Charging problem

[Keoke]

Greg, on the Zenner ratings in watts. Divide the watts by circuit voltage to get amps. Eg., 50 watts/15 volts = 3.3 amps. Assuming your alt puts out 5 to 8 amps then two of the 50 watt guys are fine. Put three if you want insurance.
The ballast resistor is found on all GM cars with point type ignition systems. And you are correct in that they are made of ni-chrome wire set in a ceramic block. These are high wattage units. When at room temp they are about 1.5 ohms but when heated by current flow the resistance rises quickly. This is why they are called "ballast" instead of just regular resistors.
If you want to reduce current flow through zenner put another resistor in series (RT=3 ohms) with first one. If you want to increase current flow put another resistor in parallel (RT=.75 ohms) to the first one.

cheers,

 

[Keoke]

Keith, I agree with what your saying about the value of going around an OEM unit. Also, an automotive replacement VR is not likely replacement for I know of no auto alternators with a PM field. Every auto reg I have seen modulates field winding current.
The Zenner clipping circuit I drew is based only on a low amp (5) PM alternator.
Anymore amperage then that and the Zenner should now be used only to cycle the base on a high amp transistor and the excess wattage dumped through the Q's emitter/collector, high amp resistor and then on to gnd. Even this modified circuit has it's power handling limits.
On the OEM voltage regulator, other then triggering a charge light circuit, why in the world would a voltage reg have two modes for starting? Do you know??
On real heavy amp alternators the voltage regulator will turn off alt field current while cranking engine to take the alternators load off the starter motor. But, Greg's unit has a constant PM field.
Also, I think the open circuit (no battery in tractor) protection is unique feature. Good insurance for a tractor with PM alternator.

cheers,

 

[htiek126]

My comments about the circuit diagram are wrong if the VR includes an additional rectifier circuit. That would explain why Greg's VR does not have an additional wire for the voltage feedback from the battery.

When the battery is removed from the circuit, the VR does not have a good voltage feedback, therefore, the VR will lose regulation and the tractor accessories will receive the unregulated voltage from the alternator/rectifier circuit (which may or may not cause damage and safety issues, we would need to take some measurements).

I do not have my service manual with me, but this what I can remember. The VR has a starting mode for the zero rpm case in which the alternator is not producing (perhaps this is to reduce the load on the starter/battery). And then the VR goes into a slow rpm mode in which the alternator is hardley producing (I think the current is directed through some load in the VR, but not to the battery). Once the alternator is turning, it seems like the VR is always trying to keep the alternator output to pass through some sort of a load.

I have not had the opportunity or need to look at auto VR systems.

Keith

 

[normde2001]

This is getting awfully boring......It's supposed to be a tractor Forum, not rocket science.

 

[Soundguy]

"Putting 78xx and 79xx VRs in parallel is a bad idea. I am fairly certain that they will suffer from secondary breakdown without proper current balancing circuitry, however, it will work because of they are thermally protected. They will probably turn on and off like Xmas tree lights, and they will take turns running very hot. "

I realize they don't parallel well, but they are thermall protected.. and we are talking about a chargine system on a 20 something year old tractor.... And a limited capacity charging system at that.
In the beginning, I recomended a series pass regulator, but was unsure if a non-electrically oriented person would want to build a circuit with more than a couple parts from a schematic.

As for the relay.. I wouldn't even considder it... But if he wanted to spend some money.. a pulse width modulator and some irfz40's or cheaper irf511 mosfets will do a bang up job.. make some nice emi noise probably too.

"The wires in the 1110D schematic are not correctly connected to the full bridge rectifier. The Y wire should connect from the VR to point R on the rectifier. The R wire should connect from the VR to the + side of the battery. For the 186D, there is also a wire for the battery voltage feedback from the keyswitch to the VR and a lamp indicator wire output from the VR."

A couple of us noticed that as well.. the schematic, as posted would not have functioned 'as advertised'.


"Long story short, it would be an interesting project to build a VR, but probably not cost effective if you include the protection circuitry, additional modes of operation, and packaging. I am certain there are lots of alternate VRs available that would work great and cost less (like the Datsun one!), the trick is to find the information to cross reference and/or check the circuitry compatiability."


Pretty much same conclusion as well. FWIW I put a mitsubishi alternator (50 bucks), and an old style chrysler reg ( 10 bucks )on my ym1700 . Could have just as easilly put a gm job, and been done with it.... all self contained.

I knew I shouldn't have changed my major from electrical to civil... most of my 'fun' work is based around electronics anyway....

