Helpful hint: if you continue to post on this forum, read the replies.
Had you mentioned specifically connecting the battery ground back to the Arduino, it would have been obvious.
When you are dealing with a subject that is new to others, but not yourself, details matter
Please identify the exact type of servo, and post one or more hand drawn wiring diagram(s) showing your attempts. Include all signal, power and ground connections.
You were asked;And you did not reply, do the details not matter ?
What part of "connect the grounds" is not clear to you?
Because someone with both knowledge AND tact replied before I was able to read the follow-ons.
I thought I made it clear before, but if not - that's doesn't work.Arduino 5v to servo - worksBattery from ESC to servo (6v) - doesn't workBattery from ESC to resistor on breadboard to servo (4.8v) - doesn't work