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I'm going to bump/update this thread with some relevant information here.
I spent all day researching exactly what happens with the belt alternator starter (BAS) system. It was news to me that the mild hybrid system in the A8 actually generates power. I thought it was a pure recuperation system/start stop system only but I was wrong. The system can actually generate up to 16hp and/or 44 lb/ft of torque to help the internal combustion engine (ICE). As with everything, the devil is in the details. Some reports have mentioned that this system only assists the ICE in certain conditions, so I decided on doing a few tests.
These are *butt dyno* tests so please take with a grain of salt. I noticed that in sport mode, that even with manual shifting, the A8 hauls harder than in normal mode, especially at the lower rev range (think torque from BAS!). My guess is that when the reference materials say "certain conditions", that they meant only in dynamic/sporty driving. That makes sense to me. Why add cycles on the mild hybrid battery when doodling around town? There is a more noticable lag in normal mode and I suspect it's because the mild hybrid system is not assisting.
Thus, going back to the topic at hand. The key to battery longevity is 1) not using it as much as possible to minimize cycles/wear and 2) temperature management.
#1 includes things like keeping it in normal mode, and/or not using the start-stop system. Also, the 48V and 12V systems are connected electrically with a DC/DC converter in the right side of the trunk (above the 12V battery). Thus, be very careful if you're like me and spend an hour listening to music in the D5 with it off (one downside of 1920 watts and 23 speakers....). You don't want to drain said batteries. I have also been researching about battery tenders/maintainers. I did not end up buying one because the issue is that these things measure the voltage of the 12V system to determine when it is charged. There is no logic with a secondary 48V system combined with a 13 cell lithium ion battery. One doesn't want to overcharge these systems....and since I cannot find any in depth documentation from Audi for their techs either, I'm not going to use them.
#2: I have been tracking my garage's temperature. Over the last few months I have insulated my garage door (the heat from the sun is scaring me in the summer. Last year at times it hit 120F after parking the car in the garage, closing the door, and having the afternoon sun beam/radiate heat through my garage door.) Since adding insulation, it's been a very drastic improvement. Also, I have devised a whole system of garage ventilation. I have a two door garage, and have since devised ways to keeping it cooler. E.g. cracking the garage door and having a vertical blower fan laid down horizontally to bring in cool air. I also have devised a mini fence system made out of metal fencing about 6" high to keep the animals out. During the heat wave of summer, my intent is to cool down the garage throughout the night and then closing the garage door during the afternoon heat. Hopefully with enough cold energy the room will stay cool enough. If things get bad, I have figured out a way to install portable AC in there too, with essentially a large piece of insulation at the bottom of the garage door replacing the mini fence and then having a garage AC with an exhaust and intake (thus minimizing pressure differential vs the garage room) installed into the insulation (cutting out two holes).
I will battle my #1 enemy (heat) in this case. 1) It's sort of fun and 2) I plan on keeping the D5 a long time. The thought of having to replace a $3500 battery is a bit...well, let's just say that while all of us can afford it, I think I'd rather spend that on a first class seat to somewhere warm in the winter .... and of course 3) I love cars. Most of the time, I'll pop the hood and take off the engine cover to help cool the turbo and engine down quicker...yeah, laugh away. it's ok, I can take the heat........
Last edited by angrypengu; 05-12-2019 at 03:13 PM.
I'm going to bump/update this thread with some relevant information here.
I spent all day researching exactly what happens with the belt alternator starter (BAS) system. It was news to me that the mild hybrid system in the A8 actually generates power. I thought it was a pure recuperation system/start stop system only but I was wrong. The system can actually generate up to 16hp and/or 44 lb/ft of torque to help the internal combustion engine (ICE). As with everything, the devil is in the details. Some reports have mentioned that this system only assists the ICE in certain conditions, so I decided on doing a few tests.
These are *butt dyno* tests so please take with a grain of salt. I noticed that in sport mode, that even with manual shifting, the A8 hauls harder than in normal mode, especially at the lower rev range (think torque from BAS!). My guess is that when the reference materials say "certain conditions", that they meant only in dynamic/sporty driving. That makes sense to me. Why add cycles on the mild hybrid battery when doodling around town? There is a more noticable lag in normal mode and I suspect it's because the mild hybrid system is not assisting.
