Kubota tractor worklight circuit

Thread Starter

Willjame

Joined Mar 27, 2019
4
Hello all. I'm having a problem with the work lights on my Kubota tractor. I have two 15 watt LED lights wired to the existing "worklight" leads from the tractors circuit. In addition, I have two 15 watt LED lights, and a 360 watt LED light bar wired from a 24 volt converter which is wired to the battery via a toggle switch to prevent the converter from draining the battery. The 15 watt lights are wired to a switch on the dash, and I have them facing rearward for reverse lighting. The light bar is mounted on the ROPS facing the front, and is wired to a separate switch on the dash beside the switch for the rear lights. However, when I use the lights for more than a few minutes, the battery is drained to the point where it will not start the tractor. I have checked the battery with a voltmeter at 12.78 volts. Then I started the engine and got a reading of 14.2 volts, so I know the alternator is working. However, as soon as I turn on the lights, the voltage drops sharply. Could the regulator within the alternator not be working? I would greatly appreciate any advice or suggestions to help solve this problem. Thanks in advance.
 

Ylli

Joined Nov 13, 2015
1,058
360 watt light bar + two 15W LEDs fed through a 12 volt to 24 volt converter... That will draw 35 - 40 amps. Not surprised the voltage dips. Is your alternator big enough to supply this 40 amps plus whatever else the tractor needs?
 

drc_567

Joined Dec 29, 2008
1,156
... How old is the battery? Sometimes individual battery cells will deteriorate after a few years. The nominal battery voltage will still be measured, but the actual charge that is stored by the battery will be diminished. A load test should confirm that the battery is weak even with the measured no-load voltage that you see. Maybe an auto parts store could test the battery.
 

jpanhalt

Joined Jan 18, 2008
11,088
You don't say which model Kubota or its alternator. Alternators on small tractors of 25 A or so are not uncommon. It is likely you are well over that with your lights on.
 

Thread Starter

Willjame

Joined Mar 27, 2019
4
You don't say which model Kubota or its alternator. Alternators on small tractors of 25 A or so are not uncommon. It is likely you are well over that with your lights on.
My tractor is a MX5000DT. The part number for the alternator is T1060- 15680. I also forgot that I changed the forward facing pair from 15W up to 48W. However, the light bar is actually 324 watts not 360.The total current used by the work lights is 22.75 A if my math is correct. Using A=W/V for the forward facing 48 watt lights it's A= 96/12 or 8 A. For the light bar and rear facing 15 watt lights it's A=354/24 or 14.75 A. This was my reason for running these through the 24 volt converter, so as to reduce the current needed. The converter has a max output of 360 watts and 15 A. I know that I am pushing the limits of the converter, and probably the alternator too. I could always switch the 48 watt lights back to 15 watt on the 12 volt circuit to reduce the total current. Any ideas?
 

Ya’akov

Joined Jan 27, 2019
5,994
If you really need that much light the right thing to do would be to upgrade the alternator and add a second battery for lighting.
 

mvas

Joined Jun 19, 2017
539
My tractor is a MX5000DT. The part number for the alternator is T1060- 15680. I also forgot that I changed the forward facing pair from 15W up to 48W. However, the light bar is actually 324 watts not 360.The total current used by the work lights is 22.75 A if my math is correct. Using A=W/V for the forward facing 48 watt lights it's A= 96/12 or 8 A. For the light bar and rear facing 15 watt lights it's A=354/24 or 14.75 A. This was my reason for running these through the 24 volt converter, so as to reduce the current needed . The converter has a max output of 360 watts and 15 A. I know that I am pushing the limits of the converter, and probably the alternator too. I could always switch the 48 watt lights back to 15 watt on the 12 volt circuit to reduce the total current. Any ideas?
354 Watts is 354 Watts, whether you use 24 Volts or 12 Volts.
Yes, you have 14.75 amps flowing between the 24 volt converter and the LED's but
you still have more than 29.5 amps ( maybe 32 amps ! ) flowing between the battery and the 24 volt converter.

I doubt the 12-to-24 Volt converter is more efficient than just using heavier gauge wire.
 

Ylli

Joined Nov 13, 2015
1,058
This was my reason for running these through the 24 volt converter, so as to reduce the current needed. The converter has a max output of 360 watts and 15 A.
The converter does not magically reduce power. If it is outputting 15 amps at 24 volts and you are driving it with 12 volts, the input current to the converter is 30-35 amps.
 

jpanhalt

Joined Jan 18, 2008
11,088
Just adding together your amps, I get 37A+ losses in the converter. That is a 40A alternator. Despite the better performance of alternators compared to generators, that output ability does vary with rpm. I could not find its rating at 1000 or 2400 rpm.

I suspect you are simply pulling more current than your system can supply.

A few years ago, I went though a similar exercise with my Case DX45 (45 HP CUT). I wanted to attach a snow plow to the FEL and use the electric hydraulic pump to provide angling. It was/is a Meyers plow. A few calculations of the current drain for that pump, which is fine for small trucks, showed it was way too much for my tractor. I was able to sell the pump alone for more than I paid for the entire plow. The plow is now sitting on front of a small skid steer, and we are both happy with the result. The geometry of the FEL is great for what it does, not so great for plowing.
 

Thread Starter

Willjame

Joined Mar 27, 2019
4
Just adding together your amps, I get 37A+ losses in the converter. That is a 40A alternator. Despite the better performance of alternators compared to generators, that output ability does vary with rpm. I could not find its rating at 1000 or 2400 rpm.

