Battery or something else?

[skydriller]

Hi all,

Mine's a 2004 Porsche 996 C4S Cabrio, owned 2 1/2years now...

First a little history :

I have a CTEK plug in maintainer that I have had a year or so (since once returning to a dead car after a 4 week trip abroard!!) and it plugs into the cigar lighter when the car is in the garage. Have had no problems with this arrangement until about a month or two ago. Came home once again from 3 weeks away and started the car no issues, but having driven it for 10mins or so, left it for 30-60 minutes and it then again wouldnt start...jump-lead started it and since then have used the CTEK and its started OK as before...

Then Yesterday, returned from a 20minute blast, and wanted to go out next day, so didnt plug it in, and once again had a problem starting it - she turned over once, then clicking!! - plugged in the CTEK for an hour and she started no problem once more....went for another quick blast and on returning again she wouldnt start after leaving standing a couple of hours. This time plugging in the CTEK didnt help and I needed to jump-lead start it to be able to move it off the drive and into the garage...

Now Voltmeter on the battery terminals shows 14V with engine running, then initially ~12V (decreasing slowly) engine off, but after a couple of hours voltage appears to have dropped to 10.4V and several hours later is still at 10.4V....This probably explains why I get a single slow turn over, but no start...

So, is the Battery dead, or could it be something more sinister??
Is there anything else I should be checking for a diagnosis??

Any advice or pointers gratefully received,

Regards, SD..

[LordHaveMurci]

Not sure but is it worth running the RECON program on your CTEK to see if that helps? Supposed to do it annually I think, bet most of us don't though!

[Trev450]

A good battery should be reading at least 12.5 volts. How old is your current one?

[Orangecurry]

...and change the earth strap(s).

[Demort]

Engine running the voltmeter is seeing the battery being charged , but is the battery actually takeing the charge ... voltmeter on the battery engine off should stay at approx 12 volts for several weeks/monthes if there is no discharge.

The drop you have seen would indicate a dead cell .. 6x2volts=12 , 5x2 volts = 10 .. a discharge would lower the battery continually and not stop at 10 volts.

Sounds like just a battery to me.

Edited by Demort on Tuesday 3rd November 19:22

[skydriller]

Thanks for the replies/help.

I have changed out the Battery for a Bosch S5, which is supposedly the one to get, and all now appears well.

The local Bosch distributer/outlet down here in France had a guy there that apparently used to work for a Porsche Garage, and he checked out the ground strap (OK) and said the alternator was working, but might be a little on the weak side and I should think about replacing it at the service in 6 months...not sure what to make of that, to me it either works or it doesnt...but hey-ho...

Regards, SD..