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K100-forum.com » Technical, repair and troubleshooting » Electrical » Battery charging light - absolutely necessary?

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Dai

Dai
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Everything that I've found on this forum says 'yes' and it's certainly an absolute requirement for the charging on my Guzzis but... I've been riding around for the last month or so without a battery charging light and the battery has been charging quite happily.

Now... that's not quite the full story. I have a K100LT 50amp alternator on the RS and further, I converted the 50amp alternator to 60amp output by using the guts from a K1200(??) lichtmaschinen. So, I guess the real question is; did BMW change the charging regulator on later bikes, even though the visual appearance is the same? You can see the voltmeter is registering a charge after revving the engine to about 2300rpm.


Battery charging light - absolutely necessary? Brick_bat1

Battery charging light - absolutely necessary? Brick_bat2


__________________________________________________
1983 K100 naked upgraded to K100LT spec after spending time as an RS and an RT
1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

Rick G

Rick G
admin
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Yes it is necessary to have it but often the residual magnetism will start the charging by itself. So consider yourself lucky but I would put a new globe in the light.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1999 K1100 LT with a Big Block 1200
    

Inge K.

Inge K.
VIP
VIP
Quite interesting, have never tested to remove the bulb the see if the charging stops.

But start to be curious about the subject when reading about owners who have
changed out the bulb for a LED (which also would be like a open circuit) and it
just needs a bit more revving to start the charging.

From working on cars with Bosch alternators and the same type of electronic
regulators it was normal that you lost charging if the warning lamp circuit was
open.......even using a bulb with wrong wattage would disturb the charging.

Could be that the internals in the regulator have been changed later on, but on
the other hand also these little doodads eksist With a lot of different part numbers
but looks identical.


__________________________________________________
Inge K.
K100RS -86. (first owner), K1100LTSE -94.
    

robmack

robmack
Life time member
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Inge, 

You might recall the discussion earlier this year in this forum about LEDs versus bulbs as charge indicators.  LEDs are diodes and allow current to flow in only one direction, which is not to say that they are an open-circuit.  They are an open circuit to current flowing on one direction and near short circuit for current in the other direction. Evidence indicates that LEDs work, but their operation in this application is not well understood. Maybe the initial trickle current in the field coils permitted by the LEDs starts the rotating magnetic field in the alternator.

I agree with Rick G.  You've been lucky that the residual magnetic field in the rotor has been set up without the need for a exciter current.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

Inge K.

Inge K.
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VIP
What I did have in mind with open circuit is that it isn't any physhical connection
between the contacts like the filament in a bulb.
Anyway I believe that the small current a LED letting through don't make any
difference in either direction.


__________________________________________________
Inge K.
K100RS -86. (first owner), K1100LTSE -94.
    

Avenger GT

Avenger GT
Life time member
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Residual magnetism Inge. My old Scudo van was charging away happily with a blown bulb in the charge circuit. I replaced it when I was replacing the other bulbs in the instrument panel.

    

Dai

Dai
Life time member
Life time member
Interesting. I'd like to see the circuit diagram for that regulator because that would definately satisfy my curiosity and answer what's going on. If you pull the charging light on a Bosch alternator setup on a Guzzi then it will *not* charge, residual magnetism or not.

One of the most odd charging problems I ever had was a Guzzi 850-T3. The rotor had been rewound and I'd also fitted new brushes to the stator (b*gger of a job that is without a humongous soldering iron). The bike would fire up and the charging light would go out, but the battery was definately not getting power. I dropped the battery into my V1000G5 - no problem; put it back in the 850-T3 - no charge. By elimination and a shedload of patience later I finally figured that the rewound rotor had absolutely no residual magnetism in it whatsoever. It would generate just enough power to put the charge light out and no more. A good whack with a pair of leads from the battery fixed that problem.


