DC electric problem

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Oswego John
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Joined: Feb 5th, '05, 20:42
Location: '66 Typhoon "Grace", Hull # 42, Schooner "Ontario", CD 85D Hull #1

D.C. Electrical Problem

Post by Oswego John »

Charlie,

It looks like you're going to be okay, now.

FWIW, many automotive and marine technicians advise you not to run your engine without the alternator being hooked up to the battery. By doing this, it often produces blown diodes.

It might be a good idea to take your multimeter and check the diodes.

Good luck,
Happy, healthy New Years to all.
O J
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Lee Kaufman
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Location: CD25 #12 "Morning Star"

one more ?

Post by Lee Kaufman »

How do I check the diodes?

Thanks for the help. This has been driving me crazy (though it is a short trip,)
marilou
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This is not an "Alternator"

Post by marilou »

The Nissan small outboard is available with rectifier kit. This produces electricity, but is not really intended to be used to as a charger...it could be considered a trickle charger...so unless you run your engine for days, it will not recharge your run down/dead battery (not that your's is).

If it will produce enough electricity to power your lights, cell phone, depth meter, etc. it's ok...it does not have enough power to fry your battery. As mentioned above, if it will run your lights, it is working OK, I believe.
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Lee Kaufman
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Thanks

Post by Lee Kaufman »

I really appreciate all the help. The folks on this board are really an invaluable resource. Thanks, Ya'all.

By the way, for those up North, the plural of ya'all is all ya'all.

Happy New Year
The Patriot
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Re: Thanks

Post by The Patriot »

Lee Kaufman wrote: ... By the way, for those up North, the plural of ya'all is all ya'all ...
What's the plural for those not up North?
Oswego John
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Location: '66 Typhoon "Grace", Hull # 42, Schooner "Ontario", CD 85D Hull #1

D.C. Electrical Problems

Post by Oswego John »

Charlie,

I honestly decided not to get involved in this thread, just sit by and enjoy it. (Not that someone's problem is enjoyable.) I mean, read up on how others treat a problem such as this. However, I was slowly seduced into it, probably because of how interesting it is. I Just couldn't resist.

Let me say a few words about just what a diode is and what it does. This way, you will know what you are checking for.

Generally speaking, a generator produces Direct Current (DC). An alternator produces Alternating Current. (AC). You can also relate this to the polarity of the voltage being produced.
Again, I say "generally speaking". There are some exceptions to the normal use of these voltages. These facts apply to what we are concerned with today.

With DC voltage, the hot wire is usually positive and the ground wire is usually negative polarity.

With AC, the polarity reverses itself, or alternates, as many times in a second as whatever its cycle, expressed in hertz is. If something is 60~, its polarity reverses from positive to negative and back 60 times per second. It would be said that it had a frequency of 60 hertz.

Here's where the diodes come in. What I say isn't exactly what happens but it will give you a pretty good idea what goes on.

Draw a circle on a piece of paper. Pretend that it is the face of a clock. Where 9 o'clock is, outside of the circle, write zero volts. 0 V.
At 12 o'clock, write +12 V. At 3 o'clock, write 0 V, and at 6 o'clock, write negative 12 Volts or -12 V. Now, going to the right, make about four or more identical circles with corresponding voltages noted. The side edges should abut. Are you still with me. Here comes the meat.

When an alternator starts to rotate, at that time, the voltage is 0 V as read at 9 o'clock. As it rotates clockwise, the voltage produced will increase up to +12 V as shown at 12 o'clock. Farther rotation brings the voltage wave to 3 o'clock, designated by 0 V. Moving onward, the voltage drops to minus 12 V, as shown at 6 o'clock. To complete one rotation, or one cycle, the alternator rotor returns to 9 o'clock and zero voltage.

It works that way somewhat, but that's really not the way it happens. If you had made five clock faces touching each other, you could begin to see a sine wave being made.

Use a red or other colored pencil for this. Starting at 9 o'clock on circle #1, draw a curved line clockwise up to 12 o'clock and then down to 3 o'clock. Instead of continuing onward around the bottom of circle #1, let the red line jump over to circle #2. Since we are speaking of alternating voltage/current, the line will continue in a COUNTER clockwise direction around the lower half of circle #2, from 9 oclock past 6 o'clock and up to 3 o'clock.

At this point, the sine wave will jump across to the right from 3 o'clock to 9 o'clock on circle #3 and alternate back to a CLOCKWISE rotation. This wave continues on and on as long as the alternator is rotating.

This positive, negative, positive, negative wavy AC isn't suitable for a 12 volt auto or boat battery. Most storage batteries for cars and smaller boats are usually 12V DC. Attaching something to it that produced anything other than 12V DC would prove harmful.

