AC> -> So I connected a permanent diode in a lead from each of the panels.
 CH> But you lost the .7 volt drop across the diode in the process...
 AC> That is NO great "loss". Solar panels operate at about 50% efficiency, 
o
 AC> charge a 12v battery you use a panel with an output of
 AC> about 30v. To lose 0.7v from a 30v source, is to "lose" just 3 percent.
Um, I'm not sure what sort of efficiency you're talking here, Alec, when the 
very latest experimental solar cells are getting to around 25%, and 
production ones are more like 15-20% tops?  Also, as I mentioned, 12V panels 
that I've measured usually run about 18-22V open circuit?
Kali - you remember Kali? - says that on really hot days the o/c voltage can 
drop to where a diode might start to be be a current limitation, but I've not 
struck that much loss with heat myself, and most panels are designed with the 
use of blocking diodes in mind anyway.
 AC> In a practical set up this is negligible compared with the
 AC> 50% loss permitted.
 AC> The intentional waste of 50% of the generated energy, is in
 AC> the interests of
 AC> maximum power flow. For every watt of electricity produced
 AC> by the sunlight,
 AC> half a watt is lost as resistive losses and half a watt is sent to the
 AC> battery.
Still can't figure this, but knowing engineers, I'm sure there's some tricky 
explanation :)  I mean I get needing headroom from o/c voltage for regulation 
into say 13.8V float plus the 0.7V plus wire losses, but this 50% figure has 
rather thrown me .. ?
Cheers, Ian
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