D17 Battery Polarity has Reversed

chappie

Member
I bought an Allis D17 several months ago and it ran well. In fact I drove it over 30 miles to get it home, and had no problems. Right after getting it home, I rewired the headlights because they were disconnected because the wires were shorted. Besides disconnecting the battery while working on the lights, and testing the lights afterwards without starting the tractor, I did nothing to the electrical system. However, I got busy with other projects and the tractor sat for well over a month. I left the hood off, so the engine got rained on. When I tried to start it, the battery seemed a little low, and the distributor was wet, so it would not start.

I got my battery charger and when I connected it (PROPERLY), according to the + and - markings on the battery, I had a massive amount of sparks. Thats when I got my VOM meter and discovered that the battery is REVERSE CHARGED. The terminal marked + is negative and vice versa.

The battery is 12V and is supposed to be POS ground. It still has a Generator and voltage regulator.

I've already decided to get rid of that generator and replace it with a GM alternator with built in regulator, which I know will mean buying a new battery. I'll also convert it to a NEG ground at that time. (which I know means reversing the wires on the coil and the ammeter). I know all too well that generators are a pain in the butt and the sooner it's gone, the better. I dont even want to attempt to try to fix the generator problem and likely ruin another battery on the process.

However, it's the middle of winter and too cold to make brackets for the alternator, working out in the cold. Spring will come soon enough to do this work. However, I really need to move the tractor and if at all possible, be able to use it a few times this winter to clear snow from my roadway.

My question is whether it's safe to connect my battery charger backwards (as the battery *IS* now polarized), and is it safe to start the tractor without doing any damage. If this does more harm to the battery, I dont really care, because I will be replacing it. (As long as it dont explode).

One other thing. Does anyone know of a place that sells aftermarket ready-made mounting brackets for a D17, to convert them to an alternator? (Or can someone furnish details plans with measurements, so I can have my local welding shop make one). I do NOT need a complete "KIT". I have the alternator from an old 78 Chevy truck, and have wire and a diode. I just need the mountng brackets.

Thanks for all help!
 
Using the headlights (or a spare headlight), fully discharge the battery, then charge it with the correct polarity (don't let it freeze), connect the cables properly, polarize the generator, then start the engine.
 
You say you don't want to fix the generator problem. But I don't see where you describe a generator problem? Did it charge on the long drive home? Generators don't care which polarity they run. I don't have any problem with generators. It's the voltage regulators that are sometimes a pain.

You can discharge and charge the battery as Bob describes. I suppose if you can't get the tractor to charge for now, you can keep it charged with a battery charger. I would make sure that cut out side of the regulator is normally open, as your polarity issues may have compromised it.
 
If you are ditching the genny, I'd like to have it. I prefer to keep my stuff original and have an alt on my D17. Didn't think it was possible to flip the polarity of a battery.
AaronSEIA
 
Just because it is a gen. doesn't mean it is pos. ground,GM had neg ground with gens. for years,and a battery doesn't know which way
the current is flowing,just like a gen.I think you have another issue in the wiring.
 
Yes changing a battery can happen if you have one that is completely dead and then hook it up back wards and charge it back wards you can reverse one. But when that happens most of the time they will not hold up well after that has happened.
 
I could be wrong but I don't think a lead-acid battery can reverse its polarity. The lead plates and sulphuric acid electrolyte at full charge sets up the polarity. At discharge the plates become lead sulphate and the electrolyte solution is toward water. Charging reverses the reaction but can't change the polarity. Also coils are made for + or - ground. The difference is in the internal connection. They will work the other way but will have a weaker spark.
I'm probably opening myself up to some scathing criticism with these statements but I'm trying to help.
 
If a batty is dead and a person hook it to a battery charger backwards it can in fact be changed up backwards .BTDT. Once that happens the life and CCA of it will not be the same but yes they can be changed up backwards and work that way all be it not near as strong as it would be if charged up correctly
 
Bob and old, below, both indicate a battery can be discharged enough that it is possible to charge it backwards. I will add a third vote to that. In all the years I worked in a shop I saw it once. I recall the boss running a battery dead with a headlamp, so he could hook up the charger correctly. I don't know it worked out.
 
