On (18 Nov 97) Alec Cameron wrote to Ian Woofenden...
 AC> Solar panels operate at about 50% efficiency, to charge a 12v
 AC> battery you use a panel with an output of about 30v.
 IW> Where are you finding PVs with this sort of output? Most
 IW> panels available here are around 20 to 22 volts open circuit
 IW> voltage.
 AC> I say, about 30 volts.
Are you saying that 20-22 is "about 30 volts"? I'm not following
you.
 AC> I run a 16v system- paralleled 12v auto batteries, the lot in
 AC> series with two industrial wet nickel alkaline cells.
16 volt nominal? First I've heard of that.
 AC> I wouldn't disagree with you on your 20/22 v values but I
 AC> assure you, if a source can only deliver 20v at open cct then
 AC> it will not deliver its maximum power at 12v, and much less at
 AC> 13.8v.
The typical panel around here runs at about 17 volts at max power,
according to catalog specs I'm looking at.
 AC> No very great loss, except for those economical installations
 AC> like off- the - grid rail signals, water navigation lamps and
 AC> isolated public phones. These tend to rely on trickle charging
 AC> from the panels, without the luxury [and vulnerability] of a
 AC> regulator.
That's hard on batteries. But they probably see the batteries as
expendable and replace them on a schedule.
                        Ian
... Double your computer speed -- plug it into 220 volts.                     
 
... "Liberty lies in the hearts of men and women.  When it dies there, no
constitution, no law, no court can save it." -- Judge Learned Hand
--- PPoint 1.96
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