I can help with that one.
I keep a BT battery monitor on each of my cars in the garage and can read the voltages from my phone app.
I regularly check them.
The 992 GT3 battery like the 991 GT3 battery before is massive (to run the 4WS system) and will not deplete even with the longest time I have had my car parked up between track days (2+ months). The 992 uses a LiOn cell now and reads around 13.3-13.4v after full charge. My car has currently sat unused for three weeks and is sitting on 13.28v. Even after 9 weeks it read 13.20v. The 992 now incorporates battery saver tehe effectively renders all systems low voltage or cuts them off the system after 5 days. I loose remote management of the car using the MyPorsche app after this time too as the SIM card in the PCM is no longer active.
The 991.1 & 991.2 GT3 did not have such cleaver battery saver technology and ran AGM batteries. Again huge batteries for the 4WS. I would fine that these would need a top up with the CTEK after 6 or so weeks but to be honest I think you could leave those cars for 3-4 months before voltage became an issue.
My garage is temp controlled year round. It will not drop below 10c in winter or go above 28c in summer. The BT battery monitor app does download the historical voltage data when it connects and I have monitored this with all my car over the last 2 years and can say that when its cold the Lead Acid and AGM batteries definately loose voltage but the LiOn seems pretty stable with year round temps in that range.
Older pre 991 GT3 without 4WS have smaller Lead acid batteries. I used to find around 6-8 weeks was the longest those could reliably sit before a top up.
With my boat which will sit in storage for up to 7-8 months unused I fit a battery cut off switch which eliminates any voltage loss. Ive not had to top the boat batteries up in 5 seasons!
When I lived offshore but kept my cars in storage in NZ and returned every 3-4 months I would have battery cut off switches fitted and they worked perfect to manage my cars for 12 years. They are for me the best solution. I have used CTEK for 14 years (have 3 or 4 of them) but I have had one fail once which actually drained the battery of its power back to the grid. For long storage battery cut off switch or removing the terminal is best IMO. Its also cheaper and safer...
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2022 Toyota GR Yaris, 2021 992 GT3, 2017 Alfa Romeo Giulia QV, 2009 Lotus Elise SC
