More VW frustrations.
 

My boy has a 2015 GTI that is now giving him grief. He works graveyard security and runs a fairly small flashing light on his roof. After a week of this (and I assume radio play as well) his battery is dead. From what I can tell, it won't take a charge at all. He had been starting the car every hour or so and letting it run for 30 minutes. Now it won't start at all even after being on a small charger for 8 hours.

So, buying a new battery but how does he not kill this one too? The car is turbo so I assume running it at idle is bad. Starting and stopping hasn't worked. What else?

Have him take it to a mechanic or an Autozone or O'reilly's or something like that and they can test the battery and charging system to see which has failed. A mechanic can also, easily, check for a short...

Heading that direction too. I can't imagine much would be wrong with the car itself. I was just figuring that it was how he was using it at night while at the job site.

Trickle charger while at home?
Or as has been suggested find the drain.

Would an LED light draw minimal current ?

The roof ones are a half amp or more. Add the radio - apparently a couple of amps - and the undersized 70Ah GTI battery and yes, you could in theory drain it down to the point it won't start.

After you totally flatten the battery a couple of times it's done. I killed an optima yellow top in a week with a radio drain once. Two charges from fully drained and it wouldn't hold charge.

Warranty?

Ummmm....not exactly a VW issue. I'm just sayin'....

It isn't charging enough at idle and he is running too much draw. Get a new battery and buy a deep cycle for the trunk which you hook up the light to. Charge the deep cycle in the daytime in the garage.

+1 on this not being a VW issue ... and I'd certainly be happy to give VW grief! :)

Does he have a keyless ignition? If so, having a spare key "in" the car basically keeps the car's system "alive" so that it can be started with the push-button ignition. We found this issue with my dad's 2013 Golf TDI. Battery kept on draining till I finally found that the problem was a spare key had accidentally been left in the car...

Make sure there is not a battery drain issue.
Then just get a charger and mount in the car so can plug it in when sleeping. It will get him used to the electric cars of the future.

Had a car the the glove box didn't close quite enough to turn of the small light bulb. You couldn't see that it was still on even in the dark. Sometimes it would start the next day, sometimes not. Definately killed the battery. Was so happy when i accidentally found it on. Bumped glove box with elbow doing something else with everything off and saw a crack of light. Stopped all my battery issues.

^this

Remove the flash and let VW check the system ... and change the battery.