Topic: Problem with Reverse Current Protection?

[w1sa]

Hello,
Hope someone can help me here!
I have a charging system that uses a 100w 12v DC generator charging a 7ah battery via a electro-mechanical voltage regulator. The regulator has a 12v - 8.5A stamped on its face.

The factory service manual paper states that the reverse current protection should activate at less that 7 amps at 12v battery and that with a decrease of rpm to below 2000 the regulator should prevent more than 7 amps flowing from battery to generator.

I want to replace the unserviceable original unit with a solid state regulator.
The lowest amperage rating I can find is 10A. If I install this , what protection or other affect will it have on my generator etc.

Geof

[TomC]

Hi Geof
     As no one else has responded I will give it a try. The factory service manual sounds like some Honda manuals I have used. That is, translated from Japanese by some one who knows nothing about motorcycles and has never talked to some one who is a native English speaker.
     Generator regulators, most not all, have three sections.
     First a cut out. The cut out connects the generator to the battery when the generator is putting out more that the cut out voltage and disconnects when the generator voltage falls below the cut out voltage.
     Second voltage control. Voltage is controlled by how much current goes through the field coil in the generator.
     Third maximum current output.
     Using a different regulator. Cut out is OK. Voltage control 12V is 12V. Not really but two different nominal 12V will control to very close the same voltage. The problem is how the field coil is wired in the generator. The field coil may grounded in the generator. If so the regulator provides 12V to the field. Or the field coil is connected to the hot brush in the generator. In this case the regulator grounds the field wire from the generator to get things going.
     My guess is that the 8.5 and 10 amp ratings are for maximum current output. 12V X 8.5A = 102 watts 12V X 10A = 120 watts Is producing 18 more watts going to kill your generator? My guess is no. On some British Bike e-groups that I am on people have been pushing Lucas generators to much more the the rated output with good results. But your Kawasaki may be different.
          TomC in Ohio

[TwoTired]

I should keep my mouth shut, I suppose.  But, there is simply not enough info given in the question.

A circuit diagram would have helped.  Or, at least, basic info about the generator.  PM type? Field coil type?  Commutator?  Slip rings?  Is there a rectifier?

I'm not going to guess about the many different types of generator/alternators.  And, far more types of methods to control their outputs.

I write long posts, frequently.  But, to cover all variables would require a book.

Sorry.

[TomC]

Hi TwoTired
     I would be interested in knowing more about a "100w 12v DC generator" that uses a slip ring or a rectifier. I can see that a DC generator could work with a PM. Can not remember ever seeing one. You could use a rectifier in place of a cut out relay. I think you can buy such a set up for a Model A Ford. As I think Geof is working on a motorcycle that is in a number of ways similar to a BSA A7 or A10. I guess that it's generator may be one of those ways. I feel confident that it does not have a third brush generator.
Hi Geof
     My response makes the assumption that your DC generator is similar to a Lucas motorcycle generator or any number of different automotive generators I have had to deal with over the years.
          TomC in Ohio

[TwoTired]

TomC,
If you read this forum long enough, you will see questions about the generator on the SOHC4.  Technically it's an alternator.  Are you arguing these questions should be taken literally?
You are making the assumption Geof is using the right terminology.  I want clarification.

As I think Geof is working on a motorcycle that is in a number of ways similar to a BSA A7 or A10. I guess that it's generator may be one of those ways. I feel confident that it does not have a third brush generator.

You are free to make assumptions or guesses on Geof's behalf.  And, offer advice for those guesses and assumptions. I choose not to.  I was willing to help with the proper information base. 
As I said, I should have just kept my mouth shut. 

As far as I'm concerned, TomC now owns the problem.  Good luck to you both!

[w1sa]

Thanks for the input guys,

I am sending 3 files (separate posts),  which are page extracts from the Service Manual
I hope this helps clarify the charging system.

The regulator operation is also described (probably nothing new to youl) and the regulator performance requirements / specifications are separately mentioned as
Regulator Specifications;
Cut-in voltage         13~14 V
Cut-out voltage        8~12  V
No-load voltage       15~16.5V
No-load current        more than 7.5A at 13.5V
Reverse current        less than 7A at 12V of battery

Hope this helps.  Let me know what you think.

Thanks......................Geof

[w1sa]

Next file

[w1sa]

Third file.

One to go

[w1sa]

Last file

[TomC]

Hi Geof aka W1sa
     Looks like what I expected. The field coil is shown connected to the hot brush. If the regulator that you are looking at is set up to ground the field wire when maximum generator output is wanted it should work. But may allow the generator to make a little more power that the original regulator.
     These bikes were used as Police bikes in Japan. I wonder what the charging system was on a police version?
          TomC in Ohio

[w1sa]

TomC,

At this stage I'm focussing on a regulator apparently suited to late 60's early 70's HD sporsters, some of which I think also used 12N7 batteries.

