See Post on condition charging
viewtopic.php?f=8&t=12038I purchased a Carcoon Automatic Battery Maintainer & Charger (& Regulated DC Power supply for DC ventilation fans) in Feb 2005 as I was having problems starting my 2.7 944 if it hadn't been out for a couple of weeks in the winter!
I have used it since then on 2 subsequent 944's an S2 Cab and my current 944 Turbo.
It has been an absolute godsend. It is supplied with a set of leads with a quickly detachable plug and a set of leads with plain crock clips. I have had no problems with the unit or any problems starting the cars, wouldn't be without one now and would certainly recommend this product.
HTH
Clive