Engine will not start with full battery

Hi, I have an '08 Cayman S with manual transmission. I has been in my garage since the start of winter with a battery minder on it. I have always had a battery minder attached when not driving. Needed to move the car today and the engine would not start, all the lights came on the dash and everything seems to work fine. When I try to turn it over only a click and the lights flash, plus the drivers side window comes down just a little. Then, PCM and ABS failure comes up on the dash. I have owned the car since new and never had these errors come up before. I unhooked the battery to try and see if there was a problem with the minder and the smart charger I have did not even charge, it was showing 14.8v when attached. Any ideas? My next course if action is to attach my Softronics cable and see what comes up. Regards, Phil

Phil, Odds are your battery is shot. Getting a relatively full voltage reading doesn't mean it can supply the amperage required to start the car. If you can pull it and take it to a battery shop, let them test it for you. They have the right equipment to do a complete diagnosis. Good luck. Joe Henley

+1 on the battery . Battery minders don't stop an old or defective battery from dying. They do however, make a non defective battery last a lot longer then they otherwise might. Replace and drive.:cheers:

Try jumping the car from either a box or another car - hook the leads up: good battery positive, good battery negative, porsche positive, find a good ground on the porsche chassis or if nothing handy go to the negative on the battery ... Take a look at the battery posts and see if they are clean. Pull the battery and take it to a shop to have it load tested - that'll tell you if the cells are OK which gives the voltage and amperage. The PCM and ABS lights coming on are normal - happens when the electricals are interrupted. They go out after a few miles of driving after the cars computer gets enough clean data to say everything is OK.

And how old might this battery be?

Exactly my thought. Since OP has owned the car since new (2008) if/when he last replaced the battery would be a very pertinent piece of information to provide when asking for help. A tender won't make a battery last forever and 10-11 yrs is an extremely long lifetime for a battery . You can't go by the static voltage. It must be load tested, which it seems to fail in real-world conditions.

As others have responded, sounds like the battery . Yesterday my buddy & I went to get his Cayman (2018-maybe it's a 2019) it's a few months old out of my storage space. It had been there about a month. Car was so dead he was unable to open the door. Eventually, got the door open-not even sure how he did it. Due to brilliant Porsche engineering ingenuity we were unable to open the electrically operated frunk or release the electrically operated brake. Plan was to push it out and jump it with my car. Back to my house to get a jumper box. Back to his car--to jump it, battery too dead Back to my house for 2nd jumper Back to his car Now screw around with the crappy little Red Jumper tab in the fuse box Managed to get frunk open using both jumpers piggy backed 1st tried 1 jumper to start, as we thought not enough juice Piggy backed the jumpers again Voila, started right up I run into this quite often with my Boxster if I let it sit too long. The real PITA is, if battery is too drained you can't open the frunk to access the battery . You need to access the fuse panel on lower left side and pull out the little RED jumper connection. Had this happen to me a few times and had to use 2 jumper boxes to get the frunk open and start the car. The thing is to drive the car or at least if possible get a battery tender on it.

It would seem Phil3270 is a man of few words... 4 posts since July of 2009, we may never know! :hilarious:

The question is what is the voltage without the minder hooked up. i.e. what is the open circuit voltage. Having been on a minder the battery should measure 12.5V when just sitting at rest, open circuit. If not then it is your battery .

...and step 2 is to have someone measure the voltage while you attempt to crank the engine. Should not drop below ~9V. If it does drop lower than that the battery is likely bad (or not charged). Could also be a starter issue, but bad battery is way more likely.

Hm... I have an 08 base. I don't know if this is the original battery . I'm starting to wonder if I should just plan to swap it soon and be proactive about it. I don't like surprises.

If the present battery is good, then what comes to mind next is the starter solenoid or the starter motor or the lockout switch that prevents the car from being started when the clutch pedal isn't depressed....or...god help you....a frozen crankshaft.

10 - 12 years is very good for a battery that has been maintained with a maintainer. One should have a replacement plan in place for a battery that old. Also, be diligent listening for any degradation in starting power and/or the anount of time it takes the engine to fire up. You will sense impending battery doom (degridation) if paying attention and be able to catch it before it catches you. As noted above, if the voltage doesn’t dip too low under starting load, it still has life. The minute starting voltage goes lower, replace it.

I have a 07 cayman s I have to cycle the key twice to get to start.at times I depess the clutch pedal land no click.try again and I hear a click and it starts.i was suspecting poss neutral saftey switch and yes it's a man 6 speed.any thaughts.batter tested good.3 year old battery .

Hi my 06 Cayman has similar sympton. Have to re-cycle key to start. What did you find out? I have Tiptronic. I have replaced fob battery . Thanks