Thomaspin

Just bought my 2006 C4S Cabrio 997.1 and the first job was to replace the lead acid battery with an Optima Absorbed Glass Mat leak proof one.

First I procured a cigarette adapter cable for my Deltran motorbike trickle charger and inserted it in the socket in the console. The socket is live at all times - ignition key in or not - and saves all the programmed settings (radio, seats, etc) while the old battery is disconnected:


I found that the Optima 34R was a perfect fit. No need for the provided tray. The size is identical to the Interstate I removed. The 'R' denotes reversed terminals, which are required for the 997. 10mm socket for the terminals. Remove the ground first and attach it last.


However, as the Optima's terminals are further from the edge of the battery's casing, the Optima has to be moved all the way to the right (facing the car) for the ground cable (on the right) to reach the related terminal - it just does so.

I had to loosen the 13mm ground connection to the firewall and rotate the cable slightly to permit attachment - 13mm socket:


As a result the left short edge of the battery is too far from the stock hold-down bracket (13mm socket) so a small extension steel plate is inserted under the stock retainer before tightening, thus:


This steel hasp came from a U shaped threaded bolt at the local hardware store. Naturally it has been drilled for lightness .... no need for costly aftermarket adapter plates in my experience.

I have long used Optima Red batteries in my cars and enjoy the enhanced cranking power as well as the peace of mind that I will not be dealing with corrosive acid eating the precious body parts at any time. Mine came from US Parts Outlet and cost $147.33 shipped.

The Battery Tender power feed worked fine and all radio station, rear view mirror and seat settings were preserved. However, the window drop function (this is a Cabrio) was lost, and had to be reset by closing the window then holding each button in the closed position for 2 seconds. Further, I got PSM and PASM error messages (as predicted in the factory manual on page 261). Two restarts from cold cleared the faults.

Ben Z

Hmmm this is interesting about the corrosion. My MY05 is going on ten years old and so far no corrosion with standard battery. How soon do you think it will start?

jhbrennan

Nice job - I've done this before using the 34R but I've used an aftermarket tray such as the one sold by Yellowdog. The Optima is not the same size as OEM - it is not as long and just a little bit taller as evidenced by the position of your hold down clamp (third hole from the end instead of the second hole) but it looks like your mod works just fine.

http://www.yellowdogmotorsports.com/details.php?id=104

ADias

The issue with the Optima is that it does not provide for a vent line and Porsche requires it. The battery is not 100% sealed - it does have pressure release outlets and it is too bad these are not plumbed to a venting line. When all is good there are no releases, but there could be.