6-volt Bat Installed Wrong

[Farm130]

What damage can be done by running a 6-volt positive ground tractor as a negative ground. It is a 1957 130. A neighbor thought he would be helpful by fixing my in-laws tractor and thought he found the problem that the battery was installed backwards so he reversed the terminals and connected it as a neg ground then jump started it with his 12 volt car. After he got it running he mowed a field and put it away. When I finally made it over there a few days later the battery is completely dead. So what damage could have been done? All 6 volt systems ARE pos. ground, correct??

 

[John T]

If you start her but the Genny was polarized at opposite from the battery, it can harm a Voltage Regulator. Thats whay its good to re polarize the genny prior to start up if in doubt cuz she can still charge at EITHER polarity provided the genny was correctly polarized. Id polarize the genny n re start her n see what happens. If it has an ammeter and battery polarity was changed but the ammeter leads werent reversed, it would read bass ackwards so be aware of that.

John T

 

[Bob M]

As John T suggests running the tractor with the battery in backward MAY have harmed the voltage regulator.

Way to tell is install a charged battery (with the correct terminal grounded of course!), then polarize the generator and finally fire up the tractor and see what happens. If the battery charges you should be all set.

Of greater concern however is the battery. If it was being "charged" the wrong polarity during that mowing run it may well have been irreparably damaged. Best thing to to is put it on a slow charger for 24 hours, then try it to see if will start the tractor.

But even then I would not trust it. Battery's simply do not tolarate reverse charging very well...

 

[John T]

Bob, Ive also heard of putting a small load like a light etc on the questionable battery for a long time to COMPLETELY DISCHARGE IT deader n a door nail and thennnnnnn hook her up to a charger for a longggggggg slowwwwwwww charge n see if she ever recovers. You think a complete discharge prior to a recharge attempt may help or no difference???????

John T

 

[Farm130]

John, would you so happen to have a wiring diagram for a 130?

 

[John T]

NO I only have a few for JD but most of that wiring can be figured out fairly easy. Bob or Jim or myslef can probably walk you through it if needed.

John T

 

[Bob M]

Hey John - I've too heard the recommendation to completely discharge a reverse-charged battery before attempting to recharge. However I think this is for the benefit of the charger rather than the battery.

My reasoning: The current flow in a battey-charger circuit is a function in the difference between charger and battery terminal voltages, and of the internal resistance of the charger/battery combination. (Ohm's Law...) Now consider this:

----

With a normal battery and charger arrangement this difference will be about 2 volts or so. Example: Charger at 14.5 volts and battery at 12.5 volts:

14.5 - 12.5 = 2.0 volts difference

----

However with a reverse-charged battery the voltage difference could theoretically be as much as this:

14.5 - (-12.6) = 27.1 volts difference

----

Means that compared to connecting to a normal battery, the first connnection to a reverse charged battery it might flow over 13 TIMES the charger's normal charging current (27.1 / 2.0 = 13.6)

Good chance of letting the smoke outta the charger internals in that situation(!)

Makes sense to me anyway...

Bob

 

[Janicholson]

Some really good chargers will detect the wrong polarity and never attempt a charge. But most will see an opportunity to self destruct. I do not know that his battery was ever charged by the tractor. (I doubt it) it probably just went dead as it was used that day and can be charged easily. JimN

 

[Hugh MacKay]

Bob, John and Jim: I read your reasoning with some interest. When I bought my 140, and the tractor probably had less than 500 hours since new. It had been stored in a heated warehouse roughly 15 years and the owners had several different mechanics work on it, however never got it going in 15 years. We started it and kept it running long enough to load it on trailer with a 12 volt battery and jump cables. At that time it was 6 volt positive ground with battery in backwards.

When I got it home we discovered battery, generator, regulator and amp meter were all toast. I have no idea what these so called mechanics might have done during those years. I bought a 12 volt battery and alternator, wired as per your disgarms, except I use a push button to excite alternator, in place of light or diodes. 12 volt coil no external resistor needed. I had to replace the ampmeter in order to make it run.

I guess my question is how could someone destroy all those items?

 

[Janicholson]

My quick response would be that they got it started and then tried to polarize (incorectly with the bat in backwards and it running) the result might have been the cutout latching in and the resulting 15 or so volts heating and roasting the whole thing. JimN

 

[Denny ('60 Lo-Boy)]

No harm, no foul. Charge the battery. If it won't charge, it wasn't any good anyway. Put in a charged battery, hook it up with positive ground, polarize the generator then start it.