Soundguy

 

[Soundguy]

"A 12 volt regulator would not work at all since battery voltage, with engine running, is almost always above the standard 12.6 volts. "

I think you are missing the technical aspect of the idea. A 12 v battery can be charged to 6v with a 6v charging circuit..... A car battery that is normally sitting around 12.6 - 13.?? can be charged to 12v from a regulated 12v circuit like is being discussed here. In short.. the ambient battery voltage, after loading, will drop to what the maximum charge level will allow... it doesn't matter whether the battery is designed for 12.6 or 24..... if the charging source is 12... that's all ther is... and if there is a conductive path, and the batteries potential is less than the charging circuit ( i.e. after a load.. starting, etc )... curent will flow. ( we already determined that 12v is nearly on the unsuitable side of the scale... but as normde pointed out.. were not shooting for rocket science.. just something that keeps the tractor battery at a point where it starts when the key is turned... after all.. if the charging system is only rated at like 5 amps anyway.. they were'nt putting much time/effort in the charging system anyway... they just made a system that slowly replenished the storage cell in preperation for the next starting occourence... they obviously weren't planning to subsidize any extensive electrical circuits of any appreciable load..... anything over 5amps is a discharge situation...

Soundguy

 

[Soundguy]

""This is getting awfully boring......It's supposed to be a tractor Forum, not rocket science. ""

Normde.. it's a good thing that we aren't aaerospace. eng's.. as we might have taken offense at that /w3tcompact/icons/smile.gif

( are there any AS eng's out there... we seem to have a collection goint here.. electrical, civil, structural, etc... )

Soundguy

 

[Keoke]

Soundguy, I get Normde's point so this will be my last post on this subject.

In regard to your last post shown quoted below:

(I think you are missing the technical aspect of the idea. A 12 v battery can be charged to 6v with a 6v charging circuit..... A car battery that is normally sitting around 12.6 - 13.?? can be charged to 12v from a regulated 12v circuit like is being discussed here).

My reply is as follows:

A single wet cell fully charged (1.260/ 1.280 specific gravity) has static 2.13 volts per cell. This 2.13v times 6 cells = 12.78 volts for a fully charged battery. A 12 volt battery at 12.0 volts is less then 50% charged. Batteries continually kept at this low charge rate will die very quickly from sulphation of their plates.
In addition, there will be a voltage drop from where the VR ties into the alt to battery circuit so that when alt current finally get's to the battery it will no longer be at the VR's 12 volts but at a lesser value.
Bottom line, why would one want to design a voltage regulator that would keep a battery at less then 50% charged?
Also, if one was to put a fully charged battery in this tractor then, with tractor running, all loads would run off the battery (higher EMF) instead of the alternator until the battery is down to less then 50% of it's potential.
It doesn't cost much more, if any, to go a VR in the std 13.8 to 14.8v range so a VR in this range seems like a better bet to me for this application.

P.S., A quick rule of the thumb when converting battery voltage to battery strength is to add .25 to the true voltage (not surface chg) and take total of the last two digits in % of charge. EG. battery voltage is 12.4 volts so 12.40 plus .25 = 12.65 or a battery of approx. 65% strength. This formula is by no means super accurate but it is very close. You must use a digital voltmeter for this measurement.

 

[bruce1966us]

I have to agree with soundguy that the system is designed only to maintain the battery. We all know that a diesel requires no energy to run. This is why we are working with very small volts/amps.

Thanks,
Bruce

 

[htiek126]

The HEXFETS (IRFs) are a great idea, and you could just make it a steady state voltage reference/current limiting circuit. They have reversed temperture coefficients, therefore, you can put them in parallel without suffering from secondary breakdown (thermal runaway). I just built a special application battery charger with two IRF5305's (internal resistance = .06 Ohms and $1.60 each) in parallel, and they work great at dissipating about 75 watts of heat.

Keith

 

[htiek126]

The 78xx and 79xx fixed voltage regulators are available in variable voltage formats. I believe that RadioShack has the 317 regulator, and there are other inexpensive regulators available at places like www.dgigkey.com. Or you could use the 7815 with a power diode in series to drop the voltage about .6 volts to 14.4 volts. I am not real familiar with wet cell battery chemistry, but I know they are easily damaged when they are not kept fully charged.

Keith

 

[Keoke]

Quote:
I have to agree with soundguy that the system is designed only to maintain the battery. We all know that a diesel requires no energy to run. This is why we are working with very small volts/amps.

Bruce, maintain the battery at what state of charge, 100%, 50% or maybe a lessor value?? I am all for keeping a battery at it's normal 100% charge. What state of charge do you think a battery should be maintained at?
By the way, the shut off fuel solenoid requires around 2 amps to keep open while engine is running.
Bottom line, there is no free electrical ride, and don't forget the starter draw needs to be replaced, even on a diesel.

cheers,

 

[bruce1966us]

I have a question that is somewhat off subject. What type of regulator did the old Murray, Craftsman, etc. riding mowers use?

