Why did we stop using a single giant battery, and now use 3 tiny batteries?

24 volt was common 45 years ago. And I’ve never seen a group 31 in a pickup truck.

 

Some diesel pickups have them.

Complete 24v systems have never been in civilian trucks. Some trucks used a dual system that started on 24v, but the rest of the truck was still 12v. Those dual systems were problematic and complicated. A compete 24v system would work much better, but it would require only pulling trailers that were setup for 12v.

 

One major thing the group 31’s did was allowed the older trucks with 24v start/12v run to remove and scrap the series/parallel switch and just be 12v. Older 40mt 24v starters work fine on three 31’s without being converted and sometimes just two 31’s will work on older high compression ratio Cummins’ with compression releases.

 

The common practice to do after the 31’s caught on was remove s/p switch and wire in a remote Ford style solenoid to the existing delco solenoid on the 24v starter. This would keep the starter from “burning” out due to the lower 12v. Worked like a charm and got rid of heavier weight and bigger batteries that always rotted out boxes and the s/p switch that had to be thrown every time you shutdown and fired up.

 

I've seen lots of them in pick up trucks. My own. I've upgraded to a 31 in about every truck I've ever had. Lol.

 

What do you do about the stud post?

 

Put a stud terminal on the cables? Or, if you're lazy, lead post screw-on adapters are available.

 

A screw on post adapters.

 

Just an fyi but they also make a group 31P.
It has traditional posts instead of studs.
Hino Medium Duty trucks come oe with them.

 

If my memory serves, they're original equipment in Thermo King reefers. Seems like a few times I've re-used the odd good ones out of a truck into a reefer unit, I end up changing the terminals since the screw post batteries are easier to come by when the next one is needed.