Battery condition/draining?

I'm new to Porsche ownership, having had my 996 4 months, and I have a question on battery draining - whether there's something wrong with my battery, or whether "they all do it". My 1998 C2 is connected to a C-TEK charger in my garage. I've noticed that the C-TEK traffic light indicator is green after a decent drive (for example, when arriving somewhere and I first remove things from the front boot), but then drops to orange after the car's sat for a while (for example, returning to the front boot later to get a coat etc). I've got two other cars with these indicators and they don't do it - their batteries remain green for several days if disconnected. From this I'm imagining that my alternator is working (because an hour of driving keeps it green, but an hour of parking doesn't), and that there's a drain on the system, like the immobiliser for example. What I don't know is if the drain is normal for a 996, or whether my battery is just weak and should be replaced? I know the previous owner stored the car in a tent on the drive without power, and with the battery disconnected, if that's at all relevant. Thanks

My 996 doesn’t do that, I have same charger. The 996 does have some drain but not a lot (for instance the remote door opening receiver, which shuts down to conserve power after a few days of non-use requiring the key).

Hi Rob, As above, the CTEK should maintain the battery’s charge, so it sounds as though your battery could be on the way out if you’ve not replaced it during your ownership. Any reputable battery supplier should be able to check it out for you, usually FOC. I’ve no idea if the fact that the battery was disconnected for periods is relevant, but modern car electrics are designed to be active, and as noted certain systems power-down automatically after a period of non-use to conserve the battery. Jeff

You will be lucky to get more than three weeks' life out of a good battery on a locked 996 before you start having problems. Another good thing to check is that the key actually opens the door. If you're not aware, the locks can develop an issue where the internal linkage fails. This will cause you a lot of grief, as it's the only way to open the car and wake up the fob. so it's worth checking. When I was Register Secretary, I had numerous members with this issue.

Great, thanks very much. It sounds like a new battery is in order, if not just for peace of mind.

A 1998 car will be a 996.1 whereas mine is a 996.2 so it may be different to how yours works, but if you lock mine after a few days of not being used it goes into what the OPC called "sleep mode" to conserve the battery (even if on a trickle charger) and using the remote control to unlock it doesn't work. To "wake" it I have to unlock it with the key in the door (but NOT open the door as it sets the alarm off) then press the lock button on the remote control, and then the unlock button again. When the battery has run out in the past and I've tried to unlock it with the key and start it, it has set the alarm off (I assume it has another battery somewhere to power it) and Porsche assistance have had to come and sort it out for me.

In case it helps, I've attached details of the proper way to test the battery drain. After 30 minutes, you should end up with a drain of 40-50mA (ish). Significantly more, and you can start pulling fuses to try to track it down. Often, it is an old tracker causing excessive drain, which is another challenge in itself

Thanks for the warning - I checked this evening and the mechanism works fine. Something to keep an eye on though.

Mine actually sits unlocked, because the front boot is open for the charger cable and I didn't want the alarm going off or anything. If my .1 has a sleep mode, I guess that means it never enters it.... I presume it's ok because it's on the trickle charger, but it's something I hadn't considered, thanks.

It will only enter energy-saving (sleep) mode 5 days after you lock it, so if you leave it unlocked it will never enter sleep mode.

Rob, I take it that you’re connecting the CTEK directly to the battery using either the croc-clip or the eyelet leads, so you can feed the cable between the wiper panel and the top of the bonnet which can than be closed without pinching the cable, and then you can lock the car. Jeff

Oo- thank you. I had just assumed the cable would be pinched. I've just tried it though and yes, the cable is free, even when the bonnet is closed! Thanks. I guess rainwater must enter the boot, but stay in that plastic lined top area and drain through the holes. Yes, I'm running the CTEC traffic light socket - I've got them on all three of my garaged sports cars and really like them.

My 996 turbo was dead flat last Friday after sitting for 2 nights and 1 day, the battery is 1 month old. The car is now "ok". I have noticed now i am paying attention that the display screen sometimes when turned off shows a faint "dazzle camouflage effect" The radio has been playing up, locking up for some time. I also need to press the right hand knob to make the cd auto changer work.