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Last week i replaced the battery on my 2011 Audi Q5 2.0T.
Got the new battery from my local Audi dealer, i installed it, coded it (using VCDS), and then proceeded to check and see if everything was fine, and these are the readings i'm getting:
Not being an expert, the only thing that caught my attention was the fact that on Group 018, Power Supply (Battery), i'm getting between 13.100V and 13.400V, and my understanding is that, while the engine is running, the voltage on the battery should read between the high 13's and low 14's....
This, being a brand new battery, is not an immediate problem, however, i would like to address the situation before it becomes one.
I don't want to just jump to replacing the alternator, without first checking for other possible (and cheaper) solutions.
i guess i could perform an output test on the alternator... (and i do have a voltmeter around here somewhere...); in that case, what would be the procedure? (again, not an expert here, so, please bear with me...).
Even if the alternator's output is ok (14V), the wiring that goes from the alternator to the battery could be the problem, let's hope that's not the case....
I also think that maybe i could just replace the voltage regulator on the alternator and see if that solves the issue... and if so, what would be the way to troubleshoot it?
A new alternator would cost me around $500 + labor... so i'm just trying to check with you guys first, and see if i can save some cash here...
Thanks in advance!
Last edited by virtuallyreal; 03-22-2019 at 04:11 AM.
Last week i replaced the battery on my 2011 Audi Q5 2.0T.
Got the newt battery from Audi, i installed it, coded it (using VCDS), and then proceeded to check and see if everything was fine, and these are the readings i'm getting:
Not being an expert, the only thing that caught my attention was the fact that on Group 018, Power Supply (Battery), i'm getting between 13.100V and 13.400V, and my understanding is that, while the engine is running, the voltage on the battery should read between the high 13's and low 14's....
This, being a brand new battery, is not an immediate problem, however, i would like to address the situation before it becomes one.
I don't want to just jump to replacing the alternator, without first checking for other possible (and cheaper) solutions.
i guess i could perform an output test on the alternator... (and i do have a voltmeter around here somewhere...); in that case, what would be the procedure? (again, not an expert here, so, please bear with me...).
Even if the alternator's output is ok (14V), the wiring that goes from the alternator to the battery could be the problem, let's hope that's not the case....
I also think that maybe i could just replace the voltage regulator on the alternator and see if that solves the issue... and if so, what would be the way to troubleshoot it?
A new alternator would cost me around $500 + labor... so i'm just trying to check with you guys first, and see if i can save some cash here...
Thanks in advance!
You alternator is most likely working correctly. It is a "smart" alternator with variable voltage regulation depending upon the electrical load. Go hook up your VCDS again, start your Q5, then turn on the high beams, rear defroster, blower motor on high speed, and heated seats on. What voltage do you get then? Turn all those electrical loads while the engine is still running and read the voltage again.
It can be way more complicated than that. This is an Audi. It has an alternator (with internal regulator) PLUS a charge control computer someplace. If that computer goes nuts, changing everything else won't help.
"while the engine is running, the voltage on the battery should read between the high 13's and low 14's...."
Not quite. I've seen 12.6-14.4 while running on the highway. Apparently the charge control computer will selectively shut down the alternator, to increase your mpg, when there are light loads and a fully charged battery. A battery will read 12.6-12.8 volts when fully charged (depends on the type) and anything above that is either "float charge" (false voltage from recent charging) or alternator output.
The VCDS numbers...are like a feeding station at the unicorn ranch, I suspect. No one seems to know what or if the cars actually do with all that data.
Whoever sold you the battery (Audi?) should be able to actually load test it, free of charge, to confirm if it is working or not. A resting voltage ("quiescent voltage") of 12.4 volts would indicate a battery that is only 70-80% charged. Similarly the 60A stated capacity would be less than a good stock battery. If Audi won't load test it for free--then any auto parts chain should. Not all of them really know how to use their test equipment, you're looking for one that uses a machine which runs for several minutes and then prints out a detailed receipt.
Could just be your car hasn't fully reset yet, or there's some other drain on the battery. If you make daily short runs to the corner store--that'll pull down the battery too. They need longer runs in order to really charge up all the way.
And then, if the battery was wet acid and manufactured more than 90 days before it was sold to you? Yeah, some capacity is permanently lost. The manufacturing date is usually cleverly hidden under a label, on the side but near the top of the battery. By the whole industry, not just Audi.
