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Battery overcharging and going flat


lofi

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Today my driver side window has been doing odd things.  I did not do the reset or relearn.  When I lock the car it seems to not park correctly or it drops slightly too far.  I'm guessing my one touch might not work also.  I will try it next time I drive the car.  For now I would not assume anything is broken.  Just know that removing the battery will cause all these systems to go into factory reset.

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1 hour ago, ATM said:

Regarding the alternator.  I believe these modern cars have complicated electrical systems.  Not sure why I think this but thats my belief.  So these alternators do not charge constantly like older cars.  This is for emissions as an alternator constantly blasting out peak amps will cause a drag on the engine and increase emissions.  Not sure if that helps explain whats going on with your car.

Pretty sure there's a CAN bus connection to the voltage regulator so the alternator does "intelligent" battery charging rather than just voltage based charging.

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Also found this 

Don't know how applicable these are to either 981's in general or your car but from reading on here it seems good candidates for parasitic drain are:

The backup battery in the alarm siren - they die over time, and keep trying to charge themselves from the main battery,

Trackers - old installs that are now faulty 

PCM - given the short time the car will keep the PCM alive with engine not running - seems they are a "current hog", no unknown for them to fail to sleep

3rd part head units 

Regulator module of the alternator (might not be so simple in the 981 - but older models have been know to drain a battery "quickly" ) - I have used a (not on a Porsche) IR thermometer to look for "warm things" on a cold car - access might be an issue but it's a thought.

 

Another "trick" I have seen done ( again on older models) - if ifs possible force whatever scanner you have to ignore the fact the ignition is off then run an full scan - modules that are awake and shouldn't be might respond - may of course lead you down a rabbit hole - but it's another "tool" 

Oh and...

 

Edited by Paul P
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thanks @Paul P I have watched that and I am drawn to the alternator regulator (but only because I am still of the incorrect view that the charge rate from the alternator is wrong).  I have tried it without the alarm siren fuse in and still have an issue - BUT - I dont think I have left the car long enough to go fully to sleep given that doc says 35mins

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1 minute ago, lofi said:

thanks @Paul P I have watched that and I am drawn to the alternator regulator (but only because I am still of the incorrect view that the charge rate from the alternator is wrong).  I have tried it without the alarm siren fuse in and still have an issue - BUT - I dont think I have left the car long enough to go fully to sleep given that doc says 35mins

 

Yes the sleep time in the clip seems short vs the doc - but one thing came to mind - when he swapped the alarm horn and retested he got the "something open" chirp - which wasn't there 1st time around - seems like a quick way to see if the alarm is at least on the surface healthy?

Did you pull the horn connection or the fuse?

There's several discussions around about charging voltage - here's one from pistonheads - with the interesting observation that OPC reckons the car will tell you if it thinks its overcharging https://www.pistonheads.com/gassing/topic.asp?h=0&f=231&t=2012393

Good luck with the digging.

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You can put a Bluetooth Victron SmartBatterySense (SBS) https://www.12voltplanet.co.uk/victron-smart-battery-sense.html  onto your battery and monitor the battery voltage without having to unlock or open the car - it will log battery voltage and allow you to view it on your iphone

 

 

 

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Thanks for all the advice. Update to follow but can someone confirm that the car should ‘chirp’ irrespective of any settings if you try to lock the car from the remote button with a door open?

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On 2/21/2024 at 5:14 PM, ATM said:

Today my driver side window has been doing odd things.  I did not do the reset or relearn.  When I lock the car it seems to not park correctly or it drops slightly too far.  I'm guessing my one touch might not work also.  I will try it next time I drive the car.  For now I would not assume anything is broken.  Just know that removing the battery will cause all these systems to go into factory reset.

One touch on mine is working fine without doing any form of reset after removing the battery. All I have done is press up until it hits the top seal a few times because until I did this it would stay open slightly after locking.

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2 hours ago, lofi said:

Thanks for all the advice. Update to follow but can someone confirm that the car should ‘chirp’ irrespective of any settings if you try to lock the car from the remote button with a door open?

I think my siren has been disconnected. It never chirps.

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2 hours ago, lofi said:

Thanks for all the advice. Update to follow but can someone confirm that the car should ‘chirp’ irrespective of any settings if you try to lock the car from the remote button with a door open?

Pretty sure it should.   Previous generation (987 ) do and the video shows it doing it with the bonnet open.  
 

@daz05 has a video on YouTube showing a “not working” siren and his replacement process.   

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So, an update.

I sat with the car whilst it went to sleep. every 20 secs or so there was the click of a relay from the frunk.  It sounded like the relay sound when the DRLs switch off after locking the car. Every time there was a voltage drop, and there was not enough time between them for the battery to recover. Pretty sure this, whatever it is, was making the battery flat.  I also remembered I had an issue where the frunk lamp didn't light even with the frunk open.  I thought the bulb had gone but I tried it in the rear and it was fine.  So I had a good old pop around the frunk latch, opening and closing it with a screwdriver, spraying contact cleaner etc.

Shut the frunk, locked car, all noises ceased and the battery stayed fine over night.

Have had a code reader on the car and once all the codes i suspect are related to the original battery dying have been cleared and the codes re-read all that remains is the following:

000401 Current distributor, terminal 30 reset

C13212 Communication with alarm siren (rear 2)

Car has been fine since but still has these codes and there is no sound at all when trying to lock the car with the doors or frunk open.  My guess is the siren is broken (as seems quite common).  At the moment I am considering leaving well alone as it all seems to be working properly (including the charging voltage when driving, 15v for a bit then dropping to 13.7v which is as I remember it) or opening the siren and having a look.  The siren appears to need cutting open. 

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