My RB433ah works as well as the RB333 it replaced. I power them with 15v maximum and 10.5v minimum. Doesn't require a diode.
Just out of curiosity, why did you choose a 24v solar system over a 12v system?
My thoughts exactally! We use 12v everywhere and a voltage stepper like this one (http://www.virtualvillage.com/12v-to-24 ... 2-013.html
) which works very well. We usually set the output voltage to 18V (almost everything will work with that) and it dosent matter what the input voltage is, it will still output 18V (tested it with a 5v-2A power supply and a 12v battery output voltage remained the same). Not sure if the stepper will step down IE 24V IN and 12V out.