| Author | Message | ||
     Azxb9r |
Does anyone know how much of an amperage load you can safely put on an xb charging system? I got a pair of heated gloves for xmas. I dont think the draw from the gloves should be a problem, but it made me wonder how much it would take to over tax the system. I have not yet found a spec. for what the charging system is rated at. | ||
| Reepicheep |
Its been discussed quite a bit on other threads, and its fuzzy. Gloves are no problem, and can be combined with a GPS with no problem. I think until you get into 50 watts worth of vest, with an extra 50 watts to run both high and low beam, and another 30 watts for gloves / grips, then the bike starts to fall behind at low RPMS. You can check it with a simple DVM... the Voltage Regulator will run a higher voltage then the battery at rest. So turn on the ignition (but don't start the bike), and measure the voltage (anywhere) with a DVM. Then start the bike and let it idle and re-measure... it should be higher, meaning the battery is getting some charge even at idle. Then rev it slowly... the RPM at which the DVM voltage is no longer climbing, is when the Voltage Regulator is "throwing away" all the extra power. Mine is just over idle when the HID, high beam, GPS, and heated grips are all chugging away. | ||
| Azxb9r |
I was concerned about overworking that little generator. If you ask it to work at peak output all the time, it will fail sooner. The gloves draw 2A, I checked it with an inductive amp probe out of curiosity(slow day at work). So, what I really want to know is,what is this charging system rated at? I have had several customers with repeated alternator failures because they have added monster stereos to there cars, and worked the alt. to death. On a car you can remedy this with an alt. with a higher amperage output. On the xb this is not really an option. | ||
| Bumblebee |
The alternator on the bike is rated for 405 watts, that's just a touch under 30 amps, I run an electric jacket liner, (40 watts - 2.9 amps) with no problems what so ever. my guess is that you could draw up to an additional 100 watts (7.2 amps) with out any issues (smoking voltage regulator, flaming wiring harness, complete fuel injection zap-out...) at all. I wouldn't go too much over that though. | ||
| Ft_bstrd |
Strap enough stuff onto the bike so that the lights dim and then take one item off. Overworking the stator isn't the problem. Under working the stator and voltage regulator is the problem. Unused power is shunted back into the stator and is bled off as heat. Under work the stator enough, and you cook the stator. The voltage regulator must also absorb the excess charge and dissipate the heat. Once it get's cooked, it allows excess power to be sent to the battery or not at all. The 08 Uly's came with a SMALLER stator than the 06's or 07's. Why when the Uly probably has more powered crap strapped on it than any other bike would it get a smaller stator and not a larger stator? The larger stator installed on the 06 and 07 Ulys was TOO large, and unless you had a chandelier, a bank of KC lights, and a microwave oven, your stator can cook. I run heated grips and heated vest with no problems. | ||
| Azxb9r |
When I got home from work, I looked through my repair manual and found a spec on the alternator. It is rated at 34 amps. Ft. b- an alternator produces more heat as amperage output increases. Amperage increases with load.The smaller the load,the lower the output. You can not underwork an alternator, but you can overwork one. As far as why the 08 has a smaller stator than the 07, you will have to ask the engineer that made the change. It could have been to cut cost or weight. Losing some reciprocating mass may have been a worthwhile trade. Getting back to my original point with this thread, with an output of 34A from the charging system it should not pose a problem to add 5-8A worth of accessories. Thanks for the input. | ||
| Ft_bstrd |
The faster the stator spins, the greater the power output. Unused power is shunted back into the system. I don't know which creates more heat, power generation or shunted unused power, but my stator cooked like a slab of bacon as did the voltage regulator and battery. I suspect the shunted power creates more heat. I also suspect the smaller stator wasn't used due to "over use" but I could be wrong. My understanding (which ain't much) is that it's a fixed magnet rotor system. As such, the output is dependent upon the speed of the rotation of the rotor and the stator windings. Weaker (less dense) windings would provide less output. Run the stator at near redline unloaded and it is still generating power at peak. Is this correct? Now if the power output exceeds usage, the power get's shunted back into the system. This shunting causes heat. Load it up and you aren't shunting as much unused power back into the system but you are adding heat from the loading on the system. Where am I wrong in my understanding? | ||
| Azxb9r |
If the alt. was producing peak output any time it was rotating, your theory would be correct. The thing is , the alt. does not produce peak output any time it is rotating. As amperage draw goes up, voltage goes down. When voltage starts to drop, the regulator responds and "excites" the field windings to bring voltage into the specified range. When voltage rises due to a decrease in load, the amount of time that the field windings are "excited" decreases. Alternator output is limited to what is needed at the time. Have you ever heard of full fielding an alternator? It is how you test peak output. Basically, you apply constant voltage to the field windings. When you do this, you will here the alternator scream,and there is a noticeable increase in the amount of energy needed to turn the alternator. If you where to leave the unit full fielded, it would not be long before it cooked itself. Basically, the alternator is constantly being turned on and off to control its output. The throttle does not always have to be wide open.  | ||
| Reepicheep |
Axb9r, you are describing an alternator beautifully, but the Buells have a simple fixed magnet field stator. No field windings, just permanent magnets. My Kawasaki KLR-250 has a virtually identical system. On the down side, this produces variable output with varying RPM, and is ultimately more limited in the power it can produce. On the upside, short of physically shattering them, you will never break or wear out a permanent magnet. And there are no brushes to wear. The Voltage regulator is even more simple and primitive, but elegant in it's on simple way. | ||
| Reepicheep |
Oh, and to answer Ft Bastards question, all the "extra" power gets shorted to ground through the voltage regulator. The voltage climbs until it hits the reverse breakdown voltage of a zeener diode, at which point it triggers the gate on a Silicone Controlled Rectifier (think a diode with a switch that is turned on by a current). When that gate gets triggered, the SCR shorts to ground. Now not all that power is disspated by the SCR / Voltage regulator. The stator has a fixed resistance, as does the wiring in between, and there are voltage drops on the diode bridge and SCR. But the bulk of the power is turned into heat on the Voltage Regulator and Stator. | ||
| Ft_bstrd |
Thanks Reep. I knew I wasn't describing it right. It's a linear output system on the stator side between idle and redline. The faster you go, the more power is generated. The only thing that prevents too much power flowing into the system and battery is the VR. Accessories would bleed the power off as well. The more power the accessories draw the less "excess" power must be shorted to ground and diverted back into the VR, wiring, and stator. | ||
| Azxb9r |
I am fairly new to motorcycles, but have a quarter century in auto repair. I seem to have made the mistake of assuming that an alternator is an alternator after glancing at the wiring diagram. I need to remember that not everything is a direct jump from cars to bikes, and look at the manual more closely. Using a zener (or clipping) diode to control voltage is ingeniously simple. It also explains why the voltage regulator is mounted where it is, you need to cool that heat sink somehow. | ||
| Ft_bstrd |
Yup. You shoulda seen my burned stator and VR. | ||
| Azxb9r |
btw, my main concern about loading the system was based on my desire to "keep the smoke inside the box". I feel a bit more comfortable about adding accessories now. | ||
| Ft_bstrd |
Cool. I just want to keep the smoke out of my primary. If I lose another, I may be shopping for a custom wind to reduce the peak output. |
