A G M battery?
 

As you can tell by this and my last thread, I need a new battery. I live in a cold winter climate and don't drive the Boxster Dec./Jan. Would an AGM battery be a good replacement choice? They are a little more expensive and somewhat heavier, but I've read that they hold a charge much longer and have more CCA, both of which would help in the cold. Your thoughts? Please no "Move to California or Florida" comments :rolleyes:.

If you store your Box away often get a battery tender.
It'll help keep the battery topped off until you take her out of storage.

Yah yah, I know all about battery tenders (and I have one). My storage unit doesn't have electricity, and I don't want to have to run an extension cord out to the car every time I come home, or leave it plugged in if I'm out of town for a week or 2. Now then, does anyone know anything about AGM batteries?

AGM or absorbed glass mat design batteries have been around for a long time. Probably the best known brand is Optima. While much more durable, longer lived, and vibration resistant than a conventional design battery, they will still go dead in a stored Porsche without a proper maintainer attached due to the car's inherent parasitic current draw............

+1
If you disconnect the battery completely an AGM will hold a charge better than a lead-acid battery. If you leave it connected for months, it will still be dead and battery damage will be done.
Optima AGM are about 10 lbs lighter than stock
Odyssey PC 680 AGM is about 30 lbs lighter than stock.
Shorai is Li-Iron Battery, 5lbs total

More info:
ODYSSEY Batteries - FAQ

+2
I run an Odysssey that is under sized for weight savings....it will go flat without a maintainer. I have ruined one already by trying to leave it on the car over winter coupled with schemes to keep it charged. You will need to pull it or disconnect it. These batteries need a proper high amperage charger on them

I had no electrical outlet so I had to pull the battery out. It's in my dining room under the flatware cabinet with a ctek on it

DOn't forget, if you do buy an AGM battery get a charger designed to work with it. AGM batteries require a higher cutoff voltage. More than one AGM battery, or charger, has been ruined by using the wrong charger.

I have one of these ETX-30L batteries in mine:

http://www.dekabatteries.com/assets/base/0278.pdf

I have had it for about a year, mounted on its side with a battery maintainer on it whenever parked in the garage, and it has been doing great for summer and winter use.

Be warned, it is a lot smaller than a regular battery, so you have to fabricate your on hold downs. If you can't fabricate then just get a big heavy Optima that fits.

If I didn't have any electricity available, I would get some quick disconnects from Pegasus Racing, and just pull the battery out whenever storing for more than a couple of weeks.

I had two traditional lead acid batteries go out in my race cars, which I attributed to high G loads, so I will never use anything but an AGM again.

I cam accross this recently in my search for Boxster odds n ends and thought it might help ... AGM mounts.

Battery Mount Kits-Rennline, Inc.

Umm, He's asking for more battery power, and more reserve capacity. Why are some of you recommending these lightweight batteries?

yes
 

Went to these for my boat many yrs ago, have been very pleased. Then added to my Dad's tractor, and aside from one defective/damaged Optima very happy in that app. So added to my 2001S about a year ago, with better CCA, lower wt, hopefully longer life, no maintenance, and no vent tube spewing caustic gas into the bowels of my car. In summary --- a positive change I can recommend based on my experience. BTW, went with a big name auto store brand this last time (reputable manufacturer) and fitment was not an issue, cost was much less than Optima or Odyssey, no special trays or hold-downs needed.

I know they're a pita to make...yes, I make car batteries for a living and the Optima AGM's are tough to build :p
Heavy plates and lots of dust...ugh.

I've heard there is some quality problems with Optima's lately, with many not lasting through the warranty period.

Used my low end Porsche branded maintainer for several years with my Optima battery with no trouble. Did just what it had done with the normal battery.

Thanks all for the input. I'm leaning towards an Exide Edge AGM 94R. Not light (heavier than lead-acid in fact), but with much better CCA and 4 year full replacement warranty.

We see a lot of Optima's, old and new (and in fact currently have a car in the shop that we installed one in 7+ years ago), and have not had problems with any of them.

I bought a Optima (smallest red top) about 4 years ago & I was disappointed at how quickly it discharges in my Box here in SoCA. Needs recharging after sitting 4 days unlocked alarm off in my garage. When my IS350 oem battery (Panasonic AGM) died after 5 years I decided to swap the Optima to the IS350. I called Costco to inquire about warrant exchange while I had the Optima was out. Costco said they would exchange it but they did not have any & did not expect any for a least 2 months. This was about 10 months ago. The Optima works fine in the IS350 & never sits more than 2 days & the Odessey680 performs a little better in my Box & weighs about 12lbs less including the alum bracket. The Odessey has sat for 3 months in the Box with Porsche Maintainer on it during my Cayman airbox/suspension overhaul so I will report back if it has any issues in a couple weeks.

My daily driver (camry hybrid) came from factory with AGM 12V battery. So far, 5.5 years and 91K miles, the battery still works fine. I left the car in the garage for 4 MI winter weeks before and it started just fine.
I don't know if the hybrid battery helps to maintain the 12V or not though... So far this battery last longer than any other battery that I ever had...