It is really cheap, may be about 25Rs or so. Of course a DC power supply - adapter or any other source is extra.

Ankur - Aren't you missing out on a great cost opportunity by not soldering it yourself ?     

actually currently i can't  solder since i have broken my hand so can use my left hand only
when it'll recover i'll definitely try it
meanwhile anyother ideas/comments

Quote from: ankurgr8on on December 03, 2009, 01:37:50 PM
i cAN do soldering tell me the circuit

To safely charge a LIPO, one has to follow the charging algortham for the LIPO. There are many Lipo charger ICs available which has these built in algoritams implemented thru Timers/ comparators/ temperature sensors etc.
I had made a charger as part of an GPS tracker board, (pl see the photos)few years back, using MAX 1758 IC. I was using this board for some time for my RC purpose till i bought a standard charger.
For another DIY pl see this link. this uses a microchip controller.
http://www.rcgroups.com/forums/showthread.php?t=793441

QuoteSince the mah rating of the lipo was not mentioned, how was this calculation done ?

The relevant part was the minimum voltage needed to charge a single cell LiPo since there is a drop across the regulator.  The 1C refers to the current rating of the Lipo. If it is 600 mAH then 1c would be that. If 2,000 MAh then 2A, and so on.

So the gist is that at 6V is needed to charge something to 4.2V accounting for the drop on the regulator ? Was the 6V calculated by consulting the datasheet of the regulator, or was it an approximation ?

the mah of the batteries are 850 and 138
please tell me the adequate chargers

I would suggest a supply with a minimum voltage of 7.5 DC. 

Referring to the circuit, R1 - which is the current limiting resistor - would be 0.75  and 4.7 ohms for 860 and 138 mA. Please note that these resistors will limit the MAXIMUM current. Actual setting of the charge current (within this limit) will be set by R4. You will also need to change R2 to 2700 ohms.

All these refer to the first diagram in the link.

Quote from: sushil_anand on December 21, 2009, 11:31:34 AM
I would suggest a supply with a minimum voltage of 7.5 DC. 

Referring to the circuit, R1 - which is the current limiting resistor - would be 0.75  and 4.7 ohms for 860 and 138 mA. Please note that these resistors will limit the MAXIMUM current. Actual setting of the charge current (within this limit) will be set by R4. You will also need to change R2 to 2700 ohms.

All these refer to the first diagram in the link.

setting r1 to the desired values will work for this circuit?
http://shdesigns.org/pdf/lionchg2.pdf

also can diode d1 in the above circuit be replaced with a led[since i have a bunch of them just i need to get that LM317T adj. regulator and 2N2222A NPN trans. i 'll make it

am i right?
please answer my question soon as i m not able to make my charger circuit due to these confusions

No you cannot replace D1 with LED. D1, R6, Q2, R5 and DS1 are for LED indication that charging is going on. If you use other means to monitor the current, for example using a meter, then you can get rid of all these components and put a short in place of D1.

Ankur

My apologies for not replying to you earlier. I was out of town for 10 days in locations not too accessible to the net.

Rotorzone is correct. But do note that the "monitor" circuit just tells you that some charging is taking place but not the actual current.

ok,thanks for help

i have built this charge and works fine ! but precautions have to be taken while using the charger !!!

http://www.rcindia.org/batteries-and-chargers/diy-lithium-ion-charger-1-3-cellsselectable-current-for-60-conditions-apply-!/

does those loingchgrs stop charging automatically or is it mannual??

they stop charging automatically and as an indication the led light goes out (meaning battery fully charged n on standby)

ok thanx