Car batteries are fun!
I opened the trunk on my 85 911 the other day and noticed the trunk light was not working. It had been three weeks since I last drove it, so I plugged in the maintainer, and drove it the next day with no issues. The battery was an Interstate MT5-49/H8 with a 30 month warranty. I installed it in May of 2016, so well past the warranty date. I will be driving in HOT weather and that is hard on batteries. So I replaced it with the new version, the MTX-49/H8 36 month warranty. The same 900 Amps of cold cranking amps, 95 amp hr capacity. It is a challenge to get it out and the new one back in place, but just simple mechanical work.
My wife has a 2017 Macan, and it still had the OEM battery. It is all computerized and a space ship compared to the 85 911. I had to plug in my Autel MaxiCheck MX808 OBD2 tool to check the battery level and it was at 11.4 volts and the computer reported it at 57% of life. OK, time to proactively replace it as well to avoid it dying at a very inopportune times.
It uses the exact same battery, but a bit more involved installation. Remove the cargo floor that just lifts out easily, remove the factory subwoofer with two Torx screws, unplug he electrical connection, the remove the space saver spare tire. Open a little compartment and there sits the battery.
Remove the 13 mm bolt, and move the strap out of the way and a 10MM wrench to loosen the terminal clamps. The new battery drops right into place.
Then the hard part, go to the Autel, and get to the "Gateway" and then the battery function and input the 95 AMP capacity, the battery type (AGM) and the hard part is the serial number and Porsche part number. I used my old serial number and changed the last digit, then for the part number, it did not like the part number from the old battery. I had to add one more digit, and then all was fine. The car was happy, and most important my wife was happy.
I called the dealership and asked what a battery cost, and just the battery, no installation was $750.00! No doubt they would charge 200 bucks or so to put it in. The Autel paid for itself again. I bought it to do oil changes on her car and reset the oil service warning.
The Autel works on most any modern car on the planet. Stuff I have never heard of. No limit on how many cars it will do. My buddy came over the other day and we cleard the codes it had popped up on his Ford Excursion.