ELJG

FWIW - All on my 928GTS: no charger, medium use, parked out in all weathers:

Started well throughout and then just died totally: Bosch battery after 1 year, 1st Porsche battery after 2 years and replaced free under warranty; replacement Porsche battery died after 2 years. Now purchased latest Bosch S6001 (6 year free replacement) and will see how it goes.
On my VW Passat - manuufacturer's battery for 7 years and another VW battery for 3 years when the car was sold (and still working then).

dr bob

I'm going to work on a theory that considers that the maintainer 'cycling' isn't really good for the battery. I'm just disconnecting the thing when I travel, and will be working on a bracket for a disconnect switch for under the hood by the jump post to make disconnecting the main CE electrics a lot easier. In the meanwhile, new Duralast is starting the car quite briskly. Radio sounds better too with the higher voltage available-- alternator is able to keep up better now that it's not wasting charge current on a battery that wouldn't keep up.

More on the bracket when I have a good one. I spoke with Ed (obehave) at Frenzy anout fab'ing stuff like this from my CAD drawings, so there's a some-time-in-the-future possibility that this bracket and the no-holes front plate frame will be available from our Usual Suspects.

JPTL

Interesting theory. Having owned boats for decades I'd always subscribed to "maintainer when not in use". But that's the rule with deep cycle batteries which are better equipped for 'cycling'.
..but doesn't the everyday use of a standard automotive charging system 'cycle' the way that a maintainer does?
Keep us posted w/your findings.....

Tony

My Duralast is about to give up the ghost. I have a quick disconnect in the rear that i use at the airport or when parked for long periods. It barely started this AM after siting for 3 days unhooked..chilly here, but still, it should be stronger.!

dr bob

J.P.: I've fol;lowed the same ptotocol with boat battteries and had good results. But on the boat, there's nothing draining the battery except internal current leakage/depletion. So the maintainer cycles on for a short while, then is off for days. My 928 has a slow (<25mA) static drain when sitting, enough to cause the maintainer to cycle a lot more often as it lets voltage drop to 13, then brings it back upto about 14 before shutting off. I think the shallow, low-current, high-cycle charging/discharging may be tougher on the battery than I've presumed in the past. The Duralast wasn't keeping up nearly as well as the previous (NAPA) batteries did. Adding the maintainer may have improved the near-term performance of the battery, but may at the same time have accelerated its demise. The use pattern on the car has changed in these years too; previously it would sit for a few days at a time between drives. Now it can go a week or two regularly.

Solution in the end may be a yellow-top deep-cycle starting battery from Optima, the disconnect switch at the jump post to isolate the CE panel, possible memory maintainer battery in the RF under the headlight similar to what Alan has done on his GTS, and use the maintainer directly to the main battery only on extended (>1 week) periods of non-use. Right now it's the new Duralast as of last week, and one more after that under warranty (2 year no-cost replacement) before I have to actually pay for battery 'rental'. We'l see how the current Duralast responds to the disconnect and maybe maintainer for longer periods protocol. No worries-- it's under warranty...

S4ordie

Dr bob, I spent a lot of time researching the different Optima options to include communicating directly with the guy from the 911 forum that works directly for Optima. After many questions relative to fit I was convinced the Yellow Top would fit. It does, almost. Greg Brown needed to fab a new holder down in the battery bay. Unfortunately it contacts the top of the bay cover door Needed to put in a thick rubber pad to insulate.

As I purchased the batteries (2, one for the Turq and Zyc cars) several months before installed I had no recourse to return. So far, I've had no problems in terms of holding charge. I do keep the doors locked so the alarm is engaged and I do drive the car at least weekly. If interested I can dig up the model number of the battery.

JPTL

If they Yellow Top and the same group Red Top share the same casing, the YT will fit - but like you say Dan, you'll need to fabricate a special hold down to keep it properly anchored. My RT didn't come in contact with the top of the box, but I modified the disposable plastic insulator that covers the + terminal & used it as an insulator in the box just in case.

dr bob

Thanks for the insight Dan.

As I mentioned, this isn't an issue for me for another two years at least. I would really rather have a Group 48 battery living in the original hold-downs, but good ones are the same price as the Optimas with the Renn connection. So I'd be willing to compromise. I can fab a clamp for it, and have insulating material for the lid if it comes to that. I have those couple years to research the Duralast problems and see if changing the storage/maintainer protocol helps any. Making the Duralast work is my favorite option, others follow.

My butt is parked in a power plant where we are cranking out over 500 megawatts. And for some reason I'm spending mental capital on a few battery watts. Makes no sense until the car doesn't start, right?

Jim Devine

The Interstate Route manager for the area made
a good point. In a given case size there is only
so much room. To get higher amps, there has to
be more plates, thinner & closer together. He
recommended the next amp rating down from the top
( more space between plates)
so that a battery that doesn't get constant use
would be less likely to sulfate the plates together.
Seems to make sense.

dr bob

Good thoughts, and correct on the plate spacing vs ampacity. Generally, the surface area on the plates determines ampacity, more is better. But I'm not suffering from internal discharge, the symptom of sulfation. The electrolyte density on the brand-new Duralast is marginal to start with, and that may be part of the problem too; low density speeds sulfation.

Might be another interesting experiment to fully charge the new battery, then swap the electrolyte for new full-density fluid and see if that makes a measurable difference in performance and life. I've filled more than a few "dry-charged" batteries in my lifetime, and t was easy to see right away if the things had real capacity. I wonder if the local parts places even carry battery acid any more.


FWIW, I'm not so sure that Autozone doesn't have a hidden agenda to get the batteries out, then get them back for more cash during the prorated period. As we've discussed, we get kind of locked into their program once we buy one, since it's a relatively cheap hit replacing it during the warranty period. Need to discover the battery vendor who isn't that interested in seeing me within the next five years or so for another 'fix'.

Earl Gillstrom

I had to sell two different cars to get rid of the DIE QUICK 12 month batteries from Sears.

For many years I have used DEKA batteries and never a failure and up to 12 years service.

The only problem with DEKA (East Penn Manufacturing co.) is, I think they are sold only in the Northeast US and Eastern Canada.

I could tell stories all day about how reliable DEKA are and how unreliable the other batteries are.

Check out their web site to find a dealer near you.

dprantl

http://www.dekabatteries.com/ZipSearch.aspx?pageid=843

Dan
'91 928GT S/C 475hp/460lb.ft

Jim Devine

East Penn / Deka batteries are at Carquest stores.
Not the cheapest, but well made.
Buying cheap batteries doesn't seem to work out.

JPTL

Do you guys get the banner ad at the top of this topic from Advance Auto: "Get 25% off Car Battery!".Talk about targeting potential buyers.

928mac

I use a over size deep cycle battery
But I also picked to use the Gel battery

http://www.optimabattery.co.uk/engli...top_optima.htm