I just bought a few and I can make them fit, the parts man said they were way more stout than the stock 6500 series Ford recommends...


950 CC amps and way more energy storage.....

 

Group 31 drop right in the earlier trucks, later trucks may need some minor mods for clearance. Either way, group 31 is the only way to go. I got a pair of NAPA group 31 for about $100/ea at 1000 cca each.

 

My truck is getting a pair of group 31s mounted back on the frame once turbo time rolls around.

 

Yeah, it's a good way to go, even had one in my Bumpside for quite a while.

 

You can get away with a single 600+CCA battery for starting, generally.

Where the capacity matters is when you have to crank and crank and crank. That's when you want the most lead available.
Make sure that your chosen batteries are both 600+ CCAs AND have a good reserve capacity or amp-hour rating. The more RC(minutes of capacity at 25 amps), the more active lead physically available in it.

Bigger and heavier is better when it comes to batteries.

 

I wonder how well 1 will do in these trucks....

 

Just fine, until you have to crank for more than like 30 seconds.
Also, in winter it may get a bit pickier, depending.

I know I've run 1 battery more than a few times; everything from group 31 batteries like that, to various other sizes; I recently had no problem starting a 6.9 with a single 6XX CCA deep cycle battery*
(Note: in addition to being undersized cca-wise, it was also one I picked up at the dump. At least 5 years old, but evidently in decent shape).

edit:
That being said, I'm tempted to get a single /massive/ battery(CCAs will probably be lower, but the added capacity is what's needed when you run out of fuel and have to prime it), and mount it under the bed somewhere. Clear up some space up front for a cold air intake etc.
Something like this: http://www.oreillyauto.com/site/c/de...0369&ppt=C0327
It has 34 full *minutes* of cranking at 210 amps.
(Note: I took an idi starter rated at 2.5KW@12V = 210 amps)

 

my starter is 3.5KW one group 31 will work fine, two is twice as fine, if remote mounting go to your local welding shop and get cables made, is worth the money...

 

mounting a battery on the frame can be a pita during install and maintenance.
other than that, its a great place to put them.


I opted to keep 1 in the engine compartment and put the passenger side on the pass side frame rail.


im running 2 GP 31's


I ran the positive cable to the starter, and the negative cable to the stock location on the front of the engine.


I used marine grade 00 cable with soldered lugs and sealed heat shrink(the kind when you heat it up, it oozes goo)


ive had zero issues with both batteries.
when I first started this swap, 1 GP31 wasn't enough. it would crank slow, id advise 2.


as long as its a 12 volt battery, the bigger, the better!

 

What happens if you run 1 group 31 and then a smaller battery together ? The group 31's are on sale today for 110 at Advanced and it's a CARQUEST brand and weighs 60 pounds.


The battery posted in the link above at Oreilly is the BOMB. One battery that weighs 100 pounds and cost 160 ish is the way to go if you could mount it.....

 

Everyone will say not to run mismatched batteries.
Optima: https://www.optimabatteries.com/en-u...eries-parallel

That being said... I've done exactly that with no issues.
You have to make sure that your batteries are both in good shape(if one has a sketchy cell, it'll drag the other down), but I've gotten away with it.

All of the stuff about charging dissimilar batteries is great... If you were charging the batteries 'properly' in the first place. Alternators just create 14-14.5V chopped DC, and each battery will effectively regulate it's own charging.
We are running a 12V system, so both batteries are in parallel; series systems(24+V) are a lot trickier and I *wouldn't* run two differing batteries.