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The porsche stock sizes are 90, 91, 92 (smallest to largest, there are three mounting holes in the tray). These correspond to sizes 47, 48, 49 where the length and the width are the same but the 40 series batteries are 1/2" taller. Cranking capacity increases by about 50CCA as you step up in size if you stay within brand/model. Weight increases by about 10# for each step in size.

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  • 2 weeks later...
Group size 48 from Autozone, if you have Autozone in your area.  The battery is mad by Johnson Controls, a very big company.  Johnson Controls also makes the group size 48 battery sold by Sears, but when you buy it from Sears it is $90-100.  It comes with a vent tube.

I just bought a new battery from Autozone, as suggested. I tried Costco and while the prices were excellent, my Costco did not have group 48 and were all sold out of group 47. I got a group 48 from Autozone for $65. It is a "Duralast" brand but does not look the same as the one pictured. Also, mine did not come with a vent tube and there does not appear to be anywhere for a vent tube to go. Dumb question but is that bad? Since there is a vent tube attached to the original battery that leads in to the firewall area, what the heck do I do with it? Just let it hang loose?

Edited by Kevin369
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Group size 48 from Autozone, if you have Autozone in your area.  The battery is mad by Johnson Controls, a very big company.  Johnson Controls also makes the group size 48 battery sold by Sears, but when you buy it from Sears it is $90-100.  It comes with a vent tube.

I just bought a new battery from Autozone, as suggested. I tried Costco and while the prices were excellent, my Costco did not have group 48 and were all sold out of group 47. I got a group 48 from Autozone for $65. It is a "Duralast" brand but does not look the same as the one pictured. Also, mine did not come with a vent tube and there does not appear to be anywhere for a vent tube to go. Dumb question but is that bad? Since there is a vent tube attached to the original battery that leads in to the firewall area, what the heck do I do with it? Just let it hang loose?

Guess who's battery died today? (mine).

I got the Autozone Duralast and the guy said it didn't have a vent tube - I asked him to check again or look at another battery - Oh, he says... I guess it does have one. This is what I bought and installed today...

post-2-1097367387.jpgpost-2-1097367402.jpg

post-2-1097367416.jpgpost-2-1097367445.jpg

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If the paper vent instructions say Johnson Controls then for some reason they made the top red.

This is the instructions from the AutoZone battery I picked up in April, except my battery does not have a red top, and your vent instructions look identical to mine. Guess they want it to look like an Optima. I paid $60. Bet they raised the price.

post-4-1097369621_thumb.jpg

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Group size 48 from Autozone, if you have Autozone in your area.  The battery is mad by Johnson Controls, a very big company.  Johnson Controls also makes the group size 48 battery sold by Sears, but when you buy it from Sears it is $90-100.  It comes with a vent tube.

I just bought a new battery from Autozone, as suggested. I tried Costco and while the prices were excellent, my Costco did not have group 48 and were all sold out of group 47. I got a group 48 from Autozone for $65. It is a "Duralast" brand but does not look the same as the one pictured. Also, mine did not come with a vent tube and there does not appear to be anywhere for a vent tube to go. Dumb question but is that bad? Since there is a vent tube attached to the original battery that leads in to the firewall area, what the heck do I do with it? Just let it hang loose?

Guess who's battery died today? (mine).

I got the Autozone Duralast and the guy said it didn't have a vent tube - I asked him to check again or look at another battery - Oh, he says... I guess it does have one. This is what I bought and installed today...

post-2-1097367387.jpgpost-2-1097367402.jpg

post-2-1097367416.jpgpost-2-1097367445.jpg

Loren,

Funny timing that your battery died. That looks like the battery I got and the model numbers are the same. (48-DL) Mine did not come with the orange cap over the positive terminal nor did it come with a vent tube. It looks like you plugged the vent tube int the center of the battery. Is the vent home on your battery an oval shaped end? If so, I have that too and didn't realize it was a vent hole. Correct?

Edited by Kevin369
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Other than the red top and $5 price increase Loren's battery looks like the one I got in April, and the specs are identical. My part number is 48-D which I guess is now 48-DL. Hope my battery fails soon so AutoZone will give me the red top racing version.

You have a vented AutoZone battery. The vent is oval - the first yellow line. The yellow lines are to the vent in the middle rear, unlike the side vent on the Moll battery. The second yellow line is to the black rubber vent tube that comes in the plastic bag, and there is also an adapter in the bag for the clear plastic oem vent tube.

On your battery, someone removed the orange cap over the positive terminal, and the plastic bag with the vent tube/adapter/instructions inside the bag, as the bag should have been glued to the top of the battery.

post-4-1097376775.jpg

post-4-1097376953.jpg

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Yes, the vent is the oval opening in your pic.