OK, I stand corrected. I did work on a Cub for someone once. She had some work done on it but it didn't run. It was an older one, 6v, and the battery was installed with the negative to ground. Changed it, polarized the gen and it ran fine.
 
Yes you can charge a totally dead battery backwards and reverse it's polarity. I saw it happen once on a John deere.
 
LOL!

As to reverse-charged batteries, I don't know the chemistry of it, or if "science" permits it, but I have encountered several in my 58 years on this earth and seeing/observing/testing with a meter is believing.

As to "Kettering" ignition coils, it is most desirable/efficient to have the spark occur as a negative-going pulse at the sparkplug.

Reversing the primary connections at the coil will allow a particular coil to do just that, with either battery ground polarity.

Ever tried (got shocked by) the "lead pencil method"?
Treatise explaing
 
Once a battery is completely dead it can be charged either way, I would just charge it the way it is and use it. If you run it
completely dead and reverse it you will shorten the life. Once you are sure which way the polarity is I would put a piece of red tape
on the battery indicating the current polarity, not the way it was made. When this battery is shot then you can buy a new one and do
what ever you want.
 
To mount an alt on a d17- cut a piece of 1 in. rod to fit between the mounting ears on bottom of alt. Drill length ways for mounting bolt 3/8. Cut left front motor mount flanges to allow 1 in rod fit 1/2in. down between flanges . Put gen. pulley on alt. to clear power steering belt. Set alt in place - line up fan belt& weld mounting rod to motor mount. You may have to make belt tightener or slot longer & bend hood to clear pulley.
 
I dont have a wiring diagram here but i think I think on mine you have to use the original resister? or diode? to stop engine when you turn the key off. It is mounted under the gas tank on mine.
 
(quoted from post at 10:08:10 01/08/16) Once a battery is completely dead it can be charged either way, I would just charge it the way it is and use it. If you run it
completely dead and reverse it you will shorten the life. Once you are sure which way the polarity is I would put a piece of red tape
on the battery indicating the current polarity, not the way it was made. When this battery is shot then you can buy a new one and do
what ever you want.

I plan to wait till warmer weather to replace the generator. I'd like to just get it running for now. Aside from just charging the battery as it now is (reversed), I have left the battery disconnected for weeks, because I was worried about this problem doing some damage. That means I need to polarize the generator. Several of you said this, and my search on the web for "generators" showed the same. But I'm left more confused than before as to HOW to Polarize it. There seems to be a mixmatch of information as to which terminals to put the jumper, and worse yet there appears to be several variations and regulator styles. Some say to jump from BATT to GEN terminals, other say BATT to ARM, yet others say BATT to FIELD. ((((WHICH ONE)))) ????

I'll assume all the D17s have the same parts, thus use the same polarizing methods. What do I REALLY need to do? (A diagram would be real helpful).

Once Spring comes, I'll be real pleased to be rid of this generator system. Seems they are nothing but trouble. (Which is why they stopped using them years ago). I bought this tractor to USE, not as a show piece. Although I'd still like to keep it original, fighting with a troublesome generator is not something I want to cope with. Especially since I like to disconnect the battery whenever a tractor is not going to be used for more than a few days, so I'd have to repeatedly have to polarize it, everytime I use it. NO THANKS for that hassle!

THANKS to everyone who replied to this.
 
(reply to post at 19:47:34 01/08/16)

Most of this sounds pretty simple, but having to modify that motor mount sounds like a huge problem. What's going to keep the motor in place? Isn't there a way to just raise the alternator a little by welding up something to raise the old bracket, or just making an entirely new one? Even if the fan belt needs to be changed to one a tad bit longer or shorter, I'd much rather change the belt.
 

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