986 Battery Drain

[BIGBLUE1212]

Hello All,

I know I have seen this topic before, but I think I have some interesting new info regarding the battery drain issue on the 986.

I have a 2000 Boxster S. I noticed the battery drain issue that a lot of you are having. I have a 1AMP Noco battery charger/tender that struggles to charge the battery. When investigating the battery drain issue and leveraging a lot of the suggestions on this and other forums, I came across something interesting. A few years ago I installed a bluetooth adapter to the back of the factory CR-220 radio. It uses the CD Changer input, which was open on my car as it was not equipped with that option from factory. What I noticed was with the car off, and whether it was unlocked, locked (with or without the fob) and everything presumed to be off. The bluetooth adapter was still active and my phone could connect to it. The radio looks to be off and I also did the disable flashing alarm LED trick.

Now this begs the question. Where do I go from here?

[JFP in PA]

Originally Posted by BIGBLUE1212

Hello All,

I know I have seen this topic before, but I think I have some interesting new info regarding the battery drain issue on the 986.

I have a 2000 Boxster S. I noticed the battery drain issue that a lot of you are having. I have a 1AMP Noco battery charger/tender that struggles to charge the battery. When investigating the battery drain issue and leveraging a lot of the suggestions on this and other forums, I came across something interesting. A few years ago I installed a bluetooth adapter to the back of the factory CR-220 radio. It uses the CD Changer input, which was open on my car as it was not equipped with that option from factory. What I noticed was with the car off, and whether it was unlocked, locked (with or without the fob) and everything presumed to be off. The bluetooth adapter was still active and my phone could connect to it. The radio looks to be off and I also did the disable flashing alarm LED trick.

Now this begs the question. Where do I go from here?

The base parasitic draw on one of these cars is 40-60 mA, anything more than that is a problem that has to be located and removed.

[mikefocke]

Some thoughts.

First fully charge the battery to its max appropriate level (AGM 12.8+, conventional 12.6) . Load test it. (Battery shops will often do it for free.)

Do this to determine if the battery has gotten tired by being discharged below a certain level many timess. Eliminate that first. Because no matter what else you find, that needs to be right.

OK, now with one of the three items (battery, maintainer, adapter) known good you still would have a problem. I see two choices.

Find a connection point where the power is switched off when the car is turned off. Research first to see what will happen to the settings in the adapter when there is no power. Are the settings maintained. Connect the adapter that way..

Or, get a charger/maintainer. These units will fully charge at a higher rate and then switch into maintainer mode.

Isn't the car still looking for the fob even when it is not near and the car otherwise off? Depending on the model year there is a drain that tapers down after the car is switched off and reached a low after 31 or 61 minutes depending in MY.

[Rob175]

I don't believe my 98' Boxster "looks" for the FOB. That's my assumption because my FOB needs it's button to be pressed, and the little red light on the FOB lights up when I open the car up.

I assume the little tiny "pill" shaped thing inside the FOB has something to do with the cars starting system "sensor".

But I could be wrong.

(even with new batteries in the FOB I still need to be right next to the car to unlock it....since my car is 26 years old I'm guess the FOB's radio signals are weak and just aging.)

[mikefocke]

Something has to be looking for the button to be pressed for the unlock sequence be activated. Yes it doesn't proximity sense like more recent car designs.

Communications requires me listening to see if you are talking. If I am not listening, then you talk to no effect. But if I am, I can answer with the appropriate action. Or the way my wife wants....

To listen, some electricity is used... by a circuit called immobilizer/central locking. 6.5 mAmps after an hour.

[Rob175]

I don't believe that's the way it works on the older systems like on my 98'.

I believe the press of the key FOB's button acts like many remote controls, It turns the system on and THEN the system "looks" for the code to unlock the car. (that's why there is a button on the fOB in the first place)

My Harley Davidson and BMW key FOBs work the exact opposite way. Those FOBs are always trying to communicate, which is why I keep the FOB far away from those vehicles so as to not constantly communicate and wear down the FOB batteries prematurely. They are "PROXIMITY" FOBs, while my 98' Porsche FOB is only a basic radio transmitter that must be activated by pressing in order to begin communicating..

I assume the newer Porsche FOBs are typically "proximity" FOBs like most of the industry so as you get closer to the car the car responds.