Well after a couple of PM's with Lyen, and talking about my 84 volt pack...my requirements could not be met with these convertors...so I went down the local dump and came back with about a dozen small mains power supplies form things like LCD monitors, video cameras, portable speakers, printers etc etc.
all ranging from 100 to 240 volt input and various outputs, from 5 volt to 18 volt. Well sticking 84 volt DC in to them, and they pretty much all worked.. Often taking a few moments longer to power up than if feeding them with 240v AC. SO now I have a variety of small SMPSu's all usable with 84 volt in.
So my problem solved, all with PSU's from the dump
Mongoose frame, Fox F100 forks,26x2.3 tyres
100V 20Ah LiPo
Lyen 18 FET 65 Amp,5304 in 26 inch Mavic rim
To illustrate the vain conceit that the universe must be somehow pre-ordained for us, because we are so well-suited to live in it, he mimed a wonderfully funny imitation of a puddle of water, fitting itself snugly into a depression in the ground, the depression uncannily being exactly the same shape as the puddle."
-- Richard Dawkins, in "Lament for Douglas" (14 May 2001)