ADVrider

Go Back   ADVrider > Bikes > GSpot > GS Boxers
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 10-09-2002, 01:52 PM   #1
2Laud 2Bro OP
Gnarly Adventurer
 
2Laud 2Bro's Avatar
 
Joined: May 2002
Location: MN
Oddometer: 304
Alternator output vs. RPM

Do alternator output Amps increase with RPM?
Max 50 Amps @ 14 Volts.

Think I'm getting a shot of heat in Gerbing heated clothing with higher RPM.

2000 1150GS
2Laud 2Bro is offline   Reply With Quote
Old 10-09-2002, 03:46 PM   #2
Frank Warner
Traveller
 
Frank Warner's Avatar
 
Joined: Mar 2002
Location: Sydney, Australia
Oddometer: 6,593
Well yes but ...

The alternator's output current is regulated by the 'voltage regulator' which tries to keep the votage at about 14 volts. If the voltage falls then the regulator tells the alternator to put out more current. If the alternator is puting out as much as it can at this speed then increasing the speed will result in more current.

The simplest way to monitor this is a voltage indicator.

50 amps at 14 volts = 700 watts .... you must have a lot of extras to drain that amount of power.
__________________
Regards Frank Warner
motorcycles BMW R80 G/S 1981, BMW K11LT 1993, BMW K75 G/S
http://www.geocities.com/fwarner_au/
Frank Warner is offline   Reply With Quote
Old 10-09-2002, 04:49 PM   #3
Prehensile
No Brain, No pain!
 
Prehensile's Avatar
 
Joined: Jun 2002
Oddometer: 258
I checked the factory Maintenance manual.
This has a standard alternator setup with a built in voltage regulator. So youíll have a baseline rpm at which max power output can be achieved. The book says that you can get nominal output at 1,000 rpm and then at and above 4,000 rpm you 'can' create maximum output.
In short, in order for your bike to carry a full electrical load the engine needs to be turning at or above 4,000 rpm. Below that the power output varies. Most systems are designed to create just enough power at idle to keep running. Often times the battery is taking up part of the load. Once youíve reached the peak alternator rpm, in this case at 4,000 rpm, increased speed doesnít create more power output.
If your vest is comfortable at cruise and then you do some start and stop stuff you would feel the temperature increase and decrease. Unfortunately the easiest way to check out the alternator is to hook up to the MoDiTec port. Try your vest on another bike or try something else out on your bike. Look at your headlight and see if it is dim at idle and gets brighter when you rev the bike. And how much stuff are you using when you use your vest? It is possible that your alternator is weakening and the load of the vest is exaggerating the varying power output. With the information given in the BMW manual Iíd say that the only thing I could be sure of is maximum power output. Hook up an amp meter, crank it up to 4,000 rpm and then put a load on it, all the lights the vest, whatever. You have to ask it for power to get power out of it.
You arenít burning any fuses and the alt light isnít coming on?
Prehensile is offline   Reply With Quote
Old 10-09-2002, 07:21 PM   #4
2Laud 2Bro OP
Gnarly Adventurer
 
2Laud 2Bro's Avatar
 
Joined: May 2002
Location: MN
Oddometer: 304
Thanks. When running above 4000 RPM I'm noticing the warmth. Typically running 3200-3600 rpm on backroads and on occasion bumping up the rpm's to corner, clear myself of traffic or just running through the gears getting up to speed.

Not having any trouble with the charging system or fuses, just wanted to know what was happening.

Jacket liner 77 watts
Gloves 22 watts
Heated grips ?? watts
Lights ?? watts
Bike draw ??watts

Concluding that the alternator at 4000 rpm can put out 700 watts or 50 amps @ 14 volts.

Thanks again for the advice.
2Laud 2Bro is offline   Reply With Quote
Old 10-09-2002, 08:05 PM   #5
Frank Warner
Traveller
 
Frank Warner's Avatar
 
Joined: Mar 2002
Location: Sydney, Australia
Oddometer: 6,593
You say (and I add some guesses)
Jacket liner 77 watts
Gloves 22 watts
Heated grips 50 watts
Lights 100 watts (standard lights only)
Bike draw 150watts (ingnition & fuel & some ABS)

total say 400 watts. Not a problem. When everything is working.

The best way of determining if the electrical system is working is to connect a VOLTMETER. Not an ampmeter. When the voltage is above 13.5 volts (say) then the alternator is supplying all the load and the battery is getting charged or charged enough. When the voltage drops below 13.5 (say) (and the bike has been running for a while -so you have restored some battery charge) then the battery is supplying some of the load - not a good long term thing.

