Voltage reading

Mickey_Fx · Aug 28, 2005

( If Yanmar has a weakness it is their "current limiter". )

What is the tech purpose of this devise?

All a LA battery needs is a well regulated source voltage to control charge rate and not permit overcharging.

evofxdwg · Aug 28, 2005

Check the battery electrolyte level after each few hours use. If you have to add water freqently, it is charging too fast. If not, i wouldnt worry about 14.8.

Probably just better to get a new current limiter if yours is overcharging.

You could run with the lights on all the time. That will probably drop it a little (measure it and see). Or you could put a silicon rectifier (diode) in series with the '+' wire from current limiter to the battery to drop the output about 0.7 volts. You need to figure out the max charging current of your system to size the diode. For my 1610D, a 5 amp diode would work.

However there is a down side. at low RPM, the dynamo (alternator) voltage goes down drastically, and it already has to overcome the rectifier drop inside the "current limiter"- so it may not be charging the batttery at idle after you add an external diode. You didnt say what RPM you measured 14.8V.

Also, finding a reliable place to mount a diode may be a problem, it may have to be heat-sinked to some metal. But if it is a metal body diode, it will have to be electrically insulated.

normde2001 · Aug 29, 2005

"In Yanmar's case the VR also contains the bridge rectifiers for the conversion from AC to DC and circuitry to control the battery idiot light."

It depends on the model. Some Yanmars, (YM240, YM2000, for instance), have the rectifier in the alternator.

reb · Aug 29, 2005

( ( If Yanmar has a weakness it is their "current limiter". )

What is the tech purpose of this devise?

All a LA battery needs is a well regulated source voltage to control charge rate and not permit overcharging.
)

Not really. The term "voltage regulator", especially for the simple charging circuit of some of these tractors, is a misnomer. What the circuit does is pump current into the battery. The voltage is determined by the state of charge of the battery and the voltage drop of the internal impedance of the battery due to that charging current. In more sophisticated "voltage regulators" the charging current is controlled by a circuit which monitors the battery voltage. In the simplest circuits, as my 1500, the current limiter keeps the charging current down to a reasonable amount, preventing overload of the alternator and low enough to avoid damaging the battery when it is charged.

A simplified explanation of the simple Yanmar current limiter "voltage regulator:"
The alternator produces an AC voltage which is converted to DC with rectifiers to, let's assume, 20 volts. That voltage is connected to the battery through the current limiter. I don't know the resistance of that current limiter, but let's assume it is about 5 ohms. When the battery is low, maybe 8 volts, right after starting the engine, the alternator supplies 25 - 10 volts divided by 5 ohms, or 3 amps to charge the battery. As the battery charges, the voltage rises, and the charging current decreases. When the battery is at full charge, say 14v, the alternator is still pumping 25 - 14 volts divided by 5 ohms, or 2.2 amps, a value that can be applied continuously without damage to the battery. These numbers are mostly SWAGs, but the idea is to explain the principle.

Soundguy · Aug 29, 2005

I've seen lots of GM alternators kick in the 14.4 - 14.7 output region.

If it were me.. I'd check the ground at the battery, and frame.. and also that the alternator has a good ground. ( yes.. I've seen heavilly painted brackets mess with an alternator...

Also check the condition of the charge wire from the output stud to wherever it hooks up.. ( hot side of solenoid.. battery hot post.. etc... )

On tractor generator to alternator conversions.. i like to run a ground wire with a star washer to the hinge bracket onthe alternator to ensure no ground loops.. etc.

I'd like to add.. that on a system that has otherwise been 'fine'.. sometimes a tired/ageing battery will start to show a higher charge voltage as the cell/cells degrade.. new battery usually takes care of it..

Soundguy

Mickey_Fx · Aug 29, 2005

( ( ( If Yanmar has a weakness it is their "current limiter". )

What is the tech purpose of this devise?

All a LA battery needs is a well regulated source voltage to control charge rate and not permit overcharging.
)

Not really. ... )

Yes, really. What the preferred method of charging LA batteries is and what equipment manufacturers do though may be different.

Looking at the electrical schematic in the manual I have (Murray Publishing) it doesn't show a current limiter for the F series tractors. The connections for the VR are: ground, alt (2), battery, charge indicator lamp, power from fuse panel.

Giving the schematic some thought with only 2 wires for the alt, it must have a permenent magnet field. Being such, controlling the output voltage is more difficult than with a conventional alt. Maybe this is why there is a current limiter on some models. Anyone have any knowledge on what the current capacity is for the alts on the F series models?

Still a lot to learn about my tractor and how Yanmar as implemented various needs. From some other posts I read in TBN, it looks like how Yanmar has implemented the electrical charge system is a weak point.

Someone else asked at what engine speed I measured the voltage I reported. I tried at various speeds between 1000-1500, both with lights on and off. Voltage held fairly consistent.

blackd · Aug 29, 2005

"Anyone have any knowledge on what the current capacity is for the alts on the F series models?"

I believe that my FX24 alt puts our @ 30 V in the 1500-2000RPM range. I have burned out the original and a replaement VR. Right now it has NO VR. I just put the battery charger on it @every 2-3 weeks.

Don

bruce1966us · Aug 29, 2005

We had a discussion about 3-4 years ago if some of the regulators actually regulated anything. We concluded that some of the reguators simply charged low voltage all the time. We even used a kohler regulator in place of the YM and it worked fine. I know it only charged at 1.5 amps. Just food for thought. Soundguy, do you remember this far back? Maybe on the old Yahoo site?

reb · Aug 29, 2005

Peace, Mickey_Fx

It is obvious I did not spend my career as a diplomat. Instead, I spent it designing and analyzing electronic circuits. Based on my experience and training, it is impractical to charge a battery by paralleling it with a power supply without current limit. Any practical voltage regulator that charges a battery must have some sort of tracking circuit to maintain its voltage somewhere above the varying battery voltage and use some sort of current limiting device. Perhaps the internal resistance of the battery could serve that purpose. At any rate, the Yanmar schematics I have seen for these circuits are not that sophisticated. The simpler ones apparently merely limit the current as I described. An earlier thread evofxdwg posted the schematic for his (I think) YM1602. It was more complex. He intended to design and build another. That was about the first of this year. Haven't heard any more about it.

Soundguy · Aug 30, 2005

( I know it only charged at 1.5 amps. Just food for thought. Soundguy, do you remember this far back? Maybe on the old Yahoo site? )

I do remember.. and yes.. it might have been back on yahoo.

in any case.. I wasn't overly thrilled by the super lo-tech stone knives and bear skin implementation o fthe yanmar charge system.. however.. though.. it worked.

On my unit.. I popped in a hitachi alternator and old style v-reg from a chrysler.. and it works fine.

Soundguy