Kubota B2400 charging issues

[Gravelier]

This is a 1998 4x4, 24 hp diesel tractor. The factory generator had an output supposedly of 9 amps. That’s only about 100 watts. Some years ago I replaced the generator with one about double capacity. The problem previously was that the battery would not charge unless the engine was at least 1500 rpm. Full throttle is 2600. The larger generator works exactly the same. Must be a characteristic of the permanent magnet generators. So, even if the tractor is sitting idle, I have to run the engine fast or chances are it won’t start without a jump. So, I carry a HF battery pack jump starter with me. There’s plenty of life in the battery. With the jump starter, it’s one click and it’s running. Present battery is 10 months old, with a 3 year warranty. This situation hasn’t changed over a lot of years. I am original owner.

So, my question is to all the great minds out there. Would a small engine alternator keep the battery topped off running at much lower rpm’s. It would take building a bracket to hold the alternator and some voltage regulator circuitry. It would need to work at idle on the tractor which is about 600 rpm. I’m thinking I might be doing a lot of work and have the same problem.

Any constructive thoughts would be appreciated

 

[ILENGINE]

With the engine running, and while using a volt meter with the red lead on the + and the black lead on the - what is the voltage at the battery.

 

[Gravelier]

With the engine running, and while using a volt meter with the red lead on the + and the black lead on the - what is the voltage at the battery.

See, that’s the whole point of this conversation. At idle rpm, it’s battery voltage depending on whether I have run the engine fast. So without fast rpm’s, voltage is 12.3 to 12.5. About 1300 rpm the voltage will begin to climb. About 1500 rpm, 12.7 to 12.8. At 2600 rpm, about 13.9 to 14. Again depending on how long running at what rpm and how long since using the starter, dictates charge back into battery and battery voltage. There is a car size battery in the tractor and the total wattage from the generator is less than 180 watts.

 

[ILENGINE]

When you first posted I was assuming Alternator which would be more stable voltage/current. But if you are running an actual generator, those voltages are very typical output.

 

[Gravelier]

When you first posted I was assuming Alternator which would be more stable voltage/current. But if you are running an actual generator, those voltages are very typical output.

So, back to my original question. Would low rpm (idle speed, 600 rpm) give me better voltage with an alternator or would I still have the same problem.

 

[ILENGINE]

600 rpm may put you in the 12.5 volt output but I would think something closer to 13.2 would be more realistic.