Help needed for building LI-Ion 9volt battery charger - diyAudio
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Old 21st February 2016, 08:01 AM   #1
bwolf is offline bwolf  India
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Default Help needed for building LI-Ion 9volt battery charger

how to build charger circuit for
9 volt li ion battery.600mah
I read somewhere on the net
you should not charge a battery with a higher voltage than its capacity.
so it must be< 8 - 9V
??charging batteries with 10% of their current. Is this true? Should I be resisting my current to 60mah? my battery capacity 600mah.

external adapter 15v 1.5amp, I have Linear voltage 9v regulator but I dont know how to control current / limit it to 60 mah??

sorry for my bad English

Thank you
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Old 21st February 2016, 08:23 AM   #2
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Hi, maybe configure a 78XX as a current source ?!
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Old 21st February 2016, 08:48 AM   #3
AndrewT is online now AndrewT  Scotland
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Li batteries can easily be damaged by bad charging.

They are VERY intolerant of the incorrect charging rate/time/temperature.

Stay with lead/acid or NiCad or Nimh if you want easy to charge batteries.
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Old 21st February 2016, 08:48 AM   #4
bwolf is offline bwolf  India
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thanks for the Circuit diagram
frnd can you explain Io = (VO/R1) + Io Bias current ??? with my requirements pls
how to get desired out put current with above circuit ?

in general how to get desired out put current??

Last edited by bwolf; 21st February 2016 at 08:54 AM.
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Old 21st February 2016, 08:59 AM   #5
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Quote:
Originally Posted by AndrewT View Post
Stay with lead/acid or NiCad or Nimh if you want easy to charge batteries
Yes, that circuit is what I used with Ni/Cd many years ago.
I wouldn't mess with Li-ion because it's very over-my-head
( I've been looking for anything related to electric bikes last year...some sites were displaying some circuits -most ready-made/available on the market -and were intended for RC cars/planes)
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Old 21st February 2016, 10:26 AM   #6
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LI-ion 9V are most likely dual cell batteries at 8.4V (2x4.2). applying a current limited voltage higher than 8.4V will destroy the cell or shorten it's life considerably.
so a precision current limited voltage source is needed. a standard 9V NIcd cell charger will not do the job as that one has a much higher voltage. one option is to build a precision shunt using a TL431set at 8.4V, and charge using a voltage with series resistor as limiter.
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Old 21st February 2016, 11:22 AM   #7
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If you're not experienced with Li-Ion charging I would recommend getting a charge controller for them, you can buy them really cheap on eBay. Lithium cells are pretty intolerant of bad charging, so if you don't understand their charging cycle it's definitely not recommended to build your own charger.

If you want to learn more about LiPo charging I highly recommend you to watch this EEVBlog video.
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Old 21st February 2016, 06:16 PM   #8
bwolf is offline bwolf  India
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Thank you frnds.

May I know how to bring my current down from
0.8A to 60 mA??
Or 1.5amp to 60mA ?
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Old 24th February 2016, 02:47 PM   #9
bwolf is offline bwolf  India
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how to calculate this
Io = (VO/R1) + Io Bias current??
help me components needed ?
i have lm7808, lm7809 regulators
im noob here. :-/
thank you

2cell li ion 8.4v (9volt)
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Old 25th February 2016, 01:24 AM   #10
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bwolf, what is Io bias from the datasheet for the device you want to use?

Have you looked at the tutorials for the LM317 device?
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