Don't know if 4,000 rpm is enough for max power, but it should be at least say 90% of it.
__________________
Regards Frank Warner
motorcycles BMW R80 G/S 1981, BMW K11LT 1993, BMW K75 G/S
http://www.geocities.com/fwarner_au/
Frank Warner is offline   Reply With Quote
Old 10-09-2002, 08:31 PM   #6
Waco
Renegade Sickle Hound
 
Waco's Avatar
 
Joined: May 2002
Location: Waco, Texas
Oddometer: 14,967

Mount an oscilloscope on the handle bars and adjust it at about 80 mph.
__________________
Support the AMA.
Waco is offline   Reply With Quote
Old 10-09-2002, 08:58 PM   #7
Prehensile
No Brain, No pain!
 
Prehensile's Avatar
 
Joined: Jun 2002
Oddometer: 258
But, if during operation, the alternator output is greater than battery voltage, but less than system operating voltage, the alternator has a low output. Your voltmeter wonít do you any good in this instance. So you would need to at least to do a no load and load test of the alternator. Since he hadnít mentioned an alternator light or battery problems, dim lights, determining if the alternator were capable of running with a near maximum load would be to measure the load. Theoretically a problem like this may never affect the bike and only be noticeable under self-induced heavy electrical loads.
And BMW gives the figure of 4,000 rpm in its manual. I suspect like most vehicles this is the case because at 4,000 rpm my GS is cruising at 75-80 mph. Having an alternator that needs say 5,500-6000 rpm to put out max load would have you riding around at 100mph if you wanted to run a vest, extra lights, GPS, radar detector or whatever.
Prehensile is offline   Reply With Quote
Old 10-09-2002, 09:11 PM   #8
Frank Warner
Traveller
 
Frank Warner's Avatar
 
Joined: Mar 2002
Location: Sydney, Australia
Oddometer: 6,593
Quote:
Originally posted by Prehensile
But, if during operation, the alternator output is greater than battery voltage, but less than system operating voltage, the alternator has a low output.
That is most unclear. The output of the alternator is directly connected to the battery. No fuses - switches. Just wire. So the voltages must be equal.

To test the entire system I suggest a voltmeter is the simplest and quickest way to determine if a fault exists.
Testing the individual components was not my object - just a measurement of the overall system rather than a subjective "my vest gets hotter".

Possibly the battery is dragging the voltage down? We cannot tell because there is no measurement. (number)

Quote:
And BMW gives the figure of 4,000 rpm in its manual. I suspect like most vehicles this is the case because at 4,000 rpm my GS is cruising at 75-80 mph. Having an alternator that needs say 5,500-6000 rpm to put out max load would have you riding around at 100mph if you wanted to run a vest, extra lights, GPS, radar detector or whatever.
Me "But officer I have to run at this speed to keep my vest hot"
Hardcore "My CRO told me too"
Now what is your excuse Prehensile?

===
Most of the speed limits here are 110 km/h so that would mean that the max output would be at that speed? 69 mile per hour. 'They' could also gear the thing to do that speed. But I don't think they do that either.
I think they size things so that in normal city driving the thing will survive. Stop start city driving has a lot more load on it than highway stuff.
__________________
Regards Frank Warner
motorcycles BMW R80 G/S 1981, BMW K11LT 1993, BMW K75 G/S
http://www.geocities.com/fwarner_au/

Frank Warner screwed with this post 10-09-2002 at 09:17 PM
Frank Warner is offline   Reply With Quote
Old 10-09-2002, 09:22 PM   #9
Waco
Renegade Sickle Hound
 
Waco's Avatar
 
Joined: May 2002
Location: Waco, Texas
Oddometer: 14,967
Quote:
Originally posted by Frank Warner

Hardcore "My CRO told me too"
What the Hell is a CRO?
__________________
Support the AMA.
Waco is offline   Reply With Quote
Old 10-09-2002, 09:46 PM   #10
Frank Warner
Traveller
 
Frank Warner's Avatar
 
Joined: Mar 2002
Location: Sydney, Australia
Oddometer: 6,593
Quote:
Originally posted by Hardcore
What the Hell is a CRO?


