Battery question - Dodge truck and diesel tractors

I've got a first-generation Dodge truck with the Cummins diesel. It uses only one starting battery which is kind of unusual. All my Ford and GM diesels use two smaller batteries - as well as most of my diesel tractors.
It can get 30 below zero here - but it's unlikely I'd try to drive a diesel at that temp. Still, I want to have the option to start it at zero temps - even if I forget to plug in the heater. Battery capacity gets cut in half at zero. Dodge calls for a single battery in my truck that has a minimum of 1100 cold-cranking amps at zero temp and a reserve of 170 minutes. It is a BCI type 31 battery. I'm finding out that hardly anybody makes such a battery anymore. Most for sale now - the commercial 31s - are only 925 CCA. Deka still makes one that is rated 1100 but it costs $140 with only a 1 year warranty. As I said - I tend to think a bit too hard at times. But - if I buy the $140 battery - it only comes with a one year warranty - because it's commercial. On the other hand, I can buy two smaller batteries - like my Fords and GMs use - at around $60 each - and get a much longer warranty - and much more reserve capacity and cold-cranking amps. Is there something here that I am overlooking? I am wondering a bit if a larger single battery can be more long-lived than two small ones - regardless of warranty. I had an Exide type 31 in my IH tractor - bought it in Jan, 1999 and it just went bad last month. But - it was not started every day like a truck will be - not even close. I've also been told that some CCA claims are make-believe - but that was from an Interstate battery dealer. I see it like this. Battery weight is the all important factor. Any size battery can be custom tailored to put out more amps at a fast rate - but then sacrafice how long it can do it. I checked around at many lists of batterys - and weight seems to be the determing factor with all of them. In regard to the BCI type 31 battery my 92 Dodge W250 calls for - I found this.

Deka type 31 versions: 1231MF - 1125 CCA, weighs 61 lbs., 195 reserve capacity.
1131PMF - 925 CCA, weighs 56.5 lbs., 170 reserve capacity
931MF - 650 CCA, weighs 51 lbs., 145 reserve capacity

I found several type 31 brands for sale locally - all listed as commercial with one-year warrantys and all no more than 925 CCAs. So, I assume they are equivalent to the Deka battery that weighs 56.5 lbs.

If I put in two, type 27 batteries - it will be cheaper, the warranty is much longer, I'll have 94 lbs. of batteries, and 1500 cold-cranking amps.
Is there an advantage to using the single battery that I am not seeing? And, I guess this applies to tractors as well.

A lead acid battery is an electrochemical energy storage device and "generally" speaking since they use lead n acid to do so, the more lead n acid which also amounts to the more size n weight can store more energy. One advantage of two batteries in paralell is that the available cranking amps and amp/hr ratings is additive, where two in series that isnt true (only the voltages add). HOWEVER, batteries may be more prone to feed n cannibalize off each other in paralell versus them being in series.

Regardless if in series or paralell you wanna use matched batteries to lessen one feeding off the other in my opinion

In the old days they sold batteries rated in Amp/Hrs which gives a good indication of their energy storage capacity while nowadays its more CCA.

For good diesel starting fast cranking to help raise the cylinder temperature and avoid compression leak off is important so those initial CCA'a are needed. Another battery may actually be able to store more energy and could provide more amp/hrs to crank the engine longer but nottttt ttt have the high initial CCA to crank it faster. Looks like for a gas engine the longer crank time may be more important but in a diesel its that initial good fast crank over thats needed (even if not as long) i.e. a high CCA rated battery.

I also used to buy those 1050 to 1000 CCA batteries but havent seen them around as much lately?????

best wishes

John T

For the type 31 batteries - the long-term draw specs are given in "reserve capacity" instead of "amp hours" - both are valid. The "reserve capacity" is the time the battery can deliver 25 amps and maintain a minimum terminal voltage of 10.5 volts at 80° F.
A amp-hour rating is a little more ambiguous and is based on one amp draw per hour - but the amp hour ratings used for batteries have to be accompanied by an extra number or they don't mean much.

One example is a Deka 900 cold-cranking-amp battery. It has a reserve capacity of 180 and a 20 Amp Hour rating of 95, a 10 Amp Hour rating of 80, and a 1 Amp Hour rating of 50.

The battery Dodge calls for OEM for the first-gen. Cummins diesel has a reserve capacity of 170 minutes - so I suspect around a 20 Amphour rating of around 90.

I think I'm going to put in two group 27 automotive batteries. At least they come with a long warranty. Walmart has them for $69 each - 750 CCA and 180 reserve capacity. So, for $138, plus $20 in extra cables - I get 1500 CCA and 360 minutes reserve capacity. Seems to make sense.
I realize, that in most cases - not that much battery is needed. But, when the rare case comes up - it's nice to have the extra cranking power.

A lead acid battery is an electrochemical energy storage device and "generally" speaking since they use lead n acid to do so, the more lead n acid which also amounts to the more size n weight can store more energy. One advantage of two batteries in paralell is that the available cranking amps and amp/hr ratings is additive, where two in series that isnt true (only the voltages add). HOWEVER, batteries may be more prone to feed n cannibalize off each other in paralell versus them being in series.

Regardless if in series or paralell you wanna use matched batteries to lessen one feeding off the other in my opinion

In the old days they sold batteries rated in Amp/Hrs which gives a good indication of their energy storage capacity while nowadays its more CCA.

For good diesel starting fast cranking to help raise the cylinder temperature and avoid compression leak off is important so those initial CCA'a are needed. Another battery may actually be able to store more energy and could provide more amp/hrs to crank the engine longer but nottttt ttt have the high initial CCA to crank it faster. Looks like for a gas engine the longer crank time may be more important but in a diesel its that initial good fast crank over thats needed (even if not as long) i.e. a high CCA rated battery.

I also used to buy those 1050 to 1000 CCA batteries but havent seen them around as much lately?????

best wishes

John T

Also I would recommend getting a stud type or combo post top if they are available and use the tall led nuts to hold the cables. They are so much easier to service vs the standard post.

Always buy the batteries in matched pairs.
or like for like.

Also his batteries would usually test over the CCA rating, which was a good thing.

I've been wondering if one large battery might have thicker plates that two smaller ones because all is one case - so less space is wasted.

What the heck if "FWIW?"

Are the two batteries installed sideways in your Dodge? I checked on mine, and it looks as though two put in sideways and hooked in parallel - will just fit.

not,F'in W-ild I-n W-oods LOL