So, if the alternator produces 12V AC and we want 12V DC, how do we charge the battery with power from a 12V AC alternator?

One half of one cycle of an alternator, the upper half of the clock dial from 9 o'clock to 12 o'clock to three o'clock, is in the positive zone. That is good. We want that.

The remainding 180° of the bottom half of a cycle, CCW from 9 to 6 to 3 o'clock lies in the negative charge area. That is no good. We don't want that.

So if we want the part of the charge that has a positive polarity but don't want the part that is negatively charged, how do we eliminate the latter? The answer is by the use of a diode. (Not to be confused with an LED, or light emitting diode.

A diode is to the flow of electrons as a check valve is to the flow of water. They both allow flow in one direction but not in the reverse direction. With the use of a diode(s) in a charging circuit, we can allow the positively charged portion of a cycle to pass from the alternator to the battery while restraining the negatively charged portion.

To better understand what the altered sine wave of the rectified AC now looks like, cover up the portions of the lower halves of the clock dials below nine and three o'clocks. The remaining positive half waves are called by some people as 12V positive, pulsating DC. This charge is stored in a storage battery. The 12V DC that comes out of the battery for shipboard use is straight, or pure, DC, not pulsating. I would want pure, uninterrupted DC to power my electronics rather than pulsating DC.

I have no idea what the make of your alternator is, Leece Neville, Mopar, Motorola, whatever, or one that is made by some oriental company tha is relatively unknown in the USA. Whatever the make, somewhere adjacent to where the charging wires emerge you will locate the diode(s).

Remove the diodes from the frame and separate, or at least electrically isolate them from any other wiring. The only electrical power used to check them is from the battery(ies) in your multimeter, which is polarized DC. Voltage doesn't matter, you are testing for current directional flow. I like to take a picture before I take some unknown thing apart in order to reassemble it correctly. At the very least, write down what you are about to disassemble.

Set your multimeter to ohms-resistance. Most diodes used for rectification have two terminals. Testing one diode at a time, place either meter test probe on one terminal and the other probe on the remaining terminal. Check to see if you get a reading on the meter. Now reverse the probes on the diode and check for a continuity reading.

A good diode will have a reading with the probes in one position and will have no reading with the probes reversed.

If the diode is bad, you will probably get a meter reading whichever way you place the probes.

With no reading at all, no matter which position you place the leads, there is a break in continuity within the diode.

I realize that this post is much longer than I had intended it to be, so I'll close after this. Several posters correctly stated that a 10V charger couldn't charge a battery with 12V, but I was waiting for someone to give the reason why.

Whether speaking of a gas, water or electricity, they all have similar properties in relation to one another. Most people are somewhat familiar with water properties but are somewhat hazy or reluctant when it comes to electricity. I'm that way with snakes.

The greater rules the lesser. Another way to describe voltage is electrical PRESSURE. Water can be measured in pressure as well as gasses. High pressure supercedes low pressure. Let's say a healthy person could, arbitrarily, blow a balloon up to 10 psi. While pinching its neck, someone handed that person a blown up balloon that had 20 psi in it and said "Blow it up some more".
The person couldn't blow the balloon any higher with 10 lbs of lung power. When the person released his fingers to blow into the balloon, the 20 lbs in the balloon would rush out in reverse direction to the lower 10 lb pressure.

10V DC can't buck the 12VDC in the battery. Chances are that the battery voltage could go so far in reverse until it was possibly stopped from continuing by the one way, unidirectional diode.

Well, its a thought,
Happy New Year all,
O J
(Ken, Bottomscraper, edit this, please) I'm sure I goofed somewhere.
SPIBob
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rpms and alternator output

Post by SPIBob »

I vote for low rpms as the culprit. A typical alternator/generator must reach a minimum rpm before it begins to produce its designed output. This is well known to wind generator owners.

If this is the problem, the obvious remedy is to increase rpms. Make sure the motor is in top tune (electrics, fuel, air) and the prop is clean and free-spinning.

If this doesn't help, the prop pitch change would be the next step.

Good luck, Bob
Oswego John
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A New Twist On Things

Post by Oswego John »

Marilou
SPIBob
D Rush
and all other posters,

First of all, hurrah for Marilou. She spotted something that never occurred to me and possibly to some others. She pointed out that the generator was that of a dynamo type. That signifies that it produces electricity through electro-magnetic induction with the use of a pickup coil.. Sure enough, upon further searching, I found the info and illustration on page 35 of the handbook.

