CCA ??? 6 volts in series or 12 volt in parralel???

JD Seller

Well-known Member
The old school way was two 6 volt batteries in series. Then later model tractors switched to 12 volts batteries in parallel. Years ago I was always told that the two 6 volt batteries would give you more CCA. Lately I have been told the opposite, that two 12 volts will give you more CCA.

So in layman terms (old fart understandable ) which is better and why???

The reason I am asking I just switched one of my JD 4450s over to the two 12 volt batteries for two 6 volts. My reason is I can buy the 12 volt batteries much cheaper and they seem to last better than the 6 volt ones. The tractor cranks better but that could be because of new batteries and good cables/conenctions too.
 
Jim's opinion. The 6 volt battery has much greater dependence on internal and external conductivity (ampacity, a John T term) to conduct the rated CCA. The 12v much less. The weak battery in series is still a limitation in that circuit. A pare of 12s in parallel can disguise the weaker battery, and make them operate longer successfully. 6v batteries may sit on the shelf longer than the 12s. Jim
 
You could have a room full of electrical engineers and ask that question and it may turn into a fist fight trying to settle it.

The John version goes like this.

Years ago it was better to have two 6 volt in series but today it is better to have two 12 volt in parallel.
First it has to do with the quality of batteries and cables sold today.
You can buy much bigger CCA 12 volt batteries today than you use to be able to.
Also finding fresh 6 volt batteries that have not set on the shelf for a year can be a problem.

Second two 12 volt batteries may mask a problem and have you ruin both batteries where a problem with two 6 volt batteries will show itself and force you to fix the problem now.

In theory if both banks have the same CCA they will be the same.
Remember you double the voltage on the 6 volt set and double the AH on the 12 volt set.
So two 12 volt 200 AH batteries would be the same as two 6 volt 400 AH batteries if the cables are the right size.

You did not mention the AH or CCA of the batteries in question so we can only speculate.
 
pound for pound
peanuts or feathers
spiral wound or flooded lead acid
agm or ?

whatever suits your fancy and pocketbook at the time
what's available?
each at what cost?
claimed elctrical capacities?
post types interconnections cables?
dealer network for warranty issues?
lets get back to brand
do they make suitable quality 6 volt batteries?
seems like 12 volt might be more widely available
 
Well, here's my theory. Back when your tractors were designed, battery design tended to favor storage capacity (amp-hours) over starting capacity (cold cranking amps). Since then, 12 volt batteries have been developed to deliver much more CCA at the expense of storage capacity. Six volt batteries, particularly those used in golf carts, are still optimized for maximum amp-hours. So I think you've done the right thing going to dual twelve volt batteries. Not to mention the cost savings.
 
I have switched all my 30,40 and 50 series over to 12 volt semi batteries (group 31). Its a lot cheaper that way and I always keep a spare set on hand.
 
two 6v in series the total cca doesn't increase. It's the same as one 6v. Only the voltage increases to 12v.

Two 12v in parallel, the voltage stays the same, the cca of each battery adds together making cca double.

It's possible a huge 6v battery may have more plates and be able to produce more cca than a 12v battery. I think that's why old golf carts used six 6 v batteries in series instead of three 12v batteries.
 
There is no one single answer to your question.
Two 6-volt batteries in series will give you 12 volts. CCA will depend on the size of the batteries used in this configuration. CCA will not add, but will be equal to the lesser of the two batteries if they are not the same size. '
Two 12-volt batteries in parallel will still be 12 volts, but the CCA will be equal to the sum of the two batteries used.
So, two BIG 6-volt batteries CAN be better than 2 smaller 12-volt batteries. But, in general, the 2 12-volt batteries will probably be better simply because they will be higher capacity.
The real answer is to look at the sizes and ratings of the batteries in question. The preferred setup would be the ones with the higher capacity CCA.
 
...and if the previous two guys didn't get the message across I will explain it for a third time:

In series VOLTAGE adds up.

In parallel CCA adds up.

In the 3EE vs. 3EH argument, it's pretty much a wash. Both configurations have somewhere around 800CCA. A single, quality, group 31 battery has both configurations beat.

Electrically, they are THE SAME. Any claims that one is significantly better than the other are due to new vs. old batteries, new vs. old cables, clean vs. dirty connections. You rip out 50 year old cables and 10 year old batteries, and replace with new, the tractor is bound to start significantly better.
 
Today's 12 volt batteries might offer more power per dollar and more power per pound than equivalent 6 volt batteries.

Battery technology is advancing. The market for 12 volt batteries is much larger than for 6 volt batteries. I doubt that much effort or money is going into updating 6 volt batteries anymore.
 
Best answer on the subject. I always think of the possibility that somebody making these changes MIGHT get confused and connect two 6 volt bats in parallel or two 12 volt bats in series. Two 6 in parallel OK, two 12 in series SMOKE, SMOKE!

