I was away for 6 weeks and left my 2017 Turbo in a parking garage at work (had cameras, etc). I was a bit worried about the battery but thought it should go 6 weeks. Got back, key fob opened car, no problems. Thought I was good, but when i went to start the car, no dice with a weird message. I forget exactly, but it was something like key fob problem, put in certain area--but it did not tell me where that area was (turned out to be cup holder). It was yesterday (Sunday), and it was cold. Called Porsche Roadside. I shivered for an hour until the guy showed up. He said it was not the battery (turned out to be true). He thought the starter "froze," which even at the time I thought was BS (which it was). Took Uber home (where I had a spare key). Today, I took both keys to the Porsche dealer (luckily near where I live). Turned out the key at issue had a dead battery. I bought the car this year and did not realize that the key lights up when it has a good battery. Got a new battery for the key (free as it is certified), took Uber to garage, and started right up. It turns out that it pulls more battery power from the key to start the car than to open the doors. Not sure why this is. It is not as if the key starts the car, as such. It just sends a signal. Be that as it may, I was out $100 for Uber but still glad it was nothing more significant. Next time I am bringing the spare key with me.

 

The 3V button battery lasts about a year to two at the most. Usually, the dash warning will tell you your remote battery is low.

 

I keep a spare battery in my center console.

also, you can use the mechanical key in key fob to start car but tricky and why I have a spare battery.