__________________________________________________
1983 K100 naked upgraded to K100LT spec after spending time as an RS and an RT
1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

robmack

robmack
Life time member
Life time member
Dai wrote:Interesting. I'd like to see the circuit diagram for that regulator because that would definately satisfy my curiosity and answer what's going on.
http://www.buchanan1.net/charge.shtml


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

Rick G

Rick G
admin
admin
Just the physical handling while rewinding the stator would be enough to get rid of any residual magnetism.
I have seen alternators where you have to rev to 5-6000rpm to get it to start but once it starts it is self exciting.
A 3 watt bulb is usually the standard for the light and if I am remembering this right (50 years since I did the maths) as the current rises the exciting rises exponentially.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1999 K1100 LT with a Big Block 1200
    

robmack

robmack
Life time member
Life time member
LEDs will pass current in the forward direction (anode-cathode) as demanded by the load up to the design value I-fwd, the maximum carrying capacity of the device.  LEDs will block current in the reverse direction up to a design potential, V-rev, the maximum reverse voltage.  Beyond V-rev, the diode will break down -- short or open circuit -- and fail.  When current flows in the forward direction through the LED, a small measurable potential exists across the LED, V-fwd, usually around 2 volts for most LEDs.
Inge K. wrote:What I did have in mind with open circuit is that it isn't any physhical connection
between the contacts like the filament in a bulb.
There are physical connections between the leads like a bulb but the junction behaves in a non-linear manner, unlike a bulb's filament.
Inge K. wrote:Anyway I believe that the small current a LED letting through don't make any
difference in either direction.
In the forward direction, the current can be substantial, about 20-50mA for most LEDs.  In the reverse direction, the current is insignificant, 1-10 uA.



Last edited by robmack on Wed Oct 22, 2014 8:57 pm; edited 1 time in total


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

robmack

robmack
Life time member
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RicK G wrote:Just the physical handling while rewinding the stator would be enough to get rid of any residual magnetism.
I have seen alternators where you have to rev to 5-6000rpm to get it to start but once it starts it is self exciting.
A 3 watt bulb is usually the standard for the light and if I am remembering this right (50 years since I did the maths) as the current rises the exciting rises exponentially.
It's been a while for me too, but I believe the reactive current rises as a sinusoidal function (not exponential), and the real current is linear.  Real current would be a function of the resistance of the field coils and reactive current as a function of the inductive nature of the field coil.  The reactive current would determine how quickly the magnetism could be built up in the field coils and the alternator become self-sustaining.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

Dai

Dai
Life time member
Life time member
robmack wrote:
Dai wrote:Interesting. I'd like to see the circuit diagram for that regulator because that would definately satisfy my curiosity and answer what's going on.
http://www.buchanan1.net/charge.shtml
Ah. The trap for the unwary Guzzi owner! That's the same circuit as used on both BMW airheads and Tonti Guzzis; except that the diameter of the step on the stator is 1.0mm greater than the seemingly-identical stator on the Guzzi. The rotor is the same item, right down to the part number. Funnily enough, that was the only rewound rotor that ever gave me that problem.

The regulator on our alternators has to be solid-state to sit inside that (relatively) small housing. That's what I'd be really interested to see, but 'sealed unit' usually means 'no circuit diagram'. Or am I wrong? (Please say 'yes' Very Happy ).


__________________________________________________
1983 K100 naked upgraded to K100LT spec after spending time as an RS and an RT
1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

Inge K.

Inge K.
VIP
VIP
Could be that it's more differences even with Bosch than what first look like.

Also the solid state regulators seems to regulate the negative side of the field coil,
opposite to the old boxers in the link.....which I think all have mechanical regulators.


__________________________________________________
Inge K.
K100RS -86. (first owner), K1100LTSE -94.
    

Inge K.

Inge K.
VIP
VIP
Dai wrote: The regulator on our alternators has to be solid-state to sit inside that (relatively) small housing. That's what I'd be really interested to see, but 'sealed unit' usually means 'no circuit diagram'. Or am I wrong? (Please say 'yes' Very Happy ).

I don't think they all look like this inside......since it's a lot of different part #.

Voltage regulator


__________________________________________________
Inge K.
K100RS -86. (first owner), K1100LTSE -94.
    

Dai

Dai
Life time member
Life time member
Inge: you're right about the mechanical regulators and you're also right about them being different. You can put a Guzzi one on an airhead BMW and vice versa; they are completely different construction but they both do the same job. I've taken regulators off airheads that have an external power transistor (as shown in the diagram you've linked to) but on a very few, I've also found the same type of regulator as fitted to Guzzis. Just once, for the h£ll of finding out if it worked (because theory said it should), I hung a Guzzi/airhead regulator on a Honda CB750K4. It worked.


