Charging Batteries

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carl
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Charging Batteries

Post by carl » Thu Apr 18, 2002 2:37 pm

Can anyone help me with the charging requirements of LITHIUM ION batteries, ie: charge voltage, charge current, charge time

DICKEYBIRD
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Re: Charging Batteries

Post by DICKEYBIRD » Thu Apr 18, 2002 3:13 pm

Hi there,<p>I don't know the answer to your question but I'm very sure you will get a good response at http://www.rcgroups.com/forums/index.php?topic=ezone They use the Li-on batteries in electric motor powered "slow-fly" indoor R/C model aircraft. It's a free forum....just ask away and someone will answer!<p>Good luck!
Milton Dickey

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Chris Smith
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Re: Charging Batteries

Post by Chris Smith » Thu Apr 18, 2002 3:13 pm

You need to use a controller that pulses, measures temperature, and backs off etc for a fast charge. They are referred to as "smart" chargers.
Or, You can trickle charge them at 1/10 of the amperage for long slow safe charging.
The battery should be labeled as to how many AH its rating is @ what voltage if its a pack?

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MrAl
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Re: Charging Batteries

Post by MrAl » Thu Apr 25, 2002 8:25 pm

Hi carl,<p>The Li-ion batteries come in at least two types:
1. coke (4.1 volt float)
2. graphite (4.2 volt float)<p>Both types have almost no self discharge, similar
to alkaline batteries, but they require a little
more care when charging and discharging then
your typical common run of the mill battery.<p>With either type, you first regulate the current
to 1 amp or less, and after the voltage comes up
to 4.2v (graphite) you regulate the voltage.
The voltage set point has to be accurate to
within 1 percent however, so you cant charge
them to 4.25 volts and expect them to last.<p>In other words, you build a 4.2v voltage regulator
that also has a current regulation limit of 1 amp.<p>Because of the 1% voltage spec, you can't use a
zener or a 780X regulator to set the voltage
set point. You have to use a reference diode.<p>National makes Li-ion charger chips that do this
already, but dont usually have an adjustable set
point.<p>One other word of caution:
You shouldnt drain them down to less then
2.5 volts either, or damage may occur.<p>I'll probably be selling specially designed
charger boards in the near future that have
adjustable voltage output (4.1 or 4.2 volts)
and use fairly common parts, and supply a kit
of parts. Contact me if you are interested.
Projected completion time about 4 weeks from
now. The charger boards will run off of a
common 9vdc wall wart.<p>Now here's my question:
Where did you get your Li-ion batteries?
Im having a little trouble locating more
batteries. I have about 4 good ones now,
but because they turned out to be so
darn useful, i intend to get more if i can
find a source.
It's really nice to have 3.6v nominal from
one battery, that is rechargable, and doesnt
have much self discharge like the NiCds or
NiMH cells do.<p>Good luck with it,
Al
LEDs vs Bulbs, LEDs are winning.

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