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Author Topic: LT40 Kubota 2 Alternators  (Read 1103 times)

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Offline flatrock58

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LT40 Kubota 2 Alternators
« on: July 22, 2021, 03:56:08 PM »
I have been having a few issues with my LT40 and noticed that when both hydraulic pump are engaged and hit their limit it draws down the voltage from 14v (output by the alternator) down to 8-9 v.  Recently  my motor was shutting down when the voltage dropped, which I am assuming that the accuset/or other controllers does not like the low voltage.  After changing batteries and a lead or two the motor is not shutting down, but the voltage measured at the solenoid in the hydraulic box drops down to 8-9 volts still when the hydraulics is maxed out.  

My Kubota motor actually has two alternators.  One is smaller and not used.  I was wondering if anyone had ever hooked up the second alternator.  I would assume it would work and be like a higher output alternator.  Any input would be appreciated.
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Offline terrifictimbersllc

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Re: LT40 Kubota 2 Alternators
« Reply #1 on: July 22, 2021, 05:38:39 PM »
I never used the small alternator on my 42 kubota. It was just there to tension the belt properly. It isnt needed and I dont think it would offer much extra.

You should not see those low voltages with the proper battery if your alternator is working correctly. LT40 super has a 140 amp alternator and a group 31 Deka AGM battery. Im pretty sure together these keep the voltage above 11v at maximum amp draw.

Id  get Woodmizer electrical on the phone and give them your figures and take it from there.




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Re: LT40 Kubota 2 Alternators
« Reply #2 on: July 22, 2021, 07:46:44 PM »
You very possibly do not have good contact between your contactor and power strip.  Shine the strip and be sure that your contactor has plenty of adjustment.  Whatever it is, find it to prevent burning your hydraulic pump motors.
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Offline mike_belben

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Re: LT40 Kubota 2 Alternators
« Reply #3 on: July 22, 2021, 08:04:13 PM »
Whats the resting engine off voltage,  the voltage at idle and the voltage at WOT? 


If it comes up to 13.x or more and has magnetism at the back of the housing from the field flux, its working.  If it sometimes does and sometimes doesnt, id pull the alternator apart.  I will bet the brushes have worn a deep groove in the commutator on the armature shaft..  
Isaiah 48:10

Offline Ben Cut-wright

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Re: LT40 Kubota 2 Alternators
« Reply #4 on: July 23, 2021, 09:03:07 AM »
I read your voltage tests were taken at TWO points, (1)"14v output by the alternator" and  (2)"solenoid in the hydraulic box drops down to 8-9 volts.  It must be determined if the current source is at fault or the load is excessive.  Obviously, the alternator is capable of making proper voltage, but it (the charging system and circuits) may not be *capable of transmitting current while maintaining voltage. 

Using only voltage as a test result and testing only the engine/saw-head side of the circuit should eliminate the contact strip having too much resistance. Too much resistance at the strip should NOT cause "engine shut-off". It would cause loss of voltage to the pumps. 

If the voltage in the entire electrical system drops dramatically when the pumps are in use this could mean (1) excessively high current demand from the pumps, (2) battery and charging isn't sufficient. Current/amperage tests can determine which one is the case.  Voltmeter tests might show which side, source or load, is at fault.

Two parallel charging sources for one battery is possible, but there CAN be problems with doing that.  My thought is that the engineers would have included the small amount of wiring needed if it would have been beneficial.  Circuit and control devices are available to help ensure such a circuit is protected and operates properly, but....these devices are expensive. 

Offline ladylake

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Re: LT40 Kubota 2 Alternators
« Reply #5 on: July 23, 2021, 09:42:40 AM »


 I wouldn't be running the hyd pumps up against the limits very long.  Hugh amp draw and hard on everything.  Steve
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Offline mike_belben

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Re: LT40 Kubota 2 Alternators
« Reply #6 on: July 23, 2021, 09:54:39 AM »
i guess i skimmed the first post too fast, bens post filled in the picture better for me. 


Why is woodmizer installing a dead alternator?  Just for a tensioning idler?  


If the alternator is making 13+ vdc at its output lug while some load on the other end is dragging it down to the 8s theres probably a high corrosive resistence somewhere creating the big voltage drop in the circuit.  

 A temp gun could find it if its in the positive wires.  Or chomping on jumper cables for expedient grounds between alternator case and pump case would prove it out if this machine uses steek chassis grounding instead of wire.