Yes, I've wired up a lot of different bikes over the years and I'm always curious about the ones that I don't know much about. Like bricks.


__________________________________________________
1983 K100 naked upgraded to K100LT spec after spending time as an RS and an RT
1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

Mossy1200

Mossy1200
Platinum member
Platinum member
Quick question for those who may know.
I have ordered 2 times 1.5 watt leds (bigger than normal).
I was going to wire them in parallel to start my regulator.  1.5 watt parallel equalling 3 watts.

Is this going to work or will I still need a resistor?
Next is a 25 watt resistor going to harm anything seeing its a lot bigger than 3watt?

Does the alternator light go out when charging starts? Sorry I have only had bike going once and never looked. I gave my instruments  away soon after stripping bike down.

    

Rick G

Rick G
admin
admin
The alternator light goes out when the alternator starts making its own charge but that does not necessarily mean that it is charging the battery. The light has 12volts on one side and the rotor gives it an earth so it comes on and when the alternator starts generating current the voltage at the earth side of the light only has to increase to 10 volts to make the light go out but 10 volts doesn't charge the battery.
The 2 x LEDs would work but I would choose the resistor unless you want a visual signal of output.
Some of the guys here have used small LEDs and found that all that is needed is about 2500rpm to get output.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1999 K1100 LT with a Big Block 1200
    

Mossy1200

Mossy1200
Platinum member
Platinum member
RicK G wrote:The alternator light goes out when the alternator starts making its own charge but that does not necessarily mean that it is charging the battery. The light has 12volts on one side and the rotor gives it an earth so it comes on and when the alternator starts generating current the voltage at the earth side of the light only has to increase to 10 volts to make the light go out but 10 volts doesn't charge the battery.
The 2 x LEDs would work but I would choose the resistor unless you want a visual signal of output.
Some of the guys here have used small LEDs and found that all that is needed is about 2500rpm to get output.
Would a blinker resistor be ok Rick or is 25 watts to much for this application?

    

charlie99

charlie99
VIP
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I wouldn't be using leds mossy (but some have ) 

the charge principle and excitation of the field relys on there being a voltage reference .....having leds in the circuit presents 2 problems
  1> the voltage drop across the led is significant (like having a battery measuring 10 volts or so ) which may have some form of limiting the regulator to do its job properly ...in fact you may find the leds on constantly even after excitation has already started ...the regulator trying to achieve - get to some form of equilibrium at its reference voltage  (lets say 14.0 volts whilst running ) but with an extra 2 volts drop could be trying to charge to 16 volts ? until voltage output of the alternator achieves correct voltage ...some have done the mod but notice that the charge indicator doesn't extinguish till a much higher than normal rev range ,,,like 2,5- 3  k
  2> the current limit on the leds will be a factor as you need to drop voltage - limit current to the rating of the led in circuit to the regulator ...
the author of the description of the early r series regulators had a solution in employing a 470 ohm resistor across the lamp (so that there was some flow at least in case of the lamp failure ) and a wise idea to me

 3 > the current flowing to the field whilst it is outside its references (low revs )  is limited by the rating of the lamp so it wont burn out the coil and controlling circuitry the leds would limit this until more voltage is realized out of the alternator by revs

certainly leds could be used ...but I figure not with the internal circuits employed in the regulators that we have at hand, already designed with the principles of using a globe - lamp in the circuit .

if you prefer low running revs like sitting in traffic idling away rather than at speed  use globes ,,, if you jump straight on the highway almost outside your door ...try leds

just what I think




sorry mossy modified my post to reflect what some folks have done - experimented with



Last edited by charlie99 on Mon Nov 03, 2014 4:20 am; edited 2 times in total


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

Mossy1200

Mossy1200
Platinum member
Platinum member
charlie99 wrote:I wouldn't be using leds mossy

the charge principle and excitation of the field relys on there being a voltage reference .....having leds in the circuit presents 2 problems
  1> the voltage drop across the led is significant (like having a battery measuring 10 volts or so ) which may have some form of limiting the regulator to do its job properly ...in fact you may find the leds on constantly even after excitation has already started ...the regulator trying to achieve - get to some form of equilibrium at its reference voltage  (lets say 14.0 volts whilst running ) but with an extra 2 volts drop could be trying to charge to 16 volts ? and blowing up all the electronics throughout the bike in the process
  2> the current limit on the leds will be a factor as you need to drop voltage - limit current to the rating of the led in circuit to the regulator ...
the author of the description of the early r series regulators had a solution in employing a 470 ohm resistor across the lamp (so that there was some flow at least in case of the lamp failure ) and a wise idea to me

