The AGM Battery

[PaulE]

Originally Posted by 10/10ths

If they are over rated, then why do OEMs invest in AGM batteries in their Auto Stop/Start versions of their cars?

If they didn't work better, they wouldn't spend the money to put them in those vehicles.

I bought this one:

NSB-AGM 94R/L4

I keep it alive with this:

CTEK Multi US 7002 - CTEK Battery ChargersCTEK Battery Chargers

Two years in, so far, so good. Car sits a lot.

Good luck.

Maybe it's just overkill for an older car without auto start/stop? I am only on my second battery in my 03 S, it is an Interstate that I put in in 2009 to replace the original battery. I use the older version of that CTEK - same as the one Porsche sold at dealerships but without the "Porsche" label and premium pricing. If I can get this long out of a traditional battery (OEM -6 years, Interstate - 7 years and still kicking), what's the benefit of AGM to me?

Now that I've said that, my Boxster has been out at the body shop for a week, and then goes back to my independent garage for installation of the sport suspension. With the car off the battery tender for that long, I may have just cursed my battery!

[Gelbster]

Cursed ?
No
It is just chemistry. If the SOH is 50% or less but it still takes at least 90% charge, try to desulphating it. That is the specific problem that causes most lead+acid batteries to fail.