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After sitting for about 2 weeks without driving while I find time to check the CA to change the tires. Before going to get the tire changed, the engine started right up, the batter indicator was 40%, drove to the place, it came back up to 100%. The weather was about 32-35F in the morning. Checked the TMPS and it was OFF. In the afternoon, taking the car back home, the TMPS worked perfectly. This morning, the TMPS is OFF again. In what condition the system turns off the TMPS? Low battery? I checked the battery, 12.3V nicely. The key battery was out again after replacement 1 1/2 years ago. I don't really care for TMPS but it's good to have it.
I have a similar issue after replacing my battery. I bought the car used (2004) and emailed Varta in the UK with the battery code, since it did not have an obvious date code. Varta responded the same day - battery was made in 2004...most likely original. I went to the dealer, bought a new Varta and planned to have a friend code it over the weekend before winter firmly set in. After I installed it (but before I had access to a VAG), the MMI battery meter never went above 70%. I kept testing the battery every morning for a week - low 12's V. Upon starting, the battery was throwing off 14.7V. Then the MMI meter started to drop - 70 to 60 then 50. I returned to the dealer, explained that I thought there was an issue with battery, and they could not get it to code. They replaced the battery and were able to code it. However, the meter has never gone above 80%. I even put a trickle charger on the second battery one night - tested at over 13V the next morning. I am now back to 12.2V and the MMI is firmly planted at 70%. I need to rule out a parasitic draw but I don't think that's the issue (since the original battery lasted 13 years). I just can't figure out why the MMI isn't reading 100% with a new battery.
What are the chances that I received a second battery with an issue, such as a weak or bad cell?
What should the battery read "at rest"?
Could the battery energy management module be failing? Would a VAG show a failing BEM or would the BEM have to be completely toast for it to kick a code?
Well, I think the consensus around here is that the battery meter is basically worthless in the car. How long has the new battery been installed? I know that without coding, it can take some time for the car to adjust it's charging to the new battery.
I have a similar issue after replacing my battery. I bought the car used (2004) and emailed Varta in the UK with the battery code, since it did not have an obvious date code. Varta responded the same day - battery was made in 2004...most likely original. I went to the dealer, bought a new Varta and planned to have a friend code it over the weekend before winter firmly set in. After I installed it (but before I had access to a VAG), the MMI battery meter never went above 70%. I kept testing the battery every morning for a week - low 12's V. Upon starting, the battery was throwing off 14.7V. Then the MMI meter started to drop - 70 to 60 then 50. I returned to the dealer, explained that I thought there was an issue with battery, and they could not get it to code. They replaced the battery and were able to code it. However, the meter has never gone above 80%. I even put a trickle charger on the second battery one night - tested at over 13V the next morning. I am now back to 12.2V and the MMI is firmly planted at 70%. I need to rule out a parasitic draw but I don't think that's the issue (since the original battery lasted 13 years). I just can't figure out why the MMI isn't reading 100% with a new battery.
What are the chances that I received a second battery with an issue, such as a weak or bad cell?
What should the battery read "at rest"?
Could the battery energy management module be failing? Would a VAG show a failing BEM or would the BEM have to be completely toast for it to kick a code?
Thanks and Merry Christmas to all.
My hunch would be parasitic draw. Could be things varied like a component not going to sleep, or the alarm battery failing and messing up the inside electronics (another oldie that comes up on board off and on for years now). Needs VCDS probing to sniff out; I was fortunate to never have to endure. Poor man's version is pull various fuses and see what happens. Don't rule out alternator either; reliable on D3's but comes up once in a while.
My battery is still new, I'm experimenting without coding the battery with vcds. Here's what I've learned so far.
- The battery indicator does work, if I don't drive for a long time, the weather is cold, the battery hasn't been charging for a while, it did show 40%. If the battery and charging system is good, it would come back up in a few minutes of driving.
- If the battery and the charging system are not running for a while, the BMS will shut down unnecessary devices like TPMS. When it senses everything is good, it will turn everything back on.
Mine is all good and the battery from Walmart.
So, when I don't understand the system software, everything is trials, errors and guessing... Gotta love the Audi Engineering.
Cheers,
Louis
Last edited by ltooz_a6_a8_q7; 12-25-2017 at 11:40 AM.
Battery has been in for about 2 weeks. Unlike Louis, my meter has never touched 100%, even when I was leaving the dealership with the newly-coded battery. (I asked before I left and they told me I just needed to drive it before it adapted to the new battery, at which point the meter would rise. That hasn't happened.)
A component not going to sleep could be the issue. If I manually set the trunk latch (so I can leave the trunk open for access) and arm the alarm, how long do I need to wait for the car to sleep before I start checking the amperage across the fuses?
Where might I locate/test the alarm battery that you mentioned? (I assume it is not the battery in the key fob.)
12-24-2017, 11:53 AM
my A8L doesn't like cold weather?