 3 > the current flowing to the field whilst it is outside its references (low revs )  is limited by the rating of the lamp so it wont burn out the coil and controlling circuitry

certainly leds could be used ...but I figure not with the internal circuits employed in the regulators that we have at hand, already designed with the principles of using a globe - lamp in the circuit .

just what I think
Ok im starting to think ill get myself a 3 watt lamp and install it in my carbide light so it shines through the air holes.
I might use the 1.5 leds on the running light circuit.

    

Rick G

Rick G
admin
admin
Mossy1200 wrote:
RicK G wrote:The alternator light goes out when the alternator starts making its own charge but that does not necessarily mean that it is charging the battery. The light has 12volts on one side and the rotor gives it an earth so it comes on and when the alternator starts generating current the voltage at the earth side of the light only has to increase to 10 volts to make the light go out but 10 volts doesn't charge the battery.
The 2 x LEDs would work but I would choose the resistor unless you want a visual signal of output.
Some of the guys here have used small LEDs and found that all that is needed is about 2500rpm to get output.
Would a blinker resistor be ok Rick or is 25 watts to much for this application?
They are set up to work correctly with a 3 watt bulb which will give 0.25 amps and a 25 ohm resistor will give 0.5 amps or close which is a bit much current for initial excitement. A 100 ohm resistor or close to that would be best.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1999 K1100 LT with a Big Block 1200
    

Mossy1200

Mossy1200
Platinum member
Platinum member
RicK G wrote:
Mossy1200 wrote:
RicK G wrote:The alternator light goes out when the alternator starts making its own charge but that does not necessarily mean that it is charging the battery. The light has 12volts on one side and the rotor gives it an earth so it comes on and when the alternator starts generating current the voltage at the earth side of the light only has to increase to 10 volts to make the light go out but 10 volts doesn't charge the battery.
The 2 x LEDs would work but I would choose the resistor unless you want a visual signal of output.
Some of the guys here have used small LEDs and found that all that is needed is about 2500rpm to get output.
Would a blinker resistor be ok Rick or is 25 watts to much for this application?
They are set up to work correctly with a 3 watt bulb which will give 0.25 amps and a 25 ohm resistor will give 0.5 amps or close which is a bit much current for initial excitement. A 100 ohm resistor or close to that would be best.
I think Rick 100ohms may be 1.5 watts but I might be missing something.
100ohms seems to equal 0.125 amp.
If you can have another look in case im doing something incorrectly. DC voltage confuses me a bit.

Just pulled this off a online dc calculator.

Online ohm's law calculator: calculates voltage / current / resistance / power.

DC Ohm's law calculator

Enter 2 values to get the other values and press the Calculatebutton:


Resistance:R=ohms (Ω) kilo-ohms (kΩ) mega-ohms (MΩ)  48.00
Current:I=micro-amps (μA) milli-amps (mA) amps (A) kilo-amps (kA) mega-amps (MA)  0.25
Voltage:V=micro-volts (μV) milli-volts (mV) volts (V) kilo-volts (kV) mega-volts (MV)  12.00
Power:P=micro-watts (μW) milli-watts (mW) watts (W) kilo-watts (kW) mega-watts (MW)  3.00
   
At 13volts is 56 ohms.
At 12volts is 48 ohms.

Do we think  50 ohms is a good safe figure?

    

charlie99

charlie99
VIP
VIP
47 ohm 5 watt resistor seems about right to me ...and a preferred value you might find at jaycar    about 50 cents


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

Rick G

Rick G
admin
admin
Yeah I doubled it twice now I think about it. Got a lot on the mind at the moment.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1999 K1100 LT with a Big Block 1200
    

Mossy1200

Mossy1200
Platinum member
Platinum member
Thanks guys.
We have a Jaycar store in Wellington so ill pay them a visit.

