Julian Ilett demonstrates his Arduino Solar Charge Controller. The new voltage and current sensors on the battery side mean that Watts in and Watts out can be measured and an efficiency percentage calculated.
He has mounted all of his Arduino modules to a piece of wood to keep everything nice and neat.
High efficiency values (96% – 97%) are achievable when the buck converter is stepping down from 18v to 12v. With a 72-cell panel and the converter stepping 35v down to 12v, the efficiency drops to around 88%.