battery 11.8v at rest after draining,jumping and starting

Hi - My 996 40 Jahre was purchased in October last year. The battery seemed to drain reasonably quickly, maybe within a couple of weeks, but nothing too dramatic. The PPI noted poor battery condition and so at the time of MOT in March I had a new one fitted. Things seem to have got worse though rather than better. The battery seems to drain within days. I pulled the "radio" fuse to see if that made a difference, but it did not. I know there are a lot of threads about this and I am not about to go chasing electrical drains as I will probably leave that to a garage. I did get my multimeter out and tested the battery at 11.8v today. What I dont know however if that is normal for a battery that: has drained, has just been jump started, has then been run for about 10 minutes, has then been turned off and left to sit for 10 minutes Any views on whether this sounds normal? Thanks.

Yes. With the engine running check the voltage. Anything less than 14.5v indicates an alternator fault. If so just replace the regulator pack. I did a write up with pictures on how to do it. As far as batteries go I should buy shares in Tanya Batteries as so far this month i have bought a new one for the 997 and for the volvo and the TT!!!!!!!!!!!!!!!!

Thanks - that's helpful as I just did that and it was showing 13.8, sounds like an alternator then rather than the battery......!

I had a quick search but couldn't find it, did you post it on this forum or is it elsewhere? Thanks!

Here it is http://911uk.com/viewtopic.php?t=145619&highlight= 997.1 alternator

Healthy battery doesn't need constant 14,5v all the time though

I know this is really interesting stuff: I got some good data this morning which might help: 12.03 - 12.3 then 12.8 - 13.5 with everything turned on. I turned everything off and the battery sat at 14.3 Turned engine off - tested immediately at 12.1. 5 minutes later tested at 11.85 My wife started it and it bottomed at 9.01 on start up, although it sluggishly started. This is obviously a lot lower than I would expect for a new battery

Cheers!

Could be a duff battery. Get the supplier to put a battery load tester across the terminals, it could be a faulty cell.

11.8 volts .. i would class that as a battery with no issues that has been sat for approx 2 weeks without being started . A battery drain and depending on how much will reduce this time period .. some cars go flat overnight .. some after a week or 2 .. these have drain issues or indeed a faulty battery . I have posted this many times before but again .. how i test an alternator Engine at operating temp , volt meter on the battery .. 13.6 ish volts measured .. turn on the headlights main beam .. heated seats if you have them , interior fan at full speed .. If you read 13 volts or lower then yup the alternator needs replacing . AGM battery .. these are fitted to 981 onwards .. these charge at a higher rate and 14.5 - 16 volts is what i would expect .. 16 is kinda top end though . A battery test , alternator test and a discharge check are standard checks at a garage and should be in the region of 0.5 hrs labour .. fault finding after that is extra . This needs doing first . ref a discharge we crack out the amp hound ( a tool ) measure the current draw on each fuse .. find the excessive draw on a fuse and isolate it / track down what's on that fuse basically . This is merely how i do things and what i think i should see .

What he said. hello Iain, hope you are well

Make sure your glove box light is not staying on. Same for frunk compartment. I've seen glove box lights staying on and draining the battery in a week to the point starting is very sluggish. Just an idea

Thanks very much for that - appreciated

Thanks - I did wonder about the frunk light, will check that

One other thing I have noticed is that my ctek will charge to stage 4, but then throws an error at stage 5 'won't hold charge" and never gets beyond stage 5. Should probably have mentioned this...... not sure it means but it seems relevant - next up, I think I will disconnect battery and test the battery outside of the car. I assume if that charges fine, the issue is with the car not the battery!