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John Deere Tractors Discussion Forum
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12 volt batteries in parallel

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Andrus Burr

01-22-2007 13:28:56




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I have a JD 70, which of course has two 6 volt batteries hooked up in series. On a cold New England morning it's very slow cranking and often won't start. Would it make sense to hook up two 12 volt batteries in parallel for more cranking power?




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buickanddeere

01-23-2007 19:57:50




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 Re: 12 volt batteries in parallel in reply to Andrus Burr, 01-22-2007 13:28:56  
It should whip right over. Measure the volatage from battery post to battery post while cranking. Not battery clamp to battery clamp either. Then measure between the large brass post at the starter motor and the starter motor's cast iron body. If there is more than 1/2 to 3/4V drop between the batteries and the starter, the cables/connections are duds. If the combined battery voltage drops below 10.0-10.5V while cranking the batteries are duds. Does the tractor have bypass starting? A gasser doesn't need high cranking rpms to start. Just lots of electrical system voltage to fire the plugs.

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Glen in TX

01-22-2007 22:48:05




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 Re: 12 volt batteries in parallel in reply to Andrus Burr, 01-22-2007 13:28:56  
You are going to get what you pay for and if using small cheap batteries and old small crummy cables would be no better off. Put on bigger cables and use as large of 2 12V batteries you can fit in there in todays batteries and it will be better. JD put 2 6V on many earlier new generation and generation II tractors with many of those being converted later to two 12V in parallel. BTDT on several and military 6x6 fire trucks that had 4 6V for 24V and best we thing ever did was change to two bigger 12V in series or parallel depending on whether 24V or 12V. Not many places today even stock a decent 6V battery either with the HD CCA needed but they might can order them and charge for extra freight. Working machines don't have time to wait for that so many still being converted.

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Frank in Florida

01-22-2007 19:08:25




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 Re: 12 volt batteries in parallel in reply to Andrus Burr, 01-22-2007 13:28:56  
Been there done that on a Belarus 800 I have been using since 1984. It came with two six volt batteries in series. Two years was the best I could get with the six volt batteries of the best NAPA sold at the time. Finally decided to try two 12 volts in paralell
and got two from Sams Club that were the biggest that would fit. The ratings for cold cold cranking amps were a little higher with 12's but they weighted a lot less than the sixes. The paralel 12's cranked faster and lasted seven years. Frank

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jdemaris

01-22-2007 17:25:33




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 Re: 12 volt batteries in parallel in reply to Andrus Burr, 01-22-2007 13:28:56  
If the batteries are of comparible quality, it makes no difference. As a general (but not perfect) rule of thumb, just look at battery weight. A two 60 lb. six volt batteries hooked in series will usually yield the same amp and cranking-voltage output as two 60 lb. 12 volt batteries hooked in parallel. We used to change over a lot of Deeres to dual 12s instead of 6s - but not because the batteries were any better. The batteries connections tend to work better on two 12s since the voltage is higher at the cross-over cable and two grounds are usually used. We had too much trouble with dual six-volt battery hookups when the cables got just a little corroded. There is also one other benefit. When I worked for Deere, the OEM 6 volt tractor batteries only had a 1 year warranty. But, if you could fit in a 12 volt car or truck battery, it would have a 3 - 5 year warranty. Much better deal.

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55 50

01-22-2007 19:02:15




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 Re: 12 volt batteries in parallel in reply to jdemaris, 01-22-2007 17:25:33  
please define the cross-over cable.



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jdemaris

01-23-2007 05:19:51




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 Re: 12 volt batteries in parallel in reply to 55 50, 01-22-2007 19:02:15  
If you hook two 12V batteries in parallel - power is drawn from a center-tap where a cable hooks the two postive poles of the two batteries together. That cable is what I'm calling a "crossover" cable. With dual 6 volt batteries hooked in series, the "crossover" cable connects the postive term. of one battery to the negative term. of the other and power is carried through the cable from one battery to the other - thus carrying all the current flow.

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John T

01-22-2007 17:06:24




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 Re: 12 volt batteries in parallel in reply to Andrus Burr, 01-22-2007 13:28:56  
Andrus, Its indeed true if two batteries are connected in paralell the amperage rating is the sum of the two i.e. if each has a 500 amp rating the two in paralell could deliver 1000 amps. HOWEVER as my ol buddy Gerald noted thats NOT TRUE of two in series, if each had a 500 amp rating the two in series remains only 500 amps (although the voltage is additive)

What you gotta do is NOT compare apples to oranges cuz the CCA and/or amp/hr ratings need to be taken into account i.e. two wimpy twelves in paralell may still not deliver the amperage of super heavy duty (like a golf cart type for example) six volt units. A battery is an energy storage device and generally speaking in lead acid batteries the more lead n acid (usually corresponds to more weight) the more stored energy capability.

There are other factors involved, if two are in series and theres no load and no electrical current path theres less chance then when two are in paralell for them to interact and feed/canibsllize off of each other. When connected in paralell even when all is turned off the batteries can interact ya know !!!! Its best if the batteries are exact matched in age n type n brand n size etc. and if it were mine I would likely buy two new matched super heavy duty 1000 CCA or so 12 volt batteries (in paralell) and use 0 or 00 gauge battery n starter n ground cables, I bet that would crank her provided the starter n switch/solenoid are in good shape.....