Idd likely have built the café racer and got about 18amps of ignition firing away from home before my battery went flat without your help.

Next question is how far would that have got me with headlight also drawing 55watt also and calculating about 50kg weight savings on the bike with a moderately fit bloke how long would it have taken to push my bike home?

    

Two Wheels Better

Two Wheels Better
Moderator
Moderator
Recognising that this is an old thread I thought I'd have a read, musta missed it when it was happening. I've been riding my Big Block round the neighbourhood since Spring, well over 500 miles now. I have not had an instrument cluster of any type on it at all. I use my Android HTC set to a speedo app, mounted on a Ram mount for velocity readings.

Using my digital multimetre alligator clipped to the battery posts, at idle I get 13+ volts. At medium-low revs (no tacho) it registers 14+ volts. I've not had to charge the 9amp Lithium Ion battery since installing it. I am using a '90s-era 50amp alternator from a K11. What gives with the charge indicator light not being there? Is this thing simply 'residually' charging to peak efficiency?!

I've purchased Robmack's excellent mini board with input and output connection for the final drive speedo sensor's signal to work with my Trail Tech Vapor and will fit it upon my return from OZ in November, meantime, the speedo app does a swell job.


__________________________________________________
"A long ride is the answer to a question you will soon forget!" ~ Anonymous
1977 R75/7-100, '93 K11/K12 Big Block, '93 K1100RS, '95 R100 Mystic, '96 K1100RS, 2 x '98 K1200RS, '06 K1200R & '09 K1300GT
    

Rick G

Rick G
admin
admin
The current through the charge light (when lit) goes through the alternator to ground. This gives a tiny bit of magnetism to the rotor and that is enough to give it the kick needed to get going. If the rotor has some residual magnetism (left over from running) that is often enough to give it the kick needed and it will charge without the help from the current from the charge light.
Once the alternator starts charging the charge light has 12v on both terminals so there is no current through it and it doesnt light and naturaly from that when the alternator stops charging the light comes on.
Once the alternator starts charging it supplies its own current and is therefore called a self exciting alternator.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1999 K1100 LT with a Big Block 1200
    

Two Wheels Better

Two Wheels Better
Moderator
Moderator
We'll that's got me self excited coz I didn't wanna have to connect a light, minimalist that I is.

Thx, Rick. See you soon.


__________________________________________________
"A long ride is the answer to a question you will soon forget!" ~ Anonymous
1977 R75/7-100, '93 K11/K12 Big Block, '93 K1100RS, '95 R100 Mystic, '96 K1100RS, 2 x '98 K1200RS, '06 K1200R & '09 K1300GT
    

29Back to top Go down   Battery charging light - absolutely necessary? Empty Just put the bulb... Tue Sep 27, 2016 1:17 pm

Bumblebee

Bumblebee
Silver member
Silver member
I also have a 'Guzzi V-1000, 1981 model year.  The alternator warning light is necessary to get the charging system "started".  I had it fail once and the system didn't charge.  The 'Guzzi has an old style mechanical regulator.  I could go into all the "hows" and "whys" of why this is, but needless to say the lamp should be in the circuit.  LED replacement, will not work, putting a resistor across the LED to "dummy up" the lamp might work, a certain about of current needs to pass through the lamp to excite the rotor.  An incandescent lamp has some properties that an LED does not, mainly that it's internal resistance is less when the lamp is off, more when it's on.

With the K-100 system charging system is different, I have never had an issue with the charge warning lamp or the charging system, so I can't comment on that.

- John

http://Bugsmashers.org/phpbb
    

Two Wheels Better

Two Wheels Better
Moderator
Moderator
Same thing with Airheads; the bulb must be functioning for 'excitement' to take place. There are ways to trick it such as Motorrad Elektrik's bypass.


__________________________________________________
"A long ride is the answer to a question you will soon forget!" ~ Anonymous
1977 R75/7-100, '93 K11/K12 Big Block, '93 K1100RS, '95 R100 Mystic, '96 K1100RS, 2 x '98 K1200RS, '06 K1200R & '09 K1300GT
    

31Back to top Go down   Battery charging light - absolutely necessary? Empty One thing about LED's.. Wed Sep 28, 2016 12:18 pm

Bumblebee

Bumblebee
Silver member
Silver member
It's a diode, and unless is specifically deigned to run off 12 volts it will need a current limiting resistor in SERIES with the LED, otherwise the LED will draw too much current and burn out.

