Forum

[JTL]

Hi Gwilly... If the ignition coil uses as much power as the headlight, I guess a 10.5 amp stator will deliver slightly too little power for the overall use on a running bike. Maybe a 14,5 amp stator will suit my bike better in the end. By the way, what is the math for calculating power consumption (watts) for the ignition coil or any other electrical component on a bike? And how do I measure how many watts my current stator is delivering? Another question, can I use the OEM rotor with a new more power producing stator (single or 3-phase)?... The idea to insert a condenser somewhere in the circuit has pop up before, so I bought one (4700 microFarad; 63 Volt), but have not yet installed it. I'm a little bit reluctant with buying a Boyer Power Box to fix my stator, if the stator is the problem. But I do need a new reg/rec. So stator and reg/rec issue has to be sorted out at the same time. This is why I'm thinking of buying a whole new "power plant" (stator, rotor and reg/rec) at the same time. And preferable a 3-phase system... Jacob

[ChrisD]

“The 3 ohm coil works out about the same as the main headlight 69.12 watts.”
Surely not, Gwilly?
Using the formula V=I/R, and using the given volts (12) and ohms (3) I get 36W for the coil. But it is only taking charge for ~2/3 of a cycle when the points are closed. So an average of ~25W is closer?
Or am I wrong?
Cheers, ChrisD

[Frank]

It's V=IR orI=V/R. 12/3= 4 AMPS not Watts. VxI=W so 12x4=48w. I think

[Gwilly]

Chris thanks for the input, it made me check again, always a good thing..

Frank's math is correct though long winded.. I must point out that i use the highest normal voltage expected and that is in the range 13.5 - 14.4VDC

Use P=V squared, divided by R, or Watts= 14.4 squared, divided by 3 ohms...

Trouble is things get complicated when modifying as cable sizing (amps) should also be born in mind if straying too far from standard..

[JTL]

Hi all... I really appreciate all your replies. There is so much for me to learn about electrics on a bike. Some useful info might be that the wiring is all new made up from 16.5 amp thin walled 1 square mm wire (http://www.vehicle-wiring-products.eu/p ... sq-32-0-20). If my ignition coil only uses 48 watts a 10.5 amp stator might be powerful enough for my bike. Using Gwillys figure (14.4 V) for charging, a 10.5 amp stator can produce up to 151 Watts, if I have understood the math behind it correctly. Please let me know if I'm wrong on this. My reason for preferring a 3-phase alternator is that it does not drop in delivering power at low speeds, which, if I understand things right, will secure less electrical flux (?)... Jacob

[ChrisD]

Frank – Thanks for the correction. Its been ~50 years since I’ve used that formula and still I got it wrong. So 48W for the coil whilst it is drawing current and zero while it isnt, so an averaged requirement for perhaps ~30W - so a 120W alternator should be OK. ChrisD

[Dennis C]

You can leave the 4700uf capacitor on the shelf, the bike already has a bigger one fitted but it's called the battery, you don't need both.

[JTL]

Dennis, the reason for buying a condenser was to help sort out my problem with flux in the electrical current. I have no problems in leaving it on the shelf, if I can just fix the flux one way or another. It was my impression that a battery would do so, but in my set up it doesn't. So I guess it can be the alternator causing the flux and my wiring design that let the flux has an effect on electrics on the bike. To be more specific: causing the tacho needle to move up and down on the scale instead of a steady reading of the revs... Jacob

[Dennis C]

Hi Jacob, reading back through this thread and also previously following other threads where people have converted the electrics from AC to DC on these bikes I think that it is always a dubious conversion, the inequality between the different sets of coils is always going to be a problem. Fitting a capacitor in parallel with the battery will serve no useful purpose, just change to the correct alternator and all should be well.

[Adrian]

JTL,



I think you're just going to have to go for it, choose a 3 phase or single phase kit as you see fit and stick it on there! I don't think either will be a wrong choice as people have been happy with both types. Follow the instructions, and with decent wiring and connections all will be well.



A.