When someone mentions an alternator to me, my first thoughts are of a round case with windings in the field as well as the rotor. It would be gear or pulley/belt driven. Not so on this outboard. Electricity is produced by a Wells type pickup coil that is actuated, probably, by one or two permanent magnets in (maybe) the flywheel. An open-air rectifier harness plugs into the coil leads. That really changes the complexion of things. It also explains how the electrical output is directly proportional to the engines rpms.

SPIBob and D Rush,
I agree with you and others that the rpms have a direct effect on the electrical output of this motor. At half to three quarters throttle, the book says that the rpms should be somewhere between 5,000 and 6,000 rpms. That engine is used mostly on lighter skiffs and transom mounted on much lighter sailboats. Because of motor well restrictions, it is impractical if not impossible to use larger size engines with a boat of this weight. Yes, some older, larger two stroke engines would fit, if you can find them. So, as I see it, the easiest, most practical solution to increasing cruising rpms is to go to a lower pitch prop.

The main reason that I wrote that overly long call it what you want is because Charlie asked how do you test a diode. With this type of plug-in diode, testing is a piece of cake. So Charlie, don't pay any attention to what I wrote earlier. It doesn't apply to you. (It's still valid for rotary type, or conventional alternators.

See. Didn't I say earlier that I'm not going to get enmeshed in this thread. :D

Happy New Year, all
O J
seadawg
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D. C. Electric Problem

Post by seadawg »

I'm getting the feeling that what Lee has is not designed to charge a battery at all. According to his maintenance manual drawing there is a diode but no voltage regulator. Marilou mentioned this earlier. It looks like when the motor quits the running lights or what ever go out. There is just not much in Lee's manual to explain much. Charlie
Oswego John
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I'm With You On That

Post by Oswego John »

seadawg

That's how I feel, too. I have a riding lawnmower with a Briggs and Stratton engine. It has battery electric start and also two switchable headlights. It has the same type pickup coil for producing electricity.

When the engine is at idle, the headlights are very dim. The higher I rev the engine, the brighter they become. At high rpm, the lights are very bright. When I shut down the engine, the lights go out.

I think Charlie's engine has a similar setup.

Happy New Year to all
O J
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Lee Kaufman
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Post by Lee Kaufman »

O J

Thanks for the explanation of the workings of an alternator. We are in the process of buying a travel trailer and what you wrote will definitely apply.

Yes, the alternator is, indeed, a coil that operates off the flywheel with a rectifier which I assume is to convert the AC to DC. After reading O J's explanation, I realize I tested the diode with the help of the technician. It is working OK. So, at this point, I guess the consensus is that the engine is not producing enough RPM to develop a voltage that is capable of putting energy into the battery (20 psi balloon). As stated earlier, the 6 pitch prop only produces 4300 RPM. If there is no way to increase the RPM adequately, which I was unable to do with the 6 pitch prop, then the alternator is, for all intents and purposes, useless to me. Or is it producing a very small charge that I have not been able to test for? Those seem to be the two possibilities. How do I know?
marilou
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I agree with you all

Post by marilou »

If, you run the engine in neutral and give it some gas, you will take the electrical output to the max. Changing the prop will change the rpm of the flywheel under load (not electrical - but the prop spinning - in comparison to the flywheel r.p.m)

Changing the prop may help incresase the output under load, but unless you are running the engine for longer than usuall/needed/required it is not going to be a great benefit to charging your battery, I believe. The small outboard was designed to be run at high rpm (and it likes it - under load/prop spinning under water, as John O. points out (relative to being a engine that is intended to be run at idle for long periods of time).

Again, this recitifier is intended to power the running lights, bilge pump, etc. on a small craft.

Happy New Years!

P.S Judith can correct me on the "You All"
seadawg
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Location: Cape Dory 22D
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D. C. Electric Problem

Post by seadawg »

Lee, since there is no regulated output on your outboard engine now may be a good time to think about using solar power trickle charger to keep your battery up. Just a suggestion/thought. Charlie
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Lee Kaufman
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solar panel

Post by Lee Kaufman »

I have a solar panel that I removed from service when I got the alternator because I assumed at that time my power problems were solved. Since this problem occurred I reinstalled the solar panel. It looks to me like I need to buy a charger and hook to shore power. I guess I wasted $170 plus the cost of installation. Live and learn.
Oswego John
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Oh My O My O My

Post by Oswego John »

What a dummkopf I am. All along, I've been calling Lee, Charlie.

I just now realized that Charlie is seadawg. Sorry, Lee. :oops:

I've always maintained that it's not considered a mistake if you catch it yourself before the boss does.

Whatever,
O J
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