How to get 12V power from 24V system?

cfk · Jul 26, 2023

Tractor is a JD 4020 with the 24V system, and I need to get power to my planter marker control box. The easy answer is to run a + wire to the + terminal on one battery and a - wire to the - terminal on the same battery, but that pulls a load from the one battery, and I have read that those systems (batteries specifically) don't like uneven loads placed on the batteries.

Is that true? And if so, what's the best way to pull power from them? A + wire connected to each of the + terminals and spliced together into 1 wire?

wore out · Jul 26, 2023

''A + wire connected to each of the + terminals and spliced together into 1 wire?''

That's going too make a nasty spark and let lots of smoke out of the wiring if actually connected as you are thinking!

Have you tried running the marker control on the RH battery and verified if uneven discharge would actually be a problem?

(ASSUMING the batteries are wired correctly/as they were when the tractor left the factory.)

(Depends upon how much power the marker control actually uses.)

One ''workaround'' ''back in the day'' was to use alligator clips on the control box power wires and switching between batteries every so many hours of use.

Doing that depends upon if the negative power wire is connected to the chassis of the marker control.

If it IS and the box is mounted/grounded to the tractor you CANNOT power it from the LH battery. (Again ASSUMING the tractor is wired ''as original.)

Bob Bancroft · Jul 26, 2023

I had rewired my 4020 with parts from JD. Included were two circuit breakers and a bracket to mount them on the starter. One was
neg. ground and one was pos ground. I pulled 12V from the neg ground one for electronic scales. Never had a problem. I doubt your
load will be a problem.

John T · Jul 26, 2023

The tractor ALREADY uses 12 Volts off either 12 Volt battery for lights etc. Sure in
a perfect world each would be loaded the same but it still works as is and has for
years. One other method is to use a 24 VDC to 12 VDC Converter like some 24 or 48
Volt RV's use, they aren't all that expensive or difficult......... Depending on the
equipment it may be best to use THE BATTERY THAT USES THE FRAME AS GROUND IE the Neg
grounded battery. I doubt your equipment uses that much current in which case its
less a worry, but if it is great I would opt for the 24 to 12 VDC Converter

Im rusty on those new gen tractors, see what Tx Jim or Wore Out have to say they are
more current then I am

John T NOT any New Gen man

cfk · Jul 26, 2023

(quoted from post at 14:13:28 07/26/23)
''A + wire connected to each of the + terminals and spliced together into 1 wire?''

That's going too make a nasty spark and let lots of smoke out of the wiring if actually connected as you are thinking!

[b:88f5326f40]Good to know! That's not what I saw happening in my head, but I won't do that then!
[/b:88f5326f40]
Have you tried running the marker control on the RH battery and verified if uneven discharge would actually be a problem?

[b:88f5326f40]I have not. I'm not sure how to do that? [/b:88f5326f40]

(ASSUMING the batteries are wired correctly/as they were when the tractor left the factory.)

[b:88f5326f40]Left battery (drivers side) negative to starter, positive to negative on right battery (and grounded to the frame), right battery positive to starter. [/b:88f5326f40]

(Depends upon how much power the marker control actually uses.)

One ''workaround'' ''back in the day'' was to use alligator clips on the control box power wires and switching between batteries every so many hours of use.

Doing that depends upon if the negative power wire is connected to the chassis of the marker control.

[b:88f5326f40]Not sure what you mean by that.. You mean if the black wire just terminates on a screw somewhere inside the box? As opposed to what?
[/b:88f5326f40]
If it IS and the box is mounted/grounded to the tractor you CANNOT power it from the LH battery. (Again ASSUMING the tractor is wired ''as original.)

I put my answers in bold in your quote above!

Tx Jim · Jul 26, 2023

I have no experience with a 24V to 12V converter but I think that would be a good solution short of changing tractor over to 12V system. I can guarantee you from experience yrs ago when I installed a new cab on a JD tractor with 24V system that one can't operate a 12V cab fan on one 12V battery of a 24V system due inability of being able to recharge the two 12V batteries with tractor charging system.