I suspect you are simply pulling more current than your system can supply.

A few years ago, I went though a similar exercise with my Case DX45 (45 HP CUT). I wanted to attach a snow plow to the FEL and use the electric hydraulic pump to provide angling. It was/is a Meyers plow. A few calculations of the current drain for that pump, which is fine for small trucks, showed it was way too much for my tractor. I was able to sell the pump alone for more than I paid for the entire plow. The plow is now sitting on front of a small skid steer, and we are both happy with the result. The geometry of the FEL is great for what it does, not so great for plowing.
 

Thread Starter

Willjame

Joined Mar 27, 2019
4
Thanks to everyone for the input. Obviously electrical circuits are not my strong point. I am a good mechanic, and a fair fabricator, so I think I'd better stick to what I know. I am going to remove the 24 V converter, and use larger gauge wire to reduce resistance. If that doesn't work, I'll just go with less powerful lights. I can get by with half of what I'm using now and still have decent visibility. Gotta admit though it's great to have that 324 watt LED light bar. It just about turns night into day! Anyway, thanks again for everyone's comments.
 

Ya’akov

Joined Jan 27, 2019
5,994
Thanks to everyone for the input. Obviously electrical circuits are not my strong point. I am a good mechanic, and a fair fabricator, so I think I'd better stick to what I know. I am going to remove the 24 V converter, and use larger gauge wire to reduce resistance. If that doesn't work, I'll just go with less powerful lights. I can get by with half of what I'm using now and still have decent visibility. Gotta admit though it's great to have that 324 watt LED light bar. It just about turns night into day! Anyway, thanks again for everyone's comments.
You could upgrade the alternator and add an accessory battery for the lighting. That would work. Increasing the wire size will not help.
 

mvas

Joined Jun 19, 2017
539
When the TS removes the 12v-to-24v converter, and then changes the 324W Load down to a 12 volt system,
the 14.75 amps @ 24 volt load, will increase to a 29.5 amp @ 12 volts Load
The appropriate AWG Gauge Wire must now be installed for a 30 amp load.
And that will most likely require larger / thicker wire than existing.

If the battery voltage is above ~12.8 volts when all LED's are ON and
the engine is running ( slightly above idle ) then you should be OK.
Always turn the LED's OFF, before turning the engine off.
You need some LED "Off Time" to recharge your battery.
 
Last edited:

Ya’akov

Joined Jan 27, 2019
5,994
When the TS removes the 12v-to-24v converter, and then changes the 324W Load down to a 12 volt system,
the 14.75 amps @ 24 volt load, will increase to a 29.5 amp @ 12 volts Load
The appropriate AWG Gauge Wire must now be installed for a 30 amp load.
And that will most likely be a larger wire than existing,
Yes, if he reduces the voltage he will have more current to deal with, but it will not solve the problem of exceeding the ability of the alternator to handle the load.

So, it's not a solution to the problem.
 

mvas

Joined Jun 19, 2017
539
I said, "The TS needs bigger wire because the LED's will pull about 30 amps @ 12 volts" - did you not read that?
And yes it is part of the solution to his problem, because he is removing the 12v-to-24v converter - did you not read that?
And by removing the 12v-to-24v converter - that will make the LED's more efficient ( ie use less amps from the battery )

I asked the TS to next, check the Voltage of the battery with the engine running above idle.
If the voltage is above 12.8 Volts then his problem is solved.

The TS has never stated what the Voltage was with the engine running, above idle.
That may be all he needs to do, after the re-wiring
He has a 40 amp alternator.
 
Last edited:

jpanhalt

Joined Jan 18, 2008
11,088
He is pushing that alternator to its max, depending on the rpm, despite the fact that diesels don't need a power source for ignition. I think his decision to use less blinding lights will work fine. With dark-adapted eyes, it takes a lot less light to work outdoors . A full moon is almost sufficient.
 

Ya’akov

Joined Jan 27, 2019
5,994
I said, "The TS needs bigger wire because the LED's will pull about 30 amps @ 12 volts" - did you not read that?
And yes it is part of the solution to his problem, because he is removing the 12v-to-24v converter - did you not read that?
And by removing the 12v-to-24v converter - that will make the LED's more efficient ( ie use less amps from the battery )

I asked the TS to next, check the Voltage of the battery with the engine running above idle.
If the voltage is above 12.8 Volts then his problem is solved.

The TS has never stated what the Voltage was with the engine running, above idle.
That may be all he needs to do, after the re-wiring

He has a 40 amp alternator.
He said: "I am going to remove the 24 V converter, and use larger gauge wire to reduce resistance. If that doesn't work, I'll just go with less powerful lights."

I am saying it will not work, and he should either upgrade the electrical system or reduce the load.
 

mvas

Joined Jun 19, 2017
539
And therefore my suggested solution still remains ...
1) Remove the 24-to-12 converter
2) Install fatter wires <<<
3) Measure the voltage at the battery with LED ON, with engine above idle

You wrote, "... increasing the wire size will not help ...".
Increasing the wire size is required for the 324 Watt of LEDs.
 

Ya’akov

Joined Jan 27, 2019
5,994
And therefore my suggested solution still remains ...
1) Remove the 24-to-12 converter
2) Install fatter wires <<<
3) Measure the voltage at the battery with LED ON, with engine above idle

You wrote, "... increasing the wire size will not help ...".
Increasing the wire size is required for the 324 Watt of LEDs.
We’ve miscommunicated, sorry. I won’t make it worse. What you said is not wrong.
 
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