Lithium Ion Charging: Constant Current vs Constant Voltage

[redwan hasan]

Good afternoon.

I was going to make a 4.2v Lithium ion charger circuit, but so far what i have learned is, i will be needing constant current charger, so my question is what will happen if i charge with constant voltage? Like from a regulator maybe a linear one and i give like 4/4.1 volt constant.

Any help will be highly appreciated.

 

[milesyoung]

You can charge a lithium-ion battery using a voltage source, but you have to limit the current the battery can draw to protect the battery chemistry from deteriorating (and also for safety reasons). Usually the best way is to charge it first using a current source and then switch to a voltage source at a specified level of battery voltage. You can find many easy to use solutions that handle both stages in a single package, e.g.:
http://www.linear.com/product/LT1512

You can read more here:
http://www.digikey.com/en/articles/techzone/2012/sep/a-designers-guide-to-lithium-battery-charging

 

[meBigGuy]

You must buy a lithium-ion battery charger controller. Lithium-ion batteries require multiple phases of charging and the voltage across them must never exceed 4.2V. Basically they require A> Precharge, B> Constant Current, C> constant voltage. There are no shortcuts. milesyoung's links are good, especially the digikey link.

http://www.digikey.com/en/articles/techzone/2012/sep/a-designers-guide-to-lithium-battery-charging

 

[sophiecentaur]

A thread on this topic has just been closed on the basis of safety. Charging lithium ion batteries safely is a specialised business and should be left to the experts - or you need to become one yourself.
In any case, just how expensive are those chargers?