To pull off this feat, he installed two sets of folding panels that generate 120 watts in good sun. The bike's batteries hold 2400 watt-hours, so a Michigan summer's 9 hours of daily sun charges the battery about 1/2 full. Don estimates his ride uses only 25% of that. So, even with the occasional cloudy day (unfortunately, not uncommon in Michigan) doesn't mean the bike is dead. But, just in case, the factory charging apparatus is still intact.
In order to ride, the panels fold in close to the body of the bike, and lock down. When charging, the panel's symmetric layout reduces the possibility of tipping in the wind (though Don tells us he is considering adding parking outriggers to protect against this). He also plans to add a protective skin to the sides of the panels to protect against gravel on unpaved roads.
Charging is handled by a regulator stored under the seat, with room left to still store a small bag of work gear. While no speed demon, Don says it's more than enough for his needs, and very reliable. His EVT 4000E has over 900 miles logged so far. When he's not riding it in the winter, the bike gets plugged into his home to add extra power back into the system.