lurchphil

Somehow, I managed to leave the key in the ignition in the "on" position while I was tinkering with my 2011 GTS cabriolet. It was "on" for a whole day. Needless to say, I had no battery power whatever and couldn't open the frunk. The most embarrassing part was the the ignition key wouldn't come out. I have an overpriced Porsche battery charger which I plugged into the cigarette lighter for an hour or two and Voila!, the frunk opened and the key released. I disconnected the battery terminals and hooked up my fancy Battery-Minder with numerous lights and charged it overnight. The battery, a Bosch AGM, was fully charged the next morning. The only downside is that my airbag light stays on now. Off to the dealer again... This is after I had the dreaded engine light come on 400 miles from home two weeks ago. I called the service manager and was told that if the engine light wasn't flashing, it was safe to drive. They mentioned a loose fuel tank cap but I always double-check that. If it clicks it's on - right? I took it in and they put it on their magic computer but they couldn't find anything wrong other than the engine light stayed on and it wouldn't reset for them. They said that they may have to do a "smoke test" to see if any of the emissions stuff was leaking. Otherwise, it could be a module of some sort. I went out of town for a week and left it with them. They called and said it was the fuel tank cap. I made sure that they replaced the cap with a new one. I am losing the will to live... Not really, the GTS is a wonderful car!

keynes

I like that Porsche charger. It's compact and I use it while messing around with the stereo on. When I don't drive during the week, I'll plug it in.
I wonder, does it condition a fully charged battery as well?

Racetwin2

I have the CTEK 45 (same as Porsche charger) but with a quick connector with LED indicators.

It makes it super easy as it is connected directly to the battery but accessible with the hood closed. It means that I can always get access to the battery even if car is completely dead. Another advantage is the LED indicatord that show green, yellow or red depending on battery charging level.

I have placed the quick connector just under the hood where the windscreen wipers are. Then I can always see charging level and its easy to access. I highly recommend it. Maybe it even works with the porsche charger as it is the same manufaturer? Picture below.

Ben Z

I have a CTEK MUS-7002 with the 12v lighter adaptor pigtail, it does condition, and it also has a supply function to keep settings intact if I need to disconnect the battery.

max540i

+1 on this approach
To adapt my porsche charger to the CTEK (56-382) i used a CTEK (56-573) Comfort Connect Cig Socket:

DesmoSD

That's awesome, glad it gave enough juice to unlock your car.

+1 on the cigarette lighter adapter. There is no need to Mickey Mouse something as simple as a battery tender and cigarette lighter adapter charger.