Subject:
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R: RCX as programmable battery charger
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 14 Oct 2002 21:24:48 GMT
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Original-From:
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Camp0s <camp0s@(nospam)libero.it>
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Viewed:
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1025 times
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Thanks for that info, i also searched with google about maximum output
power, but the only thingh i got was 10 mA from the the microcontroller chip
and a lot about firmware, programming and other stuffs.
What i'm whising to do, is not just a "current producer for the cell phone
battery", it's something you put the battery into it and pressing two button
you can choose to:
fast charge;
discharge and then charge;
do many discharge/charge cycles;
keep the battery on with some pulse;
....and so on.
I've just few question before the practise:
the 350 Ma output is from a single output, or from all three outputs?
and, if i'm using one output i should do not use the others two if not just
for little power, for example lighthing those little lego lights ?
About the discharge, i just need to set the output to "reverse", setting a
"slow velocity" (so 1/8 pwm) and then check the voltage to not let it run
too much down (3 nicd--> about 1.2 v per battery, stop discharge at
3.6~3.4V) what could happen if i drain too much batteryes, about 2.7 V ?.
Last, monitoring the voltage. How can i do that done by the RCX ? just need
the 0~5V range, are there some RCX sensor preset?
About negative-pulse charging:
start cicle
max (350) milli amp charge for 1 second
2 millisecond rest
max (-350) amp Negative-Pulse for 5 milliseconds
10 millisecond rest where battery is evaluated and if everything is OK and
the battery in not yet fully charged the 1 second pulse cycle is repeated
end cicle
would this cicle be ok ?
-----Messaggio originale-----
Da: news-gateway@lugnet.com [mailto:news-gateway@lugnet.com]Per conto di
Terry King
Inviato: lunedì 14 ottobre 2002 21.53
A: lego-robotics@crynwr.com
Oggetto: Re: RCX as programmable battery charger
In article <NGBBLFNPCLBPEJNIJPOEKEIJCCAA.camp0s@libero.it>, lego-
robotics@crynwr.com says...
> I was looking at my 1 years old cell phone, its battery is deteriorationg
so
This could be done... I think. Learning how it all works is
enough of a reason to make a $100 microcontroller charge $10 batteries...
The Rcx outputs current limit at about 350 Ma, as I recall
(Info is on the WWW - search on "Rcx Internals" ).
The output voltage is about
1.5 volts LESS than the supply. I assume you'd run
this off a plug-in power supply.
So, let's say you want to charge 3 nicads, putting out
up to 1.5 volts into them. Decide what MAXIMUM current
you want to limit to, as use a series resistor to
limit the current. MAybe that would be something
like 100 Ma. So, figure it out, like this:
3 Nicads max voltage= 4.5
9Volts (Into Rcx) minus about 1.5 equals 7.5 out of Rcx
So you want a voltage drop of 7.5 - 4.5 = 3 volts at .1 Amps (100Ma)
R = Voltage Over Current R = E / I so R = 3 / .1 = 30 ohms.
A standard resistor value is 27 ohms. Ooops, how much POWER ??
P = E * I so Power (Watts) = 3 * .1 = .3 watts so you need at least
a 1/2 watt resistor.
Now, the Rcx has pulse width "speed" control, from full-on down
to on 1/8th of the time. It's fine to charge batteries with a pulse.
So you can set the current lower than your maximum by setting the
"speed". Oh, some Nicad and alkaline charges actually put a short
NEGATIVE (Opposite polarity) pulse thru the battery when charging.
Search on "Pulse Battery Charging" on Google.com
So, you can control charging current, possible negative-pulses,
and time. If you want to make a fast-charger, you may want to
measure temperature of the battery too.
There's plenty to start experimenting with!
--
Regards, Terry King ...In The Woods In Vermont
tking@waitsriver.k12.vt.us
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Message has 1 Reply:
 | | Re: R: RCX as programmable battery charger
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| (...) What you're trying todo is known as "reflex" loading. Search for it on the internet. The protocol is about this - load with 5 times the capacity for 1 sec (so it's full in about 10 minutes !!) - discharge with 50!!! times the capacity for (...) (22 years ago, 14-Oct-02, to lugnet.robotics)
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Message is in Reply To:
| | Re: RCX as programmable battery charger
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| In article <NGBBLFNPCLBPEJNIJPO...ibero.it>, lego- robotics@crynwr.com says... (...) This could be done... I think. Learning how it all works is enough of a reason to make a $100 microcontroller charge $10 batteries... The Rcx outputs current limit (...) (22 years ago, 14-Oct-02, to lugnet.robotics)
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