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Random Battery Failure Experience

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Old 01-05-2017, 05:52 PM   #1
mfanatic325
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Default Random Battery Failure Experience

Just thought I'd share the peculiar experience I had recently with my '01 996TT.

Preface:
- Purchased car a few months back
- Had been driving the car regularly (started up at least once per week for the past few months).
- Had just driven the car daily past two days, albeit in the rain, as it's been raining in this area as of late.
- Car has never given me startup trouble under my ownership

Out of nowhere, overnight, I couldn't start the car early in the morning.
I have a portable jumper unit which I attached to the battery leads, and the voltage read something like 11.6V

1) I've no idea what could've caused the battery to lose voltage overnight, to a point that it couldn't start the car
2) Not sure why even with the portable jumper turned on, and voltage clearly being bumped up to ~12.4V , the car still wouldn't turn over

In any case, I went to the local Walmart and picked up a Everstart Maxx Group H6 battery for about $120 USD: https://www.walmart.com/ip/16782658. Specc'd at 730 cold cranking amps.

All in all, swapped out the "old" battery, and car starts up right away.
However, the old battery shows it's from 2015. Very peculiar...why would a battery fail so suddenly? Should I be worried?
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Old 01-05-2017, 06:12 PM   #2
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Batteries do sometimes die prematurely. Especially if the previous owner let the car sit for long periods.
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Old 01-05-2017, 06:13 PM   #3
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That puts me at ease, thanks.

Additionally, it seems from other threads, others were recommending battery replacements with ones that are specc'd at 790CCA. Mine only has 730...
But it was supposedly the proper fitment for the car, according to Walmart's battery finder thing online.
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Old 01-05-2017, 06:15 PM   #4
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These turbos have parasitic battery draw. I would get a $20-40 tender from Costco or Amazon and keep the car constantly on the tender when not driven. That should solve any future battery issues.
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Old 01-05-2017, 06:18 PM   #5
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Really? Any idea where the draw is coming from?

The odd thing is, I had just been driving that car the prior day or two, with absolutely no signs of battery fatigue. It was cold, wet weather out, but it had started up every morning, and multiple trips during the day just fine. Until it didn't lol, after 'sleeping' overnight in the garage.

I shall invest in a tender for sure though
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Old 01-05-2017, 06:27 PM   #6
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Quote:
Originally Posted by mfanatic325 View Post
That puts me at ease, thanks.

Additionally, it seems from other threads, others were recommending battery replacements with ones that are specc'd at 790CCA. Mine only has 730...
But it was supposedly the proper fitment for the car, according to Walmart's battery finder thing online.
Porsche Turbo factory manual calls for an "80/380" battery. 80Ah and 380A. I don't know what the CCA call out is this is not stated in the reference I have.

730CCA seems low to me. IIRC my Boxster's battery has more CCA than 730 but I don't recall now what the number is. BTW, Porsche could have spec'd a 730CCA battery but changed this and spec'd one with more CCA's.

This what happened with my Boxster. Some years ago when I went to get a new battery for my Boxster the parts manager looked up the part # and found a new part # and this referenced a higher capacity -- and slightly larger in size -- battery.

These cars are "hard" on the battery. When you park the car you must ensure you do not leave any parasitic electrical loads on. I unplug the power cables for my V1 and NAV units even though these units are off. I lock the car.

With no way to attach/connect a battery charger/maintainer to my Turbo's battery I have found the car needs to be driven at least twice a week and for at least 30 miles and more if one drives the car with the A/C on or the lights on. This 30 miles (or more) provides enough engine run time to top up the battery with what the battery lost from the car just sitting and from the engine start.
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Old 01-05-2017, 06:30 PM   #7
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Modern Porsche ECUs are notorious for killing batteries. There is a ton of electronic stuff going on even when the car is turned off. The best way to preserve the battery is to lock it when it will be parked for few days. Double click the lock button when you do. That turns off the motion detectors in the car. The horn will sound to let you know you have put the car to "sleep".

It is also not unusual for a car battery to seem in good shape on day and be completely dead the next. It happens.
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Old 01-05-2017, 06:32 PM   #8
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Confirm you connected the drain tube?
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Old 01-05-2017, 06:32 PM   #9
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Quote:
Originally Posted by mfanatic325 View Post
That puts me at ease, thanks.

Additionally, it seems from other threads, others were recommending battery replacements with ones that are specc'd at 790CCA. Mine only has 730...
But it was supposedly the proper fitment for the car, according to Walmart's battery finder thing online.
The exact CCA doesn't matter that much just so long as it is close to spec. Last I check Walmart's batteries are made by Johnson Controls. They make pretty good batteries.
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Old 01-05-2017, 06:36 PM   #10
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Interesting...Well, if this 730CCA battery recommended by Walmart fails prematurely, at least I have the 3 + 2 year warranty. (3 years free replacement, and if it fails within the 4th or 5th year, then they reimburse me partially). I chose Walmart because they're known to be low-cost, and I know they have good return policies

Oh, another interesting thing to note: when I changed the batteries, I didn't lose my radio presets, although I did need to input the radio code. This might be due to the fact that I had a USB charger plugged into the cigarette lighter port.
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Old 01-05-2017, 06:37 PM   #11
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Quote:
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Confirm you connected the drain tube?
Yes sir, I made sure to connect the tube as securely as possible
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Old 01-05-2017, 06:37 PM   #12
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Quote:
Originally Posted by LexVan View Post
Confirm you connected the drain tube?
Good point.
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Old 01-05-2017, 06:38 PM   #13
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Quote:
Originally Posted by mfanatic325 View Post
Oh, another interesting thing to note: when I changed the batteries, I didn't lose my radio presets, although I did need to input the radio code.
Normal.
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Old 01-05-2017, 06:39 PM   #14
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Awesome. All is well then. Thanks all! Happy motoring
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Old 01-05-2017, 06:39 PM   #15
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Quote:
Originally Posted by mfanatic325 View Post
Oh, another interesting thing to note: when I changed the batteries, I didn't lose my radio presets, although I did need to input the radio code. This might be due to the fact that I had a USB charger plugged into the cigarette lighter port.
The radio saves the presets automatically.
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