Thus, going back to the topic at hand. The key to battery longevity is 1) not using it as much as possible to minimize cycles/wear and 2) temperature management.
#1 includes things like keeping it in normal mode, and/or not using the start-stop system. Also, the 48V and 12V systems are connected electrically with a DC/DC converter in the right side of the trunk (above the 12V battery). Thus, be very careful if you're like me and spend an hour listening to music in the D5 with it off (one downside of 1920 watts and 23 speakers....). You don't want to drain said batteries. I have also been researching about battery tenders/maintainers. I did not end up buying one because the issue is that these things measure the voltage of the 12V system to determine when it is charged. There is no logic with a secondary 48V system combined with a 13 cell lithium ion battery. One doesn't want to overcharge these systems....and since I cannot find any in depth documentation from Audi for their techs either, I'm not going to use them.
#2: I have been tracking my garage's temperature. Over the last few months I have insulated my garage door (the heat from the sun is scaring me in the summer. Last year at times it hit 120F after parking the car in the garage, closing the door, and having the afternoon sun beam/radiate heat through my garage door.) Since adding insulation, it's been a very drastic improvement. Also, I have devised a whole system of garage ventilation. I have a two door garage, and have since devised ways to keeping it cooler. E.g. cracking the garage door and having a vertical blower fan laid down horizontally to bring in cool air. I also have devised a mini fence system made out of metal fencing about 6" high to keep the animals out. During the heat wave of summer, my intent is to cool down the garage throughout the night and then closing the garage door during the afternoon heat. Hopefully with enough cold energy the room will stay cool enough. If things get bad, I have figured out a way to install portable AC in there too, with essentially a large piece of insulation at the bottom of the garage door replacing the mini fence and then having a garage AC with an exhaust and intake (thus minimizing pressure differential vs the garage room) installed into the insulation (cutting out two holes).
I will battle my #1 enemy (heat) in this case. 1) It's sort of fun and 2) I plan on keeping the D5 a long time. The thought of having to replace a $3500 battery is a bit...well, let's just say that while all of us can afford it, I think I'd rather spend that on a first class seat to somewhere warm in the winter .... and of course 3) I love cars. Most of the time, I'll pop the hood and take off the engine cover to help cool the turbo and engine down quicker...yeah, laugh away. it's ok, I can take the heat........
I am pretty sure I read that the BAS system kicks in some power to smooth out acceleration from a full stop as there can be some turbo lag after a full stop - with or without the stop/start feature active. That would suggest many minor battery discharge/charge cycles on most any trip. I don't recall reading if this is so for just the dynamic setting or all drive settings.
I am pretty sure I read that the BAS system kicks in some power to smooth out acceleration from a full stop as there can be some turbo lag after a full stop - with or without the stop/start feature active. That would suggest many minor battery discharge/charge cycles on most any trip. I don't recall reading if this is so for just the dynamic setting or all drive settings.
If you do come across further documentation on this I would really appreciate it if you share. The turbo lag is a common complaint on the EA839 engine. Notably, plenty of complaints on the B9 S4 system (not a MHEV) and on the Audi Q8 (Also a MHEV). Because those complaints are universal with the EA839 engine no matter the application, that is why I believe in normal mode the BAS does not kick in, otherwise I would expect complaints to exist on the B9S4 and not on the Q8.
That said I am comparing Apples to Monkeys here as they are tuned differently and a Q8 could have a B9 for lunch from a weight perspective....
If you do come across further documentation on this I would really appreciate it if you share. The turbo lag is a common complaint on the EA839 engine. Notably, plenty of complaints on the B9 S4 system (not a MHEV) and on the Audi Q8 (Also a MHEV). Because those complaints are universal with the EA839 engine no matter the application, that is why I believe in normal mode the BAS does not kick in, otherwise I would expect complaints to exist on the B9S4 and not on the Q8.
That said I am comparing Apples to Monkeys here as they are tuned differently and a Q8 could have a B9 for lunch from a weight perspective....
Couldn't you log battery input/output or something to the like from VCDS and see if under acceleration in different modes there is a large battery drain? Just an idea anyway.
