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.