Hi All, does anyone know how many Amps the 720w alternator puts out on a 2011 R1200GS ?? Thanks in advance. Geoff
actually it's E=IxR... "E" is the concept of electromotive potential, which is measured in Volts. "I" is the concept of the intensity of the current which is measured in Amps (6.241 × 10<sup>18 per second) </sup> "R" is the concept of resistance, measured in ohms. and one measure of power.... "watts" (named after James Watt)... is: P= IxE so it's 720/system voltage (12ish).... but the engine speed plays a part too.... max electrical power is delivered at higher engine RPm... you get the picture?
Approx. 60 at mid to high rpm(watts/volts=amps). I'd design at 40 and you'd still have a good margin for error.
Geoff, hi! Your bike should be putting out 60 amps at 12 volts, which gives you 720 watts (60x12=720). Max's BMW fiche shows a 60 amp alternator. But here's the confusing part. Generally an alternator is producing 14 volts, or just under that. Many manufacturers and aftermarket suppliers will quote their alternators as putting out 700 watts (50amps x 14volts = 700watts) and 840 watts (60amps x 14volts = 840 watts). Then others will do the wattage calculations based on 12 volts, which people can relate to because they have a 12V battery. It's the same battery, obviously. In your case, the fiche confirms 60amps. Is this helpful? Liz <table style="max-width: 520px; min-width: 520px; width: 520px;" border="0" cellpadding="0" cellspacing="0"><tbody><tr><td align="center"> </td> <td valign="bottom"> </td> </tr> </tbody></table> <table style="width: 512px; border: solid 1px #666;" cellpadding="0" cellspacing="0"><tbody><tr style="font-family: Arial; font-size: 11px; font-weight: bold; background-color: #666; color: #fff;"><td style="width: 17px; border-top: solid 1px #666; border-bottom: solid 1px #666; border-right: solid 1px #666;" align="center">#</td><td style="width: 85px; border: solid 1px #666;" align="center">Part Number</td><td style="width: 235px; border: solid 1px #666;" align="left"> Description</td><td style="width: 30px; border: solid 1px #666; cursor: help;" title="Weight in Pounds" align="center">lb</td><td style="width: 35px; border: solid 1px #666; cursor: help;" title="This is the recomended quantity. Price is for each one. Once you click on BUY, you will be able to specify how many items you want to add to your cart. 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border-bottom: solid 1px #666; width: 100px;" align="right">$0.79</td></tr><tr style="vertical-align: middle; font-family: Arial; font-size: 11px; background-color: #ddd;"><td style="width: 17px; border-bottom: solid 1px #666;" align="center">04</td><td style="width: 85px; border-left: solid 1px #ddd; border-bottom: solid 1px #666; font-weight: bold;" align="left"> 46 62 1 453 668</td><td style="width: 235px; border-left: solid 1px #ddd; border-bottom: solid 1px #666; font-family: Arial Narrow;" align="left"> CAP - M6</td><td style="width: 30px; border-left: solid 1px #ddd; border-bottom: solid 1px #666;" align="right"> </td><td style="width: 35px; border-left: solid 1px #ddd; border-bottom: solid 1px #666;" align="right">1 </td><td style="border-left: solid 1px #ddd; border-bottom: solid 1px #666; width: 100px;" align="right">$0.60</td></tr><tr style="vertical-align: middle; font-family: Arial; font-size: 11px; background-color: #fff;"><td style="width: 17px; border-bottom: solid 1px #666;" align="center">05</td><td style="width: 85px; 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font-family: Arial Narrow;" align="left"> PULLEY</td><td style="width: 30px; border-left: solid 1px #ddd; border-bottom: solid 1px #666;" align="right">0.73 </td><td style="width: 35px; border-left: solid 1px #ddd; border-bottom: solid 1px #666;" align="right">1 </td><td style="border-left: solid 1px #ddd; border-bottom: solid 1px #666; width: 100px;" align="right">$50.38</td></tr><tr style="vertical-align: middle; font-family: Arial; font-size: 11px; background-color: #ddd;"><td style="width: 17px; border-bottom: solid 1px #666;" align="center">08</td><td style="width: 85px; border-left: solid 1px #ddd; border-bottom: solid 1px #666; font-weight: