Control alternator voltage back to 6vlt battery?

[Firdog]

Can someone on here help make a suggestion to regulate the voltage on this diagram included?

I am Thinking I can add a inline diode or resisters to control voltage back to my battery on this diagram below for my 1981 Suzuki GN400 motorcycle. It is a 6 volt system and the only battery that fits is a wet style battery. After riding it for a couple hundred miles the acid seems to be expelled from the battery and if you don’t catch it and refill with distilled water in time it cooks it and you have to replace it. The bike only uses the battery for lighting head lamp, turn signals, controls lighting, brake, and tail light. It is not needed to start the bike because it only has a kick start. Bike will run without battery but lighting goes from bright to dim with out the battery. It seems they did not do a very good job regulating the return voltage from the alternator. So I am looking for help to put something in place to keep from overcharging it. Thinking I need to control to 6.9-7.2 volts.
For reference The 4 AH battery model is a
Yuasa® 6N4B-2A - Conventional Battery

 

[duke37]

I am not familiar with small motorcycle generators but have a vague memory that they have a constant current output, It should be possible to restrict the voltage to 7V by adding a load such as the headlights when the current is too high.

I do not see how to maintain 7V when the generator is not up to the job.

Diluting the acid to replace spurted out acid by adding water is not a good thing.

 

[Firdog]

Thanks for the response. I actually want to limit the voltage to 6volts as it is cooking the battery which is also 6 VDC. I never have to charge it unless it needs refilled after it’s has all boiled out.

 

[Bluejets]

One cannot charge a 6v battery with only 6v.
The daytime (lights off) regulation as can be seen in the diagram supplied is the "running light" called parking or city light and the resistor.
What we see in the diagram I would imagine be a lot different from what is actually there in the bike given it's age.
I sure it would have been hacked many times by now and not much would be original, hence the problems.

 

[duke37]

12V cars are usually charged between 13.8V and 14.4V. It is necessary to use as high a voltage as possible without gassing. A 6V system should be charged at 7V.

You should never have to charge the battery if you use the motorbike once a week or so. I have just changed my 12 year old car battery which has never been topped up or externally charged.

 

[Alec_t]

I'm not a bike guy, but it's my understanding that voltage stabilisation on older bikes with magnetos is usually achieved very crudely with simple shunt regulators. Such a regulator may be no more than a beefy zener diode or two to clamp the voltage to around 7V (for a 6V system).

 

[Firdog]

Thanks for the reply.
Zener Diode to control the voltage. OK. So what Diode would I use and can I put it in the battery connection? Would this limit voltage back but not voltage out? Looking to control to 7 VDC. Please recommend what is needed and where.

 

[Firdog]

One cannot charge a 6v battery with only 6v.
The daytime (lights off) regulation as can be seen in the diagram supplied is the "running light" called parking or city light and the resistor.
What we see in the diagram I would imagine be a lot different from what is actually there in the bike given it's age.
I sure it would have been hacked many times by now and not much would be original, hence the problems.

 

[Firdog]

I am sorry Bluejets. If you read the first post I wish to control the charging voltage back to the 6vlt battery. Please make a recommendation to control to a voltage needed to charge it. I am thinking 6.9 to 7VDC should do the trick. Currently the system seems to fluctuate and over charge the battery and kills it.

Also they show a switch in the circuit to control the headlight but the headlight is not switchable and is ON all the time when motor is running.
Thanks for the response.

 

[duke37]

If the headlight is on all the time the engine is running, then perhaps the bulb is not powerful enough to limit the voltage.

If you use a Zener diode across the battery, then it will need to be powerful and have a sharp knee so that it does not discharge the battery when the bike is not being used. You may have difficulty in finding a 7V Zener, they often have quite a large variation from the nominal voltage.

More complicated circuitry could be used for more accuracy.

A lead/acid battery can easily produce sufficient current to start a fire so be very careful. An explosion is also possible if the oxygen/hydrogen gas is ignited as my nephew found. He leapt into a cattle drinking trough to dilute the acid and was not harmed.

 

[Firdog]

Good to know and thanks Duke37

 

[WHONOES]

You could try a simple shunt regulator consisting of a beefy Darlington transistor, a power resistor a pot and two more resistors.

 

[Bluejets]

I'm certain I have commented on this schematic previously regar

I am sorry Bluejets. If you read the first post I wish to control the charging voltage back to the 6vlt battery. Please make a recommendation to control to a voltage needed to charge it. I am thinking 6.9 to 7VDC should do the trick. Currently the system seems to fluctuate and over charge the battery and kills it.

Also they show a switch in the circuit to control the headlight but the headlight is not switchable and is ON all the time when motor is running.
Thanks for the response.

