I don't think they are compatible. Your battery is probably EB-BG903BBU (like mine). The S5 takes EB-BG900BBU. From what I have read, they are not the same.
https://forums.androidcentral.com/samsung-galaxy-s5/669407-s5-s5-neo-battery.html
(see last comment by bill hughes2)
I found 2 places that sell replacements for the S5 Neo:
https://www.canadianbatteries.com/battery-for-samsung-galaxy-neo-g903fd-galaxy-neo-duos-39v-2800mah-1092wh-p-2547.html?currency=CAD&gclid=EAIaIQobChMI-IGZ4ab71QIV27rACh2-UwufEAYYASABEgJCmPD_BwE
http://www.batterybuyer.com/samsung-galaxy-2800mah-1092wh-battery-with-p-22668.html
Good luck