Hi, first post. The sealed battery of my Iseki TU 1401 has started to give off a foul (sulphur) smelling gas under heavy use - using flail mower. The battery is 12V. The voltage readings are as follows; idling - 17.86, revving - 18.74, revving and lights - 18.54. Just wondering if anyone can assist in diagnosing whether the alternator is faulty or if it's the battery? I am fairly new tractor owner. I imported tractor to France from dealer in UK. Any help gratefully received. Thanks, Ray.
Battery emitting sulphur steam / voltage query
- Thread starter dixonr2
- Start date
k0ua
Epic Contributor
Hi Ray, YES The voltage regulator has failed. Whether this voltage regulator is internal to the alternator or is an external unit I don't know on your particular model of tractor. Most modern units have the regulator built in to the alternator but your tractor is older I think.
In any case the alternator is operating full wide open and is "cooking" or "boiling" you battery. Usually the case splits from the excessive heat build up in the battery, and if it doesn't split to allow the steam to escape it will explode. What ever you do, don't take any more voltage measurements while standing next to the battery while the tractor is running as this is dangerous.
If the regulator is external, which it very well may be in this model of tractor, start by replacing it. Good luck and get back with us as to what you find. Oh, yes your battery is "toast", and will need to be replaced also, BUT you must fix this regulator problem first or you will just destroy another battery. Also the "steam" being emitted is corrosive..clean up with baking soda and water.
Last edited:
k0ua
Epic Contributor
Oh, and if we hear a "big bang" from your direction, we will know what happened. 
CobyRupert
Super Member
:thumbsup:
k0ua
Epic Contributor
As for what the voltages should be for a properly operating tractor, They should fall somewhere around 13 to 14 volts. After a start, the charging voltage may be a bit higher, like up to 14.5 and may drop to around 13.5 or so after the battery is topped off. The battery will usually be around 12.6 or so with the engine off. These are relative values, and some regulators my operate slightly differently, but anything with a charging voltage over 15 volts is a "danger Will Robinson" moment. at 17 volts you can expect battery splitting or explosion if run long enough. A huge amount of steam and hydrogen outgassing can be expected. Hydrogen, can go "boom" if exposed to a spark. All in all NOT a good time.
k0ua
Epic Contributor
One other thing, of course a service manual would tell you a lot, but if you cannot find an external regulator, and it originally came equipped with one, then perhaps changing out the entire alternator for an more universal replacement alternator with a built in regulator like all the newer tractors have is an possible path to pursue. But hopefully you can find the voltage regulator for this unit and replace it. After you replace the regulator, and the charging voltage is 14 volts nominally, (wear goggles, and a full face shield) then turn right around and buy a new battery and replace the existing "cooked" battery, then clean up any corrosion and be happy you didn't lose your eyesight.
jenkinsph
Super Star Member
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Protect your hands with rubber gloves and wear old clothes in case any acid gets on anything. Immediately take off the clothes when done working on the battery alternator replacement and wash them separately from any others. Have baking soda and water source at the worksite to use, especially if any acid makes its way to your eyes. You can rinse down all metal on the tractor that might have been exposed to the acid or fallout from fumes Put the old battery in a cardboard box with the bottom lined with a plastic bag and take it to a battery recycling center or auto parts store. Explain to them that it was cooked so they use added precautions with it.
TemporaryKubotaOwnerMark
Veteran Member
Sure sign of massive overcharging.
It's already been diagnosed correctly, but think about this: How did people on the Internet who have never seen your tractor, who may not even be familiar with your model, know right away the answer to your question?
Simple: A 12v battery CANNOT produce 18 volts. That must come from the alternator.
Not trying to grind you, just to help you learn so that you can better diagnose things in the future.
k0ua
Epic Contributor
I hope we didn't frighten the fella from France too much. But he was dealing with a potential bomb, and I didn't want him to take it lightly and get hurt. I have worked around battery plants in my former field of telephony for decades , and I can tell you those things can be quite nasty. Batteries and charging systems are a necessary evil until something better comes along. We don't think much about them until they don't work, and they work 99 percent of the time or more.