Nothingtoc

I purchased my first Porsche a month ago. It is a 2018 911 base Carrera and is the first high performance car I've owned. I have about 400 miles on it and use it as my "fair weather" weekend car and is not a daily driver. So far, I love, love, love it.

I'll be leaving on an extended vacation this summer which will result in my not driving the car for 4-5 weeks. Can anyone advise me whether or not I need to buy the accessory trickle charger and leave it connected while I am gone, or will the battery have sufficient charge to start the car when I get back? The owners manual recommends the charger when the car will not be driven for an extended time but it doesn't define what they mean by "extended time".

I have a buddy that kindly offered to drive it while I'm gone - just to be sure the battery stays charged :} !!

fast1

Why take a chance? Get a CTEK charger which costs less than $50.

Pavegeno928

I have a battery tender on all of our Porsches. I plug them in even if I am not driving them for just a few days. Cheap insurance to extend the battery life. You can do the CTEKs or the Porsche ones. Whatever floats your boat. These cars do suck down the battery when left for a period of time. How long is an extended time? In the worlds of the immortal philosopher, Detective Harry Callahan, you have to ask yourself, do you feel lucky, well, do you punk?

Sidvicious7

CTEK makes a great product. Ensure you select the proper CTEK charger that has the Snowflake mode which is necessary for our AGM batteries.
The 3300 or 7002 have that capability. Both chargers come with the necessary connectors as well.

https://smartercharger.com/collections/vehicle

Norsk

Do it. These things eat batteries.

TorqueChap

Trickle charge it. No question.

bkrantz

What they said. Even sitting for several days, with all the internal systems drains, the battery voltage can start to drop.

chris2

I use this 3A one for my other cars from Advance Auto, never had a problem with it. You can pick it up for about $35 with coupon N3KBBX. The manual states it will work with AGM batteries, even though the website description is a bit lacking

https://shop.advanceautoparts.com/p/...0cr/11148518-P

Antigravity

So in reality is should EASILY do 6 weeks... meaning easily stay charged for anywhere from 6-8 weeks in the car on a 991. Now that is provided you battery is in relatively good shape.

991s have a very good battery management system on the car that puts all the electronics and items that cause parasitic draws on the battery into a sleep mode after roughly 15 minutes. So the parasitic draw is very low on the 991s PROVIDED you DON"T have any extra accessories like bluetooth chargers, cameras, theft alarms or other accessories that are NOT stock. Once you add some device or cig lighter bluetooth charger or whatever all bets are off. Aftermarket accessories and not designed to have low draws and most the time something as innocuous as a little cig lighter USB charging device can create a draw that will over discharge the battery in a much shorter time than you think. You don't want to run the battery dead and lock yourself out of the frunk, and make you have to do that fuse box energizing scenario which is a hassle.

The reason i know this is because I have over 1000 hours messing around with discharging our Lithium Batteries in a ton of 991s... and not only myself but a lot of people on this forum who have bought our Lithium batteries have given us updates. And I can tell you that a 30Ah Lithium battery we sold (RS-30) could easily do 6-8 weeks in GT3 without a problem and a solid 6 weeks in the Turbos.... So a 70Ah Lead/Acid Battery (your stock battery) should do it quite easily. Again, providing it is in good shape, with not extra accessories.

With that being said and you being new with the Car, and not know the condition of the battery and how long it normally can sit and how discharged it gets..... I do suggest you put it on a tender so you don't come back to a dead car.

Nothingtoc

The car is brand new so I assume the battery is good. In any event, I elected to purchase a CTEK Multi 7002 and will leave it connected while I am away. I agree with you that a car should be able to hold a charge for a few weeks without need for a charge. The only reason I asked was a result of the warning in the owner manual about trickle charging. I was concerned that the 991 had some kind of unusual battery draw when the car is not driven. Apparently it does, just not to the magnitude I originally feared.

A sincere thanks to all who responded to my question. This is truly a great forum.

991.1GTS

Thanks for the detailed description, and great support. Ugh appreciated.

PCA1983

Absolutely, you should put a CTEK on it, to prevent a long period of low voltage and substantial loss of battery life. Low voltage for an extended period causes sulfation, which results in loss of battery life.
My rule is I put my CTEK on mine anytime it will sit for 3 days. or more. This prevents yields the longest battery life possible for a battery.

markjeansonne

I always heard that keeping your battery topped up reduces strain on the alternator. I am no mechanic, but I have used battery tenders on all my daily drivers for appr. 15 yrs., and a Porsche battery tender on my C4S. I would rather not have alternator issues!!! My oldest vehicle at the moment is a 2008 Range Rover, always on a tender since new -- never any issues whatsoever with electronics, alternator, etc. Have replaced the battery twice, but otherwise no issues.

MikeL31

i never use the snowflake mode and ive never had problem. am i supposed to be using the snow flake mode? i thought that was only for optima type gel batteries.

Sidvicious7

Normal charging mode charges batteries at 14.4 VDC for lead acid batteries. Since our cars come with AGM batteries they require a higher charging voltage of 14.7 VDC. The [Snowflake Mode] charges at 14.7 VDC. I always charge my battery in the Snowflake mode. The next time you drive your car and depress the [Sports or Sports Plus Mode] check the charging volts on your MFD.