It's too bad b&d is probably still out searching for his exotic "Blue Azure white AWOL rooster" or he could give his point of view.

This post was edited by Tx Jim on 07/26/2023 at 12:29 pm.

John T · Jul 26, 2023

PS Heres an entire page of 24 to 12 volt converters should you choose to go that
route for better balance so BOTH not just one battery contributes, you would have to
choose such a unit that satisfies your power requirements. If its small Id probably
just use one of the 12 volt batteries and not worry.

https://www.bing.com/search?
q=24+Volt+to+12+volt+converter&cvid=bf391e5fa2f34ae685361c7429648312&aqs=edge..69i57.
8703j0j4&FORM=ANAB01&PC=EDGEDSE

John T
24 VDC to 12 VDC Converters

cfk · Jul 26, 2023

If it IS and the box is mounted/grounded to the tractor you CANNOT power it from the LH battery. (Again ASSUMING the tractor is wired ''as original.)

The way I have been doing it for years is how I described in my original post.. I have a red wire and a black wire coming out of the box (which is bolted to the fender). The red wire is connected to the + of the left battery, and the black wire is connected to the - of the left battery. The marker box works just fine...

...but I have had battery problems with that tractor, and I'm unsure if that's what's causing it, or if I've just had bad battery luck.

cfk · Jul 26, 2023

(quoted from post at 16:19:10 07/26/23) If its small Id probably
just use one of the 12 volt batteries and not worry.

It seems to me like its small, but I'm not really sure how to test it? All it runs is a little solenoid that switches a valve from side to side.

wore out · Jul 26, 2023

It seems as if your batteries are connected ''as-original'', connect the device to the RH battery and give it a try, matching lead polarity to battery post polarity!

If you have an Ohmmeter or a POWERED test light, check to see if there is continuity between the negative power wire from the box to the case or mounting bracket of the box. (BEFORE connecting power to the box.)

IF so, and it is mounted to the tractor you CANNOT use the LEFT HAND (positive grounded) battery to power it.

This post was edited by wore out on 07/26/2023 at 02:06 pm.

cfk · Jul 26, 2023

(quoted from post at 16:30:50 07/26/23) It seems as if your batteries are connected ''as-original'', connect the device to the RH battery and give it a try, matching lead polarity to battery post polarity!

If you have an Ohmmeter or a POWERED test light, check to see if there is continuity between the negative power wire from the box to the case or mounting bracket of the box. (BEFORE connecting power to the box.)

[b:2d9038e3bb]Touch the end of the black wire with one side of the tester and the outside of the box/bracket with the other? [/b:2d9038e3bb]

IF so, and it is mounted to the tractor you CANNOT use the RH (positive grounded) battery to power it.

[b:2d9038e3bb]The right battery is positive grounded? The left battery is the one with the wire going from the + to the frame? [/b:2d9038e3bb]

If I do the above test and there is continuity and I can't use the RH battery, I'm still ok to use the LH battery?

fdt860 · Jul 26, 2023

(quoted from post at 13:43:19 07/26/23)

(quoted from post at 16:30:50 07/26/23) It seems as if your batteries are connected ''as-original'', connect the device to the RH battery and give it a try, matching lead polarity to battery post polarity!

If you have an Ohmmeter or a POWERED test light, check to see if there is continuity between the negative power wire from the box to the case or mounting bracket of the box. (BEFORE connecting power to the box.)

[b:d88ed752ec]Touch the end of the black wire with one side of the tester and the outside of the box/bracket with the other? [/b:d88ed752ec]

IF so, and it is mounted to the tractor you CANNOT use the RH (positive grounded) battery to power it.

[b:d88ed752ec]The right battery is positive grounded? The left battery is the one with the wire going from the + to the frame? [/b:d88ed752ec]

Click to expand...

If I do the above test and there is continuity and I can't use the RH battery, I'm still ok to use the LH battery?

