1 year old battery goes from 14.5 v to 10.5 overnight

Looking more like there is a faulty cell or internal connection in the battery. When it was installed in the car was the vent tube connected from the car? Have the battery professionally checked and if faulty get in touch with the retailer and have a replacement battery.

It was the correctly rated battery for your car and not just the cheapest one on the site? Also not a start / stop AGM battery.
 
This battery didn't come with any hose, to be honest, I've never seen such tubes in any car batteries before.
I've quickly looked it up on the forum and I see some has that tiny flexi hose, but I don't. This battery had those tiny plastic caps on the side, the instruction said those need to be removed before installation, which I did.
The old battery didn't have any hose either.
I got this new battery from the website been recommended a lot before called Tayna.

Is that hose an A2 spec or car battery dependent? Cheers
 
This battery didn't come with any hose, to be honest, I've never seen such tubes in any car batteries before.

Cars that have the battery stored inside the passenger cell (such as the A2) are always equipped with a venting tube. All A2s came with them, without exception.

If yours is missing, you need to get hold of one and fit it.

The other side of the battery should have the venting cap left in situ.

Otherwise you risk explosive gasses being released into the car.
 
Cars that have the battery stored inside the passenger cell (such as the A2) are always equipped with a venting tube. All A2s came with them, without exception.

If yours is missing, you need to get hold of one and fit it.

The other side of the battery should have the venting cap left in situ.

Otherwise you risk explosive gasses being released into the car.
I've been driving my A2 for over 3 years and never seen that tube, but it makes sense as the battery is in the cabin. I'll have look today, cheers.
 
I'll have look today, cheers.

The vent tube connects to the positive terminal end of the battery Shown here in the Audi workshop manual:
a2-4475.png


Completely empty your battery compartment and you may well find it. Otherwise, it's easy to get a replacement. Here by way of example is Tayna's vent pipe listings:

Maybe one of the breakers here can let you have an original.
 
The vent tube connects to the positive terminal end of the battery Shown here in the Audi workshop manual:
View attachment 101352

Completely empty your battery compartment and you may well find it. Otherwise, it's easy to get a replacement. Here by way of example is Tayna's vent pipe listings:

Maybe one of the breakers here can let you have an original.
Thanks Steve, useful info there. Looking af the pictures, I'm also missing the top holding bracket as well.
I'll definitely have a look, I wouldn't be surprised if the tube is completely missing too.
 
So here are the last 3 days, out of the car battery results. I couldn't fully charge the battery the begin with as I was busy, but I did that few days ago while leaving it in the car, almost same result too, but now with proper data:

12.7v --- 17th --- 90%
12.5v --- 18th --- 60%
12 3v --- 19th --- 40%
10.6v --- 20th --- 0%

Looks like the battery is toast.
It didn't drain voltage as much out of the car, than in the car, but either way by the 3rd day, the battery went completely flat and had no starting power at all.
I'm on my way to buy a new battery.

Possible cause:
I got the battery from recommended Tayna website few months ago, could be battery was damaged from factory, but could've been that the battery been kept a bit tilted in the car. Oh, wait for it, it's gonna be good :O Since I've had the A2, for over 3 years, the battery always sat a bit tilted, which was a tad weird, but the car worked good electronically, I left it like that.
After <2.5 years that battery gave in, so I got this one from Tayna. Now 6 months later this is done as well.
So upon checking the boot a few days ago, I'd noticed, the reason the battery was tilted all this time, because it was sat on the rear holding bracket! Real OMG moment!
However fit the battery prior to my ownership, just left it on the top of the brackets, instead of unscrewing the 2 bolts and fit the sliding tray over the edge of the battery, so 1 side was sat higher. I'd noticed this when I bought the car years ago, but it was working and sat solid as well, so I moved on to deal with other issues.
Learning something everyday :/

The CCU shows a few fault codes related to door locks, I'm gonna look into that as well, but looks like the battery and perhaps it's positioning was the main issue.

I'm not sure that caused the 6 months old battery to go bust though, as the previous battery was working like that for years, also cars do park up/down hill and they'd still work fine. Any suggestion about that? Cheers
 
If you bought from Tanya then is it not still under guarantee?
It'd be, but I can't find the receipt or the email. I'll message Tayna on Monday to see what can be sorted.
I've already got a new battery, it's on charger now and I'll fit it tomorrow.
It'll probably take over a week to send the bad battery back and get a replacement one, and I'm already without the car for nearly 2 weeks, so there was no point waiting more.
 
It'd be, but I can't find the receipt or the email. I'll message Tayna on Monday to see what can be sorted.
I've already got a new battery, it's on charger now and I'll fit it tomorrow.
It'll probably take over a week to send the bad battery back and get a replacement one, and I'm already without the car for nearly 2 weeks, so there was no point waiting more.
Really hope you have this sorted now pal.
 
So this interesting thing has happened. I took the battery out and left it uncharged for a day. 2 days ago showed 10.5v, yesterday 9.5v.
So when I was about to put it on charge today, I've check the voltage and it showed 12.3v.
Charger showed 40%, then quickly to 60% and charging slowly now.
I know voltage can bounce a bit, but +3v seems rather big jump. Also 1 hour later it's already on 80%.
Either way, I'll leave it out of the car for few day and see how does it hold the charge.
When battery is charging/on charge it should show 13.5 volts or there about at least, I think your battery maybe questionable.
 
When battery is charging/on charge it should show 13.5 volts or there about at least, I think your battery maybe questionable.
Since then I've updates the thread, just few posts above, showing 3 days test. In nutshell the battery can't hold sufficient charge anymore. I've got new battery today.
 
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Really hope you have this sorted now pal.
Yes I've got new battery today from Halfords, its fully charged and ready to go in the boot tomorrow. Fingers cross this will sort the issue, but I've kept the receipt this time :)

Edit: After new battery my A2 starts great! Battery doesn't even drop below 12v at start up, so hopefully it's gonna be fine :) Now onwards solving the next issue!
 
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