Most of the regulators (incl this one) that I've seen have voltage set points between 14.1 and 15.1. These appear to be above my original (13~14 Cut-in), but that extra voltage /current to the battery would be more of a battery consideration than a generator concern, wouldn't it?

If we assume (without making an ass out of you or me) that the generator might not be adversely affected at the higher level of output, wouldn't it still be adversely affected at outputs between idle and driving rpm (2000rpm) i.e. until the generator achieves rated output (7 amps at 12V) and also exceeds the likely current level in the battery.
I ask this because it's my (very limited) understanding that where the battery current/voltage exceeds the generator output, current flow from the battery to the generator is only limited or prevented by the reverse current (relay?) switching in the regulator.

This is my main concern. If I fit a regulator which allows battery current above 7 amps to flow to the generator at low revs, would that battery current at best, lower the battery storage quicker or at worst, cause damage to the generator during start-up/idle etc. Also, if the reverse current switching was at say, 8amps or higher, wouldn't the current flow from battery to generator at all generator outputs below that level.
 
Also, the B+ to the regulator and reg/gen wiring are independent of power/ign switch (normal?). If engine shutdown occurs before reverse current switching in the regulator, wouldn't the battery continue to drain to the generator.

Alternately, . Have I missed the obvious?

Are you saying that the reverse current switching in the regulator occurs at a predetermined voltage (say 12V), regardless of the associated current.

If this is the case, the regulator rating say (10A) only rely relates to the regulators abilty to handle current up to that level. In which case also, regardless of the generator considerations, its the current limit of any battery/current supply to be connected to it

........................................Geof

[TomC]

Hi Geof
     In a mechanical regulator the Reverse current is controlled by the cut out relay. The points close when the generator is making more voltage the the cut in voltage. The points open when the generator is making less that the cut out voltage. This is why the generator does not need to be switched off. So the difference would be in the cut in and cut out voltages of the different regulators.
     In a solid state regulator the function of the cut out relay would be replaced by a diode. The diode will only allow current to go in one direction. No issue of cut in or cut out. I suppose that a solid switch could be used in stead of a diode. But that seems to me to be more trouble that it would be worth.
    " Most of the regulators (incl this one) that I've seen have voltage set points between 14.1 and 15.1. These appear to be above my original (13~14 Cut-in), but that extra voltage /current to the battery would be more of a battery consideration than a generator concern, wouldn't it?"
     I think that you are comparing cut in voltage with output voltage. Output voltage is the voltage the battery charged at.
     "Also, the B+ to the regulator and reg/gen wiring are independent of power/ign switch (normal?). If engine shutdown occurs before reverse current switching in the regulator, wouldn't the battery continue to drain to the generator.

Alternately, . Have I missed the obvious?

Are you saying that the reverse current switching in the regulator occurs at a predetermined voltage (say 12V), regardless of the associated current."
     Yes I am saying that the cut out relay is controlled by voltage and not by current.
     I talked to a friend of mine who has his own auto electric business. He thinks that the HD regulator would work but could not find in his listings which type of field circuit HD uses. He told me the field attached to the hot brush of the generator is called an A-Circuit. He said just try it. He did not think that the generator would be in danger. I think that if the regulator is set for the field to wired the other way what would happen is that both ends of the field coil would be connect to the same point.
     Have you checked out your generator?
            TomC in Ohio

[w1sa]

TomC,

I've attached a file containing only known details of the solid state regulator I mentioned. I'm trying to get some info from transpo at the moment. When I check with them I'll ask about the reg circuit type

I haven't opened up the gen, cause it's all nicely installed.
When I refurbished it, I checked continuity in commutator and installed 4 new brushes etc. I recall the brushes were ground/terminal connected internally to the iron gen cover that houses them.This cover is thru bolted to other end cover of gen, so effectively they are ground thru the whole gen yoke and casings.

The original regulator was also earthed back to the same gen casing. Was that to effect engine ground?, because it was a lot longer path than right next to the reg for a frame ground, like the battery.

Is this then the 'A' type you refer to, Or would I have to physically open the generator and verify where the gen/reg wires terminate internally

The solid state regulator is case ground. If I don't need to ground back to the generator, I might frame ground it closer to the unit..................................................................................Geof

[TomC]

Hi Geof
     "Is this then the 'A' type you refer to, Or would I have to physically open the generator and verify where the gen/reg wires terminate internally"
     I am basing this on the wiring diagrams of the generator and regulator that you sent me. The question is how is the HD setup? The information that I have is for the Hummer and the third brush generator. Which is of absolutely no use to us.
     Ground!!!!!!
     The generator case, the regulator case, and the ground terminal of the battery need to be at the same voltage when the generator is at it's maximum output. Do what you think is best. Then when the system is up and running check for any voltage difference between those points.
          TomC in Ohio

[w1sa]

Thanks TomC,

I'll check back once I get some info from transpo or a HD source.

In the mean time any other thoughts would be appreciated.

Your assist so far has helped me enormously.

Much appreciated...............................................Geof