iPhone 5s battery swap issue

i am currently dealing with a iphone 5s that has been submerged in pool water. i washed it in 100% isopopyl etc and i reassembled it tested the battery i was going to use with a working board and it worked. i plugged the new battery in the washed board and it didn't work. so i tested the battery with the board that works and it does not boot. what way have caused the battery to be killed like that? i learned from that mistake. i would very much appreciate a detailed explanation.