Honda 50 Alternator: Voltage Output From Windings?

[John1397]

TL;DR

How number of turns effects voltage

Have a motorcycle that has alternator under flywheel where the magnet spins around the outside. Looking at wiring diagram one end of windings goes to ground center tap goes to charging battery and third tap or longest part of winding goes to lights and battery, switch determines which part of winding. My question is I assume the longer or the more turns you wind on the greater the voltage output?

 

[jim mcnamara]

Moved to EE forums, will get more responses there.

 

[berkeman]

Summary:: How number of turns effects voltage

Have a motorcycle that has alternator under flywheel where the magnet spins around the outside. Looking at wiring diagram one end of windings goes to ground center tap goes to charging battery and third tap or longest part of winding goes to lights and battery, switch determines which part of winding. My question is I assume the longer or the more turns you wind on the greater the voltage output?

A Honda 50 (motorcycle?) engine is not going to have much extra power for accessories. Are you wanting to re-wind the alternator to get more power for other purposes?

 

[Baluncore]

My question is I assume the longer or the more turns you wind on the greater the voltage output?

A PM alternator will develop a voltage that is proportional to the number of turns, and proportional to the alternator RPM. Since it is used to charge the fixed voltage battery you should not change the number of turns.
Why do you ask ? Do you have a fault with the circuit ?

 

[Tom.G]

Summary:: How number of turns effects voltage

My question is I assume the longer or the more turns you wind on the greater the voltage output?

Yes.
This was/is common on the smaller bikes, as it avoids the need for a voltage regulator. The alternator has a relatively high impedance so it won't overcharge the battery. When the headlight is on, there is more total energy required so the longer winding is switched into supply the headlight load.

A trick to rapidly charge a dead/low battery was to get the engine started by pushing the bike then pop-and-release (rapidly engage then disengage) the clutch when in 1st gear. This usually takes two people, but doing it alone is possible on 150cc and smaller bikes. Then turn on the headlight but find the dead spot on the Hi-Lo beam switch where the headlight is not on. This switches to the longer alternator winding but with the headlight off, the extra energy then goes to the battery. Don't make a habit of this because the high charging rate shortens the battery life.

Keep the shiny side up!

Cheers,
Tom

 

[John1397]

A PM alternator will develop a voltage that is proportional to the number of turns, and proportional to the alternator RPM. Since it is used to charge the fixed voltage battery you should not change the number of turns.
Why do you ask ? Do you have a fault with the circuit ?

I found this online should be right "
6 to 12 Volt Conversion:

One of the most common modifications for mopeds is to convert them from 6 to 12 volts. There is one basic rule of thumb that should be followed to make it an easy transition. When the AWG number is decreased by 3 the area of the wire is doubled. Number 22 AWG is about twice the area of number 25 AWG. When the area of the wire is doubled, the current carrying capacity is doubled also, and the resistance is halved.

What this means is in a system of 30 watts at 6 volts, reducing the size of the wire by 3 AWG numbers will cut your amperage in half and it will double the voltage. Six volts at 30 watts would give 5 amps, while 12 volts at 30 watts would only provide half that or 2.5 amps. The 6 volt system might have 22 AWG wire which handles 7.0 amps, and for 12 volts, 3 sizes smaller, number 25 AWG handles 2.7 amps. The more copper that can be put on to a coil, the higher the output in watts. The maximum voltage the wire can handle is based on the insulation while the maximum current it can handle is based on the wire diameter. "

 

[Baluncore]

One of the most common modifications for mopeds is to convert them from 6 to 12 volts.

Why does it need to be converted ?
Are the lights going to be filaments or LEDs ?
Is there not a 12V replacement stator for the 6V model ?