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

"Tom Biasi" <tombiasi***@optonline.net> wrote in
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"Kris Krieger" <me@xxxxxxxxxx> wrote in message
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"Tom Biasi" <tombiasi***@optonline.net> wrote in
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"Kris Krieger" <me@xxxxxxxxxx> wrote in message
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Apologies in advance if this is a dopey question, but, when it
comes to recharging batteries, and using a solar cell to do that,
what I've been assuming, based on th info that peopl ehere have
kindly provided, and also that I've foind on-line, is that teh mA
output of the solar cells should not exceed 2/10ths to maybe
3/10ths of the battery's mA rating, and teh voltage produced by the
solar cells should be as close as possible to the total voltage of
the battery or batteries. But I wanted to check whether that
assumption is correct, becasue I think I'm getting closeto getting
some parts and trying a couple of assemblies.

Thanks In Advance!

- Kris

Hi Kris,
Different batteries need different charging conditions.
Look at the specs for your batteries.
The charging requirements will be discussed.
Some batteries may say: Charge at .1c for 10 Hrs.
This means to charge them at one tenth the AH rating for 10 Hours.
The VPC (volts per cell ) will also be specified.
For example: NiCads are about 1.2 VPC and can charge at about
1.3-1.5 VPC (follow manufacturers specs) at .1 -.3 c. (again, follow
specs.).

Ah, OK, that at least gives me a ballpark figure - thanks :) !

(I do try looking all these things up via Google before posting
questions, but often, I don't know the terms that will get me the
correct *type* of answer - IOW, if I want info about charging, I
don't want to look at endless lists of people selling battery
chargers, but the latter is the sort ofthing I've been having to
trudge through...so even just getting the right terminology has been
a huge help).

So if you have a 12 volts NiCad pack that would be a 10 cell NiCad
battery. If you are using lead acid cells, the numbers are
different. Keep in mind that photo cell manufactures inflate their
specs by using bright sunlight averages.

Tom



THe Max I'll use will be 4 1.2V NiMH batteries, for small lighting
units. What I'm trying to figure out is how to avoid "cooking" the
batteries ;) by putting in *too much* voltage, but I also want to
take into account the very thing that you mentioned, i.e. the
"brightest possible sunlight" rating for the cells.

I had bought some Malibu NiMH batteries at WalMart, but now i'm
looking at ordering something more along the lines of Energizers (for
example,
http://www.rei.com/product/719570?cm_mmc=cse_froogle-_-datafeed-_-
product-_-na&mr:trackingCode=B42A264C-BE3F-DD11-98CA-001422107090
&mr:referralID=NA or these
http://www.circuitcity.com/ssm/Duracell-AA-Rechargeable-Batteries-4-Pa
ck- DC1500B4/sem/rpsm/oid/52666/catOid/0/rpem/ccd/productDetail.do)
or one of the other known/name brands, because just today I read some
cautions regarding "bargain" batteries.

I at least found some interesting LEDs at
http://www.optekinc.com/viewparts.aspx?categoryID=53 , some of them
claim to put out 18,000umc average using 20mA and typical "forward"
voltage of 3.4, so that I can run off of a reasonable LED driver
(considering some Maxim items, or the "Micro-Puck").


ANyway, I'll look around and see whether ther eis info about
recharging. THis is good to know because, assuming I can do what i'm
intending, and call sell the units, I can also incoude costomer info
as to the best replacement batteries, should replacements be
necessary.

Thanks again :)

- Kris



When you search you may try something like "solar battery charging
tutorial" When you add 'tutorial' you will get better hits on your
search. BTW: NiMH have very fussy charging characteristics.

Thanks!, I'll try that.


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


.

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