What's with the batteries in the 993 anyway? Is it just me or do these cars seems to eat up batteries more than normal? I know my car is not a daily driver, but it still gets fairly regular use. However, if it sits for more than two weeks without a start, then the engine tends to turn over very, very slowly and may even refuse to start. My Mercedes E500 doesn't do this. Does anyone else have this issue? Obviously, over time (and after replacing a few batteries) I've learned to keep a Battery Tender on my 993 and highly recommend you do the same.
Over time, I've noticed the following:
1. If I leave the car sitting for a couple of weeks, but don't engage the alarm, the battery will be fine. I think between the LED light on the door and whatever the alarm has engaged internally, this provides some type of drain on the battery. The result is, when the car is in my garage (which has it's own alarm) I no longer engage the factory 993 alarm. This has help tremendously in saving the battery.
2. In the event that the battery does discharge fully or gets disconnected, the data for the engine electronics (which is stored in the control unit) will be erased. So, when you recharge and or reconnect the battery the engine needs to run for about 10 minutes in order for the control unit to reprogram and re-acquire the proper data. While this is happening, it's possible for the engine to idle fast and uneven.
3. If you use a regular lead-acid battery vs. the new sealed or gel batteries, you need to maintain the water level properly (especially in hot climates). Loss of electrolyte (which the water is part of) is said to be the cause of more than half of early battery failures and this happens through simple evaporation during the summer and in hot weather. If you keep a close watch, ensuring that all the plates in the battery are covered, you effectively extend the life of your battery. Make sure you only use distilled water when you replenish your battery cells.
Lastly, don't forget that if your battery discharges or you disconnect it, you will have to re-active your stereo with a code (this assumes you have the stock radio installed by Porsche). When the battery comes back to life, or you reconnect it, the display will ready "CODE", with a flashing letter "C". At this point you need to enter you code, which if you're anything like me is highly unlikely as you won't remember it and you lost the radio code card long ago. Hopefully, your sales person or dealer was kind enough to write in down somewhere on one of your manuals or put a copy somewhere in your glovebox. After desperately searching, if you still can't find the code, try calling the dealer with your VIN#; if you can convince them that you are the true owner of the 993 in question, they should be able to give you the code.