Dead Short in Battery, Again

kb9trc · Sep 5, 2014

My 1720 failed to start 2 wks ago, ended up being a dead short in the battery. The new battery started three times before it failed also, took it back and guess what? Another dead short! could something on the tractor cause this or just bad luck? I'm kinda afraid to put the latest replacement in.

Thanks

mfreund · Sep 5, 2014

Make sure the alternator is charging and battery is secure in the tray.

murphy1244 · Sep 5, 2014

mfreund said:
Make sure the alternator is charging and battery is secure in the tray.

And not over charging. Should not charge over 14.5 volts and after starting volts should go down to 12.5 to 13ish

kb9trc · Sep 5, 2014

murphy1244 said:
And not over charging. Should not charge over 14.5 volts and after starting volts should go down to 12.5 to 13ish

Thanks, does a charge of over 14.5 indicate a faulty alternator or is there a voltage regulator causing it? Or if there is a voltage regulator is it built into the alternator?

mfreund · Sep 5, 2014

Take the new battery and put it on a battery charger and make sure it is fully charged before you put it in the tractor, then check the voltage.

SPYDERLK · Sep 5, 2014

What do you mean by dead short? Usually early failure is caused by a break in a conductor between cells inside the batt. Symptoms are you can measure a voltage if theres no drain on the batt, but when a load is applied v drops to zero. If this has happened twice go to a different battery mfg.
larry

kb9trc · Sep 5, 2014

The first battery had been in the tractor since I bought it 2 yrs ago. It wouldn't start, checked all connections, new grnd cable, etc. still nothing but showed 12 volts, took it to auto parts store and they put it under a load and said it had a "dead short". Bought a new one (battery, not tractor) ran it twice and same thing, (different) auto parts store said dead short. Figured I'd better get a handle on things. But I'll about have to get another batttery before I can check anything.

I called 2 New Holland dealers one said to "check volts at starter with new battery, probably a bad starter." the other wanted to sell me an alternator.

k0ua · Sep 5, 2014

SPYDERLK said:
What do you mean by dead short? Usually early failure is caused by a break in a conductor between cells inside the batt. Symptoms are you can measure a voltage if theres no drain on the batt, but when a load is applied v drops to zero. If this has happened twice go to a different battery mfg.
larry

Like you I have never seen a "dead shorted" battery either..Here is why. Batteries, when fully charged contain a heck of a lot of energy.. If you dead short that battery, that energy has to go somewhere.. It goes into generating heat, and a whole lot of it.. If you don't believe me, take a good large solid wrench and drop it across your battery terminals and run like "heck", as something really really bad is going to happen. I have no idea what happened to these two batteries, and the gentlemen that tested them for you doesn't either.

k0ua · Sep 5, 2014

The first thing to do, is take your new charged battery and hook up the positive terminal and measure on your 10 amp current scale between the negative terminal and the negative battery post. See if the tractor is drawing any current with everything turned off. If it drawing more and a milliamp or 2, find the problem and repair it. If no appreciable current draw, hook up the battery, start the tractor and immediately measure the charging voltage, it should be no more than 14.5. Measure it at idle and at high rpm. Turn on the lights, what does it measure? is the voltage slowly dropping or is it staying above 13?.. Turn off the tractor, the battery will slowly drop over time to around 12.6, but there should not be much current draw with everything off. Your tractor I don't believe has any onboard computers or electronics. If you see large current draws with everything off. look for bad diodes in the alternator (diode trio), or other fault to ground. If the charging voltage at high RPM is not at least 13.5, look for either bad regulator (often inside the alternator on modern machines) or external regulator, or grounding/cable issues.