Re: Unusual Battery Charging System
From: Robert C Monsen (rcsurname_at_comcast.net)
Date: 07/19/04
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Date: Mon, 19 Jul 2004 03:14:13 GMT
"Geoff" <geoffgalgon@earthlink.net> wrote in message
news:4f5b2278.0407181857.518f7841@posting.google.com...
> I'm going to be going into rural Nepal for 8 months starting this
> winter. I would like to be able to take pictures for this time.
> However, there will be no electricity. I've got a nikon coolpix
4500,
> which uses a Li-ion rechargeable battery (#EN-EL1) which is 7.4V /
> 680mA. The proprietary charger (#MH-53) takes AC at 100-240V and
> outputs DC 8.4V / 600mA. The MH-53 supplies only a slightly greater
> power than the EN-EL1 (5.04W vs. 5.032W)
>
> Anyway, I'd like to design a design a charger that acts as a
> substitute for the EN-EL1. I plan on doing this with a solar panel,
> which will probably end up being 7-10W, outputting, ideally at the
.6A
> that the charger would. However, I suspect that the panel will end
up
> being quite a variable source, and, as I don't want to damage the
> battery, I'll need to stabilize it to outputting at 8.4V/.6A.
>
> Now, I've never done this sort of thing before, but I've taken an
E&M
> class recently and would be confidant putting anything that's
> relatively simple together. Having done some research already I
think
> that if the panel put off a constant flow at .6A, then I could use
> something like the LM338 in conjunction with a few resistors (and
> perhaps a potentiometer, in case I'd like to re-use the system for
> something else) to regulate the voltage to the 8.4V. However, this
> will probably not be the case.
http://www.national.com/ds/LM/LM138.pdf
> details a 'adjustable current regulator' (on page 12) that looks to
be
> something, but I don't know. (help?)
>
> Ultimately, is there a self-contained object that I can build that,
> having a variable source put into it, outputs a pre-set current at a
> pre-set voltage? Or is there no way to get around not having a
> constant current to start with?
>
> Thanks for your help.
Bob Pease of National Semi did something similar, and its documented
here
http://www.elecdesign.com/Articles/ArticleID/4251/4251.html
His experience might help with your design.
Regards,
Bob Monsen
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