[QUOTE=Redd;25291074]
Similarly the 60A stated capacity would be less than a good stock battery. If Audi won't load test it for free--then any auto parts chain should. Not all of them really know how to use their test equipment, you're looking for one that uses a machine which runs for several minutes and then prints out a detailed receipt.
/QUOTE]
The VCDS 60Ah capacity indication is another bogus number. My 95Ah battery has indicated 78Ah on the day I purchased it, charged it up out of the car, installed it, ran VCDS readings before I started the car - 78AH, while running 78Ah.. We all know that the only way to measure the capacity of any battery is to fully charge it and then discharge it measuring the load and time to go to zero. There isn't any way the Audi can do this...…….. If there is someone please tell me how?
Last edited by Bob Petruska; 03-18-2019 at 08:18 PM.
Batteries should not be discharged below 80% of their AH rating or damage will result. 80% of 95AH is 76, so it looks like that number is the usable amp hours. I live off-grid and these are the facts of life with AGM batteries. Lower charging voltage prevents gassing a battery that can't have water added.
Batteries should not be discharged below 80% of their AH rating or damage will result. 80% of 95AH is 76, so it looks like that number is the usable amp hours. I live off-grid and these are the facts of life with AGM batteries. Lower charging voltage prevents gassing a battery that can't have water added.
That is quite possible for that number to be the 80% DoD (Depth of Discharge) for AGM batteries. I have a problem with the 76 Ah as the battery capacity will decrease with age and this number stored in the Audi Power Management System should change accordingly to maintain that 80% factor. I need to scan my Q5 with VCDS again as I have not done so since I installed the battery last fall.
Tom makes a good point, although the depth of discharge will also affect the total number of charge cycles, and if the DoD is kept to 50% or better to 30%, the total number of charge cycles can easily triple or quadruple. (i.e. 50 cycles using 80% capacity could wear a battery down more than 1000 cycles to 30%). 80% would be somewhat arbitrary. JCI, who make the Varta-branded batteries in the US, also suggest that any SLI battery is only supposed to be used in the 0-10% discharge area, that is, a 100Ah SLI battery should always be recharged fully and promptly before it gets below 90Ah capacity. (Yes, that little, really.)
Now I suppose I'll have to send the servants out to use VCDS and see what mine has to say...Except, they have off today.(G)
Tom makes a good point, although the depth of discharge will also affect the total number of charge cycles, and if the DoD is kept to 50% or better to 30%, the total number of charge cycles can easily triple or quadruple. (i.e. 50 cycles using 80% capacity could wear a battery down more than 1000 cycles to 30%). 80% would be somewhat arbitrary. JCI, who make the Varta-branded batteries in the US, also suggest that any SLI battery is only supposed to be used in the 0-10% discharge area, that is, a 100Ah SLI battery should always be recharged fully and promptly before it gets below 90Ah capacity. (Yes, that little, really.)
Now I suppose I'll have to send the servants out to use VCDS and see what mine has to say...Except, they have off today.(G)
Well this if from the Audi Tech Training course, read and weep...………
Looks like Audi is completely happy with under charged batteries, their goal is to make money and thus selling batteries is one service the dealer loves to do.
Personally I put a new battery in last fall, I forgot about it. If it dies in a year or so, I buy another one. I just can't see anyone who spends $50-60K on a Q5 worrying if they need a $150 battery every 2-3 years. If they do then the Q5 is not for them.
Read lately the post on bad steering rack - $4300 to replace. $7K engine rebuild if the chain tensioner goes. $4-5K to replace pistons/rings for excessive oil consumption. Front control arm bushings going $1-2K, Engine mounts leaking - $1-2K. $800 - 1K for a brake/rotor service.
A new battery is peanuts!
If one can not handle the costs of owning an Audi then there are other alternatives……...
You know, if someone picks my pocket and I don't even feel it, I can at least admire the skill. But with Audi....I've spoken with enough battery engineers at battery companies and solar charging equipment companies to know that the entire chorus says "Lead acid should be recharged to 100%, repeatedly and immediately". OK, the last 5% is going to take a long time to put in, the acceptance rate just is what it is. But this FUD from Audi...if it got any thicker they could charge extra by insisting it was a mineral healing mud bath.
60-80% normal...Yeah, like the children of Lake Woebegone, where every one of them was above average. [Garrison Keeler]
03-18-2019, 09:18 AM
Bad Alternator?
