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Battery life when car is left unused

Albionmuz

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28 Oct 2016
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My 993 seems to discharge to the point where the car just doesn't want to turn over properly after 3 weeks (in the winter). Is this normal?

Car is going to become a garage queen this weekend so will be on a charger in a garage for the next few months, so the problem will go away.

Just curious as my other cars retain their charge much better at this time of year. Battery is only about 3 years old and holds it's charge well when used regularly.
 
That's my experience as well. My Ctek has come in handy.
 
3 weeks is pretty good going, the more you let it go flat the shorter that time will get as the battery gently dies. A smart charger is the answer if it's not getting used.
 
Battery life

Definitely a smart charger is the way to go, I personally removed the bulb from the frunk light, offers no real light to the frunk. It also means when the conditioner is connected no worries about leaving the bonnet ajar.
For convenience I have my battery conditioner connected with push in wire fittings, much safer than crocodile clips on the battery posts.
 

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Yeah I have a Ctek with a permanent 1 click connector to the battery but the car has been on my drive whilst I was away. Ctek will be connected this w/e. I'm just shocked how quickly the battery loses charge. Must check out jev911's suggestions as there are far fewer electrical components on the 993 than my Alfa 159 which copes fine with being left.
 
The battery on mine was only lasting a week until I discovered the OBC display was staying lit. Now I've fixed it it lasts about 2 weeks or so.
Be careful thinking taking the frunk light bulb out will mean you can leave the bonnet ajar. The interior llights at least on mine appear to be on the same circuit and will stay on. Easier to clip the latch closed with a screwdriver or something.
 
Thanks all, good to know I am not alone with this annoying foible!
 
Mine runs flat after about 3 weeks.... or at least too flat to start. I now just disconnect the battery which take 2 mins.

Also.... when I do use my trickle charger, I find the bonnet seal is soft enough the let the thin charger wires be 'squashed' into it.... so I can still close the lid, so no need to remove bulb.

Old cars eh? Don't yah love 'em!
 
I use the Ctek with CTEK M6 Comfort Indicator Eyelet. If you push the bonnet locking catch down there is no need to remove the frunk bulb. Of course this relies on your car being garaged. If you disconnect the battery remember to go through the ecu self learning proceedure at startup.
 
I always recommend to disconnect the battery from the car if a charger is connected. I've see far too many overvoltage damages in the control units in these cars. The OBC tachometer is especially vulnerable to this, the internal overvoltage circuit can fail spectaculary. Non-OBC tachos does not have this.
Cheers,
Tore
 
My battery sounds similar to the above. I've not counted the days out but in my head it is two weeks - maybe a bit more, could even be a but less. I have a battery switch connected and as long as I turn it off when I leave the car I never have any issues other than resetting the clock when I next use it.
 
ToreB said:
I always recommend to disconnect the battery from the car if a charger is connected. I've see far too many overvoltage damages in the control units in these cars. The OBC tachometer is especially vulnerable to this, the internal overvoltage circuit can fail spectaculary. Non-OBC tachos does not have this.
Cheers,
Tore

Great something else to worry about, although I don't have an OBC. I do have a tracker though so disconnecting the battery is not an option..I don't think?
 
ToreB said:
I always recommend to disconnect the battery from the car if a charger is connected. I've see far too many overvoltage damages in the control units in these cars. The OBC tachometer is especially vulnerable to this, the internal overvoltage circuit can fail spectaculary. Non-OBC tachos does not have this.
Cheers,
Tore

I hadn't realised this was an issue either. I do have an isolator fitted though so would be easy to do when I plug the charger in.
 
Modern 911s not much different in my experience, 2-3 weeks not used and my 997s were hard to crank, if at all in the case of the GT3 which had a Porsche battery. CTEK trickle always now, even on the 991 which supposedly has a higher capacity battery for stop/start, but a battery with a Porsche badge on it is hard to trust.
 

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