I'm going to be in the process of building new battery cables shortly and am planing on replacing my batteries at the same time as they are getting some age to them. I've been doing some reading about guys switching to the group 31 batteries which are found in larger trucks. From what I gather, some modification may be needed to make them physically fit. Anyone with experience regaurding that, I'd be glad to hear about it.

I'd like to swap the batteries mainly for two reasons, 1) because the 31's are available with 3/8" threaded studs on top (which are more user friendly IMO), and 2) because they have more cold cranking amps (more starting power for the colder climate).

My first question is: Some folks have said that a threaded post battery does not conduct the amperage as good as a standard top post (not as much contact area), is this true? I can sort of understand their theory by visually looking at the two connections, but this is a large battery how could it not be designed to carry high current loads? It's used in medium and heavy duty trucks and farm and industrial equipment I would think high amp loads are accounted for in it's design?

And secondly for anyone running these batteries, which one's are you running? And what cca and price are they? Most I've seen are in the 950-1000 cca range and are slightly more expensive than our stock 65's. I know of the odyssey and northstar batteries, those appear real high-end for sure, but a little pricey for my tastes. A solid middle-of-the-road performer is what I'm interested in hearing about.

Looking forward to hearing all your thoughts! Thanks

 

I do not think it is worth it to convert over to group 31 batteries. They are quite a bit bigger and I do not think you will see any benefit. Group 65 batteries usually have 800-900 CCA which is more than enough to start the 7.3L.

If you want threaded posts, you can buy terminal clamps that have threaded posts on them.

 

Do you have a link or pic of these? Or are you referring to the military style terminals?

 

QuickCable STUD Post Converter 1 Piece

 

as the 31 have studs this converts em over to top post so you dont have to modify the wires

 

31s can be gotten with studs or posts. The OP wants studs, not posts, which will require wire modification. Studs provide less contact, and those marine terminals with the studs just mean one moe connection, one more point of failure. If the original terminals are in good shape, they provide the most robust connection.

IIRC, 31s are about the same size physically, and can usually be had with higher CCAs, in the 900-1000 range. But since they're sold as farm or commercial batteries, they're always sold with shorter warranties. Most of the top-end 850 and 875 CCA 65s have a three-year free replacement and 84-month pro rata warranty.

 

Lynx/Marine battery terminal (06070) | Battery Terminal End and Adapter | AutoZone.com

I think he is looking for the exact opposite.

The group size 31 batteries are actually quite a bit longer than group size 65 batteries.

 

Just to clarify, group 31's are about 1" longer, about 2" taller, and about 3/4" narrower than group 65's. The height is what I've heard there may be an issue with regaurding contacting the hood.

BCi Group Sizes:

BCI 31: 13L x 6-13/16W x 9-7/16H
BCI 65: 12-1/16L x 7-1/2W x 7-9/16H

 

I stand corrected; knew they were longer, but I somehow had the impression they were the same height.