How To Wire Momentary Normally Closed Button, 30 Amp Battery Disconnect

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=146649
Printed Date: May 02, 2025 at 11:45 AM

Topic: How To Wire Momentary Normally Closed Button, 30 Amp Battery Disconnect

Posted By: a.beam.reach
Subject: How To Wire Momentary Normally Closed Button, 30 Amp Battery Disconnect
Date Posted: January 04, 2021 at 10:40 PM

I have a snowmobile that has a funny electronic 'gremlin' when I shut it down, the computer and fuel pump stays on. The system is designed to stay on for 30 seconds or so and sometimes does but it is very irregular. . . sometimes completely draining the battery. I have searched for an answer to the problem to no avail. If I simply disconnect the battery for even a second and reconnect it, the system stays off. SO. .. . A simple fix is to install a momentary, normally closed button whereas when the button is depressed the battery is disconnected momentarily. The positive wire is fused 30 amp and the buttons are not rated for that. I would appreciate help on how to wire a button like this one AMAZON Momentary / Normaly Closed Button to a relay that can carry the 30amp draw.

Replies:

Posted By: the12volt
Date Posted: January 05, 2021 at 7:41 AM

A normally open switch that closes when pressed would be better for this application. Wire as follows with a 30/40 amp SPDT relay:

One lead of momentary switch to ground.
Other lead of switch to terminal 85 of relay.
Terminals 86 and 87a to the battery side of the 30 amp battery lead you wish to interrupt.
Terminal 30 to the other side of the 30 amp battery lead you wish to interrupt.
Relay terminal 87 not used, insulate.

When you press the button, the normally closed terminals of the relay will open and interrupt the 30 amp battery lead.

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Posted By: a.beam.reach
Date Posted: January 05, 2021 at 9:13 AM

Thank you! There is currently a 30 amp fuse on the lead at the battery. Does it matter which side of the fuse I connect to with this setup?

Posted By: the12volt
Date Posted: January 05, 2021 at 9:16 AM

Interrupt it after the fuse, leaving the connection between the fuse and battery intact.

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Posted By: a.beam.reach
Date Posted: January 05, 2021 at 9:22 AM

Perfect, thank you for your help!