The supplied tubing is larger than ours but it is not a problem as the small plastic coupler is large on one end (for the new supplied tubing) and small on the other end (for our original tubing). I did have to cut the original battery fitting off the the original tubing as it seemed glued on. The clear plastic is original and the black is supplied with the battery.

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Went to Autozone today to get brake pads for my truck. Have not been there since April. Now all the batteries have a red top, but other than that they look indentical to the all black batteries they had in the past sans the $5 price increase. The paper instructions for the vent tube still say Johnson Controls.

Group size 48 was out of stock - guess the word is out in 986/996 land as that is not a common size.

They had 47 and 49 with vent tubes, so I took a picture of both side-by-side. 47 is a bit smaller than a 48, and 49 is larger than a 48, in length. The width and height are the same. Since there are multiple threaded holes in the battery tray for the hold down clamp you have a choice as to what battery to use. If I lived in Alaska I would go with a 49. If I wanted a lighter battery I would go with a 47. The original size 48 is fine with me.

But I have a 1997 Boxster and all 4 holes in my battery tray are threaded, as are other 1997 Boxsters I have looked at. I would have to use the last hole for a 49 because it is so long. On the 1998 up Boxsters and 996s I have looked at the 4th hole was not threaded, for some strange reason.

For Kevin, I took a picture of the oval vent. One of the batteries on the shelf did not have the plastic bag with the vent tube glued to the top of the battery. The rest of them did.

post-4-1097438761_thumb.jpg

post-4-1097438883_thumb.jpg

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Thanks Jeff!

I went back to Autozone today and lo and behold, the shelf was full of batteries with vent tubes taped to them. I must have bought mine on an off day. I grabbed a vent tube and one of those orange positive terminal covers. It's all hooked up now. Thanks again.

I think the "red top racing version" adds a couple of extra HP. ;)

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While I do not know for a fact I would think that "Sealed Maintenance Free" batteries still have some kind of vent, even if only an emergency over pressure vent. Under normal circumstances the batteries wont vent. Under extreme circumstances the battery would vent to prevent bursting.

Also I believe Optima batteries do not have a vent so if you do not want to use a non-vented battery you could use one of those (more $ and you have to make/buy an adapter to fit it to the existing tray).

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Guess who's battery died on Thursday? In the parking lot at a Sales kick-off event at my new job. Caught lots of s**t "poor new guy's battery died- in his PORSCHE" and all that... such is life ;) . I'll run out to Autozone this afternoon for a 47 of 48.

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Was at Sears today and looked at the DieHard International in sizes 47, 48, and 49. They all had the black top but otherwise looked identical to the Auto Zone batteries, right down to the vent tube instructions that says Johnson Controls. The CCA rating is identical to the Auto Zone 47 and 48, and on the 49 the Sears the CCA is a bit less than the Auto Zone 49. $106.99 is the Sears price for either of the 3 sizes.

Sears has a 3 year replace it free warranty and I think Auto Zone is 2 years. Maybe that is part of the reason for the $42 price difference

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Excellent thread. Question for Loren and others: How old was the battery you just replaced? and what kind of usage did it have (daily driver, weekend driver, short runs, etc.)?

Questions for Loren/Toolpants:

1 - noticed that the vent on the OEM battery is on the side, and the Johnson Controls battery is on the center (needs a longer vent tube) - is that a problem?

2 - Also... the OEM MOLL battery seems to be exceptionally good and well built. Although pricier would it be preferable? Thanks in advance.

Edited by ADias
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Excellent thread. Question for Loren and others: How old was the battery you just replaced? and what kind of usage did it have (daily driver, weekend driver, short runs, etc.)?

Questions for Loren/Toolpants:

1 - noticed that the vent on the OEM battery is on the side, and the Johnson Controls battery is on the center (needs a longer vent tube) - is that a problem?

2 - Also... the OEM MOLL battery seems to be exceptionally good and well built. Although pricier would it be preferable? Thanks in advance.

My battery was 5 years 3 months and 9 days old. Car is driven weekly but not daily.

1- Then vent on the car extra long and the Autozone battery vent tube and connector add another 8-10 inches. I had plenty of tubing even after cutting off the old connector.

2 - YMMV, I tend to look at the CCA, size/fit, and warranty.

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6 years 7 months (bought 03/98), not a daily driver, just weekends and the car did sit for 1-2 months on several occasions. Did not use battery maintainer.

Of course my 996tt battery lasted all of 2 1/2 years. Was not covered under warranty as I did not drive the car enough (per the dealer).

I do not think that the Moll batteries are all that great. I think they are only 350 CCA versus 500-700 for aftermarket (hard to get hard numbers on the the Molls). Also I would be surprised if the Porsche dealer gives you more than a 2 yr warranty (and that warranty is only good if you drive your car 12000 miles per year (again per the dealer).

So aftermarket batteries are cheaper, have better warranties, may have more power and you do not have to deal with the porsche dealer.

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