I was washing my car today, put the Targa top, rear window and the spoiler up and down a couple times to clean and dry, had the stereo on, the headlights were probably on for a bit, etc. When done, I went to start the car and the battery was dead, wouldn't start, low battery warning. I charged it for an hour and it started right up, then I ran it on the highway for a bit to ensure it's fully charged. All seems fine now. It's a 2016 and I'm pretty sure its on the original battery (I'm the second owner), it's got 25k miles. I keep it on the trickle charger in winter when I'm not using the car, and it's always started until today.

Is 5 years a reasonable life for the battery, should I replace it now as a preventative measure?

 

It's an AGM. You should get 6-10 years out of it easily, provided you don't repeatedly kill it. My record is about 15 years on an AGM, and that's after I flatlined it three or four times near the end of its life. I'm still on the factory battery on my '17 and it's showing no sign of slowing down. I expect I won't need to replace it until 2024 at the earliest.

A lot of people will say 3-4 years and replace it. Frankly, I believe these people are going out of their way, consciously or not, to actively murder their batteries. On its own, left to its own devices, the 911 does not have enough parasitic draw to kill a battery this fast.

A lot of these same people put trickle chargers on their cars and rarely drive them. Trickle chargers, in my experiences, are terrible for batteries. This is my going theory for how these people are killing their batteries. The second theory is that people are just considering a battery with more than 25 CCA missing as "dead". Fortunately, batteries don't self-discharge in a matter of weeks like some people would have you believe, and since the 911 doesn't have ludicrous parasitic drain (unless you've installed electrical gadgetry), you can go literal months with the battery hooked up to the car without it getting too low to start up and drive away.

</soapbox>

 

I think it depends, if it never is completely depleted, and/or left depleted and it’s not in crazy temperatures, it should be fine, however my understanding is that the auto stop and start is very hard on batteries. So that might play a role too. The vehicle I believe is suppose to charge at 14.4v if you see the battery voltage go up between 14.7-14.9 (estimate) it’s probably getting close to new battery time. The lower the battery voltage the better, while vehicle is running.

 

This is an extremely inaccurate way to determine battery health.

Healthy AGMs have charge voltages approaching (and sometimes exceeding) 15 volts if it's cold enough.



The chart above is a general rule-of-thumb and should be taken with a grain of salt. If you want to determine the health of your battery, charge it up completely out of the vehicle, wait 12-24 hours, then perform a load test on it. If you do not have the equipment to do a load test, bring it to your local auto parts store -- most of them will load test a battery for free. For an 800CCA battery, anything above something like 650 is A-OK.

 

Why? Lots of Porsche owners run trickle charges, and IMO, it is a life saver. I am going on 6 years on mine, and trickle charge it - not all the time - but when I feel it needs it. Average maybe once every month. During hibernation, I trickle charge it for a day or so and then disconnect. Wait about a month and repeat.

 

You will get a range of answers. Mine are:

1) Yes
2) Yes



I'm in Florida, and the heat is hard on batteries. I just replaced the OEM 80 Ah Banner on my 2017 with a 92 Ah Duracell AGM from Batteries Plus. With rebates and promotion it ended up being $189. It's a fairly straightforward DIY. At rest voltage is about 12.3, I saw as low as 11.6 at startup before. Charging Voltage is 14.0 or 14.1, with previously it being 14.6 or 14.7. I had my dealer do the BMS reset, even though I'm not 100% sure it would make any difference in the charging profile of old/new.

 

Do any of the commonly available consumer grade obd tools allow one to do the BMS? OR is this dealer/PIWIS only?

I try to drive my 911 at least a few times a week however on the occasion that I know it will be several days before being driven, I’ll put it on the CTEK charger/conditioner which has a setting for AGM batteries. I only do this maybe once a month or two.

 

i replace mine every 5 years, cheap insurance,,

 

Yes - I use iCarsoft Auto Diagnostic Scanner POR V2.0 that has BMS fuction

 

Yes they do, afaik; see below:

Yep, that's the one I'd buy too. But I already have a simple Autel unit (think it was around $100) which I use to reset the service indicator for oil changes. I just did not feel like spending more $ for another tool, since I didn't/don't plan to replace the battery for another five years.

In my case, I did get the BMS gratis as part of another service (engine air filter) at the dealer; I think the box of Dunkin' Doughnuts I left on the seat for the guys in the shop may have helped. And if I didn't, I'm not too sure I'd worry about it, to be honest. I've not heard or seen whether/how the charging profile of the battery is changed as a function of "age" or whatever parameters are entered into the PIWIS during a BMS reset. If anyone actually knows, I'd be very interested to find out.

 

Many of them do. The icarsoft POR, the Foxwell 530, the cheaper one-way Autel units, etc.

Note that you don't need to futz with reprogramming the BMS if you replace it with the same size battery, which is usually an 80AH.

This is quite unnecessary on the stock AGM. If using the 80ah battery, your car, provided if you haven't cocked up the electrical system, can sit for approximately 2.5 months before you hit something like a 75% SOC, which is right around the point where you should start to consider worrying.

 

When I leave my car it can go a few months without being used, I have a friend go and run it once during my absence but its on a charge/ maintainer until I return. It has the OG stock battery from 2017 so far no issues. I used this same approach on my boat and got 7 years out of the starting battery as I left it on the charge over the winter.

 

You can get 6+ years out of a battery. But I replace at 5 years. A good Interstate battery is $200-300. A bad battery can cause a lot of strange issues that I'd rather not deal with. I've seen PDK faults and other serious faults be cleared based on a battery change.

I also recommend keeping on a battery tender when you're not driving it. I plug in right after driving.

 

My 2012.5 OEM Banner lasted until this January....when the auto/stop stopped working I put a Champion 92ah.

It was always on a Cetek

 

Cold weather is hard on car batteries because they don't charge as easily, but short trips in hot, rainy weather can be the worst -- especially at night -- because you are using a lot of juice to power wipers, lights, accessories and fans, with insufficient time for the battery to be fully recharged. I had an Optima yellow-top in my '98 Corvette that lasted 11 years in Wisconsin weather by using a trickle-charger whenever the car sat for more than a few days. That car had 11 computers and a big dark current load, unlike my GTS.