When I used my BMW K1100RS/EMLspeed2000 sidecar here in Scandinavia in wintertime,I always dressed according the multiple layer system.The only electrically heated items were the handlebargrips( original BMW),gloves( Gerbring) and the helmvisor.(snowscooterhelmet from canada HJC).
The standard alternator of the BMW had never problems,but is if I remember correct 700W.The only time I stepped off the bike was when it was -38 after 2 hrs driving.The only thing is that the passenger in the sidecar always seems to get colder,though better protected,than the driver in cold weather conditions.
The winterdrivers with old BMW boxers used to covert their alternators to car alternators.At the time many used a daihatsu alternator that was driven by a belt and pulley system.The drivepulley replaced the original alternator rotor and the daihatsu alternator was placed on some homemade scaffolding above the LH cylinder( RH cylinder was already surrounded by the sidecar with a RH sidecar)
Rudolf
