T i m wrote:


Agreed. I was thinking that the nearer I could get to a (say) raw 12V
as a ideal supply the less regulation I might need? However, you often
deed a bit of an offset for active regulation so maybe I'd end up
looking for a 9V supply rail for the LED's? With yer std LM7809 type
regulators does that mean the surplus energy is going to be 'wasted'
in the reg?

LEDS of the silicon/gallium sort have typical forward voltages in the
1-3v region.

They need to be current driven. the cheap and cheerful wy is to bung in
a power wasting resistor. The better way is a SMPS that detects the
current and adjusts output accordingly. Essentially chop te DC to AC and
put an inductor in series to limit current losslessly - well fairly
losslesly anyway.

7809 is not what you want at all.



Of course most efficient isn't always
cheapest - 240v CFLs cost less than 12v ones.

By quite a percentage it seems. :-(

Econmomies of scale. If you have a large office or industrial space to
illuminate, you use ****loads of striplights. They are the most
efficient, and because they are produced in ****loads, they are cheap.

The mini ones are just as hard, if not harder, to make, and have
slightly more complex electronics. And probably slightly less efficient
electronics. And are sold in much smaller quantities for boat and
caravan type usage.



I have since found quite a few suppliers of 12V CFL's and it seems
they may be the preferred solution for remote buildings, stables and
sheds etc. ie, You can get kits with panel, battery and a couple of lv
CFL's.

Yup. I've got about 4 such in my camper van. No battery though. Just a
12v capable mini fluorescent pair with the inverters. YOu can in fact
get fluorescent torches as well.




While you could run a 5 footer at 240v, it would take a real long time
to replenish the energy used at just 5w.
Understood.

Really?. I don't understand at all. 5W is 5W irrespective of the voltage.


Then again if you only use it occasionally, and you've got more than
one 5w panel and a battery big enough to supply it for as long as you
use it, it would be ok. If.

Indeed, and that may well be the actual scenario / usage pattern.

I can run a couple of 12v fluoros, an occasional water pump, off a
nearly fsked leisure battery for a couple of LONG evenings before it
goes flat.

Many people with boats use solar panels to charge leisure batteries, and
run without mains of generator power at all.

Its not hugely efficient, nor is it cheap, but if te biats engine isn;
running, its reasonable compromise.



As an aside I've just bought a couple of ~1.5W 12V (not 12V but higher
of course) bare panels with the intention of making them up into fully
waterproof modules to fix the South facing wall of this house, where
it happens we park a couple of our motorbikes. A suitable non-latching
connector fitted in the right place on the bikes and the panels should
at least balance any background losses from alarms, and maybe even
keep them topped up and ready.

I think there could be a market for a long, narrow 12V 'charging'
panel that could be fitted on or on the wall underneath external
window sills. Not the ideal angle(s) maybe but probably better than
nothing and not 'obvious' to passers by?

Again, look at the caravan market. My caper has a mains to 12v SMPS
charger that is very compact and very efficient. Not weatherproof, but
that is simply a question of the right enclosure.

Meow is as usual disseminating a mixture, of truths, half truths and
mieleading stuff improperly understood.

If you want to go into a solar/leisure battery/12v lighting system,with
or without mains backup, go and find a caravan or boat specialist
suppliers. Everything you need will be there.

using an inverter to the run stuff intended for mains is a dubious path:
If you want to go THAT route, use a computer UPS - they will run a
complete mains installation from batteries for a period.

And then use proper full length striplights, not CFLs.