battery charger circuit

[hansika]

HI all,
i want to charge a li-ion battery cell(3.7V) with charger circuit , i am having 24V as input for the battery charger what my doubt is is there any ic which will take 24V i/p to charge 3.7V or 4.1V cell and how this will occur with constant current or constant volatge which is the better option for li-ion battery.

 

[hussong1555]

The lithium ion battery is easy to charge. Charging safely is a more difficult. The basic algorithm is to charge at constant current until the battery reaches 4.2 Vpc, and hold the voltage at 4.2 volts until the charge current has dropped to 10% of the initial charge rate. The termination condition is the drop in charge current to 10%. The top charging voltage and the termination current varies slightly with the manufacturer.

However, a charge timer should be included for safety.

The charge cannot be terminated on a voltage. The capacity reached at 4.2 Volts per cell is only 40 to 70% of full capacity unless charged very slowly. For this reason you need to continue to charge until the current drops, and to terminate on the low current.

It is important to note that trickle charging is not acceptable for lithium batteries. The Li-ion chemistry cannot accept an overcharge without causing damage to the cell, possibly plating out lithium metal and becoming hazardous.

 

[gtpats]

refer this link

**broken link removed**



Its not that safe to charge Li-ion batteries without knowing their properties, they may explode if overcharged.

the circuit is not smth which yuo can play with or experiement. pls take a good look at the li-ion properties before going ahead.

Also check this good site

http://www.avrfreaks.net/index.php?name=PNphpBB2&file=printview&t=27295&start=0



**broken link removed**

http://www.rcgroups.com/forums/showthread.php?t=209187

all the best !

 

[charith]

It's good to know all the theories before you start to build your own charger.

Check this out : https://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en527983

I'm using this basically to all my projects which uses Li-Ion/LiPo Batteries. As long as the charge current resides below 500mA (which is configurable using an external resistor) it works as a charm.

This operates in both Constant Current / Constant Voltage with with Thermal Regulation and takes care about all the charging cycles with uC calculated timings and cuts off the charging when it's full charged. So it's a all in one solution yet in a SOT-23 package.

 

[hansika]

Thank you for all your suggestions, i have a found an IC(MAX1737) in maxim for battery charger circuit , upto now i am not mentioned how many li-ion cells i need to use i am using a battery pack which will having 3 li-ion cells(3.6V 1.5Ah) in series that is in parallel wilh another 3 li-ion cells, so my battery pack consists gives me 10.8V and 3Ah totally, what i want to know is for this type of arrangement that IC is suitable or not.