bold;" align="left"> 07 11 9 904 701</td><td style="width: 235px; border-left: solid 1px #ddd; border-bottom: solid 1px #666; font-family: Arial Narrow;" align="left"> WASHER</td><td style="width: 30px; border-left: solid 1px #ddd; border-bottom: solid 1px #666;" align="right"> </td><td style="width: 35px; border-left: solid 1px #ddd; border-bottom: solid 1px #666;" align="right">1 </td><td style="border-left: solid 1px #ddd; border-bottom: solid 1px #666; width: 70px; color: #555; font-weight: bold;" align="center">NA</td></tr><tr style="vertical-align: middle; font-family: Arial; font-size: 11px; background-color: #fff;"><td style="width: 17px; border-bottom: solid 1px #666;" align="center">09</td><td style="width: 85px; border-left: solid 1px #ddd; border-bottom: solid 1px #666; font-weight: bold;" align="left"> 07 11 9 901 102</td><td style="width: 235px; border-left: solid 1px #ddd; border-bottom: solid 1px #666; font-family: Arial Narrow;" align="left"> HEX NUT - M22X1,5</td><td style="width: 30px; border-left: solid 1px #ddd; border-bottom: solid 1px #666;" align="right">0.11 </td><td style="width: 35px; border-left: solid 1px #ddd; border-bottom: solid 1px #666;" align="right">1 </td><td style="border-left: solid 1px #ddd; border-bottom: solid 1px #666; width: 70px; color: #555; font-weight: bold;" align="center">NA</td></tr></tbody></table>
The only thing you need to know is that if things get a bit dim, turn the gerbings and a few lights off
Liz did a terrific job clearing up the confusion - it's just simply volts x amps = watts, with the caveats due to marketing (basing claims on 12V versus 14V outputs). (With due respect to other posters, being an anal engineer myself, I could not resist. Your replies are a bit out of topic: electromotive potential does not exist; electromotive force is an obsolete term used in early days of tinkering with electricity; voltage is a difference of electric potentials. But I digress...) Here is what the OP should really know: the alternator on your GS is powerful enough for most of accessories while you are at speed. Don't sweat it. I've been running fog lights, driving lights, heated grips and heated vest at the same time, without any issues. However, at low RPM's, you may not be getting enough juice - especially if you are powering a lot of lights and heated gear. The proper way to watch that is with a voltmeter: once your system voltage starts dropping below 13.5V, it's time to shed loads. There are many solutions available; what I am using is a $25 themometer/clock/voltmeter from Cycle Chrome (? - search the Web) - my installation is shown below. The meter is not waterproof, but with the little metal shield around it I never had any trouble.
Approximately 55 DCA is about the maxim sustainable load that should be applied. Based on throughput via a 13.1VDC 6 cell battery (2.1VDC per cell).
60 amps is the rating and in the real world it will probably do even more but running constant at 90% of it's rating is a good way to shorten its life.
ha ha... ya, when I went to school some of the instructors were pretty adamant about confusing the concept with the measurement... it's a hangover, sorry if it confused the issue. anyway, the 60A is a nominal rating. I've tested countless generators that make more than rated... at least until they heat up, then maybe not. in any case, they are RPM dependent... putting around at low speed will not give you full output. best real world advise is as above, watch the voltage & if it drops too low for any extended time shed some load. whats too low? I would be OK with 13V... maybe even 12.7 as long as the battery was in good shape and didn't need a charge. thats me... YMMV. I have V-meters on my 2 ADV bikes
Thanks for your help too. I have just fitted 2 Aurora LED spot lights that draw 5 amps each so I have plenty in storage, maybe I'll buy another two, that way I can watch out for all the bloody Kangaroo's that keep trying to knock me off the bike at night . No chance of using heated grips or heated suits where I live, it's damn hot in summer and winter drops to 20 Celsius. Hardly ever rains either, we can ride 340 days a year. Thanks again Geoff.
