DIYbanter - View Single Post - 12V Battery charging problem

philo

On 12/23/2015 3:06 AM, wrote:
On Tue, 22 Dec 2015 18:41:24 -0800, mike wrote:

On 12/22/2015 6:08 PM, wrote:
I have a farm tractor with a positive ground. I hooked a 15A battery
charger to it, and had massive sparks shooting all over the place. Yes,
I did connect the polarity correctly, with the red clip on the batt +
post and black one in the batt - post.

Because of this, I removed one of the battery cables (to the
tractor)[the negative one], and reconnected the charger. The sparks were
so intense, they melted a small hole at the top of the battery post.

In all the years I have charged auto batteries, I have never had this
happen. Even touching the clips together on the charger dont cause such
intense sparks. What the heck could cause this?
My first thought is a shorted battery, but the tractor lights work fine.
There just is not enough charge to turn the starter over fast enough to
start the engine. I would think that if the battery was 'dead shorted'
it would not operate the lights, or make the starter turn slowly.

To insure the charger is not defective, I connected it to another
battery and it's charging properly, on both the 2A and the 15A settings.

Anyone have any clue what's happening. I sure dont!!

Did you actually measure the battery voltage??
If you have a GENERATOR instead of an ALTERNATOR, it's possible for
the thing to get polarized backwards and charge your battery backwards.

Yes, I think you're right. I took my VOM meter and hooked it up, the
battery *IS* backwards. The terminal marked + is now NEGATIVE, and the
one marked - is now POSITIVE. I triple checked the meter leads, and the
battery markings. It definitely is backwards, and reads about 11.5
volts.

Yes, it DOES have a generator.

I knew there was some sort of polarity issues with generators.
I did NOT know a battery could reverse polarity. In fact I cant see how
that could occur without destroying the battery, burning up wiring, or
damaging something else.

I suppose this could have occurred when I had the battery disconnected
for awhile, while I was replacing all the bad wiring to the lights.

This tractor might have an alternator by the time I finish this repair.
I only had one vehicle (my first car) with a generator, and I remember
having a big hassle with the generator system in that car, and finally
having to get a mechanic to fix it. Of course back then, I did not know
much about auto repair. But this is bringing back some bad memories
about those damn generators. Almost all old farm tractors have had their
generators replaced with alternators, but not this one. I think it's
time! It's easy to wire an alternator in place of the generator, but not
so easy to mount the alternator to fit the space and get the fan belt to
work properly.

I've worked with lead acid batteries for 38 years and have never heard
of one getting reversed polarity.

I do know that in one connects a battery to a generator however, it will
simply re-polarize and work.

I'm wondering if the battery is somehow mislabeled?