So I have a relay that is rated for 12V DC 30 amp. It will be running a couple of things; probably about a 5 amp draw. What I don't want is for those items to draw from the main battery. The button I am using is already power something off of the main battery, and I would like to use that same button to activate the relay, but I want that relay to power my other items off of a separate power supply.

I think this should work, but I just wanted to double check with others before I implement this. enter image description here

Sorry about the diagram; the button wasn't saved. The button will be between the top battery positive terminal and 85 on the relay.

  • \$\begingroup\$ You have a button and a current limiting resistor in line with the red line connected to pin 85? How about a reference or datasheet for the relay you are using? \$\endgroup\$
    – vicatcu
    Commented Jan 10, 2013 at 19:58
  • \$\begingroup\$ In its current form I don't see why this question would get a downvote. +1 \$\endgroup\$
    – JYelton
    Commented Jan 12, 2013 at 20:06

1 Answer 1


You haven't drawn the mentioned button to turn the relay on/off in there, but assuming the pin-outs drawn are correct, your circuit should work fine.

  • \$\begingroup\$ You're right. sorry about that. I completely missed the button. It was on my work sheet, but it didn't save. The button will be on the top positive wire. So the button will break the circuit between top battery positive and 85 \$\endgroup\$ Commented Jan 11, 2013 at 3:03
  • \$\begingroup\$ Yes, it will work then :-). \$\endgroup\$
    – gbmhunter
    Commented Jan 11, 2013 at 3:14

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