The consensus on the interwebs seems to be that 981 Cayman/Boxsters:
- Disconnect the cigarette lighter sockets after a few minutes, unless the car detects they are being used for charging.
- Use an AGM battery (for stop/start), which requires a special trickle charger with a slightly higher output.
However, I tried charging my CGTS with my old accumate charger, and a new CTEK MXS5.0, and the centre armrest socket still disconnected after a few minutes (even if I connected the charger with the ignition on, and locked the car after charging started).
More googling, inc. the following threads, suggests a problem with cars made early in 2016 (mine is March 2016):
- https://rennlist.com/forums/gt4/927287-charging-the-car-battery-via-lighter.html
- https://rennlist.com/forums/987-981-718-forum/947900-battery-charger-connector-question.html
A couple of solutions are suggested:
- Hardwiring charging 'pigtails' to the battery.
- Re-coding the car, to stop the sockets disconnecting. This seems to be the preferred solution for early Macans, but I read at least 1 thread where a dealer applied the Macan fix to a 981, and it didn't work. Plus, shutting everything down to save the battery seems like a good idea, which I didn't want to disable.
The MXS5.0 comes with pigtails, and instructions to attach them direct to the battery terminals. However, google suggests a few reasons not to attach pigtails direct to the negative terminal (although its OK to use the positive terminal):
- The Porsche manual says not to (and to use a dedicated earth bolt on the wiper mechanism).
- There is a safety risk from a spark near the battery (which gives off gas).
- There is risk of a voltage spike frying the battery sensor.
- Using the negative terminal bypasses the battery sensor, which prevents it optimising charging from the car, and reduces battery life.
- There is a captive nut on the negative terminal, so the only way to attach a pigtail is via a spade connector.
Ive seen threads suggesting that some OPCs fit pigtails direct to the battery terminals anyway, but nothing confirmed for the 981. So I decided to try alternatives. You cant use the earth post shown in the Porsche manual, as its an awkward shape, and only suitable for crocodile clips. The most common suggestion is a painted bolt under a rubber cover near the wing (see http://www.planet-9.com/981-cayman-.../99455-ground-connection-trickle-charger.html). However, its too much of a stretch for the standard pigtails, and I wasn't keen on breaking the paint.
I tried the horn mounting bolt first (see attached picture), but the voltage reading across this was about 0.5V less than a reading directly across the battery terminals. This may only be a poor connection on my car, but it made the charger work harder/think the battery was more depleted than it was (compared to a connection via the cigarette lighter).
Then I inserted an M8 bolt into the empty threaded hole in the strut tower. This gave the same voltage as a direct connection to the battery terminals, so I went with it. The only slight faff was needing to enlarge the hole in the M6 ring connector on the CTEK pigtail (using a dremel), to fit the M8 bolt through it. The standard CTEK pigtails were then long enough to reach the hand recess used for removing the frunk cover panel. The connector wedges in there nicely, and cant be pulled back through once the waterproof cover is in place.
Hope this helps anyone with an early 2016 car.
- Disconnect the cigarette lighter sockets after a few minutes, unless the car detects they are being used for charging.
- Use an AGM battery (for stop/start), which requires a special trickle charger with a slightly higher output.
However, I tried charging my CGTS with my old accumate charger, and a new CTEK MXS5.0, and the centre armrest socket still disconnected after a few minutes (even if I connected the charger with the ignition on, and locked the car after charging started).
More googling, inc. the following threads, suggests a problem with cars made early in 2016 (mine is March 2016):
- https://rennlist.com/forums/gt4/927287-charging-the-car-battery-via-lighter.html
- https://rennlist.com/forums/987-981-718-forum/947900-battery-charger-connector-question.html
A couple of solutions are suggested:
- Hardwiring charging 'pigtails' to the battery.
- Re-coding the car, to stop the sockets disconnecting. This seems to be the preferred solution for early Macans, but I read at least 1 thread where a dealer applied the Macan fix to a 981, and it didn't work. Plus, shutting everything down to save the battery seems like a good idea, which I didn't want to disable.
The MXS5.0 comes with pigtails, and instructions to attach them direct to the battery terminals. However, google suggests a few reasons not to attach pigtails direct to the negative terminal (although its OK to use the positive terminal):
- The Porsche manual says not to (and to use a dedicated earth bolt on the wiper mechanism).
- There is a safety risk from a spark near the battery (which gives off gas).
- There is risk of a voltage spike frying the battery sensor.
- Using the negative terminal bypasses the battery sensor, which prevents it optimising charging from the car, and reduces battery life.
- There is a captive nut on the negative terminal, so the only way to attach a pigtail is via a spade connector.
Ive seen threads suggesting that some OPCs fit pigtails direct to the battery terminals anyway, but nothing confirmed for the 981. So I decided to try alternatives. You cant use the earth post shown in the Porsche manual, as its an awkward shape, and only suitable for crocodile clips. The most common suggestion is a painted bolt under a rubber cover near the wing (see http://www.planet-9.com/981-cayman-.../99455-ground-connection-trickle-charger.html). However, its too much of a stretch for the standard pigtails, and I wasn't keen on breaking the paint.
I tried the horn mounting bolt first (see attached picture), but the voltage reading across this was about 0.5V less than a reading directly across the battery terminals. This may only be a poor connection on my car, but it made the charger work harder/think the battery was more depleted than it was (compared to a connection via the cigarette lighter).
Then I inserted an M8 bolt into the empty threaded hole in the strut tower. This gave the same voltage as a direct connection to the battery terminals, so I went with it. The only slight faff was needing to enlarge the hole in the M6 ring connector on the CTEK pigtail (using a dremel), to fit the M8 bolt through it. The standard CTEK pigtails were then long enough to reach the hand recess used for removing the frunk cover panel. The connector wedges in there nicely, and cant be pulled back through once the waterproof cover is in place.
Hope this helps anyone with an early 2016 car.