Ok how long you brought the ups and how long you had not start the the ups usaully ups is power dead change the battery and try to power up it should work be sure that all connection is connect properly before power up the ups.. if the ups doest work that will be the mainboard problem you hav to call for vedor to repair the unit.. yes these fuse for the ups but it unlikely to be blown so should worry of the fuse it self.. change of battery come with different spefc for the ups.. eg su3000rmi3u, sua3000rmi3u, su3000rmxl3u --- battery replacement is 8 pcs of 12v 7ah. sua3000rmi2u-- 6 pcs of 12v 7ah or 8 pcs 12v 5ah. su3000rminet-- 4 pcs 12v 17ah,