View Full Version : LI-ION Battery Charger

12-26-2008, 06:40 PM
Presently I am making one robot for which i require 12 v source. I have a 12.6V LI-ION battery pack (contains three 4.2V, 1400mAh cells in series), but the problem is I dont have the charger for it. The charge in the market costs high.
So how can I make a charger for the same which is cost effective as well as which can charge fast???
Can I use simply the voltage regulator 78xx series IC???
And what are the things taken to care while designing a charger???
If anyone has a charger circuit please post that to me on my mail ID.

Pls reply fast......Its urgent....
Thanks in advance...

With Regards
Rahul Shah

12-28-2008, 07:45 AM
Try this link


01-01-2009, 10:49 PM
i made a mobile charger years ago.I used trasformer and the output was around 7.3v then a attached a 100k variable resistor.Before charging the mobile i attached a multimeter for testing purpose and i made the output 5.8v by revolving the resistor.Then attached to mobile and it worked.The mobile needs 5.7v or more depending on the handset.

01-02-2009, 08:27 AM

Your post is very irresponsible and dangerous. What mobile are you talking about? What type of a circuit is that? 5.7volts? Li-Ions are too dangerous for you to post such dangerous statements.

Please refrain from post such things.

01-02-2009, 06:13 PM
Its dangerous when testing on phone but I used a multimeter before testing.It's not dangerous until you make make short circuits or overload battery.For the circuit You just need transformer,4 diodes,some capacitors and a variable resistor.I used a simiens phone.I dont remember the model.

01-03-2009, 12:38 PM
I think all mobile have in-built Li-on battery charger circuit so when you give voltage above 5.6 V the battery start charging and it stop charging after battery is fully charged.

So for charging Li-on battery directly you need proper charger
ppppking04 is correct it is very dangerous to charge Li-on battery like akshay66 mention

akshay66 your one transformer,4 diodes, some capacitors and a variable resistor charger circuit is suitable for lead acid battery not for Li-on Battery

01-03-2009, 06:38 PM
Thanks to all of you.I didnt knew about mobile batteries have an in built charger but other one's dont have.If you all feel my way is dangerous please dont try it.I only tried after looking on internet.Rahul best of luck for your charger.


01-03-2009, 06:41 PM
This is an off topic disscussion:Once i opened up a 1.2v charger it had only a transformer,4 diodes and 2 two LED's for indication.Do 1.2v recharable cells also have in bulit charging system.Plss tell i want to clear these dougts.


01-03-2009, 10:16 PM