Alternator Question?

[Greenwald]

Anybody have the specs for an '05 R1200RT, in terms of what the alternator output is, in amps?

Amps X volts (12v system in this case) = watts

Normally, about 400 watts are consumed by a modern motorcycle with onboard computer system. The balance is what you have left for accessories, such as heated grips, GPS, PIAA's, TailBlazers, etc.

However, my owner's manual does not provide this information.

Thanks.

[BLAST54]

According to the service manual , alternator puts out 660 watts at 14v max.

That would be 47amps by my figuring :scratch

Bill K.
Foster,RI
05 R1200RT
05 Vstrom

[RTs4me]

I think that I've read somewhere, that the bikes fitted with heated seats have a higher output alternator than those bikes without:dunno

Can anybody confirm/refute?:scratch

[Greenwald]

According to the service manual , alternator puts out 660 watts at 14v max.

That would be 47amps by my figuring :scratch

Bill K.
Foster,RI
05 R1200RT
05 Vstrom

Thanks - that leaves me about 260 watts to divy up among however many 'toys' I attach to the R1200RT.

Appreciate the info!

PS - Just looked at the BMW site and read the specs for the '07 R1200RT. States 720 watt alternator! Wonder if that is also true for my '05?!

[Greenwald]

http://www.bmbikes.co.uk/specpages/R1200RT.htm

Found It!!

720 watts it is!

[BLAST54]

From the sevice manual for the 05 RT:


12 31 - Alternator with drive and fasteners

Alternator manufacturer and type

Bosch



Three-phase alternator with integrated, fully electronic voltage regulator


Gear ratio, alternator

1 : 1.8


Alternator drive

Elasto belt 4PK582


Length of Elasto belt

582-4+4 mm


Maximum output power of alternator
Voltage 14 V
660 W


Maximum output current of alternator
at engine rpm 4000 min-1
55 A

[Greenwald]

Given the conflicting information, I will go with 660W, and play it safe.

Writing off approx. 400W for EFI and on-board computers on a modern motorcycle (per MCN), the remaining 260W is nearly eaten up already by heated grips, PIAA lights, a fan to cool my oil cooler and my TailBlazer bulb at the rear.

Thanks for all the feedback.

[deilenberger]

Given the conflicting information, I will go with 660W, and play it safe.

Writing off approx. 400W for EFI and on-board computers on a modern motorcycle (per MCN), the remaining 260W is nearly eaten up already by heated grips, PIAA lights, a fan to cool my oil cooler and my TailBlazer bulb at the rear.

Thanks for all the feedback.I don't know where MCN got the 400W figure from - but I suspect that is high by roughly a factor of 2X. I'd expect the FI on a modern BMW to draw 100W. The ABS will draw more (especially the pre '07 systems) - but not all the time, so it's an intermittent draw. Headlights/lights - you'll have to add up on your own since different Hexheads use different bulb configurations.

200W has been the number people have used for "house loads" on BMW's (with FI and ABS) for years - and people haven't been running the batteries down when riding. Take a look at any IronButt bike - and count the number of lights on it.. there is way more than 260W being used.

Your heated grips are probably 35-40W, the PIAA lights are easy to figure - perhaps 110W total, TailBlazer is only a few watts WHEN illuminated.

We'd need an inductive DC ammeter to really tell - dunno if there is such a beast (I think most are AC).. or a high-current load to measure the current across... then use simple math (V*A=W) and you have Watts being drawn.

[GSWayne]

Another way to check on power capacity is with a voltmeter (perhaps built into your GPS if you have one). As long as the voltage is greater than 13 volts when everything is running, then your alternator is keeping up with the loads. It should get up to about 14 volts to fully charge the battery.

[Greenwald]

Between PowerLet Products.com and deilenberger (dam -that guy really knows his stuff!), I feel I have a grip on my 'normal' power consumption (330W), and my accessorizing reserve (330W).

Normal Operation
Low Beams or High Beams (Incl. Modulator) - 55W
License Plate Light - 5W
Tail Light / Brake Lights (Incl. TailBlazer bulb) - 23W
Instrument Panel - 2W
Engine Control Module - 25W
Fuel Pump - 60W
EFI - 50W
PIAA Lights (Usually On) - 110W

Occasional Use
Cooling Fan for My Oil Cooler - 60W
Heated Grips - 40W

Stuff I Don't Have (Yet?!)
Heated Garments - 35 to 77W
GPS - 2 to 6W


660W comes from multiplying my 55 AMP alternator X 12 volts. PEAK wattage (often quoted as 720W) for the R1200RT comes from multiplying 55 amps X 13.1 volts, which is what the battery usually produces at mid to upper RPM's. The higher voltage is necessary to charge the battery while in use, as well as run systems.

However, the 720W output only exists at mid to high RPM's - sort of like periodically 'whipping the hamster' to get him to run faster. At idle or slower operation, you can't count on this much wattage - I'll stick with the 660W as benchmark for the R1200RT and consider anything the alternator pumps out via higher RPM's to be an electrical safety cushion.

[Greenwald]

Besides the devices and systems I just quoted, does anyone have the AMPS or WATTS of other 'add-on's' to BMW's?

I would be curious to know what is out there, in terms of accessories that still fall within my power reserve?

Thanks!

[deilenberger]

Besides the devices and systems I just quoted, does anyone have the AMPS or WATTS of other 'add-on's' to BMW's?

I would be curious to know what is out there, in terms of accessories that still fall within my power reserve?

Thanks!

This is a case where we need "such as"?

[Greenwald]

Such as....


Radio or CD Player?

Garmin Zumo?

AutoCom System?

[deilenberger]

Such as....


Radio or CD Player?
Probably no more than 100W - and very likely less.

Ignore the claimed output "watts" - they are typically bogus - really really bogus. Look at the fuse used. Divide it in 1/2 - then use it to get a close guess of power consumtion. If it's a 5A/2 = - 2.5A, 2.5A * 12.6V = 31.5W. I'm using a fuse factor of 2x current draw - that may or may not be accurate depending on how conservative the engineer was - so you could also NOT divide the fuse rating by 2 and be very safe in your calculation - in that case a 5A would indicate less than 63W max current draw.

Garmin Zumo?
Not enough to calculate. Less than 10W
AutoCom System?
Ditto..