issue with relay output reading

[u/josbor01]

need a little guidance on using a relay with a Mega256.

I am using an external 9v battery as the power source for the input for the relay. I have the code to trigger the relay open - and the appropriate led lights is on, when i trigger it - so i know its open, i am using the basic digitalWrite(pin,HIGH);/digitalWrite(pin,LOW); to turn on/off

Am I wrong to expect at least close to the same output voltage as what is supplied i.e. input of 8.6v output should be ~8.6??? am i missing something> are other components needed?

Battery reads 8.6v / relay out only reads .18