here is the method ^^
first, convert the save using this page :
http://www.shunyweb.info/convert.php
source: DUC
output:no$gba SAV
second, download no$gba emulator wheter it's the freeware(ver 2.6) or the "donate" one (2.6a)
third, open no$gba.exe and close and you will get no$gba.ini (the configuration files of no$gba) ... after that open the ini files and edit the savefile section, change it from "Compressed/Uncompressed" into "Raw"(without parentheses)
play the game using no$gba (offcourse with pokemon roms) and save your file when playing the pokemon with no$gba
and it will produce a "512 kb" savefile which will be compatible to pokesav ^^