This is from www.bigcee.com/klr650faq
How much power does the charging system put out?
Older models: 14V, 14A @ 8000 rpm (above redline!), newer models 14V, 17A @ 7000 rpm. We are unsure as to when this change took place, but the only part change seems to be the rotor (new p/n 21007-1283). You may be able to upgrade your charging system by switching to the newer rotor, but this is unconfirmed. The normal electrical load is around 9 amps for the headlight, tail and license lights, instrument lights. (The ignition system has its own supply coil, and does not drain the main charging circuit.) Then are the occasional loads, like the cooling fan, turn signals, brake light, etc. Generally, the KLR can handle at least one "high-power" accessory, like a high-wattage headlight, heated grips, heated vest, etc. The best way to tell for sure is to connect a voltmeter and keep an eye on the voltage while you are riding, under different load conditions.