alternator output?

[650mark]

anybody know how many watts the alternator puts out? '80 xs1100 special

[bikerphil]

FSM states 14.5V/20A @ 5000 RPM. There is some formula used to determine watts, I think it is amps X volts = watts so maybe 290 watts?

[natemoen]

No I think it is something like 226 watts.

[DGXSER]

Phil has the equation, volts X amps X power factor X sq root of 3 for 3 phase power. In this case, simply volts X amps. Which should be 290 watts.

[MPittma100]

I am curious

650mark,

I am curious as to why you would need the wattage output of the alternator. Is there something electrical that you are adding to your bike? Just being nosey.

MP

[natemoen]

Well, according to your equation then the XJ and the xs should have the same output.....

Other than the fact that there are other things that factor into the whole picture like wire size and number of wraps around the stator, or configuration of rotor and so on.

Like I said before, XS is somewhere around 226 watts and the XJ I think is somewhere in the230's.

[DGXSER]

Nate, The calculation is simply converting readings in Volts and Amps into equivalent Watts.

All of those factors you mentioned will change the output of the systen, but not the conversion of what the ouput is in volts and amps into watts.

As to the XJ and the XS having the same output. Well, if the FSM says the XJ system is supposed to put out the same amps at 14.5 volts, the same as the XS, then yes, the wattage of both will be the same. No matter what your measuring, if it is DC or single phase AC, then Volts X Amps = Watts.

[IanDMacDonald]

Lol, Ohm's Law is Ohm's Law.

[650mark]

i have an electric vest for winter time riding and it requires about 30 watts of power. the temps here in arizona are starting to cool off, some mornings down to the 40's, and i want to use the vest on my xs1100. 240-260 watts of available power will be plenty. thanks to all for the info.

[ViperRon]

These formulas will help but calculating true watts or power in reality is a little more complicated because as others have explained all factors related to wirring (resistance) have to be considered.

W = V x I or W = I2 x R or W = V2 / R
I = W / V or I = (W / R)2
V = (W x R)2 or V = W / I
R = V2 / W or R = W / I2




http://www.csgnetwork.com/ohmslaw2.html

[crazy steve]

No matter what your measuring, if it is DC or single phase AC, then Volts X Amps = Watts.

That's not 100% true.... For purposes of a vehicle or most DC systems, you can ignore the other factors as their effect will usually be too small to measure. But any AC system will have some reactance, sometimes a lot, which can skew the watts number. If you've ever been in an industrial plant that has a lot of electric motors and seen two 'power meters' on the service, chances are good that one is a watthour meter (which is what your house has) and the other will be a 'VAR' meter (volt-amps reactive); VAR is also referred to as 'power factor'. A poor power factor can increase the current needed by quite a lot compared to the 'straight' current number you'd get by just doing a volts x amps calculation. A poor power factor will have a penalty attached for power useage and is usually corrected by installing a capacitor bank.

[DGXSER]

Agreed Steve, power factor is part of the system effect. See my inital equation that included PF and, for three phase power, the sq rt of 3. I always refer to PF as the head on a beer. It is wasted energy that you never get the use of, and can not measure with a normal meter. And yes, it can effect the total power usage. In fact, if your commercial or usually industrial facility has a PF lower than 80%, the utility will charge you a boat load of money for supplying you more power than shows up on your normal electic meter. After all, they still generate that power, and send it to you over their pipes and wires, it just does not get read by the meter. For a while I worked for the local power company's ESCO arm. Sold PF correcting capacitor systems. Quick payback, and easy money.

Motor loads are the typical contributor to PF. Most other types of electical users have a PF very close to unity if not unity. Typically it is only quantifiable in three phase power applications. That is why I stated single phase power. Most motors that are single phase are so small, they do not have any real effect on total energy usage of a system. that was why I suggested you can ignore it on single phase and DC.

[IanDMacDonald]

Lmfaooo. This convo is great. But, I can assure you that the power factor on the starter, and alternator of these bikes was not a consideration in design. Especially since energy conservation was not a huge deal in the design of the motors at the time of manufacture.

And, it's my personal opinion that a lot of those companies that sold those cap banks were a scam. I'm sure those of us that are "in-the-know" with what I am talking about would agree.

With regard to the electric vest you would like to wear, I say you are just fine using it based off the electrics of our bike. If you wanted to start shaving some load off the system, you could convert the headlight to an aftermarket setup, same with the turn signals. My best guess is the headlight is one of the biggest draws on the system. Eliminate that, and you have plenty of play room to add accessories.

Not to knock you, but, I'm in Michigan with overnight lows in the 20's already which I have been riding comfortably in with the ride riding gear. Not sure if you are the bundled-up type.

[crazy steve]

I only brought this up so as to avoid confusion among those who don't have a full understanding of electrical theory. I could tell numerous horror stories of finding installs done by people who had a 'imperfect'/incomplete understanding and found a 'short cut' to making something 'work'... More than a few were outright dangerous. You and I know these differences, but not everybody does. I flinch when I see various equations posted without a clear explanation of what they're for, plus the problem that even if you try to give an explanation without the theory background a lot can go over their heads...

The one place where you see the most problems with DIYers hooking up electrical equipment is motors. Not being aware of the inrush (starting) current or the PF of the motor, they undersize the circuit which can lead to issues and sometimes fires... not good. For most electrical gear that the 'average' person will run into, volts x amps = watts will work, but not always. On most DC systems and certainly any vehicle, that's all you need or want...

[IanDMacDonald]

The electrical info given on this forum is invaluable to me!!! It gives a lot better understanding of how I can apply my knowledge better than what the manual offers. I have learned so much from this forum in this area that I am happy to pass on to others. There were days at Kettering where everyone would be so bored with the theory and laws being taught, that I would pull up the XS11 site or Triples site and give them a real-life example of ways we could apply it. One of the posts was your's Steve. Overall, these bikes can handle an add-on or two, but, nothing too crazy. The biggest errors I have seen with novice electrical connections with bikes overall is using too small of a wire gauge size, and the connector used. Quality of connection is always an issue with wiring in-general, and if you use some crappy crimp connector that will fall off with vibration, you are asking for trouble. Do yourself a favor and buy quality connectors, or break out the soldering iron and do it right.