Group 27 vs 31 battery - which to choose?

[BWolfe]

I’m replacing my alternator and doing the big 3 wire upgrade (as well as the alternator wire). Current battery (pictured) is 4+ years old, so I’m going to replace it as well.

Should I stay with the group 27 or upgrade to 31? At first I was thinking I’d do the Slee tray & terminals upgrade to the 31 battery, but now I’m thinking a 27 agm battery might make the most sense for me. I can get the odyssey agm 27f for $375 - it’s got 850 cca with 182 minutes of reserved capacity, compared to the interstate 31-mhd which has 950 and 195, respectively. Ive got the GM voltage boost regulator installed.

I’m in the south so it’s hot - 850 CCAs is probably more than enough right? Trying to understand the benefits of the size 31 upgrade as best as possible before I spend money for reasons unclear.

Thanks!

 

[x8o8drifter]

From what I understand the only real difference is weight.
You can have a smaller one with more CCAs or one with less. Same goes for larger.
It depends.

"Usually" larger = more CCA but also more weight.
And more reserve in most cases.
OEM CCA is only 650.

But that aside, Group 31T doesn't fit our trucks anyway. (supposedly)
If your not towing/off-roading alot just get the lightest/cheapest battery you can.
This is assuming a stockish vehicle/electrical system.
Groups that do fit these trucks. (in inches)
Group L W H
35 9.0625 6.9375 8.875
27 12.5 6.8125 8.9375
24 10.25 6.8125 8.875
The 31
31 13 6.8125 9.4375
That extra 1/2" in length might be too much for the stock tray.

 

[100s]

Group 24 in my 02... no issues.

 

[SmoothLC]

From what I understand the only real difference is weight.
You can have a smaller one with more CCAs or one with less. Same goes for larger.
It depends.

"Usually" larger = more CCA but also more weight.
And more reserve in most cases.
OEM CCA is only 650.

But that aside, Group 31T doesn't fit our trucks anyway. (supposedly)
If your not towing/off-roading alot just get the lightest/cheapest battery you can.
This is assuming a stockish vehicle/electrical system.
Groups that do fit these trucks. (in inches)
Group L W H
35 9.0625 6.9375 8.875
27 12.5 6.8125 8.9375
24 10.25 6.8125 8.875
The 31
31 13 6.8125 9.4375
That extra 1/2" in length might be too much for the stock tray.

. . . or get a SLEE – Main Battery Upgrade Tray – ’98-07 Land Cruiser / LX470.