Battery lite on while driving on 1990 Acura Integra

alt. replaced battery replaced check engine lite was on before replacing but that went out! car starts and runs fine drove 20mi.

Asked by for the 1990 Acura Integra
alternator new or used? the charging system need to be tested. check engine need to be scan for codes and post it here. rebuilt I'm going to parts store to have checked. also have local garage that specializes in Hondas may stop by there also to get his opinion! Thank you. will post outcome.