The 'J' stator puts out 40+V at 4,000 RPMs. It's pretty flat from here up.
In comparison, the 'F' stator doesn't have maximum output until about 6,000 RPMs.
The single LED is a slick setup. However, I prefer the
Datel Voltmeter as it shows me the exact output at any given time. The advantage is that I can see even minor variations, which can indicative of an issue. Also, the Datel unit is well sealed. I've had no issues with either of mine over the past two years. The only wear has been some minor corrosion on the brass bolts. I've since cleaned them and put some dielectric grease on them.