Thanks for the suggestion re: VCDS. I will see if there's a module I can tap into if I get it. I was using a chinese knock off before. Debating between OBDEleven Pro and VCDS...
Today's tip is: Keep your fan inlets clean, and to ensure the rear HVAC system is turned on with your vehicle. You can use the sync function so that the rear seat temps are in line with the front so you don't have to go through your MMI system to control your rear temp settings.
Why? Take a look attached.
There are allegedly fan intake ports at the bottom corner of the rear seats. I looked up cars in California, NYC and I forget whereelse in the US by putting in their VIN. This reference to VH3 does not show up anywhere. I certainly don't live in a very very hot climate, although on summer days it does get very hot (for a month or so). I just don't know if my car comes with the VH3 battery cooling package, but that is my plan today. I will report back with what I find!
Nonetheless, for those of you that don't want to go through the hassle of confirming (it will take no more than a minute to remove the spare tire/tools/spare tire floor liner) just ensure you have your air vents in the rear and B pillar turned on with HVAC on and pointing towards those corners if you don't regularly carry people in the rear seat.
If this VH3 thing isn't in my car, I'm retrofitting it in...
Last edited by angrypengu; 05-16-2019 at 11:30 AM.
I've unfortunately given up with retrofitting the air fan/cooling system for the 48V battery. If you see part #21 above, I have no idea what it would clip into. Also, there are a lot of other parts that need to be changed to support it...
So, well, in the interest of preserving the warranty and because I'm now stumped, I've given up.
It'd be very interesting to see if cars in Texas are the same (E.g. lacking this cooling system). This is very surprising to me that these do not exist on our cars, and my car, and cars in NY/California (of the VINs I've run) are classified as "mild hot climates". Texas is the only place that has A8s classified as "hot climate"
The above is what it would look like, so all of those black plates would have to go.....
Last edited by angrypengu; 05-16-2019 at 11:29 AM.
I wanted to provide some additional thoughts here in case my 'passion' for keeping this 48V battery cool is worrying some. First off, while I have a technical background, I am not an automotive engineer and have no doubt Audi did testing on this. Since I've been burned by Audi in the past, I'm just a bit more careful.
Couple of things that I have noticed since testing with various thermometers in various parts of the trunk:
1) The position of the 48V battery system actually keeps it quite cool, at least when compared to the rest of the vehicle.
2) The 'exhaust' ports of the cabin are behind the tail lamps on the right and left side of the car, so air does naturally sort of pass by the 48V battery position.
3) Looking at the underside of the car, I did notice the 48V battery is "in between" the left and right catalytic converter, but the cats are obviously covered by extensive metal heat shielding.
4) Today, my biggest astonishment was to measure the cats once the vehicle is turned off, and after the vehicle had been running around time and had reached operating temperature. I was actually pleasantly surprised at how quickly the cats themselves cooled. I've been keeping a fan blowing cold air into the garage and another fan blowing air at the cats. The latter may be a bit, overkill, I concede
5) I keep the center pass through thing opened now and have the air vents in the rear direct air through the pass through to keep the trunk cooler....
On very hot days in the dead of summer, I may just throw a few ice packs in the trunk if I have to park it outside or whatever, but short of that, I think we should be OK. I have not done extensive temperature testing with the vehicle in sport mode which should be exercising the 48V battery some more, but we will see. Obviously a big part of battery temp control comes down to the software that controls it. We obviously do not have any visibility as far as how they programmed it.
Last edited by angrypengu; 05-17-2019 at 07:01 PM.
So apparently Audi doesn't even know whether or not the BAS system is used to assist the internal combustion engine.
I've pulled out the relevant documentation and highlighted it.(see attached document)
I just also confirmed through the parts tool that both mild hot and hot hot (e.g. Texas/Georgia) climates do not have the breather/fan module for the mild hybrid battery. I'm shocked. Both came back like this. See all that greyed out?
Last edited by angrypengu; 05-18-2019 at 06:29 AM.
05-12-2019, 02:59 PM
and of course 3) I love cars. Most of the time, I'll pop the hood and take off the engine cover to help cool the turbo and engine down quicker...yeah, laugh away. it's ok, I can take the heat........
