Automotive Relay

[geoffr]

Has anyone used an Automotive relay on their boat - I'm looking to have a switch which can only do low amperage control a 15Amp circuit.

Looking in the auto parts store I see them labeled by automotive usage.. so not sure which one would make the most sense - any suggestions?

[rslifkin]

I'd be inclined to find a better quality relay (preferably sealed) than the crap most auto parts stores have on the shelves. But the concept is valid for use on a boat. There's no reason not to have a low amp switching circuit and use a relay to keep the high amperage run shorter and more direct.

[noelex 77]

“Automotive” relays are quite commonly used in marine applications.

Relays have a tough task. Switching DC is not easy. Use a name brand such as Hella. Try and over rate the specifications as this prolongs the life of the switching contacts (for example a 30+A relay to switch a 15A current). They should only be installed in a dry location.

Keep in mind the power consumed by the coil current can be significant.

[OldGreyB]

Originally Posted by noelex 77

Relays have a tough task. Switching DC is not easy. Use a name brand such as Hella. Try and over rate the specifications as this prolongs the life of the switching contacts (for example a 30+A relay to switch a 15A current).

Assuming you have 12vdc as your supply.

In dry locations such as within cabin areas try : Hella 93332011 or 933791061 or similar specifications, or sealed Hella 931680011 depending on your wallet and relay circuit criticality.

Hella HD :: 933791061 / 933791067

Hella HD :: 933332011 / 933332017

Hella HD :: 931680011 / 931680017

For engine rooms or damp areas try weatherproof such as Hella 007794301

Hella HD :: 007794301 / 007794307.

You can buy weatherproof connector with o rings to match if required.


Go to Hella.com or download their relay catalogue:
https://www.hella.com/hella-us/asset...cs_Catalog.pdf

Buy 2 and keep the spare in your spares bin.

[skipmac]

Simrad insisted I add a relay between their computer clutch circuit and my Raymarine linear drive clutch circuit. Not sure why since the output for the Simrad more than exceeds the current required by the Raymarine clutch.

So I added the relay. All that was available at the time was a Hella "auto" relay. Three years and a few thousand miles later it's still working just fine although I did get a spare for just in case.

[sailorboy1]

I use one for my engine start system.

[BillKny]

Originally Posted by geoffr

Has anyone used an Automotive relay on their boat - I'm looking to have a switch which can only do low amperage control a 15Amp circuit.

Looking in the auto parts store I see them labeled by automotive usage.. so not sure which one would make the most sense - any suggestions?

"Bosch" style automotive relays were widely used on my boat when it was built 25 years ago, and they all still work. I have added a few since without problems. Buy good brand name ones, and avoid the low priced junk on ebay. Use them only in dry locations. If you worry about water contact, they there are a lot of potted and sealed relays you can find to do the same job.

There are really only a few specifications that matter: the switched voltage, the maximum switched current, and the coil voltage. Match those to your application and they will work for you.

[Lake-Effect]

Originally Posted by geoffr

Has anyone used an Automotive relay on their boat - I'm looking to have a switch which can only do low amperage control a 15Amp circuit.

What's the application?

12VDC 20A automotive/marine switches are common and under $20... no relay required.

An inexpensive ($10) sealed 20A to 40A automotive relay will work if its coil current is acceptable and the thing isn't being cycled all the time.

On the steep end of the price range, you can find solid-state relays (no moving parts) that take very little current to control.

[geoffr]

Thanks all - I'll look into the suggested relays.

(unfortunately I can't just use the switch as it's only rated for 5A and replacing it means replacing a full switch panel which is a much bigger endeavor)