720 Diesel 24v Battery Hookup Problems! Help!!!

[jdeere630]

I'm having some problems getting my 720D ES batteries hooked up correctly. It started when I pulled the old batteries from the tractor to charge them after being stored for a while. I wrote down a diagram of all the connections and double checked the manual to make sure the connections were correct. One battery was damaged so I replaced that one with a new one. Now this is a 4 6v system, just like the original. When I reinstalled the batteries, and tried to connect them, I got a small spark from the negavtive lead on the battery where I connected it. The last cable I connected was the main negative cable running to the starter. The spark seemed to be nothing major. When I tried to turn on the switch, the lights were very dim. Now I only looked at one light, I didn't see the other one (probably should have though). I checked the batteries and found that they hadn't been charged as much as I originally thought. I removed them and recharged them. When I went to put them back in, I got a major spark when I connected the last terminal, which this time was the negative connection on the third battery to the positive connection on the fourth. This was the cable the manual recommended removing when doing electrical work on the tractor. All other connections were already connected. I also heard a small spark near the front of the tractor. I'm afraid I fried something on the generator or the voltage regulator. Does somebody have any advise on how to go about diagnosing the problem? I'm at a loss. All the connections seem correct and there was no problem with the rest of the wiring on the tractor before because last time I used it, everything worked fine. The main switch was off when I connected the batteries. I did have to replace the small ground wire running from the positive terminal on the third or fourth battery (depending which counts as the first). Is the ground not making good contact? It seemed to be ok prior. Evidently there is a short or drain somewhere, because this was no small spark. It took a small chunk out of the terminal on the battery when it occured. I'm afraid I've done some major electrical damage. Hopefully, somebody can give me some bright hope that I can fix this easily. I'd appreciate any input on this. If you need more information, just ask. Thanks

 

[Bob]

Here's ONE way to do it. I'm NOT sure the physical arrangement of the batteries is exactly "as-original", but the ELECTRICAL connections ARE correct, schematically.

<img src = "http://aycu24.webshots.com/image/50143/2005180376843204941_rs.jpg">

OBVIOUSLY, the jumper to chassis ground can be connected to either the (+) post end or the (-) post end of the heavy jumper at the center of the four battery series hookup.

(P.S.... the GENERATOR should be polarized BEFORE engine startup!)

 

[khyron]

There shouldn"t be a ground wire from the positive terminal to ground, unless it is a positive ground system. I don"t believe this tractor is. I would disconnect the battery from the electrical system, taking a terminal off should do it. Then measure continuity from the positive terminal to ground, it should be an open. Then do the same for the negative side. If the negative side shows anything over 50 ohms then you will need to clean up the connection. It looks like something was left on when you hooked it up, maybe the lights or the ignition switch? Does it have an electrical fuel pump, it could have caused the spark when the ignition was on. A tiny spark is normal when hooking up a battery, but not a huge on to take a chunk out. You might have blown a fuse when that happened.

 

[jdeere630]

Does anyone think there was any damage done to any component in the electrical system when the sparking occured. It sounded to me like there was. Is there a way to test both the generator and voltage regulator to make sure they are functioning properly without hooking the batteries up. I"m not that familiar with these 24v electrical systems on these 2 cylinders. I know there is no fuse between any of these connections, so I"m sure that was not the cause of the secondary spark noise. Can I just run continuity tests on some of these components? I"m really hesitant to do any thing with these connections till I fully understand what was the cause of the problem and how to avoid it happening again. In reference to one of the posts, does the fuse in line with the positive ground (and yes this is a positive ground system) cable make a great difference? right now there is no fuse there and my current connections match the diagram minus the fuse. I can install a fuse before I reconnect everything if it will help the matter. Also, where is the best place to attach the fuse and the ground. Right now the small ground wire is attached to the side of the battery box, which is where the ground was attached when I took the batteries out in the first place. I will mention that the battery I replaced was replaced because the top terminal ( I can"t remember if it was positive or negative) was seriously burned and melted. Was the original connections elsewhere on the tractor are wrong and that is what is causing the problem now? That might explain the burnt terminal. I still don"t know where to begin here. I hate diagnosing electrical issues. I"ve worked on a couple other two cylinders with 12 volt positive ground, they weren"t too bad. But this 24v system is for the birds. Also, I don"t know much about this tractor because I just purchased it last year, and only had it out for about two months before I shedded it. I got it because I had a 720 diesel pony start that I want to sell because I don"t really care for the pony motor. I"ve had too many starting issues with it. I thought that the electric start would be much simpler and less issues. I guess I was wrong. I appreciate the comments so far. Any additional would be great.

