Generator? Dynamo? Not Charging B7800 Battery

[charlessenf]

Boosted the battery and jump started the tractor ran it for an hour or so dragging large logs from the bottom to higher ground where I turn them into firewood.

Put the tractor away and went out today to start it and it would not start.

Before I run out and buy a battery, I'd like to know how to test the charging system on the B7800 tractor.

I don't know what I am looking for or where whatever it is might be mounted (well somewhere near the fan belt ... perhaps). I've read something about dynamo instead of Alternator or Generator back when.

Anyone know how to check if a B7800 Kubota tractor is (trying) charging the battery?

 

[Ed ke6bnl]

No sure of all the wiring BUT the first thing to do is to check battery voltage with engine running. Need to see somewhere around 13.4volts. Then i would head over to fuse box and a/c volts off the dynamo. Maybe 40 volt with engine on fast idle. I am ooen for corrections

 

[JWR]

First, get your battery tested. Many auto parts stores do it and for free. Of course clean the cable ends and connections (both ends) retighten cable bolts, etc. You will NOT find 40 volts anywhere on the tractor (unless maybe internal to the alternator diode bridge doing the conversion from AC to DC which is probably not accessible and is of no interest to you anyway in the context of this discussion.). The battery standing alone with no load and no alternator doing charging should read right at 12v. Charging voltage should be around 13.8v at the battery terminals (whether from the alternator while running or from a battery charger.) Forget the charging system until you see if the battery is good and will hold a charge.

 

[charlessenf]

I found a wiring diagram and it refers to a dynamo' not an alternator.
A member volunteered:
"The B7800 comes standard with the dynamo with a 13-14 amp output.
"An alternator kit is/was available for about $200.
"I believe the dynamo produces AC voltage.
"Trouble shooting procedures should exist in TBN somewhere."
number two Veteran Member
Northern Lower Michigan
Tractor Kubota B3030HSDC Kubota L2501HST

All I know for sure is that his last sentence is spot on!

 

[number two]

The dynamo has two leads of the same color.
Voltmeter on AC current,test leads on each wire.
Doesn't matter which as you are measuring AC current.
Voltage increases with RPM.
To 30-40 volts???
Dynamo very reliable-only really hear of bearing failure on rather older models.
Good Luck!

 

[CalG]

I just replaced the dynamo with an alternator on my B2601.

At low idle, the dynamo did not put out enough juice to detect a charge voltage to the battery. that is, DC volts at the battery were at the 12.5 volts typical of a good charged wet cell battery.

At high idle, the measured value got up to just over 13 Volts.

With the alternator, the voltage at the battery is 13.5 at low idle.

I didn't investigate further.

I have the take off dynamo and it's rectifier/ regulator in a box.
It's the same unit as fitted to my B7200, so might come in handy "someday".

Dynamos , as fitted to these Kubota tractors, are PERMANENT MAGNET, devices (AC generators).
Not electrically excited,Three phase alternators we might be more familiar with.

Certainly 14 amps will keep a wet cell charged, but ..

More is better at low revs, depending on operational envelope.

 

[charlessenf]

The dynamo has two leads of the same color.
Voltmeter on AC current,test leads on each wire.
Doesn't matter which as you are measuring AC current.
Voltage increases with RPM.
To 30-40 volts???
Dynamo very reliable-only really hear of bearing failure on rather older models.
Good Luck!

B7800HSD (SUPPLEMENT), WSM WIRING DIAGRAM

The generator Dynamo is directly connected to the IC REGULATOR I have not been able to find the location of this part on the other parts diagrams found so far. Nor can I find a KUBOTA Test Procedure for the Dynamo. I find the idea that a generator Dynamo to support a 12VDC electrical system is putting out forty volts.
If, as you suggest, I should measure the amperage at the dynamo generator - how many amps should I find?

 

[CalG]

The rectifier/regulator module is in the dash.