You mounted one on your bike .... :eek:


Cathode Ray Oscilloscope

Can also be taken for a farm yard animal. Male version of a chicken.
__________________
Regards Frank Warner
motorcycles BMW R80 G/S 1981, BMW K11LT 1993, BMW K75 G/S
http://www.geocities.com/fwarner_au/
Frank Warner is offline   Reply With Quote
Old 10-09-2002, 09:58 PM   #11
Waco
Renegade Sickle Hound
 
Waco's Avatar
 
Joined: May 2002
Location: Waco, Texas
Oddometer: 14,967
Quote:
Originally posted by Frank Warner


You mounted one on your bike .... :eek:


Cathode Ray Oscilloscope

Can also be taken for a farm yard animal. Male version of a chicken.
Excuse my ignorance. I can't spell oscilloscope (without the aid of spell check) much less use one.
__________________
Support the AMA.
Waco is offline   Reply With Quote
Old 10-10-2002, 08:48 AM   #12
CodeMonkee
Geek Adventurer
 
CodeMonkee's Avatar
 
Joined: Jul 2001
Location: Orygun
Oddometer: 5,230
Quote:
Originally posted by Frank Warner
That is most unclear. The output of the alternator is directly connected to the battery. No fuses - switches. Just wire. So the voltages must be equal.
Yes and no. You would think so, but...

Here is what I have noticed after spending a lot of time going through my Airhead charging system and affixing a digital VOM to the handlebars to watch the voltage while riding:

1) The resting battery voltage has a lot to do with what the system voltage will be while the engine is running. On my system which has less than half the working capacity of an Oilhead, it may have quite a bit more effect on the system voltage, especially under load.

When starting out at a low voltage, say about 12.2 volts (a battery that has been discharged to 50%), then on my system it takes quite a while to drive the voltage above 13.0 volts, especially when I have a load. A lot of course depends on what RPMs you are riding at.

2) For detecting whether you are keeping up with the load, it is not so much what the system voltage is, but whether the system voltage is increasing or not. If you started out at 12.2 volts, the system may or may not show 12.5 volts when first starting out, but it should go up to about that much and start increasing steadily (by about 0.01 volts - yes that is hundreths) and keep increasing to at least 13.0 volts. You need about 0.3-0.5 volts to apply a charge to the battery. If, after riding for a while at good RPMs, you are maintaining about 12.5-12.7 volts and not increasing voltage, you are barely maintaining a somewhat charged battery. You aren't really going to lose much charge - your bike will not die, and you will be able to start it again if you stop, but you either have too much of a load or your system is not nominal. On an Oilhead I would check the system if this was happening to me.

If you are maintaining about 13.0 volts, you are keeping up with the load and giving the system a charge, but just barely. If this is your steady state then you are at the limits of your system. If you calculate you are within about 100 watts of your theoretical max capacity, then I would say you are okay. If however you are well below then something is probably wrong. It could be your battery is just not accepting a charge, or your charging system is not nominal.

I am being so verbose I have to continue in a new post.

FWIW,
LCB
__________________
'09 Husaberg FE570
'99 Beta Alp
'04 Ducati MTS - sold
Not all who wander are lost
CodeMonkee is offline   Reply With Quote
Old 10-10-2002, 09:14 AM   #13
CodeMonkee
Geek Adventurer
 
CodeMonkee's Avatar
 
Joined: Jul 2001
Location: Orygun
Oddometer: 5,230
If your system goes up to about 13.0 volts and then hovers there for a while, then after about an hour it starts climbing again, this means your battery is approaching a full charge. I have seen my battery (a brand new battery) hover around 13.0 volts for a while, then suddenly climb up to about 14.5 within about 10-20 minutes. This means the battery is now fully charged and the internal resistance of the battery is such that it won't take any more charge, and as resistance builds so does system voltage until it is limited by the voltage regulator. If the voltage continues to grow much above 14.5 volts, say to 15.0+ volts, then there is something wrong with the voltage regulator. I have an adjustable voltage regulator on my bike, so I can adjust the max voltage at full charge from about 13.5-14.8 volts. Most regulators are preset for somewhere between 14.0-14.6 volts at a particular temperature. IIRC, at higher temps the max voltage is supposed to be less, and many v. regs are temp compensated.

3) The battery. It is a lot easier to tell what is going on with your system if your battery is fully charged and a known good battery. I recommend charging the battery with a good charger, until it reads about 14.5 volts with the charger attached. Some chargers won't go that high and will limit the voltage, but it should go up to about 14.0 at least and hold it there for about 2 hours. This assumes several things; a) that your battery has proper electrolyte levels (proper level and equal levels), b) your charger is not pumping a lot amps through the battery - you only need about 2-3 amps. Some chargers don't have low settings and will pump 10 amps through the battery regardless of what the battery's state is - so know your charger, there are a lot of different ones out there. I have two; a cheapo blister pack that only goes up to 12.45 volts and then stops, that I carry with me on trips - it is almost useless, and I have a good car battery charger that has good battery state sensing and a low 2 amp setting. I need to get a good Battery Tender smart charger. You can fry a motorcycle battery if you improperly use a battery charger.