Now if the alternator output lug is dropping to 8 its inside the case and id still bet brushes/commutator. Easily visible when disassembled. 

Isaiah 48:10

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Re: LT40 Kubota 2 Alternators
« Reply #7 on: July 23, 2021, 03:14:08 PM »
After changing batteries and a lead or two the motor is not shutting down, but the voltage measured at the solenoid in the hydraulic box drops down to 8-9 volts still when the hydraulics is maxed out.
I am reading that you have corrected your engine issues and are now only concerned with the low voltage at your hydraulic solenoids. 

If your connection to your power strip is as it should be, the battery voltage and the voltage at the hydraulic pumps should be virtually the same.  If it is not, then look at either the main power solenoid in the metal box or the power strip/contactor.
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Offline flatrock58

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Re: LT40 Kubota 2 Alternators
« Reply #8 on: July 23, 2021, 10:32:02 PM »
Today I went to check voltages on an LT50 that a friend owns.  On his mill the voltage at the alternator, under load, was 12v, where mine was 11v.  At the power strip and battery, his was 10 v and mine is around 9v now.   I am assuming that the battery positive lead that I changed from a clamp on to a crimped lug might have helped bring up my voltage a volt or so.

I am getting the same voltage at the power strip and the battery and at the solenoid in the hydraulic box.  So there is no loss there.     

I have only been running the pump at there limit of 2200 psi for a moment to see the drop in voltage.  Oddly enough when my motor was dropping out I was not maxing out the pump.  I would just drop out randomly when I used any or the hydraulic functions.  

The voltage with the engine running and when not using the hydraulics is always 14v -14.3 volts everywhere.

I plan on changing out the battery ground clamp with a crimped lug to eliminate corrosion and contact issues with the ground.  

I will also use my temperature gun to see if I find any hot spots in the circuit. 

Thanks for all the input.  It sure is nice to have a place to get ideas from knowledgeable people when problems do arise.  I like my older mill with the Kubota engine, but with its age comes some little problems that are not always easy to diagnose.  
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Offline mike_belben

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Re: LT40 Kubota 2 Alternators
« Reply #9 on: July 23, 2021, 11:01:05 PM »
Do these pumps that are drawing all this juice use copper wire for the ground or just steel framework?
Isaiah 48:10

Offline flatrock58

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Re: LT40 Kubota 2 Alternators
« Reply #10 on: July 23, 2021, 11:14:21 PM »
It is a stranded copper wire to ground  
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Offline barbender

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Re: LT40 Kubota 2 Alternators
« Reply #11 on: July 23, 2021, 11:20:15 PM »
The older mills ground the hydraulic pumps through the frame, that's how my '97 is set up.
Too many irons in the fire

Offline Ben Cut-wright

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Re: LT40 Kubota 2 Alternators
« Reply #12 on: July 24, 2021, 12:29:46 AM »
(1) On his mill the voltage at the alternator, under load, was 12v, where mine was 11v.  At the power strip and battery, his was 10 v and mine is around 9v now.   I am assuming that the battery positive lead that I changed from a clamp on to a crimped lug might have helped bring up my voltage a volt or so.

(2) I am getting the same voltage at the power strip and the battery and at the solenoid in the hydraulic box.  So there is no loss there.    

(3) I have only been running the pump at there limit of 2200 psi for a moment to see the drop in voltage.  Oddly enough when my motor was dropping out I was not maxing out the pump.  I would just drop out randomly when I used any or the hydraulic functions.  

(4) The voltage with the engine running and when not using the hydraulics is always 14v -14.3 volts everywhere.

(5) I plan on changing out the battery ground clamp with a crimped lug to eliminate corrosion and contact issues with the ground.  

(6)I will also use my temperature gun to see if I find any hot spots in the circuit.

Thanks for all the input.  It sure is nice to have a place to get ideas from knowledgeable people when problems do arise.  I like my older mill with the Kubota engine, but with its age comes some little problems that are not always easy to diagnose.  
(1) Are the comparison voltages at engine idle?  Those voltages are marginal to unacceptable.  They indicate the alternator has contributed ALL it can at that RPM, or load, and that the battery is now being taxed.  The "one volt" difference between the two mills is more significant than it might appear.
(2) That agrees with your initial posting info.
(3) Hydraulic motor starting amperage most likely was even higher than max load amperage.
(4) That voltage indicates the alternator regulator is operating properly. A full load amperage test would prove the alternator sound.
(5) Cleaning all grounds and eliminating corrosion is good maintenance. 
(6) A "voltage DROP test" will find poor connections instantly, no need to load a circuit until heat builds up, cheap and fast test.   