 

[5030]

Many decades ago I owned a smaller Kubota with a dynamo. In reality, if my amperage requirements weren't that great (my Kubota's have 50 amp and 70 amp alternators on them respectively, I prefer the dynamo. Nothing to wear out, no rectifier bridge to fail and no brushes to fail either, Problem is, the output is too limited for my uses.

 

[CalG]

B7800HSD (SUPPLEMENT), WSM WIRING DIAGRAM
View attachment 1057435
The generator Dynamo is directly connected to the IC REGULATOR I have not been able to find the location of this part on the other parts diagrams found so far. Nor can I find a KUBOTA Test Procedure for the Dynamo. I find the idea that a generator Dynamo to support a 12VDC electrical system is putting out forty volts.
If, as you suggest, I should measure the amperage at the dynamo generator - how many amps should I find?

The maximum continuous output amperage is limited by wire size and heat.
The minimum output is limited by resistance.

A "test" procedure for a bare dynamo would need to specify the load in Ohms, and to account for the magnetic field strength .

Are those Orsteads? or a Gausse, or a Tesla? Hmmmm

Magnets are so confusing.....

 

[CH4Ohio]

There are a couple other threads on here where we discuss B7800 / B2910 dynamo and voltage regulator problems. If your battery isn't charging, it's most likely the voltage regulator. There is a test procedure in the workshop manual.

My voltage regulator went up in smoke. Literally. You have to remove the dash display panel and it's mounted behind that. It's a large obvious aluminum looking module with heat-sink fins on the sides and a modular plug for wiring connection.

I bought a knock-off regulator off Amazon for about $30. It looked absolutely identical. It got hot and died within a couple weeks. I replaced it with a Kubota part and it's been working for a few years now.

As CalG mentioned above, you could replace your dynamo with an alternator. This eliminates the voltage regulator. Wish I'd been aware of this option cause I would have done this. There's a specific kit / part number to convert it.

 

[charlessenf]

Thank you. I replaced the battery last night and ran it today. I show an increase in voltage (measured across the battery posts) with a concomitant increase in RPM (before replacing the battery) so I am hoping the charging circuit is still functional. Time will tell, right?

I would be interested in the alternator swap - at least to see what it would cost relative to replacing the Dynamo & IC Regulator.

I am interested in accessing the area under the black cowling as I found nesting material tucked up in there on the one side and would like to be able to access the area such that finding an removing any 'infestation habitation' could be thoroughly accomplished as well as inspecting the fuel sending unit and wiring generally to see if any of it has been served to whatever brought the nesting material into the cowling area.

I looked and can find no OBVIOUS starting point for removing the gauge(s) panel or the entire cowling. Since you've been in there at least twice, I thought to ask you where I might start.

Thanks again for the feedback. If you come across any links to those discussions or the alternator swap out, IC Regulator replacement etc. please let me know, I'm all eyes!

Charles

PS HFT moving blankets seem to be a favorite rodent nesting material. Should be a way to treat them to dissuade Minnie or Mickey, just haven't heard of it yet.

 

[CH4Ohio]

Thank you. I replaced the battery last night and ran it today. I show an increase in voltage (measured across the battery posts) with a concomitant increase in RPM (before replacing the battery) so I am hoping the charging circuit is still functional. Time will tell, right?

I would be interested in the alternator swap - at least to see what it would cost relative to replacing the Dynamo & IC Regulator.

I am interested in accessing the area under the black cowling as I found nesting material tucked up in there on the one side and would like to be able to access the area such that finding an removing any 'infestation habitation' could be thoroughly accomplished as well as inspecting the fuel sending unit and wiring generally to see if any of it has been served to whatever brought the nesting material into the cowling area.

I looked and can find no OBVIOUS starting point for removing the gauge(s) panel or the entire cowling. Since you've been in there at least twice, I thought to ask you where I might start.

Thanks again for the feedback. If you come across any links to those discussions or the alternator swap out, IC Regulator replacement etc. please let me know, I'm all eyes!

