Battery

Hello everyone, first time poster. I have a 2007 3.4s Cayman 23k miles, only ever used on a dry road and am trying to keep the car to as near to factory spec as possible. The battery on the car a Bosch silver 740amp 80ah has been on pulse charge for 24hrs and won't keep the charge. New battery time. I have no idea if this is the original as I'm the second owner. I can get a good deal on a Varta blue 740a 80ah battery , were these ever fitted from new? Yes, I know this is an anal question.. Thanks in advance.

It's doubtful if a 13 year vehicle has a battery that is still the original one. Even the good German brands have a life of about 7-8 years, so chances are excellent the battery has been replaced before. And Porsche has been known to use Varta batteries in the past so your authenticity won't be compromised by using one. BTW - welcome to the forum.

Thanks for the answer & also the welcome. Varta battery it is then. .

My mech recommended Varta as well. Its also been suggested that although our cars are non-start-stop, to consider start-stop AGM battery nontheless especially if the car is not driven on longish commutes.

So, I'm not in Europe so I don't know if this applies. A few years ago, I replaced a battery with an AGM on my 06 CS. Everything was fine for a little over a year. After that, the battery stopped performing. It would periodically die and after charging, might go for a week or only a couple of days. I took it in for service and was told that the 987's charging system wasn't designed to use an AGM battery and that the AGM battery was designed to use a lower voltage charge over time and that the charging system was sending a higher output to charge the battery faster. This changed at some point - either the 987.2 or 981 - where the charging system became more adaptable to the battery type, but had to be notified which battery was in the car.

Interesting. I had been planning to go AGM for my next battery (2008 Cayman 987.1) because everything I had previously read said that they were interchangeable with lead acid types. Your comment seems to contradict that and I'm feeling forewarned. Thanks for that. I'm hoping others will chime in as well.

Great points about the AGM ... I didn't realize some of this myself. Here's a good reference for batteries in general, and they agree as well: Absorbent Glass Mat (AGM) Battery Information - Battery University

I have had an AGM (Odyssey PC680) battery on my 06 CS for over 4 yrs and 25k miles. Keep the AGM trickle charger on it in the garage when not driving and it's been fine. On a road trip last year it almost didn't crank over after sitting (uncharged) for 4 days. I'm looking to replace it soon with the Odyssey 925 AGM for more CCAs. Never heard of 987.1 having a different charging system to not handle AGM batteries .

Yeah. I think the difference is the trickle charger. According to the dealer, the CS charges at a higher rate than the AGM is designed for - I think it's more along the lines of a deep cycle battery . I don't use a trickle charger so that's probably the difference, but you are experienced what I did. Fully charge via charger - car sits for a few days and battery is dead. The difference is that mine started after about 14 months - your trickle charger may have covered up the true health of the battery for a period of time.

If your using a battery maintainer regularly and still only getting 4 years, what is the benefit? I do the same with my lead acid and get 5 years or so of battery life. AGM is a lot more expensive, up to twice as much. They're not lighter, that's for sure. So not having to check the electrolyte level every six months or so and no spill is it? Pretty sure I'll stay with lead acid when the time comes.

The Interstate H7 size AGM battery weighs 51.8 lbs. Their H7 non AGM Flooded battery weighs 42.9 lbs. Diehard batteries have a very similar weight differences. In both cases, from their web sites, the AGM batteries are actually heavier. So it appears you have found that weight saving on that particular battery brand works for you. The weight difference are immaterial to the vast majority of owners I suspect.

I am still using the Lead Acid H7 Interstate, when I bought it I asked about the AGM , they immediately mentioned the weight difference.

Yup and more expensive but supposedly they last longer.

"Supposedly"...key word. Based on comments here....not so much. Regardless, I'll be staying with the lead acid models for my 2008. If my car were a few years newer I'd reconsider or replace with the same as the factory type.

Exactly.

Repeat

Below is a link with a good comparison of the construction of AGM Lead Acid vs Flooded Lead Acid Batteries. In a nutshell, the major differences in the AGM battery include no venting needed, higher cost, longer life, more weight, ability to handle a deep discharge and frequent CCA heavy loads (as seen in auto start/stop technology models) when you move to AGM . AGM vs Lead Acid Batteries: 12 Differences + 9 FAQs | RepairSmith Also as an aside, most (if not all) newer battery chargers have different mode settings to set charging profiles specifically for AGM vs Flooded batteries. AGM setting seems to have an initial higher voltage boost before charger goes to trickle mode. I suspect that might not be OK for Flooded batteries. If you have an old charger, this option might not be available, so if you upgrade to AGM and have an older charger, you might not be properly charging the AGM. IMO, I would just stick to a Flooded Battery with the right amp hour/CCA rating as specified for your model. Does not have to be "branded" battery unless you just are the kind of owner that likes being OEM stock on all parts. Given that mind set Varta, Bosche, and Banner all seem to have been used at one time or another as OEM. Be aware some batteries have longer warranties than others too. In the USA, Costco Interstate batteries provide 3 years coverage against failure.

My two battery maintainers , Schumaker brand, do not differentiate between Flooded and AGM and in fact just calls them both "Lead Acid Batteries" while using the same settings for both. They do differentiate between Lead Acid and Lithium however, and have separate setting for each. Perhaps your comment is for battery charges verses maintainers? Just looking for clarification.

I use noco genius 5. It is an all-in-one universal charging solution - battery charger, battery maintainer, trickle charger, float charger, plus battery desilfator. It has multiple user settings. 12 lead acid, agm or lithium. Plus reconditioning mode and 6 volt mode. Works great. Second setting in modes is agm. Applies more voltage to battery during initial charge phase in AGM mode. Also use the noco g40 booster plus. Keep it in passenger compartment for safety. Will work to pop frunk or jump anyone else in an emergency.