overworked33

Hello All,
Here is a first time question from a long-time lurker: Do the C8 cars have a traditional 12 volt battery in addition to the 48 volt pack?
It would certainly seem to unnecessary, and it would be great to eliminate the extra weight and maintenance.
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2013 Audi A6
2017 VW Gulf Alltrack

SYMAWD

It does.

angrypengu

Yes, and you cannot disconnect the 48V components either. This is a system I know a lot of.

Also, none of the North America vehicles are equipped with the VH3 components that enable additional cooling for the 48V battery which worries me as I have been monitoring cell temperatures vs ambient temperatures.

Nonetheless on my vehicle which is kept garaged, the battery itself is babied by yours truly. 5 ice packs go on top of the trunk floor which drops the temperature from say 30'C in my garage to 20'C for the battery. This gets changed out every 24 hours....yes, I know, I'm going too far.

If you park your car in the dead of the desert in the sun, you might want to rethink your strategy. These battery packs are $3800CAD to replace, and are not covered outside of the new car warranty.

overworked33

Thank you for the replies. I do wonder what the benefit is of having both batteries.
I must say, I am impressed by your battery preservation regime.
All this does leave me wondering what is the cost/benefit of the 48 volt system, particularly when you turn off the start/stop feature (which I'm not a fan of).

angrypengu

Energy recuperation during braking goes into the 48v battery as does a brief 44 foot pounds of torque for up to 5 seconds to assist with acceleration.

The start stop system uses the BSG to start the engine but the on board electrics are powered by the 12V system. So unlike what I surmised on the D5 board, there really isn't much 'gain' here if you turn off start/stop.

That said, I turn it off because I like to burn gas. It's fun. Everyone should try it

If it were up to me, I'd pay $3000 to get rid of the 48V system and the stupid lithium ion battery. It infuriates me to no end that it's on our cars. Ducking environmentalists. (who couldn't afford a treehouse, let alone one of these cars.)

John Simcox

The 48v system is not there just for the energy recuperation systems although it is used for that. I have the 2.0TDi and that only uses a 12v "semi hybrid" system. The main reason for the 48v system is for features such as dynamic chassis control, air suspension and the more advanced driver assist systems which require systems that respond much faster that draw significant amounts of electrical power and would not be suitable - too many amps requiring thicker heavier cables - for a 12v system. Once autonomous features become more common then more cars will have 48v systems.

angrypengu

All of the systems mentioned either do not exist on this car or run on the 12v system.

1) Dynamic Chassis Control does not exist on the C8.
2) Air suspension (passive) does exist on the C8 but runs off the 12V system. The only active air suspension that I am aware of that runs on the 48V system is on the D5.
3) All of the driver's assist systems on all of the 2019 Audis run on the 12V system.

overworked33

I agree with Angrypengu that the 48v system seems pretty useless other than to artificially improving the MPG ratings.

I’m just not convinced that shutting down the engine at stop lights saves any material amount of fuel, while I do believe that all this stopping and starting is going to cause accelerated wear.

You mention a 44 ft/lbs. boost during acceleration. Can you tell me where you got that information? I can’t find it on-line. What I found doesn’t mention a boost during acceleration but rather providing minimal power for coasting with the engine off when approaching a stop light.

To Audi’s credit, the start/stop is a lot smother on the C8 than it is on my 2013 C7, and I like the automatic restart when traffic starts moving. Also impressive is what I guess must be electric power steering. I found on the C8 the power steering still works when the engine is off, not so with every other car I’ve ever driven.

It’s also clear that 48v power is converted to 12v in order to power all the car’s 12v systems when the engine is shut-down at a light. Must be too much of a load for a regular battery.

Overall, I’d skip of the 48v system. It looks like a lot of cost, weight and complexity for little to no real-world benefit for the consumer.

angrypengu

Found in a few press articles and measurable in OBD11. The below is from the SSP for Audi mechanics for the D5 and applicable to the C8 A6 and the A7/A8/Q8 etc (2019 models).

The problem here is that consumers are too dumb to realize there's more to life than fuel economy and don't realize the downsides of these stupid SS systems AND things like direct injection. We are to blame, as are environmentalists and the government, sadly.

Anyways, 60nm = 44 ft/lb. This occurs constantly on the highway at cruise, and at acceleration between 1000 to 3000rpm~.




To Audi's credit I have not seen the 48V battery supply energy to the 12V battery when the car is stopped. The engine itself kicks in if the 12V battery gets depleted beyond a certain threshold. That said IMHO the 68AH battery in the D5, and probably on the C8 as well, is insufficient. I manually charge up these batteries every now and then using a Tender but I do a lot of city driving/low mileage these days.

billkfromva

I may not be a senior member here, but I am an electrical engineer who researched heavily before buying my new 2019 A6 Premium Plus yada yada... If for no other reason the car needs the 48V battery to start it using the belt driven motor/generator for the "55" (3.0 V6). It is also used for all the "assist" features. Even if you turn off start stop, it is still used to start the car when you first get in it. It also powers the transmission oil pump, and on some engines the turbo chargers are electric, so I am afraid there is no living without it.

current:
2019 A6
2017 VW Passat
2013 Q5 Hybrid
Previous (all new):
2009 Lincoln MKT
2007 Lincoln MK LT
2004 Chrysler Pacifica
2000 Jaguar X Type
1999 Audi A6
1998 Lincoln Navigator
2000 Cadillac DTS
1992 Pontiac Bonneville
1990 Oldsmobile Silhouette
1987 BMW 524td
1984 Dodge Caravan
1978 Chrysler Town & Country Wagon
1978 Dodge Challenger
1973 Dodge Charger
1973 Mazda RX2
1965 MGB (from my dad)


2004 Jaguar XJ8
2001