Needsdecaf

Before you flame me, I've read most of the battery threads on here. But looking for some advice.

My 991 is not a daily driver. It's a March 2013 build car with the original battery. I bought it about 15 months and 6,000 miles ago. Total mileage now 35k. miles ago use it every weekend and usually twice during the week as well on a shorter trip. I do not use a battery tender.

I noticed after reading multiple battery threads that my voltage was almost always over 14.5v. Suspecting my battery was on the way out, I brought it to Auto Zone and had it tested. To my surprise they said it checked out fine. And I noticed that as I drove it more over the summer, my voltage was normally now in the low 14's.

The fall saw reduced use use of the car. Still every weekend but the hurricane and also several weeks of nothing but rain meant that the car occasionally sat the whole week. I noticed that sometimes the voltage at starting was 11.6 or so, the car didn't start as hard, and the driving voltage was back in the high 14's. I even once saw 15.1.

Yesterday i Went to take out the car and it again was a bit of a tough start. By tough I mean a little slow to crank but fired up on the first time. I went to dinner and then went to pick up the kids. While I waited inside for the kids, my wife stayed in the car with the car ignition on but not running for about 10 minutes.

Dead battery. Fortunately one of the other parents had a set of cables and I didn't have to call roadside.

So so obviously I need a new battery. I will continue to use the car weekly except for once or twice a year (I don't travel for work) and likely still use it a few tmes during the week. My question is, do I need a battery tender? I'd rather not have to deal with connecting it all the time if I don't have to. Based on my usage, can I expect the battery to stay in good health without one?

Thanks.

LexVan

Depends. How often do you want to replace your battery? Yes. Use a maintainer. Mine is ALWAYS plugged in, unless I'm driving it. It takes less then 45 seconds to open passanger door, plug into cigarette lighter, and close the door. The 991 is an energy hog, and does funky stuff when not fed. Our AGM batteries are not cheap. They will probably last about 2-4 years depending. Add a battery maintainer to your regiment, and that goes WAY up.

Also keep your key fob away from the car. And lock your doors, that helps with the power conservation.

STG

Pretty much sums it all up along with the rest of the comments

Easy enough to plug into the footwell outlet and run the cord out the bottom of the door.

wareaglescott

Could you expand on this please?
I generally just leave my keys in the car when it is in the garage. (not concerned with theft. other security measures in place)

Porsche_nuts

What new battery are you intending to get?

As for a battery tender, since you seem to be using car often enough, don't think you need it. I just think you battery had reached the end of its useful life.

You should buy a battery charger and keep in the car, just in case. They are small enough nowadays.

https://smile.amazon.com/NOCO-GB40-U...battery+genius

LexVan

Another note/observation.....I can drive for literally 4 hours and over 200 miles cruising on the highway. Park in the garage, and plug in. The battery still needs charging before the maintainer shuts off. For over 30 minutes. That tells you something right there. Always baffles me the car's battery can still accept more juice even after that situation. Maybe I’m easily baffled.

Are you going to do your own battery replacement? How much is the dealership quoting? OE battery or aftermarket?

LexVan

Sure. The fob and the car are always "talking" to each other when they are in close proximity, I've been told....especially with Enter & Drive.

And by locking the car, the car will go into "sleep mode" after a few days (maybe 5) and this further saves on parasitic (normal) power drain.

Rocket_boy

Really,.....4 years, 35K is not bad for a battery in these type of cars. The use of a battery maintainer would probably make it last a bit longer, but not by much IMO.

The symptom of it having a charge for a drive,....and then after 10 minutes of shutdown not able to start the car would seem like a dead cell battery to me,....and in this case there is no other option but a new one.

4pipes

I have a tender, but only use it when the car sits for a week or more. Use to use it all the time, but got tired tripping over the $%&# wire.

subshooter

OP: I'm in the same boat. My 2014 981 was built July 2013 and I can tell after each start that my battery is dying. 38k miles on it. I drove it very often until I got my 911 and now the Boxster is sitting in the garage for the winter with a battery tender now.

Let us know what battery you got. I also understand that the Battery needs to be reset with PIWIS to tell the ECU it is a new battery. Let us know how that went.

Porsche_nuts

Don't know for sure, but hear that is just a money grab. Not sure what telling ECU that a new battery is in the car is suppose to do. Anybody know if it really does anything or just Porsche folklore?

Needsdecaf

Supposedly it charges the battery less aggressively since it's newer. Same story with modern BMW's.

NF4710

When I changed my battery and brought it to the dealer I was informed no recoding was needed. Go figure.

NF

Bemo

Battery tender.
Pro tip, do not run the wire along the bottom of the door, instead drop the window just a tad, sneak it out that way, close, lock and enjoy couple of extra years out of the battery

Needsdecaf

Probably the Auto Zone Duralast platinum AGM or the Duracell AGM from Batteries Plus.