The old standard for this is 330 ohms, this will limit the current at 13.8 volts @ 41 mA, the current will be just a touch over 1/2 watt.  The actual value depends on the current requirement for the LED you have selected.

Here:

http://www.ohmslawcalculator.com/ohms-law-calculator

The calculator need two values, voltage is 13.8 volts, then pick a current to plug in, the rest of the fields will populate.

- John.



Last edited by Bumblebee on Wed Sep 28, 2016 12:22 pm; edited 1 time in total (Reason for editing : Added a neat-o link.)

http://Bugsmashers.org/phpbb
    

nods

nods
Silver member
Silver member
RicK G wrote:The current through the charge light (when lit) goes through the alternator to ground. This gives a tiny bit of magnetism to the rotor and that is enough to give it the kick needed to get going. If the rotor has some residual magnetism (left over from running) that is often enough to give it the kick needed and it will charge without the help from the current from the charge light.
Once the alternator starts charging the charge light has 12v on both terminals so there is no current through it and it doesnt light and naturaly from that when the alternator stops charging the light comes on.
Once the alternator starts charging it supplies its own current and is therefore called a self exciting alternator.
Thanks a ton Rick - this seems to summarise the whole thread quite nicely!


__________________________________________________
Chassis number0025951
Vehicle code0504
SeriesK589
ModelK 100 RT 84 (0504 ( 0505 )
Body typeK 100 RT 84 (0504
Catalog modelECE
Production date1985 / 01
Engine0514)
Transmission
Steering
CatalyzerNONE
    

Jlz52204

Jlz52204
New member
New member
Just replaced my regulator and cleaned terminals. No more charging light and got it from euro motor electrics.

    

Bumblebee

Bumblebee
Silver member
Silver member
RicK G wrote:Yes it is necessary to have it but often the residual magnetism will start the charging by itself. So consider yourself lucky but I would put a new globe in the light.

RicK speaks the truth!  If the lamp fails the alternator MAY not initialize, but my start due to residual magnetism.  Yeah, replace the lamp, it's not a big deal to do so, evil spirit
proofing!

Bumblebee.

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duck

duck
Life time member
Life time member
Question for the more electrically inclined:  When I use an LED in the cluster's charge indicator lamp it does not go out until I rev the bike up to say 2,200-2,500 RPM to get the alternator "excited" and then the LED goes out. (I understand that the LED goes out when it gets 12V from both the battery and alternator so that the net potential difference is zero - at least nominally.)

If I let the bike idle without revving it and the LED doesn't go out then the alternator does not kick in so continuing to run the bike eventually drains the battery to the point where the bike dies.

This occurs with both polarized and non-polarized LEDs.

Why is this revving required in order to bring the alternator to life with an LED but not with an incandescent bulb?


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Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
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Bumblebee

Bumblebee
Silver member
Silver member
duck wrote:Question for the more electrically inclined:  When I use an LED in the cluster's charge indicator lamp it does not go out until I rev the bike up to say 2,200-2,500 RPM to get the alternator "excited" and then the LED goes out. (I understand that the LED goes out when it gets 12V from both the battery and alternator so that the net potential difference is zero - at least nominally.)

If I let the bike idle without revving it and the LED doesn't go out then the alternator does not kick in so continuing to run the bike eventually drains the battery to the point where the bike dies.

This occurs with both polarized and non-polarized LEDs.

Why is this revving required in order to bring the alternator to life with an LED but not with an incandescent bulb?
This is not a good place for an LED.  The current drawn through the light bulb is what polarizes the alternator.  The LED draws less so this jurassic circuit might not (and it sounds like it's not) work properly with an LED.  Less current draw.  Keep an incandescent lamp in there, or put a resistor across the LED lamp.  If you want to keep the LED use a 1200 ohm resistor, a 1/4 watt will work, across the LED.  At least it worked for me.

Bumblebee.

http://Bugsmashers.org/phpbb
    

duck

duck
Life time member
Life time member
As long as you rev it a little after you start it and get the LED to go out everything works fine.  I've been running LEDs there in all of my Ks for well over a decade with no problems.


__________________________________________________
Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

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