Thanks,
Bruce

 

[bruce1966us]

George,

There is no fuel solenoid on the YM1401 or YM1100 that we are talking about so that is not an issue. I beleive that these smaller, older tractors may be designed to constantly charge at a very small rate. For example: A YM1100 running at 800-1000rpm with the headlights on will have a dead battery after a few hours. These low volt/amp dynos only charge at 13-13.5 when running at 2000rpm.

IMHO

Thanks,
Bruce

 

[Keoke]

Bruce, 13 to 13.5 volts looks like a very good range for a low output unit. Anything above 12.8 vlots delivered to battery, with enough time, will keep a battery topped off. The amount of amps absorbed by the battery is determined by the difference in potential between the alt voltage and the batteries voltage.
Keeping a battery topped off is especially critical during the winter months since a battery power drops off dramatically when temp drops. A fully charged battery is about 40% sulphric acid and 60% water. A dead battery is almost 100% water and hence subject to freezing.
I have no idea of who makes the VR units used in riding lawn mowers. However, if these units use PM type alternators/dynamo, then it would seem, that these VR's could be made to work on Gregs tractor. Of course their alt amperage outputs must be the same or more then the tractor output. This is because this type of VR converts the excess charging enegry to heat in the regulator. So, you can guess what a high output PM alt would do to one of these small capacity VR's that could not absorb the excess wattage.
Bruce, Americans tend to call charging units alternators and everbody else calls them dynamos. Technically, alternators are supposed to be AC producers and dynamos are usually DC producers. Nevertheless, we use both names interchangebly all the time and it causes no harm.

cheers,

 

[bruce1966us]

I agree

Bruce

 

[Soundguy]

""Soundguy, I get Normde's point so this will be my last post on this subject.""

I think it may be mine as well.

""My reply is as follows:
A single wet cell fully charged (1.260/ 1.280 specific gravity) has static 2.13 volts per cell. This 2.13v times 6 cells = 12.78 volts for a fully charged battery. A 12 volt battery at 12.0 volts is less then 50% charged. Batteries continually kept at this low charge rate will die very quickly from sulphation of their plates.""

Never said it was the optimum fix.. just a stopgap measure. Besides.. if a 15v reg is available.. it will be the better choice to start from.

""In addition, there will be a voltage drop from where the VR ties into the alt to battery circuit so that when alt current finally get's to the battery it will no longer be at the VR's 12 volts but at a lesser value.""

If the proper gauge wire is used, with good connections, there should be no more than a negligible voltage drop across a couple feet of copper. Maybee in the 100'ths.. probably in the 1000's range.


""Bottom line, why would one want to design a voltage regulator that would keep a battery at less then 50% charged?""

If I wanted my tractor to start, and I didn't have access to the optimum componets to make a regulator, the 12 reg. would do it.


""Also, if one was to put a fully charged battery in this tractor then, with tractor running, all loads would run off the battery (higher EMF) instead of the alternator until the battery is down to less then 50% of it's potential.""

I stated as much.. that the battery would be in a state of discharge, untill the potential of the battery was less than the charging potential.

"It doesn't cost much more, if any, to go a VR in the std 13.8 to 14.8v range so a VR in this range seems like a better bet to me for this application."

Money wasn't an large factor in my statements.. parts availability was. Radioshack is only a marginal parts house.. if the person performing this repair has access to a better house.. say like newark, etc... then ther probably won't be a problem. On the other hand... rs does sell a 317 variable vr.. but then we are getting back into building a more complicated circuit. An irf-511 powered PWM is going to be even more complicated for an individual without good electronics background. However, if they feel froggy, and want to do electronics via 'cookbook', they have more than enough options right now to go build a circuit blindly from schematics, whether it be a variable vr circuit, any one of the constant current circuits, a series pass regulator, or a pwm.... they can take their pick.

Soundguy

 

[LLove]

Real late model GM alternators are of the PM type, and are also self regulating without the field control from the ECM.
Building a retro-fit control circuit is always a Fun challenge, but if he is only reading a 15 volt output at full throttle, he might try turning on the headlights to see if the output falls into an aceptable range of 13.25- 14.75 volts.
It would be a shame if the problem is only a poor ground connection a the VR case mounting...
Seen quit a few alternators, and external regulators get replaced for problems located in wiring, connections, and so forth.
But it has been a fun thread to read. Lloyd

 

[jimstractors]

Greg,
Sorry, I got lost in the long thread....YES! the Kohler regulator works fine. I haven't had to charge the battery once since replacing it. Here is what I ordered:
Kohler reg. from jackssmallengines.com for $36.82 + $5.00 shipping, no tax.
Their part # ST435081.
Thanks,
Jim

 

[gbirky]

Jim,
Thanks for the info. Now just remind me - you put this on a YM1401.

1) Does the 1401 alternator have the bridge rectifier in the alternator or in the regulator?

2) Does the Kohler regulator have a built in rectifier?

3) Is the part # ST435081 the Kohler number?