6V Old Motorcycle - LED Lighting

[lexer98]

Hi

I have a old motorcycle that uses a 6V system and is becoming very hard to get quality light bulbs. So my idea is convert a 12 LED Bulb 12V to 6V. I Took apart one I found out that the LED Driver outputs 9V.

My idea is using a Step-up converter with current limiter as a LED Driver. Is possible ?

Here is the step up
https://www.aliexpress.com/i/32900168398.html?gatewayAdapt=glo2esp 
and lightbulb
https://www.aliexpress.com/item/1005005537872656.html

Thanks

[Kim Christensen]

Does this motorcycle have a battery?
Or does the stock headlamp run directly off the magneto-generator on AC?

[lexer98]

It has a battery the idea is running the step-up converter from there.
The headlight runs AC but stop-light, turn signals and dash runs from the 6V battery. Dosn't have a starter

[joeqsmith]

I wonder if that will mess with your timer for the turn signals. 

[Kim Christensen]

https://www.aliexpress.com/i/32900168398.html?gatewayAdapt=glo2esp

I tried reading the description of that PCB and gave up... 

But it'll probably power the LED bulb OK when set to 12V output, in constant voltage mode.
ie: Set current limiting higher than max bulb current since the bulb has it's own current limiting circuitry.
The only potential problem I see is the minimum input voltage of 5.5V for that booster convertor. So maybe when it's idling and the charge current drops, combined with wiring voltages drops, the input voltage could go below 5.5V

[lexer98]

https://www.aliexpress.com/i/32900168398.html?gatewayAdapt=glo2esp

I tried reading the description of that PCB and gave up... 

But it'll probably power the LED bulb OK when set to 12V output, in constant voltage mode.
ie: Set current limiting higher than max bulb current since the bulb has it's own current limiting circuitry.

The idea is removing the original driver from the light bulb and connect directly the LED to the step-up. To improve efficiency

[Kim Christensen]

That would work too... Makes it non standard so if you sell the bike, you'd have to inform the buyer of the mod.
But I agree, it'll be more efficient. Keep a spare modified bulb on hand.

[lexer98]

That would work too... Makes it non standard so if you sell the bike, you'd have to inform the buyer of the mod.
But I agree, it'll be more efficient. Keep a spare modified bulb on hand.

Thank you for your time.

[BeBuLamar]

You can't find LED bulb that fits your bike and is running on 6V?

[lexer98]

I did a little test with a cheap XL6009 step-up and seems to work fine. Now i'm wating for the better step-up with current limiter to be more efficient

You can't find LED bulb that fits your bike and is running on 6V?

Not in Argentina, I see on ebay some special ones for old bikes like mine but is expensive to import.

[Zero999]

Have you tried a 12V lamp designed to work from AC? I have some 12V LED lamps which have a built-in current-limited DC:DC converter and they work from a 9V battery.

[djsb]

What is the make and model of the bike? We may be able to find a wiring diagram somewhere. Also, does your country have an equivalent to the UK MOT test?

[Zero999]

What is the make and model of the bike? We may be able to find a wiring diagram somewhere. Also, does your country have an equivalent to the UK MOT test?

I've been bitten by that before.

I smashed the indicator on my bike, so soldered a few bright amber LEDs along with a suitable current limiting resistor in the holder. Unfortunately it failed the MOT because it increased the flash frequency to above the acceptable level. Fortunately, it passed, when I put a suitable resistor in parallel which corrected the problem. It was only a temporary fix. I just replaced them both with LED indicators off eBay and of course I fitted parallel resistors.

[lexer98]

Hii guys thank you for the interest

Its a Suzuki AX 100. We have something similar to a MOT test but police here don't care. If you have two light and license plate you are good.

Today I tested the "Cree LED Lamp" with the better step-up. With the voltage set at 8.5v and current limited at 300mA the LEDs provide almost maximum brightness. From the 6v side consumes 700mA

Now I have another problem since it doesn't have a actual voltage regulator, if you reduce the load the voltage spikes a lot and cooks my battery. So probably I will install some 25Wwire resistor to ground to maintain 7-8v.

The electrical part is super basic, it a single phase coil that doesn't provide more 25-30W IMO

[/quote]

Have you tried a 12V lamp designed to work from AC? I have some 12V LED lamps which have a built-in current-limited DC:DC converter and they work from a 9V battery.

Do you have a link ? I think aren't available in Arg
 

[pienari]

 I have used this for led lights.
https://www.aliexpress.com/item/1005006588790243.html

There is adjust for time but voltage have to be close to 12v.
I modified 1 resistor inside and flasher works fine 10-15v now.

[Zero999]

I don't have a link because I bought it from my local supermarket. I took one to pieces and it would be fine up to higher voltages.

Have you tried it without the boost converter? One of the pictures says it'll work down to 8V, so it's worth a try.

It also says it'll work up to 80V and your voltage source is AC, so you could try a diode and capacitor voltage doubler circuit.

[pienari]

Usually 6v ac stator works fine with 12v ac/dc regulator without battery when led bulbs is used.
I have used 47000uF to 3x 47000uF capacitor bank to my old Suzuki mopeds.

[Zero999]

Usually 6v ac stator works fine with 12v ac/dc regulator without battery when led bulbs is used.
I have used 47000uF to 3x 47000uF capacitor bank to my old Suzuki mopeds.

Have you tried it without the regulator?

As far as your battery problems are concerned. You need a voltage regulator.

A shunt regulator is often used to regulate the battery voltage. This is basically a circuit connected across the battery, which limits the voltage by shunting excess current round it.

Another way is a series linear regulator. Which goes in series. A typical example is the LM317, but you'll need something with more current and there's the issue of it requiring a certain input voltage, above the output for it to work properly (drop-out voltage).

Have you looked into buying a regulator module?
https://www.racing-planet.co.uk/regulator-rectifier-p-173085-1.html

[pienari]

I think single wire regulator is only 1 tryristor without rectifier what led needs.

[Zero999]

I think single wire regulator is only 1 tryristor without rectifier what led needs.

There's no such thing as a single wire regulator. At least two connections to the power supply are required to form a circuit.

[pienari]

Yes you are right , my english isnt best but i mean there is common gnd (ac) in frame what messup everything.
It will work fine with ac but not dc conversion when negative is connected to frame.
Only workking system is disconnect the stator (gnd wire) from motor and connect both ac wires to the 4 wire ac/dc rectifier regulator.

https://m.media-amazon.com/images/I/61V6SE5C4HL._AC_UF350,350_QL80_FMwebp_.jpg

About 5 years ago some regulator like that in picture was 2 thyristor full rectified 4A.
But 2023 made chinese quality was terrible bad.
Half rectified 1 or 2 thyristors.
Filled with sand and no screws!.

[lexer98]

I have tried running the LED Lamp without the step-up and only works at high rpm (5000rpm >).
If the step-up setup doesn't work. I will install a coil and voltage regulator, flasher, battery etc from another single phase magneto motorcycle that is 12V from factory.

Thank you guys for the sugestions

[Kim Christensen]

I have tried running the LED Lamp without the step-up and only works at high rpm (5000rpm >).

Did you try Zero999's voltage doubler circuit?