I leave window open wide enough for the wire.

 

Stored in garage 3 months while I was away - no problem, started right up.

 

Started up without a tender?

 

I got the cig lighter adapter but didn't like the cord hanging out the door or window, so I ended up connecting directly to the battery, see installation photos.

 

I seem to recall a warning that cautions us to utilize a designated negative terminal for jump starting. Would that be applicable to trickle charging?

 

How did you get the charger ring on the connector as the bolt does not come all the way off? Wasn't that your original issue? Maybe you should put a towel on the car so the wire doesn't scratch you paint.

 

Here are the guidelines from the manual for charging.

Your authorized Porsche dealer will be pleased to advise you about a suitable charger.
Always observe the instructions provided by the charger manufacturer.
If the battery is frozen, thaw it out first before charging it.
When charging the battery, ensure adequate ventilation.
Connect the charger to the emergency starting terminals.
Only plug into the mains and switch the charger on when it is connected up correctly.
Switch on the charger.
After charging the battery, first switch off the charger and then disconnect it.

The connector is installed per ctek instructions and Porsche recommends directly to mains the way I read it.

 

I took a linesman pliers and made a cut in the ring. I was then able to open the ring slightly and slip it onto the bolt. When I reconnected the nut it returned the ring to its normal shape.

 

The negative battery ground and chassis ground are connected. For safety reasons connecting the negative terminal last and away from the battery reduces risk of sparks near the battery.

Ctek chargers are spark free, that is why they have the comfort connector going directly to the battery terminals.