 

[Bob]

khyron,

Your statements: "There shouldn"t be a ground wire from the positive terminal to ground, unless it is a positive ground system." and: "Does it have an electrical fuel pump, it could have caused the spark when the ignition was on." are DEAD giveaways you have NO idea how the "split 24-Volt system on this tractor works!

 

[Bob]

The only thing likely to be damaged is the voltage regulator, if it's "CUTOUT" contact points are stuck closed.

With the 2 main battery cables disconnected, take the cover off of the voltage regulator, and see if it's pair of LARGE, HEAVY contact points are welded together.

Once you verify the points ARE NOT stuck, or unstick then, OR replace the regulator, it needs to be polarized. Sorry, as for as polarizing, I can wire one of these tractors blindfolded, but I CANNOT comfortably tell you over the 'net how to polarize the generator. With this 24-Volt system, you get ONE chance to do it right, or LOTS of smoke gets "let out" of the electrical system!

 

[jdeere630]

thanks Bob,

I'll check out the VR and see what kind of shape its in. The spark though sounded like it came from the generator but I can't be sure. I don't think the current would go that far though without first impacting something else. The VR makes sense. If nothing else, I can retrace all the wiring and make sure everything is correct, although it would seem to me that it should be because the tractor ran for two months with no problem. I'm not sure I particulary care for these 720 ES dashes missing the ammeter. I kinda like to watch that to see how the generator is operating and check to make sure the current is flowing ok.

 

[Bob]

A stuck "cutout" in the regulator WILL cause the generator to spark/try to "motor".

 

[Anonymous-0]

Dear 630,
For a quick, flippant answer I can't resist saying you should have stayed with 630s.

Do you have a voltmeter? if so hook across the plus and negative terminals and you should read 24 volts. This will verify that you have the correct series connection for the four six volt batteries. The cable from the negative post goes to the solenoid. Does it? The cable from the positive terminal goes to the side of the starter. With the positive cable unhooked from the battery connect a test light between the battery post and the unhooked cable. It should not light. If it does you have an unwanted short to ground. If the light does light unhook the negative terminal and if the light goes out I would suspect a stuck shut cutout relay in the voltage regulator.

With the test light still hooked up and the negative terminal unhooked, disconnect the little ground wire and the light should go out. If it does I would suspect a short from the positive cable source to the frame of the tractor which is isolated in the 24 volt system. The likely culprit is starter brush dust allowing current flow from the positive terminal of the starter through the dust to the tractor frame. Grounded fields in the starter would cause the same situation. Another suspect is the rubber grommets at the voltage regulator being worn. Remember the regulator like the starter and generator are isolated from the frame. Grounded fields or dust from the brushes in the generator would cause the same symptoms as would a bare wire touching the frame.

 

[buickanddeere]

Having mismatched batteries of various makes, sizes, capacity and age. Can lead to some mysterious problems. Two group 31 12 volters are better.
It does sound as previously stated that the voltage regulator cutout maybe stuck. That would draw 30-50 amps however. A major spark.
It could be very dirty and crusty generator and starter brush/commutatiors as well.
Do you have a 0-10amp DC ammeter handy ?

 

[jdeere630]

To give everyone an update on the current situation. I have diagnosed and resolved the problem, thank goodness!!!! What ended up being the problem was the starter solenoid was slightly binding and when I had tried to start it with low batteries, the solenoid stuck ever so sightly in the engaged position. So there was a constant load being pulled on the batteries when they were connected. After taking a look at the solenoid, it was pitted on the inside contacts for the battery and motor connector posts, plus there was a seriously rusted wire connection on the inside. It looks like some water had gotten inside the cover. Going back to the story now (before I pulled the solenoid), After I had noticed the stuck solenoid, I pryed it out, connected the batteries (with no sparking!!) and fired the engine. It started right up. I let it ran for a few moments and shut it off. However, when I went to start it again, the solenoid stuck as soon as I let go of the starter button, and instantly drained the batteries. All it took was a matter of two seconds. After prying it out, I tried it one more time, but the batteries didn"t have enough juice to start it. You could hear the acid in the batteries hissing when the solenoid stuck. It takes a lot of power to turn that starter over, and thats for a split second. With the solenoid stuck, It was a constant connection and that was drawing an amazing amount of juice. Anyways, it was at this point that I pulled the solenoid and took a look at it. It is in pretty bad shape. If anyone knows of a good source for one, please let me know. I"ll check on the net and see what I can find. Thank you to all those who posted comments. They were helpful. Fortunately, the voltage regulator was not damaged at all except for some slight pitting on the BAT post. Don"t know if that was caused by this mess or happened prior from polarizing it or something. It checked out ok and still functions fine. Now I have to deal with a oil blow by issue I"m having with it under heavy load. I hope I don"t have to do a ring job on it. I"ve had enough issues with it lately. But thats a post for another time, another day. The case seems to be closed on this one. thanks again.