I'm certain I have commented on this schematic previously regards the same question.
Answer then was the same as now.
The daytime running with the headlights off is regulated by the daytime running light.
If the system has been hacked, which is highly possible given the age, then the original wiring is probably not in place any longer.

Also you said you want to limit the charge voltage to 6v to which I said, you cannot charge a 6v battery with 6v and that is still a fact.

Edit:- eye sight a bit off.......downloaded and expanded the supplied diagram.......GW off the resistor,
Light sw OFF to W/R, W/R to rectifier, rectifier R to IGN sw ON to O wire, O to neutral light, horn turn sig etc. So as others have said, resistor is regulator.

 

[Bluejets]

I actually want to limit the voltage to 6volts

 

[dave9]

I would do some research into another alternative, perhaps a 2S2P array of 26650 Li-Ion would work? Maybe even a single series of 26650 or even 18650. You might still need to clamp the upper voltage, but as far as the battery fitting, if Li-Ion cells fit in a hollowed out flooded lead acid casing, like the old one you already had, then...

Surely there is some topic about this in a motorcycle forum?

Considering kick start, do you even need a battery or would supercapacitors work? Quote "Bike will run without battery but lighting goes from bright to dim with out the battery". How severe is this? Would it help to use LED lighting designed for a wider input voltage, like a basic buck current regulator design where it just has to be a volt or two above the Vf of white LEDs, in other words in the neighborhood of 5V buffered by a capacitor bank?

Granted for the headlight, a switch to LED might require a reflector or whole housing change to get good throw.

 

[Bluejets]

Considering kick start, do you even need a battery or would supercapacitors work

Battery not required as it has a magneto providing both the supply for and the pulse coil for the CDI.

 

[Firdog]

All, thanks for responses in the discussion.

I do think I found an alternative 6 volt battery which increases the AH from 4AH to 6Ah, but I am still concerned on the ability to “control the charging voltage back to it”. This would allow for more reserve capacity.

In response from above about modifications to wiring I respond the bike is completely stock without modification.

Bluejets- The headlight is always on and not switchable because the bike is in the United states and headlamp on all the time is required by law. Suzuki had the parts and design to have the switchable headlight and the switch is on the bike, however the switch does not operate to the “off position” as it was their factory modification.


Dave9- is the dimming that bad. It is and enough that if you are not in town under street lighting to interfere with vision. Something that is needed to dodge roaming deer population.
Can you suggest a voltage regulator and tell me where or how to integrate it to the system?


Bluejets- can you suggest a resistor replacement or can I double it up in series? And you are correct, you did see the diagram in a post that was asking to convert the system from 6vdc to 12vdc. I am looking to keep the bike on 6vdc.

 

[Firdog]

You could try a simple shunt regulator consisting of a beefy Darlington transistor, a power resistor a pot and two more resistors.

Can you suggest parts list and rough sketch for integration?

 

[73's de Edd]

Sir Firdog . . . . .

Why 'soitanly . . . . I can give one.
been using this design for holding down the max charge permitted to a CC Li Ion charger of mine .
Used from about 2011 to date with flawless performance. I have been setting for 4.30V shunting action.

My now having changed the R3 to a 10k resistor, as I have shown, should encompass the higher
voltage range that you need.

Think that I still have the engineering prototype board that I built it on and will show you . . . . gotta go now to prep for a
g-grand daughters b-day pty. Will research your posts total situation for replying a bit later.

TECHNIQUE . . . . .




73's de Edd . . . . .

If you are over 60 yrs. old you absolutely MUST take this Alzheimer’s Test
How fast can you guess these words and fill-in the blanks?
1. _ _NDOM
2. F_ _K
3. P_N_S
4. PU_S_
5. S_X
6. BOO_S

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V
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:
V

:
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:
V
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V
Answers:
1. RANDOM
2. FORK
3. PANTS
4. PULSE
5. SIX
6. BOOKS
You got all 6 wrong….didn’t you?
Well now, you DO NOT have Alzheimer’s….
You’re just a DAMN SEXUAL PERVERT !

 

[WHONOES]

I had in mind something slightly simpler. See attachment.
Adjust VR1 to maximum value. Connect circuit across battery terminals whilst your bike is not running. Make sure that no current is flowing in the circuit at this point. Start Bike then adjust VR1 untill you get the charge voltage required. The clamping range of the circuit is about is about 6.9 to 7.2 volts.
Note that the transistor must be mounted on a substantial heat sink and placed in unrestricted airflow as it will dissipate quite a lot of power.
R1 should be rated at 2 - 3 Watts.