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

Kris Krieger wrote:
ehsjr <e.h.s.j.r.removethespampunctuation@xxxxxxxxxxxxxxxx> wrote in
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Kris Krieger wrote:

ehsjr <e.h.s.j.r.removethespampunctuation@xxxxxxxxxxxxxxxx> wrote in
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[edited]


Only *after* I know all that, can I select the specific cells, and configuration therof...

- Kris

As you said, you are working backwards. You don't yet understand
that doing it that way can result in a specification for cells
that are "unobtanium".

Ed



"Unobtanium"??, it's a modest LED night-lamp, not an airport beacon :p

I *already* know the batteries and their output, and the input needed by the LED driver and what it will output to run the LEDs (which will run off the batteries at night) - those are not the problem.

To charge my 4 little 1.2V AA NiMH batteries, I have seen the following solar cells (and more, this isn't an all-inclusive list):
0.5V, 200mA
0.5V, 450mA
0.5V, 800mA
0.5V, 2000mA
1V, 200mA
2V, 200mA
3V, 400mA
4V, 25mA
etc.

I also know that, depending upon how I connect cells, I can up the Volts or up the Amps, or both if it's a series-parellel combination. The biggest Q. is the volts. I read that, using a 5V solar cell, charging time would be the battery mA divided by the cell mA, but what if it was a 2V cell, or a .5V cell?

Well, I'll write to Maxim, since it's their components I'm interested in. They can prob. best tell me the input I need for the battery-management IC.

- Kris


Sorry, Kris, but in terms of the necessary specifications,
you have posted nothing useful to make an informed design
decision. That is not an attack on you, it is just that
you are working in an area that is new to you.

Netting your problem out, you want to drive an unknown
(in terms of voltage and current) load for an unknown amount
of time with an unknown number (but less than 5) NiMh AA
cells of unknown capacity, said NiMh's to be charged with an
unknown number of solar cells of unknown capacity in an
unknown environment.

The key design question is: how much input power will be
available? The surface area of your device that will
be exposed to direct sunlight and that you are willing to
dedicate to solar cells will determine that, in terms of
the maximum that can be achieved. Obviously, the power
will be less if the device is in the shade or the cells
receive less than full sunlight for some other reason.

You are here asking for help - but _ONLY_ you can answer
that question.

If we don't know how much power is available, it is not
possible to say definitively if your idea is even feasible,
let alone specify how to do it.

Ed

.

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