what is the use of the second charm???

Ppl use the Second charm (also known as the acc. charm) for heals. Other than that really no use for it. The stats such as life, str or dex don't add to your total.

Its only for healing as

the only stat that has any effect on a secondary charm in that slot is EE and its only effect applies to the charm itself no other items.

So yes its only good for healing like tman said.