Yesterday I noticed an red battery light while driving. I immediately drove back to the house. En route, I discovered the system voltage reading for battery from OBD port / Carista was 11.8V when I thought to connect. I assume the light might have triggered at 11.9v, as soon as it dropped below 12. 1V too late imo, especially as engine had been running 30mins+ since last start up, bad design, should have triggered at 13V. Normal volt is 13.7-14.1v.

By time I got back, voltage was slowly dropping, some flickers, but dropped to 11.5V when I parked up and locked up. Car is parked in a location and orientation suitable for towing, if needs be.

Garage is obviously closed. But it is 15 miles away and need a motorway trip to get there.

The vehicle has commercial breakdown insurance.

However, it is DSG. Front wheel drive.

Should I leave everything to breakdown next week? Or should I proactively take the battery out to charge it inside the house and drive it to the garage in a 1 way trip for the battery? Assuming full charge is 13.9V. I don't know how much starting the engine will take off that. But I know the battery won't die at 11.5V. And from yesterday, it dropped 0.3V in 10? Mins? So should survive a 22 min trip to the garage with no air con / stereo if starting engine doesn't use too much power?

Also, how would I know if it's alternator / battery now? Taking battery out would not be helpful if that's is what's the problem.

Edited 5 April, 20251 yr by newskodadriver

1. If you run out of electric power while driving, the problem is the alternator.

2. Get your battery charged asap to save it. Batteries don't like being discharged for a long time. This charger is my favourite: https://www.ctek.com/uk/battery-chargers-12v-24v/mxs-5-0-uk

3. No idea if a full battery will last the 22 min to the garage... Do you want to risk stranding on a motorway?

4. Exchanging an alternator is no rocket science. Instead of picking up your car on a tow-truck, maybe your garage can fix your car where it is now?

On 06/04/2025 at 15:58, andrehj said:

1. If you run out of electric power while driving, the problem is the alternator.

2. Get your battery charged asap to save it. Batteries don't like being discharged for a long time. This charger is my favourite: https://www.ctek.com/uk/battery-chargers-12v-24v/mxs-5-0-uk

3. No idea if a full battery will last the 22 min to the garage... Do you want to risk stranding on a motorway?

4. Exchanging an alternator is no rocket science. Instead of picking up your car on a tow-truck, maybe your garage can fix your car where it is now?

Thank you for the reply. Apologies but here is my late update on what happened.

The AA came out on fleet breakdown insurance. They did not tow me. They swapped out my battery for a fully charged one. And just just told me to drive 16 miles (13 miles motorway) 22 mins with them following behind me.

They told me it was standard protocol to not tow vehicles with bad alternators. But to do what they did. Apparently, the longest trip he did like that was 50 miles. Swapped out another battery half way through.

Also told me a fully charged battery should do 25-30 miles with aircon / lights / music off etc.

So I guess, I could have just charged the battery up myself.

The main ecu is surprisingly sophisticated and drops out 'luxury' functions such ss aircon as battery voltage drops.

Yes a fully charged battery should give one start and 30 minutes diving - as you found out driving home in the first pland.