If you talk golf with another golfer and the conversation turns to wooden tees versus plastic tees, most players will probably die inside due to boredom. It’s not the most exciting topic but it is worth a consideration when you buy tees.
Of all the things you could read about in golf, you’ve chosen to read about rust. I agree it’s not the most exciting thing in the world but I promise to do my best and not make this as exciting as it sounds.
Rain will not ruin a waterproof golf cart charger. However, a standard charger made out of metal and left to weather continuously in the rain will be susceptible to rust, and if the interior is water-logged, the circuitry may fail.