Default Sarchy Minimum
All of these dumb charges, ie bricks in the wall, use the unused USB pins to communicate how much power they can provide. There are some resistors they put on the D-/D+ to say this is a 700ma charger or whatever. Trouble is that there are limited standards on these resistors so it's more than possible that a phone will charge but not enter high current charging when attached to a new brick in the wall. The cables however are more universal.