maximum load for the alternaor

[OldDog]

I am going to use my heated jacket in winter. Does anyone know the power output of the alternator. My old Versys 300X struggled if the heated grips and heated jacket were in use at the same time.

 

[wspollack]

I am going to use my heated jacket in winter. Does anyone know the power output of the alternator. My old Versys 300X struggled if the heated grips and heated jacket were in use at the same time.

Yes, indeed. I have a friend in Montreal with a Versys, and he mentioned the same thing: that he has to be mindful of that output, only able to add very low-current-drawing additional lighting, that sort of thing.

In regard to the C 400 GT, according to the shop manual the output is 21 amps (p. 8):



Unfortunately, this doesn't tell us how much of this output is consumed by the normal functioning of the bike, such as the headlight, fuel pump, etc. Nor do we know how low that figure dips at lower RPMs (and that could be a significant drop).

For illustration, I had a Burgman 650 (well, two of them, actually, at different times). At one point, I had a multi-LED voltmeter on it (https://tuckerpowersports.com/products/led-battery-gauge). When I had my heated jacket on high, AND the bike was idling, AND I had auxiliary lights on, the meter would show its amber "uh oh" display (below 12V, I believe). What I did was replace 2 x 35-watt halogen bulbs in Motolights I had on it with 2 x 5-watt LEDs. That savings of 60 watts did the trick (or I could've turned down the jacket, or turned off the extra lights in stop-and-go traffic).

My points here are:

1) The wattage figure for the C 400 GT is pretty low to begin with, certainly nothing to write home about.

2) You'll never really know how much of that can be spared, and at what revs, until you give it a go.

So my suggestion is to give it a shot, but keep a very watchful eye on the volt display on the My Vehicle screen, particularly at higher heat settings and lower speeds (or stopped). I assume that there are knowledgeable folks here who can help out -- I'm not one of them, in this area, but for now how about we assume that if the display shows less than, say, 12.6V then you're overtaxing the system.

I had added, on my '22 C 400 GT, and will do so again, one of these days, on my '23, an external, fused, direct-connection to the battery (see my gallery, https://www.billanddot.com/C400GT/, for details). The purpose of that outlet is two-fold: provide a very easy connection for a smart-charger, and provide a very conveniently located spot to connect heated gear. Unfortunately, for purposes of this discussion, I never got around to actually plugging in a jacket liner on the '22. I mostly bring such a liner along for out-of-town trips; at home, I rarely ride when it's that cold, or when wet leaves start to accumulate on back roads (i.e., now), or the highway departments start to salt or brine the roads, or ...

Good luck on your quest for knowledge.

 

[byee]

I can definitely confirm at lower speeds the alternator is putting out nowhere close to 21 amps.

Living in the Vancouver, BC area in Canada, the nights do get colder in October and I often ride wearing a heated liner which draws about 6A on high. I do get a warning message on the TFT indicating the battery voltage is dangerously low riding at city speeds 30-35mph or 50-60kph.

I have reached out to a couple of companies inquiring if the built higher output custom stators for the BMW C400GT/X....nope.

I'm definitely interested if someone does find a company which rebuilds stators or sells replacement high current stators. I'm getting tired of the warning message while riding....make a decision on LED lighting or heated jacket liner.

Thank you!

 

[wspollack]

@byee: Good info, thanks for the report. For instance, I didn't even know that the TFT emits a warning about this (which is reasonable, since I've never seen the message).

A couple of follow-up questions, if you have a minute:

- So, to be certain that I have this correct, you did NOT getting a warning at highway speeds, when the alternator is nearer at its max output, correct?

- Did you happen to notice what the volts display showed, JUST BEFORE the warning was issued? I'm just curious is my stab at decent acceptable voltage -- which I hypothesized, in my post above, to be c. 12.6V -- was anywhere close.

In any case, nice to have your actual-case report.

 

[byee]

Hey Bill,

At higher speeds 80kph (50mph) I can have my heated jacket set to high, seat and grips set to 2 and my LED aux lights on with no issues…..no warning message. Battery voltage hovers just past the 14 VDC

I’ve also installed a CTEK battery monitor so I can visually keep an eye on the battery voltage without the need to switch over to the My Vehicle display.

I can definitely do a test to see what the battery voltage is when the warning is displayed.

 

[byee]

I need to correct myself in post #3

I do get a warning message on the TFT indicating the battery voltage is dangerously low riding at city speeds 30-35mph or 50-60kph.

Corrected statement - I do get a warning message on the TFT indicating the battery voltage is dangerously low while riding in city stopped at traffic lights as well as stop & go traffic.

Message is when the battery voltage drops below 12.0VDC. The warning message is not displayed as long the bikes moving and not idling. I’ve attached a picture of the warning message for reference.

My bad…..apologies to everyone for the confusion.

I hope the information is helpful.

 

[wspollack]

No worries. Thanks, @byee, for posting about this at all -- useful info for the rest of us.