget it.

You can measure them individually, and add the amounts together.

Handily, my car has a removable link in the main power cable, for all but the starter. Connect an ammeter in series with the link, disconnect the link, and you can precisely measure down to 1mA.

I meant plural of 10

It can normally be nulled, to a few 10s of mA. Or at least I can with a couple of meters I have.