i used to have one nest of small red ants living in my battery charger as well. wad i did is open up the casing and vacum the hell out of them.

a better step would be, go ACE Hardware and buy Terro Ant Liquid ( something like that , but confirm the name is Terro )

put some around the place where the ants hang around and u could see them coming out to devour on the liquid. they will bring it back to their nest.. and it would spear and kill all of them works very well for me .