Actual tractor question - 24v jump start

PeterE · Dec 10, 2008

Sorry to break up the politics...

What is the best way to jump-start a 24v system that has two 12v batteries? It's a JD 730, if that matters.

My booster has 24v ability. Can I set it to that and hook up to the opposite posts on the two batteries (the ones that are connected to the starter)?

plow hand · Dec 10, 2008

Thanks for breaking it up L.O.L.-Pete when I jump heavy equip. at work 24v. I go starter to starter Hot on the starter and ground to the frame if I don`t have 24v to jump with I still go to the starter let the 12v system charge a little and then try it.

buickanddeere · Dec 10, 2008

The 730 uses a split 12/24 system. Connecting a booster cable to chassis is going to blow sparks.
If one battery is running down. It could be a slow drain due to carbon dust inside the starter.

Chris in SK · Dec 10, 2008

Yes, hook your red to the second battery's positive post, (going to the starter), and the black to the first battery's negative post (to the frame).
For safety you're really supposed to connect your black to the frame, but if your in a ventilated area you should be fine on the posts.
Chris

ken in texas · Dec 10, 2008

Some of the 24 volt systems can get complicated.Be sure you understand the hookup so you don't damage your charger or tractor.If both batteries are grounded ,it is a 12 volt system.If cables are connected pos to neg it is 24 volt system.Best to charge each battery seperately.Be careful.

buickanddeere · Dec 10, 2008

Quote" For safety you're really supposed to connect your black to the frame" Unquote.
I wouldn't on a factory stock 730 Deere 24V system.
The starter electrical circuit path is not through the chassis/frame in any way shape or form. That why two not one large cables are connected to the starter motor.

buickanddeere · Dec 10, 2008

Both 12V batteries are connected to chassis and the starter see's 24V.

Mike M · Dec 10, 2008

As you have 12V + grd. on one side and 12V - grd. on the other. Isn't that is how the generator charges the batteries back up through the starter cables to a chassis ground in the middle ?

PeterE · Dec 10, 2008

I only have one cable to the tractor.

Battery #1 has positive ground, negative connected to positive of #2. Then negative of #2 goes to the tractor.

That's the way it was when I bought it.

John T · Dec 10, 2008

Peter, Originally the bond to frame ground was ONLY at the mid tie point where one batterys - and the other batterys + were joined together. A big battery cable came from BOTH of the batterys other outer untied posts (- on one + on other) having two big cables to the starter. The starter and generator were 2 wire 24 volt FLOATING independant from frame ground...

If yours just has one cable to the starter and only one of the outer batterys post tied to frame ground, its NOT standard although it may have been jury rigged to work which it obviously must have been.

If you want to jump 24 volts, you jump it at the correct polarity of course to the outermost untied batetry ends which has two twelves in series (Im assuming it does???) totaling 24 volts..

John T

buickanddeere · Dec 10, 2008

A bit late to tell us now that the tractor has been tinkered with.
Does the tractor have a 12V or 24V starter? What voltage do the lights and fuel gauge operate at?

PeterE · Dec 10, 2008

Until now, I didn't know it had been modified. This is the way I bought it. Must be a 24v starter because it needs those batteries in series to crank it, and putting a 12v charger on one of them does nothing to help.

Lights don't work. And now I think I might know why!

buickanddeere · Dec 10, 2008

What's on it for a charging system?
I found a 12V generator on a 24V tractor one time. Some tinkerer was trying to pawn off a half baked starting engine to electric conversion.
It's possible the starter is 12V and 24V is what's required to crank 188 cu"" on each compression stroke. You have to think starter, cables and battery like you are starting a 500HP six cylinder diesel.
A two cylinder diesel needs a MT42 or MT50 delco starter when used with 12V in cold weather. Those starters won't fit the factory mounts however.

Anonymous-0 · Dec 10, 2008

Dear Mike,
The middle wire between the batteries is only used for lighting, gauges,and a remote light if used.
the generator, voltage regulator, and starter are all isolated from the frame and are charging and starting at 24 volts Starting and charging would work fine without the little wire between the batteries and frame.

John B. · Dec 10, 2008

As you described it you have 24volts to your starter. Is there a series parrallel solenoid in the circuit any where? This allows 24 volt starting and 12 volt charging. Be careful with any wrenches around a 24 volt system it will melt a 1/2 or 9/16 wrench with in seconds. I know! I seen it happen.

Sounds like you tractor has been changed for some reason. I think someone may have replaced the batteries at one time and really didn't know how to hook them up!

Anonymous-0 · Dec 10, 2008

No solenoid. A 24 volt system with the center grounded. Uses 24 volts for starting and charging, put has a pair of 12 volt grounded circuits for lights and accessories. JD did that for two, four and 6 cylinder diesels at least through 1968.

Its probably not been butchured though many don't understand it. Its not a lot different from the 120/240 volt DC electric systems that Edison used except the battery supplies the center tap, not the generator.

Gerald J.

Anonymous-0 · Dec 14, 2008

read your book

Actual tractor question - 24v jump start

PeterE

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