John T

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Gerald J.

01-22-2007 16:25:58




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 Re: 12 volt batteries in parallel in reply to Andrus Burr, 01-22-2007 13:28:56  
READ the battery ratings. Some 6 volt batteries have a wimpy CCA (Cold Cranking Amps) rating. Two in series gets the same CCA. Some 12 volt batteries claim a lot better CCA and two in parallel doubles that rating.

Then be sure the starter cables are FAT, not the skinny things sold at Walmart. Hardly anything short of stealing the battery is as hard on stiff cranking than 4 gauge battery cables when 1, 0, or 00 ought to have been used. Then make sure the connections are clean, particularly the battery posts and the connection to the frame and the stater switch/solenoid.

Then make sure the bearings in the starter and the starter brushes aren't worn out. There's a lot of magnectic pull to the side if the bearings are worn the armature will touch the field poles and will crank poorly. Short brushes won't give fully pressure and will limit the amps to the armature and its AMPS to the armature that turn the shaft.

Two wimpy 6 volt batteries have cranked that engine for 50 years, but the battery cables, connections, and those details in the starter can make it harder to get the engine started.

Gerald J.

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Ben.So.Tex.

01-22-2007 16:19:54




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 Re: 12 volt batteries in parallel in reply to Andrus Burr, 01-22-2007 13:28:56  
Name: Ben.So.Tex (Reserved Name) E-Mail: Subject: Re: 12 volt batteries in parallel
In Reply to: 12 volt batteries in parallel posted by Andrus Burr on January 22, 2007 at 13:28:56:
Body of Message:

I have just one 1 large battery in my 12 volts tractors, It was in the high 20 last week and they fired right up. Also my tractors are under a shed.
Now this is South Texas where it hardly ever freeze's except for last week.
Good Luck.

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J Schwiebert

01-22-2007 16:10:06




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 Re: 12 volt batteries in parallel in reply to Andrus Burr, 01-22-2007 13:28:56  
I am looking at the otherside of the trees. Have you checked to see what kind of voltage you are getting at the starter? Have you though about a block heater and maybe even an oil heater. It is easier to start a warm engine than a cold one plus there is less wear on the engine.



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machinery-man

01-22-2007 15:35:07




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 Re: 12 volt batteries in parallel in reply to Andrus Burr, 01-22-2007 13:28:56  
I beg to differ...why put two batteries in parrallel if you don"t have more amperage. I"ve got two diesels and they both have two batteries in parallel, I can go to one but I don"t have the amperage for cranking.



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55 50

01-22-2007 16:41:05




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 Re: 12 volt batteries in parallel in reply to machinery-man, 01-22-2007 15:35:07  
I think we are on the same page, but just using different words. The load, which is the starter in this case, is the same regardless of how many 12 volt batteries you connect in parallel. I agree that one battery will run down quicker than two, but it won't change the amperes being drawn by the starter. CCA ratings on batteries are related to time, how long can it maintain the necessary power (volts X amperes) to roll the starter. With one battery, the loss in the cables can be enough to cause the problem with cranking that you mention you have, but the number of amperes the starter needs hasn't changed.

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machinery-man

01-22-2007 13:56:08




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 Re: 12 volt batteries in parallel in reply to Andrus Burr, 01-22-2007 13:28:56  
Will give you more cranking but how about the amperage on your starter. Believe you might be buying one shortly.



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55 50

01-22-2007 15:10:57




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 Re: 12 volt batteries in parallel in reply to machinery-man, 01-22-2007 13:56:08  
The amperage to the starter will remain the same. The only concern for starter damage is how LONG you continue to keep it turning without a break. If you use the same caution (meaning don"t crank it endlessly) that should be used with the two six volt batteries in series, then there is no danger using two 12 volt batteries in parallel.



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machinery-man

01-22-2007 13:56:02




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 Re: 12 volt batteries in parallel in reply to Andrus Burr, 01-22-2007 13:28:56  
Will give you more cranking but how about the amperage on your starter. Believe you might be buying one shortly.



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machinery-man

01-22-2007 13:55:52




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 Re: 12 volt batteries in parallel in reply to Andrus Burr, 01-22-2007 13:28:56  
Will give you more cranking but how about the amperage on your starter. Believe you might be buying one shortly.



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BDT in Minnesota

01-23-2007 02:37:51




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 Re: 12 volt batteries in parallel in reply to machinery-man, 01-22-2007 13:55:52  
No...the voltage is still the same, and think of the voltage as the "pressure" in the bateries....The "flow" is the amps....The more batteries, the more capacity to flow longer at a given voltage. the starter draw will determine the amperage flow....If the starter doesn't get the amperege flow through it at a given "pressure" or voltage,,it will turn over slowly, if at all.. That is murder on a starter...

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Andrus Burr

01-23-2007 07:17:02




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 Re: 12 volt batteries in parallel in reply to BDT in Minnesota, 01-23-2007 02:37:51  
Wow! Great discussion. Thanks guys. I have new 0 gauge cables but the batteries are not matched, and the starter may have some issues. I"ll look into those things,...and if that doesn"t do it I"ll go to two 12 volts in parallel.



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