Hitchcocks Forum

Hi all... My Bullet 500 from 2003 needs a new alternator. I converted the electrical system from AC/DC to pure DC. One of the reasons to do the conversion was to gain more power for the ignition system and the headlight. The headlight is 55/60 watts Motovision from our host, and the rest is LED. The ignition coil is a "Flamethrower". I ride 50/50 city traffic/open roads.

I have got more power now after merging the two sets of coils in the alternator. But something might not be quite right, even though I have done it as described and adviced. So eventually I will swop the original alternator to a new one just to get rid of any problems on the account of the electrical system on the bike.

Well, the question is: should I be looking for a single phase or 3-phase alternator? I know from a lot of old posts here on this forum that people are very happy about swopping to the 120 watts single phase alternator. Any people out there with personal experience with a 3-phase alternator on a Bullet?... all the best Jacob

The 120W Lucas RM21 single phase alternator from our hosts will be fine for a Bullet's needs, or the Sparx equivalent from Andy Gregory. These are supposed to have better output at lower RPM than the three phase, which sounds like what a Bullet needs:



http://www.tri-corengland.com/acatalog/ ... PX005.html



There is no reason why you couldn't run a 3 phase alternator, but they cost more to do the same job, and you'd also need to fork out for a 3 phase regulator/rectifier to go with it.

The only real advantage of the 3 phase alternator is the increase output at lower rpm.


Do you ride around town (low speed) with main beam on during the day, or do you use the 'pilot' lights?


Most of the time with a 3p alternator, most of the power created is simply being converted to heat. You are never going to need more than 120 watts, unless you added daytime running lights, a stereo, heated hand grips etc, and then you would want a larger battery too...

Hi Adrian and Tim... thanks for your input. As Tim says (and what I have read all over) the 3-phase produces more (a little more or more more?) power at lower speeds than the single phase, and I do a lot of city riding at low speeds. In Denmark daylight riding light is mandatory, but I can use the pilot light with a 10 or 23 watts quartz bulb. I can't imagine that I will ever install heated grips, a stereo or such things, but a USB power outlet might be a future option. Power surplus converted to plain heat sounds like a shorter life spand on the regulator/rectifier. As mentioned earlier only my headlight and ignition coil are heavy power consumers, the rest is all LED. 120 watts should be sufficient. I don't really need 200 watts. Price wise I believe that replacing the entire "power plant" on my bike will be the same either alternator I go for. .. I still love to hear from people with a personal experience with 3-phase alternators on a Bullet... all the best Jacob

After looking around the internet I see that both single phase and 3-phase alternators come with different amps values. So if a single phase 10,5 amp alternator produces 120 watts, does a 3-phase 10,5 amp also produce 120 watts? If so I still have a choice to make between single or 3 phase, because I believe 120 watts all together is sufficient for my use... Jacob

Lucas 3 phase alternators used to be rated at 180W for the RM24, though a few years ago you could also get a 3 phase from Alan Osborn which put out 132W. Confusingly you can get a high-output single phase alternator that's supposed to be good for 200W.



Perhaps you actually need to speak to someone like Alan Osborn on 01953 884681 or Paul Goff 01494 868218 (office hours only) to discuss the actual merits of the different types for your Bullet.



A.

Hi Adrian... I thought that all the different ratings and values that comes with each alternator could be calculated into an approximate answer on whatever value wanted. We know newer Bullets has a 12V system. Mine is DC only, so I need a 2 wire single phase or a 3 wire 3-phase alternator. Alternators are marked with an amp value (10.5, 14.5 or 16). Should this not be enough to do some math when finding out how many watts they are delivering? Or will there be a difference in calculating watts on single and 3-phase alternators? Or maybe Volts and Watts are not the two vlaues needed to do the math?... Jacob

The markings usually show the peak output, (watts or amps) at a certain rpm, lets say 6000rpm so as to give some sort of bench mark standard..

Using Watts= Amps X Volts we can see that 10.5 amps times 14.4 volts (charging voltage) = 151.2 Watts..

Total up your required wattage, ie headlight bulb, brake/ tail light, ignition.

Forget indicators/horn as only occasional use.. Add 20% extra as a margin and that should be sufficient as maximum output required..

A 10.5 single phase and 3 phase both deliver the same peak, however its the way they deliver thats different.

Single phase drops to zero volts 3 times per cycle (6 coil) whereas a 3 phase never drops to zero and is 3 times more efficient in delivery at lower revs..

Out of curiosity what seems to be the problem with your modified set up??.

Hi Gwilly... this is really useful information to me. It means that I can start calculating on the electrical set up for the bike. The headlight is maximum 60 watts and tail/brake light is LED. as the rest of the lights. Ignition coil is a Pertronix FlameThrower 3 Ohm. At the moment I don't know how much power it uses. And then comes the MMB thacho; it's electronic and doesn't use much power... Well, what's wrong with my modified set up? Honestly I don't know. I have had to disconnect the tacho since the needle moves up and down the scale with no steady reading of engine revs and I can't explain why it's behaving like this. The original reg/rec unit is over charging and my aftermarket reg/rec is bust from too much power from the alternator. Even though the headlight is connected to the battery is goes slightly dimmer at red lights. And then I have the occasional blown LED bulbs caused by too strong current. After all it's just little things, but they are there and it's not supposed to work like that. Also I wan't my tacho to work right. Only thing that does not behave a little odd is the engine. The bike runs great. If I can cure all the misbehaving by swopping to a 3-phase alternator I will consider this seriously... Before deciding I need to do some road test connecting one alternator coil circuit at the time. May I have connected them out of phase from the beginning (they are connected producing the lowest Volts)... all the best Jacob

The 3 ohm coil works out about the same as the main headlight 69.12 watts..

Lower voltage reading is correct for AC connections, Reckon higher reading is actually a spike when out of phase..

Have you considered replacing the reg/rec with a boyer power box, has an internal condenser which may help smooth power delivery..


http://www.boyerbransden.com/pdf/Power_Box.pdf