Battery really only works as a capacitor to store power for large requirements such as winch and starter. While bike is running it should easily produce lots of power to run all your lights and all wheel drive.
i would suggfest you replace the battery so the excess power produced does have a place to go.
i got it figured out today called the dealer they said the charging system doest give huge loads without it because it's not supposed to be driven with a shot battery its supposed to just charge the battery and then everything uses the battery.
I know this is a little late, but ill throw it out there for anyone's future reference. the 4WD has a lot of difficulty working on a dead battery. the hubs are pulled in electronically and the 4WD is spotty if it works at all. I know this from experience on my 02 sportsman 500HO.
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