Wow, your weather sounds AWFUL! And I actually mean it: I'd rather deal with (reasonable) cold; I hate heat. My motto is that I can always add clothing, heated or not, but there is only so much I can take off. More power to you! Back to your discussion: the power-output numbers for the alternator are meaningless, because no one knows the baseline: power consumed by bike's computers and fuel injection. This adds to the original lighting and then to anything else you install. In reality, you will need to rely on anecdotal evidence provided by us in the forums. For my part, as I mentioned, I have been running two 35W HID fog lamps, two 50W halogen driving lights, heated grips (about 40W total, I believe) and 50W heated vest without any issues. I had problems in traffic jams: low output from the alternator at idle (plus added load of brake light and ABS brake pump) would cause the battery voltage to dip. Never had a problem, because I'd start turning things off (voltmeter helps), but I have observed the battery going below 13V after 10 minutes of stop-and-go with all loads on. Something to remember. Robert.
Robert, hi! Please know I'm just trying to be helpful. As you may or may not know, my bike has a 'few' lights on it. When making the decision to put them on the bike, there was a lot of research done. Somewhere, and it would take me a while to go back and find it, but somewhere I came across the point that an R1100GS's system, with a 55W headlight on draws 200 watts. That wouldn't be when running the starter. That's what I used as a baseline for my light and gerbing set up. I'll post a photo below, with the explanation that the entire set up was free. The light bar is a leg off an old steel desk (still have three backups), the lights came off one of my old rally cars, from the days when Hella sponsored me, and the wiring harness was from Hella as well. Now the base wattage used for other bikes, like KLR's, 1200GS's, KTM's etc, I have no idea. You're right though, a lot of what we know is dependent on the hive knowledge of 200,000 of us ADV inmates. Some of that knowledge is scientifically backed, some is just "... this is what i think it is ... ", but all that is what's cool about ADV and how reading these threads stimulate our minds, don't you think? Enjoy, Liz
I have worked on at least 100 different types and brands of alternators over the years, and on thousands of units. Alternators are current limited. A 60 amp alternator at a HIGH RPM with a constant temperature and constant excitation current in the rotor will deliver the about the same amps at 6 volts or 24 volts. ( within a few percent.) The temperature will reduce the current. It is not uncommon to see 20% from hot to cold, although 15 % is more normal. Where the alternator is rated is mfg choice, usually it is cold so they show the best output. So lets assume Bosch rated this one at cold. Bosch is normally pretty good, so we can use 15% hot drop, and the 60 amp alternator would become about 51 amp at 14 volts. Load it to 12 volts, and the rotor current would also fall, so the amps would fall a few more. Yes, overload the alternator and the amps fall more. Still, that is a lot of amps for a motorcycle. Since this alternator does not have to deal with hot underhood air, it would probably never get really hot, so you might stabilize at at little higher amps. I expect you will always see at least 50 amps at higher RPM's. All wound rotor alternators behave pretty much the same way except for the hairpin Nippondenso units. those are very stout. Rod
So you have 2x 60 W of LED spots? That sounds like a massive amount of light to me. Are you trying to outshine the sun, or are they for some reason not as efficient as LED's normally are :huh? Or are they are just fused with 5A, because the circuit might draw 5A peak, and then draws much less when running? I guess I need to look up what Aurora LED spots can do... http://www.alibaba.com/product-gs/693975247/6_5_72w_Cree_combo_beam.html I guess I just learned that this is actually possible, impressive as it is...
Hi, they do have a 5amp fuse on the positive lead that comes off the battery, but I tell you what they are damn bright. They light up road signs during the day, I even had a bloke flash his lights at me this morning on the way to work indicating that I should turn my lights down Each light comes with it's own complete wiring loom thus suggesting that you only need one. So I have fitted 2 separate spot lights, I can turn one on or both.
