There are at least 3 ways of charging it, and I've heard a 4th totally works, it just take a long time.
The problem is that with limited food and water supplies. If I had plenty of each, then I could do the drive to Astrape without the advanced rotors and instead install the solar panels (as there is only one set of 5 metal plates I've found). Solar power trickle charge is "probably" 4th.
Santorini usually explodes before I have a chance to visit it for its charger. Though maybe now that I've unlocked remote tram usage, I could park the rover at Santorini... Hmm I'll try that next actually.