Re: Another Novice Q. - recharging - Volts and Amps

Peter Bennett <peterbb@xxxxxxxxxxxxxxxxx> wrote in
news:kea3641d48c8bkakmddm6t3s8ghlljgg4n@xxxxxxxxxxxxxxxxxx:

On Mon, 23 Jun 2008 22:46:24 -0500, Kris Krieger <me@xxxxxxxxxx>
wrote:

"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:SN6dnboY57y6pf3VnZ2dnUVZ_gCdnZ2d@xxxxxxxxxxxx:


May I suggest deep cycle sealed lead acid.

Tom


My main question is, are they easily replaceable? THey do seem to be
easier to deal with, but these units are going into things that I'll
(hopefully!) be selling, so I need to make it all as easy as possible,
and I know that people can buy the NiMH batteries pretty easily.
That's the only reason I've sort-of "fixated" on them. THat, and it's
easy to get the mA ratings that will drive the LEDs I want to use
(found one that uses 20 mA, and 3.4V average, but gives out an amazing
(to me) average of 18,000micro-candela, which is 226 lumens, which is
a bit more than is given off by a 20-watt incandescent bulb (220
lumens). With the LED driver (I think it was you who'd recommended
those), that should work out well and I could, I think, use two such
LEDs, which should be about the lumens produced bya 40 watt
incandescent bulb - which would be super!

Anyway, I haven't seen any drivers that I can recall reference running
off of anything other than NiCad, NiMH, or Lithium-Ion batteries,so my
impression was that those are the only two that have both enough
voltage, and generate enough current, to run the drivers. I've also
used store- bought solar lights, which had either NiCad or NiMH
(depending upon th etype), so I know those will work when left
outdoors.

So, it might very well be that rechargeable lead-acid bnatteries can
perform similarly, it's just that I don't know anything about them...

- Kris


Lead-acid batteries are normally large and heavy. Your car battery is
lead-acid, for example (although there are smaller sizes, and some
variations that don't have a liquid electrolyte, available). If you
are considering AA, C or D cells for your project, lead-acid batteries
are almost certainly not a consideration. I'm not aware of any
lead-acid batteries in a "dry cell" format.


AA only.

The background, in brief:

These will be fairly small-scale units that I can put inside of
stained-glass things ("lanterns", so to speak) that I design and
hand-craft, my intent being to sell them. So the batteries will be
just the normal NiMH things that pop into regular ol' solar
garden/accent lights. Since the betteries will eventually need to
be replaced, I'd like them to be things that people can find very
easily and that don't cost an arm and a leg. Someone (Tom B.?) had
recommended an LED driver, and I've been looking around at otehrs as
well (mainly to read teh application notes and datasheets and
whatnot so as to gain a better understanding), and Maxim posted a
nifty diagram for a combination current and voltage amplifier plus
an LED driver (in case it'd be helpful to anyone else, the URL is:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/3871 )
and I *think* that, for the input, I can use the output form a
combination battery+solar-cell charging+battery management circuit.

I know that I can build a super-simple unit that will drive one
normal-brightness LED; I found a few different schematics for simple
low-brightness units, and the simplest are little more tahn a solar
cell, diode, battery, resistor, and LED, with no sort of overcharge
protection or any other accomidation for any special needs that one
or another sort of battery might have. THey're robust, but they
won't work for me because these things will be lighting stained
glass, and even clear textured glass doesn't transmit as much light
as does a smooth clear enclosure (I think the commercial ones are
acrylic). Also, the potential customers and sales venues I've
polled all have the same complaint: commercial solar lights are too
dim. Ultra-cheap is not part of my equation here - I am most
definitely not going seeking to try to compete with the "$5-$9
light" market; Wal-Mart has that very well-covered. Rather, the
units, being handcrafted stained glass, will each be a minimum of
around $60, and prob. a lot more than that, depending upon the time
and skill it takes to construct a particular design. I do want to
squeeze as many Lumens as possible out of a *maximum* of 4 NiMH
batteries, to be charged during the daytime by solar cells, plus I
want to charge the batteries in about 5-6 hours in good sunlight -
and that last part is why I'm looking into overcharge protection,
since it's likely that some lights will receive 8 (or even mroe)
hours of good sunlight.

So that is why I'd asked about whether thre is any significance to the
relationship between the solar cell(s) V/mA rating, and the battery V/mA
rating - I don't want to "cook" the batteries.

TIA!

- Kris




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