I want to build 24v, 10A charger for recharging my 20Ah lithium ion charger. suggest me some tips for this project.

 

Welcome to AAC!
Lithium batteries can explode or catch fire if not charged and discharged correctly. In the interests of safety I would advise buying a commercial charger rather than trying to build your own. The correct components for a DIY one would probably cost more than a commercial charger anyway.

 

Charging a 20Ah lithium battery at 10A is especially dangerous and must generally be done with an IC dedicated to that function.
As Alec noted, it's likely cheaper and easier just to buy a dedicated charger rather than try to build your own

 

Thank you for your reply. buy a new one is some what ok, but I want to know technical details to build charger for further process. Help me to do that..!

 

What further process?

 

As said above, buy one, do not try to make one. They are really dangerous if you get it wrong.