In many application changing from two 6 volt bats in series to ONE 12 volt bat is a sufficient upgrade and MUCH cheaper. I finally did change my JD 50 over a few years ago after obeying the "correct police" for many years.

Ron 50 + years EE experienced.
 
4520BW: You have done what I am doing. My son maintains a small fleet of semis for a local company. He/we buy a pallet if group 31 batteries at a time. Our cost for a Excide battery is under $65 after core exchange. The same exact battery at JD is over $110. No brainer on what I am doing.

I just wanted to hear why the 6 volts fell behind. I think it was the internal resistance or something being different.
 
JD, good question, here's an old retired n rusty electrical engineers answer.

The CORRECT answer is it depends, IF you want the most cold cranking amps for starting purposes the best is what combination yields the most CCA regardless if its two sixes in series or two 12's in parallel. The two sixes in series yields 12 volts HOWEVER the CCA's ARE NOT ADDITIVE. To the contrary two 12's in parallel is still 12 volts HOWEVER the CCA's are additive.

It may well be possible a certain 6 volt has more CCA then a certain 12, but even with two in series if batteries are identical you only have the CCA of one of them.

REALITY a 6 volt is less common and maybe more expensive battery you might find available off the shelf while a 12 is much more common and readily available.

IMPORTANT NOTE I haven't seen touched on below and many lay persons are unaware !!!!!!!!!!!!!!!!!!! In the event you choose two 12's in parallel (likely my choice and decent chance more CCA's) in order to achieve better load and charging balance among the two be sure to run the big main heavy POSITIVE cable off Battery A and the big main heavy NEGATIVE cable off the other Battery B. IE don't run both big heavy main cables off one battery.

John T Long retired Electrical Engineer but believe the above still rings true
 
Hello 55 50 Ron,


So is 3 OR 6 B volts batteries in parallel. The more the merrier right? HE! HE!

Guido.
 
My story is simple and requires no physics nor math explaining Ohms Law. I had a 4230DC with a 6 volt on the right, grounded to the engine block on that side with a 0 sized wire and another 0 strung across to another 6 volt on the left which continued on to the starter solenoid.

I replaced that with a 12v battery on the right side, plumbed across to the left side with 2 ea 00 wires connecting in parallel to the battery adjacent to the starter.

The negative of that battery went to and under a starter mounting bolt with another 00 since I had it handy after I pulled the bolt out and shined everything up real nice ensuring that the ground (-) lug was in good tight contact with the starter case.

The positive of that battery went with a fourth 00 over to the starter solenoid ⅜# copper input terminal.

As a result, the use of a starting enhancement mechanism, even on the coldest days was gone forever. I bought the batteries at a nearby OTR truck dealer who stocked heavy duty size 31S (S for ⅜" stud terminals) rated 925 CCA each....just bought another one from the same dealer this past week for a different tractor, with trade, farm tax exempt, 75 bucks.....that's US $ quantity 75! He had a skid full of them sitting right there in the lobby, probably 100 easily......volume purchasing as OTR trucks each use half a dozen (BTDT) means lower pricing for the purchasing public.
 
Bought a used 4240 about 8 years ago. It had 2 newer 12v batteries, First really cold day would hardly turn
over. Bought 2 new Strong Box Deere 6 volt batteries switched cables back to original. Will replace with same.
 
You will be happy with the group 31 batteries. The tractor will crank better the batteries will last longer. You will save money.
 
JD: We converted all of out old IH's with the 2 Eh batteries over to one Group 31 with the studs on top with very good results as far as starting with only one battery. This is in Mi so not in only warm weather temperatures.
2 12's will give more amperage to only about 1-1/2 of the 2. 2 6volts will give the 12 volts needed but only about the amperage of the one battery so then it will depend on the size of the batteries used in both cases. 400CCA 6 volts will give about 400 CCA's with the 12 volts in the series position. 12volts with 400CCA will only give about 600 in parallel as it doesn't seem to quite make the double amperage in the parallel set up it is supposed to though in cold weather batteries as you know are only about half or less of rated ability depending on the temperature outside.
We also converted my brothers 2940 over to one 12volt GP 31 and it has been starting fine till this last 6 months so now will have to pull starter and have a look inside. This was about 5or 7 years ago.
 

There is theory and there is what is actually built and is on the shelf at TDC.
Usually the highest CCA 12V batteries in parallel that will squeeze into the battery boxes will provide more CCA. Vs a pair of the highest CCA batteries in series that will cram into the battery boxes.
 
........yes, for 3 reasons: 1) The battery internal resistances are in parallel thus halving not doubling as in series connections (a 4x
improvement), and in parallel the only current in the long run to the right battery is the length of the interconnecting wiring. 2) The
adjacent battery only has about a foot of wire off each battery terminal....aka less wiring resistance. 3) The ground connection is at the
starter case, not across the tractor relying on a bolt to the engine block to the interface between the block and the starter....all of which
are usually rusty and greasy and poor conductors.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top