Your load is very intermittent. It should not be a problem.
The factory socket under the seat is plughed toonly one battery.

Now, if you are thinking like the guy that designed those systems, you will feed the box with three wires, and put the lh battery on the lh marker, and the rh battery on the rh marker. It cannot be more even than that, but is overkill.

Problem with heavy continuous loads on one battery is that one battery will not charge and the other one will boil excessively,shortening its life.

If youwants to be on the safe side,check voltage across each batteries while running the marker.

wore out · Jul 26, 2023

I made a BAD typo which I have corrected.

If your control box has continuity between it's black/ground lead and it's case it MAY be used with the RH battery, but NOT the left!

SORRY for the confusion!!!

Hemmjo · Jul 27, 2023

How many amps do you need for your application? I use these when installing 12VDC accessories into 24VDC heavy equipment. It is not good to use unconventional or non-standard wiring methods on things. A few years down the road, we forget what we did which makes it difficult to trouble shoot issues. ALSO, if someone else has to work on your stuff down the road, it can be a nightmare. I have run into some crazy work-a-rounds for various issues.

John

John T · Jul 27, 2023

This link didnt work below, try again.

24 VDC to 12 VDC Converters

https://www.bing.com/search?
q=24+volt+to+12+volt+converter&cvid=fb9de58dd3984cc8b29709bbc61f60d0&aqs=edge.0.69i59j
69i57.10819j0j4&FORM=ANAB01&PC=EDGEDSE
24 to 12 Converters

John T · Jul 27, 2023

https://www.bing.com/search?q=24+volt+to+12+volt+converter&cvid=fb9de58dd3984cc8b29709bbc61f60d0&aqs=edge.0.69i59j69i57.10819j0j4&FORM=ANAB01&PC=EDGEDSE
24 to 12

cfk · Jul 27, 2023

Your load is very intermittent. It should not be a problem.
The factory socket under the seat is plughed toonly one battery.

Sounds good. Maybe my LH battery crapping out is purely coincidental..

Hemmjo · Jul 27, 2023

Reading over some of these suggestions, I see conflicting views on pulling 12 volts off of one battery in a 24v string. If you that, the battery you are pulling the extra current off of will ALWAYS fail first.

It is not a coincidence. I see things wired that way all the time, and the owners always wonder why they have short battery life.

buickanddeere · Jul 27, 2023

Simplest solution would be to convert the tractor to 12V negative chassis with a high output alternator and a 5kw starter.
DC to DC converters will work fine, however it requires some basic knowledge .
Rooster has not shown up yet and daughter won't tell me what road she left him on.
DC to DC converter on amazon .

DC 24v to DC 12v Step Down 30A 360W Heavy Duty Truck Car Power Supply Adapter Converter Reducer Regulator for Auto Car Truck Vehicle Boat Solar System etc.(DC15-40V Inputs)
Brand EKYLIN
Wattage 360.00
Colour 30A 360W
Item dimensions L x W x H 15 x 12 x 5 Centimetres
Voltage 24 Volts
Input voltage 24 Volts
Item weight 248 Grams
Efficiency 96
Output voltage 12 Volts
Product Dimensions 15L x 12W x 5H Centimetres
Car Auto Truck Trailer Power Adapter. DC 24V to DC 12V Step Down Converter. (15-40V Wide Range Input) Heavy Duty Max Current 30A 360W.
IP67 Waterproof alloy housing makes the converter ideal for use in a wide range of applications including vehicles, security systems, hospital equipment, telecommunications etc
Built-in over-voltage, under-voltage, overload, over-heat and short circuit protection
The length of the line is about 12CM, slim, small volume, easy installation.
High quality and performance. 3 Year Warranty.

buickanddeere · Jul 27, 2023

Good that you are smart and checked .
Too many dull witted Bubba's connect to one battery for 12v from 24V system. Then they are upset and baffled by battery failures and no starts .

How to get 12V power from 24V system?

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