Offline maple flats

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Re: LT40 Kubota 2 Alternators
« Reply #13 on: July 24, 2021, 07:02:12 AM »
I'll hazard a guess as to why Kubota has 2 alternators. Could be Woodmizer buys a std engine just because they can get it for less than if the engine was custom designed. Woodmizer wants a bigger alternator so they add one without also redesigning the belt tension set up.
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Offline flatrock58

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Re: LT40 Kubota 2 Alternators
« Reply #14 on: July 24, 2021, 09:31:51 PM »
Ben Cut-Wright.  All these measurements were made with the engine idling since it is usually in that state when I have had the problem.  I guess I could check it with the blade engaged to see if there is any noticeable difference.

You are probably right about the starting amps too since a lot of times I would have the motor shut down while the hydraulics were not at the max but when I simply started them.  

When you say a voltage drop test are you talking about testing each line with a voltmeter to see the drop in that line?
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Offline flatrock58

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Re: LT40 Kubota 2 Alternators
« Reply #15 on: July 24, 2021, 09:35:59 PM »
maple flats.  You  re correct on having two alternators.  They left the original alternator on so they would not have to modify the pulley arrangement on the Kubota engine.  They added another 140 amp alternator at the other end to handle the hydraulics and such.  
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Offline Ben Cut-wright

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Re: LT40 Kubota 2 Alternators
« Reply #16 on: July 25, 2021, 12:35:16 AM »
Ben Cut-Wright.  All these measurements were made with the engine idling since it is usually in that state when I have had the problem.  I guess I could check it with the blade engaged to see if there is any noticeable difference.

You are probably right about the starting amps too since a lot of times I would have the motor shut down while the hydraulics were not at the max but when I simply started them.  

When you say a voltage drop test are you talking about testing each line with a voltmeter to see the drop in that line?
I only asked about to confirm that the engine was at idle.  The battery would very quickly become depleted if those voltages were at engine working RPMs. Can't hurt to test at full RPM to confirm the alternator's ability to handle the load and keep the battery charged properly.

WoodMizer advises that the engine be running to operate ANY heavy electrical loads.

"voltage drop" tests are a unique test procedure which can be used to find connections and wiring having from slight to very poor ability to conduct current. Using direct meter measurements across the entire circuit or any single connection simplifies the method.  Volt drop testing essentially requires the negative (-) lead to contact the most negative *side of the connection and the positive (+) test lead to contact the most positive *side.   Energize the circuit in order to place a load on the circuit. Read volt drop directly off the test instrument.  Good connections will have very low voltage drop. The alternator or battery voltage variance does not correlate to volt drop.

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Re: LT40 Kubota 2 Alternators
« Reply #17 on: July 25, 2021, 07:59:34 AM »
Just a note for those reading that may not know, my engine idle speed is 1500 rpm which keeps the alternator at full output at all times.


 
I have a digital voltmeter wired directly to the battery which reads a minimum of 12.7 with the engine off and ~14.4 with the engine running, whether at idle or cutting speed.
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Offline Ben Cut-wright

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Re: LT40 Kubota 2 Alternators
« Reply #18 on: July 25, 2021, 08:30:47 AM »

There can be NO specific voltage measurement for ALL operating conditions or situations.  Rather, expect a range of acceptable voltages and amperage readings dependent on many factors.

Alternators or generators, the types being discussed here,  operating at "full output at all times" will quickly destroy themselves.  It is safe to assume charging *voltage should be in a range at or near max when loads/amp draw is low. The hydraulic pumps demand MORE *amperage than the alternator can provide at IDLE.  When this occurs the battery supplies a portion of amperage to make up for the shortage.  During this period of circuit load/increased amperage demand the *voltage WILL drop. This is normal and does not condemn the alternator, nor does it prove it sound. 

Offline flatrock58

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Re: LT40 Kubota 2 Alternators
« Reply #19 on: July 25, 2021, 08:39:44 AM »
 

 Magicman  I did copy you and added a voltmeter a while back.  I recently added a temp gauge, after the temperature sensor went bad and the idiot light came on.
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