Once the battery is fully charged, remove the charger and the voltage will immediately start dropping. A few seconds after removing the charger the voltage will drop about 0.2-0.4 volts. In a few minutes it will drop below 13.0 volts. This is normal. Over the next 8-10 hours it will drop to somewhere between 12.6 and 12.8 volts. If it drops much below 12.6 volts within 24 hours (say to 12.4 volts) then you have a problem or your battery is quite old. If it is old then look into a substance called EDTA or get a new battery. After the first day or two the battery should drop about 0.02-0.03 volts if the ambient temps are around 70-80, less if it is colder. After a couple of weeks of not riding the voltage may drop down to about 12.4 volts and probably hover around that voltage for a while. This is normal, but you do not want the voltage to drop below 12.2 volts as this will damage the battery.

The above also applies to your battery after riding and the battery is charged up completely (voltmeter reading 14+ volts). However, unless you stop the bike immediately after riding at high RPMs, you will notice the voltage is less after riding. I ride out in the countryside, but I have to go through the city to get there and back. On the way back my battery voltage is dropping because I am running at lower RPMs and stopping at traffic lights, etc. - so the batter yis discharging. With my system it doesn't take long for the load to dishcarge the battery in stop-n-go traffic. If you have a voltmeter that works without the electrical system being on, then you may notice that after you stop the engine, the battery voltage may actually be increasing for a while. This happens when you have been discharging a well charged battery just a bit - it is a chemical power plant and it has some reserve power.

To conclude - I strongly recommend having a good digital voltmeter somewhere in the dash and knowing how its voltage relates to actual battery voltage (some show a lower voltage). Know how your bikes acts normally with a well charged battery under different circumstances.

I also recommend having a good and smart battery charger specifically meant for motorcycles.

Here is an good article on motorcycle batteries:

http://www.mcnews.com/mcnews/articles/battery.htm

FWIW,
LCB
__________________
'09 Husaberg FE570
'99 Beta Alp
'04 Ducati MTS - sold
Not all who wander are lost
CodeMonkee is offline   Reply With Quote
Old 10-10-2002, 09:17 AM   #14
CodeMonkee
Geek Adventurer
 
CodeMonkee's Avatar
 
Joined: Jul 2001
Location: Orygun
Oddometer: 5,230
Re: Alternator output vs. RPM

Quote:
Originally posted by 2Laud 2Bro Do alternator output Amps increase with RPM?
Yes.

Quote:
Think I'm getting a shot of heat in Gerbing heated clothing with higher RPM.
You probably will get more heat at higher RPMS and after you have been riding your bike for a while at higher RPMs. The system voltage will go up and this will mean more heat. This probably means that your system is working properly, but it is a good idea to have a voltmeter that will allow you to keep an eye on the system voltage while riding.

FWIW,
LCB
__________________
'09 Husaberg FE570
'99 Beta Alp
'04 Ducati MTS - sold
Not all who wander are lost
CodeMonkee is offline   Reply With Quote
Old 10-10-2002, 02:16 PM   #15
Prehensile
No Brain, No pain!
 
Prehensile's Avatar
 
Joined: Jun 2002
Oddometer: 258
Ok, weíve all measured whatís going into and out of the battery with our voltmeters. So, do we replace the $600 dollar alternator or the $75 voltage regulator? Or do you end up doing both? There is a difference between a $75 job and a $675 job and a corroded wire at the battery.
The idiot light is basically a voltmeter. It and a meter will alert you to a problem but they wonít necessarily tell you what that problem is. Once youíve ruled out the battery, wiring, various fuses, v-belt, and such, youíre left with an expensive decision. You can use a voltmeter to determine if the voltage regulator is operating properly with the engine running but you are still left with having to hook up an ammeter and measuring the output of the thing under a load to verify that the alternator itself is bad. For fun you could hook up a SunScope and use it as an oscilloscope to compare the three phases, sometimes the heat built up in the unit, especially as they age, can increase the resistance and things go ape shit like repeatedly wiping the rectifier.
Any way, what a good debate.
Prehensile is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 03:28 AM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014