Optima Owners - which size are you using (and why?)
 

Time to replace the LARGE Die Hard with a new battery (battery died last weekend, so I'm due). I've checked the charging system and am getting 13.6 volts across the battery terminals, so I'm pretty sure its just the battery.

I'm pretty much decided on the Optima, but the question is, which size Optima Red Top?

34/78 with CCA = 800
75/25 with CCA = 720

Car lives in the garage and the outside temps almost never go below freezing.

Yes, I've searched and haven't found a consensus on the size.

Here are some posts of mine...including further embedded posts..on various sizes, options, etc. Largely focusses on Optima...

http://forums.pelicanparts.com/showthread.php?s=&threadid=260998&highlight=batter y+48F93+AND+ferch

- Wil

Thanks Wil - very helpful. I'd already read some of them in my search. Now I'm trying to get a read on whether I need 800CCA or 720CCA.

OK.... I went to the Optima web page and other pages inside--->
http://www.optimabatteries.com/publish/optima/americas0/en/config/product_info/automotive/starter/technical_specs.html
It seems that the 75/25 is:
- 9.3" Long
- 6.8" wide
- 7.6" High
- weighs ~ 33 lbs.

In contrast, the 34/78:
- 10" long
- 6.8" wide
- 7.8" high
- weighs ~ 38 lbs.

On the one hand...you probably don't need the "bigger" unit ( although fairly equal in size)...due to apparent warm conditions where you live. But the size and weight differences are so small..why not get the "normal" , conventional 34/78 Optima that seems to be standard fitment for our 911's?. I don't think you're talking a racing or super-lightweight conversion..are you?

- Wil

EDIT- by contrast, the 49/93 "big honker" stock battery was ( IIRC) about 2" longer and weighed-in at closer to 50 lbs or so.

I had two Optima red tops die in a year and switched to the Odyssey 680MLT which is only 15lbs and 680CCA. I haven't had any problem since...

in a few years you'll be able to sneak up to a new Prius III and rip out the Li ion packs...