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Old Nov 05, 2002, 05:26 AM
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Tokyo, Japan
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Simple Li+ charger schematic

May be, this is the cheapest Li+ charger.
Because, I have ordered FREE samples of MAX 1811 USB powered Li+ battery charger chip to Maxim semiconductor.
Need the magnifier lens for senior guy to solder this SMALL chip.
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Old Feb 17, 2003, 06:35 PM
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I just got some samples of this chip today. Is it suitable for lithium polymer cells?
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Old Feb 17, 2003, 07:11 PM
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Pierre,

>Is it suitable for lithium polymer cells?

Basically, "Yes".
The charge current 500mA. So, do not use less than 500mAh
Lipo.

The 5V power source can be replace to

http://www.rcgroups.com/forums/showt...threadid=91780

And you may need the power diode on the power input line to protect reverse battery +- connection.
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Old Feb 17, 2003, 10:36 PM
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I was actually thinking on setting it on the 100 mA charge current for use with 145 mA cells, and a wall wart for the supply voltage.
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Old Feb 18, 2003, 09:50 PM
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Pierre,

>setting it on the 100 mA charge current for use with 145 mA cells, and a wall wart for the supply voltage.

My schematic shows 500mA charge.
You must change the current adjust pin2 connect to GND(pin6).
And your wall transformer peak voltage, include ripple peak must be less than 7V.
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Last edited by Takao Shimizu; Feb 18, 2003 at 10:12 PM.
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Old Feb 19, 2003, 09:49 PM
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Good idea...

This is exactly the kind of charger I am referring to in my "Multi-Channel charger" thread...

If someone were to pursue this commercially, you could make a 4-channel Li-Poly charger for about $20.00!


The Maxim 1898 might be a little better choice. Although it's not quite as simple an implementation (the 1811 has one resistor, 1 cap, that's SIMPLE!), it's a FET-controlled linear Li-Ion charger, with adjustable charge current (up to 2A+).

see: http://www.maxim-ic.com/quick_view2.cfm?qv_pk=3250&ln=



Good stuff!
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Old Feb 20, 2003, 12:17 AM
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My explanation was INCORRECT!

Quote:
Originally posted by Takao Shimizu
Pierre,

>setting it on the 100 mA charge current for use with 145 mA cells, and a wall wart for the supply voltage.

My schematic shows 500mA charge.
You must change the current adjust pin2 connect to GND(pin6).
And your wall transformer peak voltage, include ripple peak must be less than 7V.
Correct;
And your wall transformer peak voltage, include ripple peak must be less than 7V, if you do not use DC-DC converter with 100mA charge.
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Old Feb 20, 2003, 09:11 AM
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Not as bad as it looks...

Although Takao's schematic is very complete, it really makes it look a lot more complicated than it is!

See the attached image for the default implementation (even this one makes things a little confusing with the hi/low input settings)


Takao includes a DC-DC converter to allow a variety of input sources. But, any simple 5V supply (wall wart) would suffice.

Up to a 6V source can be used, but the chip may not be able to dissipate to power difference between the Li-Ion and supply at the 500mA setting. Best results would be achieved by having a power supply as close to 4.35V as possible (no lower).



For those who don't believe it... Yes, this is a COMPLETE Li-Ion charger, all you need to do is add a 4.4V-6V DC supply and one resistor and one capacitor!

see: http://pdfserv.maxim-ic.com/arpdf/MAX1811.pdf



Thanks.
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Old Feb 20, 2003, 09:25 AM
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Cheap, free and tiny...

Forgot to mention...


Maxim will send two free "development" samples out to -anyone-, and for anyone who's interested, they sell for about $1.50 ea.

Takao alluded to a small size, he wasn't kidding! See attached...
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Old Feb 21, 2003, 06:42 PM
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Re: Cheap, free and tiny...

Meteor,
Thanks for your assist.

>Takao alluded to a small size, he wasn't kidding! See attached...

here. compare to AA size battery.
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Old Feb 22, 2003, 08:05 AM
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PC has +5V power supply

Take a look the inside of your PC.
The power supply may have +5V to GND(Black) instead of wall wart.
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