Charles

PS HFT moving blankets seem to be a favorite rodent nesting material. Should be a way to treat them to dissuade Minnie or Mickey, just haven't heard of it yet.

I believe the B7800 is the same as the B2910 as relates to this repair . . . On mine, there are two slots at the top of the dash panel. Very obvious. A straight screwdriver fits perfect and a little twist pops the tabs out so you can wiggle the dash display panel out.

There's also a semi-large bolt with Phillips head right in the center of the plastic housing above the dash panel -- just behind the fuel cap. Removing that bolt lets that entire plastic cowling move -- though you have to wiggle around levers and stuff depending on what you're trying to do.

 

[CH4Ohio]

Search the forums for "B7800 Alternator". I just did it and came up with a page full of threads. Likely the info is in there. Other keywords that might be worth searching are B2910, dynamo, charging, regulator, etc.

As I recall, my BATTERY light was on continuously when the voltage regulator failed. If your battery light is not on, it's likely that yours is still good. If you're seeing more voltage when it's running than the voltage across the battery when it's NOT running, then the dynamo is charging and the IC Regulator is working. Kinda sounds like you just had a weak / dead battery.

No reason to upgrade to the alternator solution if you don't have a failure of a major part.

 

[CH4Ohio]

Thank you. I replaced the battery last night and ran it today. I show an increase in voltage (measured across the battery posts) with a concomitant increase in RPM (before replacing the battery) so I am hoping the charging circuit is still functional. Time will tell, right?

I would be interested in the alternator swap - at least to see what it would cost relative to replacing the Dynamo & IC Regulator.

I am interested in accessing the area under the black cowling as I found nesting material tucked up in there on the one side and would like to be able to access the area such that finding an removing any 'infestation habitation' could be thoroughly accomplished as well as inspecting the fuel sending unit and wiring generally to see if any of it has been served to whatever brought the nesting material into the cowling area.

I looked and can find no OBVIOUS starting point for removing the gauge(s) panel or the entire cowling. Since you've been in there at least twice, I thought to ask you where I might start.

Thanks again for the feedback. If you come across any links to those discussions or the alternator swap out, IC Regulator replacement etc. please let me know, I'm all eyes!

Charles

PS HFT moving blankets seem to be a favorite rodent nesting material. Should be a way to treat them to dissuade Minnie or Mickey, just haven't heard of it yet.

Alternator upgrade for my B7800

I have a 2008 B7800 that I just recently purchased. I have read on internet reviews that the B7800 has a headlight problem that they are next to useless unless you get a Alternator upgrade kit. My first question is, Is this condition for all of the year models of the B7800? If so I have heard...

www.tractorbynet.com

Check out that thread. There's a "tractorpoint" link that has great pics showing you how the dash / display panel comes out. It's actually the instructions for installing the alternator upgrade.

Just to add my two cents, I didn't remove my steering wheel. The wiring harness is pretty short, but you can get the modular plug disconnected and then manipulate the dash panel to get it out. (However, my B2910 does have a tilt wheel, but I still think you'll be able to get access behind the dash panel without pulling the steering wheel off.)

 

[charlessenf]

Alternator upgrade for my B7800

I have a 2008 B7800 that I just recently purchased. I have read on internet reviews that the B7800 has a headlight problem that they are next to useless unless you get a Alternator upgrade kit. My first question is, Is this condition for all of the year models of the B7800? If so I have heard...

www.tractorbynet.com

There's a "tractorpoint" link that has great pics showing you how the dash / display panel comes out. It's actually the instructions for installing the alternator upgrade.

You're correct - Great Pics! Saved me time popping that panel apart looking for a fuel gauge sending unit! D/l doc for another day - Old Boy Scout

 

[charlessenf]

OK, Dynamo works, battery was BAD. New Battery, problem solved thank you all.

 

[CalG]

Batteries are by far my biggest headache for all my "stuff" and all these new portable hand tools are not helping!

Brakes on vehicles, on the other hand are the most work intensive. Ahhh. Rust never sleeps!