dmanders

My wife's Q3 has a dead battery. I will use my Q8 to jump start it. I've jumped many cars before from VWs to Audis and Porsches. But never a Q3 or a Q8. Anything I should be aware of or is it SOP.

Thanks,
David

angrypengu

There is no reference in the self study program for technicians for using a Q8/A8 to jump start another vehicle. Should it be a problem? No. Would I do it? Oh hell no.

This is what will happen if you do this.

1) Your 12V battery will provide power to your wife's Q3.
2) Your 12V battery will be drained accordingly.
3) The DC DC converter will then convert energy from your 48V Lithium Ion battery to then charge the 12V battery, representing a significant loss of immediate power on your 48V battery. (would it drain to below 50% SOC for a while? Yes. Is that detrimental? No. Is that considered an unnecessary cycle/wear? Yes. Would it concern me? Absolutely
4) The Belt Starter Generator (BSG) will then start to provide power to the 48V battery to charge it back up.

IF you are going to do this, it is 10000% important that you leave your vehicle running (duh), but have it idling high. The best way to do this obviously is to have someone keep the RPM at 2000rpm, or, if you don't have the manpower to do this, run the car in sport mode for a while (a few seconds is OK), and then park the car. The idle (if the A8's behavior transitions to the Q8) will be at a higher idle than if your drive mode was at comfort right before you move the gear selector to park.

If you don't do this, when the Q8 is idling, the 12V system drains power at about 5-8 amps at idle (on comfort mode). By putting it in sport mode, the BSG is able to generate enough electricity such that there is no 'negative' drain on the 48V system. You absolutely want to avoid draining your 48V battery.

Personally, go and get a jump off of someone else or get a battery charger or battery boost pack.

For more details here are my detailed findings: https://www.audiworld.com/forums/a8-...ns-d5-2973388/

dmanders

Wow. What an incredibly useful reply. In the end we opted to call a tow truck to jump rather than take the chance. Thanks, David

BigHat

None of those issues would concern me. What would concern me is a potential voltage or current spike back into the Q8 they may screwup the electrical system. If I had to use the Q8 to jump another car the Q8 would be off. Jump-starting between modern cars is a crap shoot. Go buy an external battery pack or battery charger. Those small lithium battery packs work great and you can recharge it via a USB port.

Jsf721

I’d buy a jump pack. There are too many electronic systems and new stuff to risk a problem.

I don’t think anyone knows the ramifications on the 48 volt systems so early in the game so I would opt on the side of causation and buy an anti gravity LI jump pack on the largest voltage you can swing and go that route.

Just my 2 cents.