?: I have a battery charger of DC 7.4V 3800mAh can works in my gamecube
a 7,4v battery charger?
well, it may work with custom regulators
if with "a battery charger" you mean "battery":
the battery seems ok , but not sure about the 12v line of the gamecube, if you use less than 12v, like that battery, you probably will need to use custom regulators and suply 5v to the 12v line, I didnt tested this by myself, btw other members said it worked for them, so its your choice.
also,dont espect play 2 hours or more with that battery, the gamecube is power hungry, and ofc if you are worried about the power consumition, the screen of your choice, will be an important decision.
sorry for my bad english
dont worry , mine sucks too sometimes I was wondering if people can get a word from my GCp guide, or the entire guide sounds like chinese xD