Coffeelandy · May 8, 2016

Gents,
I have multiple relays I need to fit and I want then all on the ignition. I have a spare ignition live. Can anyone tell me if I can fit this live into some sort of board where that will also let me plug in multiple relays to save me cutting and crimping a lot of wires instead?

SpringDon · May 8, 2016

http://www.vehicle-wiring-products.eu/product.php/736/standard-relay-module

But you still need to wire it. And work out the draw to see if a single wire will be enough

boguing · May 8, 2016

Have you got a scrapyard that you can have a nose around?

Tomsoonn · May 8, 2016

If you don't mind me asking, what do you planning to do with all these relays of wire?

Off-topic: You should watch The Gods Must Be Crazy (1980). There was a very interesting scene regarding these thread.

fozt · May 8, 2016

I use one of these, still need to cut and crimp wires but only one single feed to power it. Can fuse everthing individually, too.

http://www.ebay.co.uk/itm/12V-24V-1...204020?hash=item35ebbb8df4:g:LTgAAOSwd4tT9vh6

Coffeelandy · May 8, 2016

SpringDon said:
http://www.vehicle-wiring-products.eu/product.php/736/standard-relay-module

But you still need to wire it. And work out the draw to see if a single wire will be enough

That's the sort of thing. I'm assuming the draw is the total watts when everything is turned on?

SpringDon · May 9, 2016

Coffeelandy said:
That's the sort of thing. I'm assuming the draw is the total watts when everything is turned on?

Yes, you'll need to add all devices together if you use a single wire to feed multiple relays.

Brown · May 9, 2016

If you're talking about the wire to activate the relays, it won't have to be very high capacity, because most of my relays have a resistance of about 70 ohms so the current draw will be pretty miniscule even with several in parallel. (1/Rt = 1/R1 + 1/R2 + . . . + 1/Rn, which you probably did at school). On the other hand, the the supply you're using the relays to switch on and off will need to be up to powering whatever appliance you're going to connect, so will need to be pretty hefty if it's an inverter or a coffee machine or something like that.

Coffeelandy · May 14, 2016

Brown said:
If you're talking about the wire to activate the relays, it won't have to be very high capacity, because most of my relays have a resistance of about 70 ohms so the current draw will be pretty miniscule even with several in parallel. (1/Rt = 1/R1 + 1/R2 + . . . + 1/Rn, which you probably did at school). On the other hand, the the supply you're using the relays to switch on and off will need to be up to powering whatever appliance you're going to connect, so will need to be pretty hefty if it's an inverter or a coffee machine or something like that.

It'll be to power heated seats, heated mirrors, some interior led lights. I intend to use an extra cigarette lighter lead that is already in place linked to the ignition.

Jam1 · May 14, 2016

Coffeelandy said:
It'll be to power heated seats, heated mirrors, some interior led lights. I intend to use an extra cigarette lighter lead that is already in place linked to the ignition.

What as the power source for the devices or to trigger the relays?

Coffeelandy · May 14, 2016

Um that's confused me now!

Brown · May 14, 2016

Heaters tend to be quite current-hungry, so for the actual supply you might be better off running yourself a nice fat cable from the battery box. With an appropriate fuse in it. If you want these to come on and off with the ignition, you can fit relays that are tripped by an ignition switched live which doesn't need to be very heavy duty because it doesn't take much current to trip the relay.

On mine I've done this kind of thing - I have a big thick cable going from the battery positive terminal through a 60A fuse to a fuse box behind the driver's seat and from there it spins out to various accessories. Inverter, extra lighter sockets, dashcam and tracker and a few other things. Some of these are switched on and off by relays tripped by an ignition live.

OK, the lighter socket supply is fairly hefty, but of you've got the seats on, the mirrors on and the lights on it is going to be struggling a bit!

Disco1BFG · May 14, 2016

you might be better to take a decent size live feed direct from the battery, appropriately fused - I.E. one the size of which you have calculated from the load you intend to apply - and use the ignition live to power the relays - I.E. to power the relay coils only. The drain on your live feed will thus be small, and probably within its capabilities.

I see @Brown types faster than me, but thats not a suprise

Brown · May 14, 2016

Disco1BFG said:
you might be better to take a decent size live feed direct from the battery, appropriately fused - I.E. one the size of which you have calculated from the load you intend to apply - and use the ignition live to power the relays - I.E. to power the relay coils only. The drain on your live feed will thus be small, and probably within its capabilities.

I see @Brown types faster than me, but thats not a suprise

Sir, you've very kind. I appreciate you posts too.

Disco1BFG · May 14, 2016

Brown said:
Sir, you've very kind. I appreciate you posts too.

Thanks. HTH.

Jam1 · May 14, 2016

Coffeelandy said:
Um that's confused me now!

I have a feeling we've been here before

As said that's a lot of stuff to run off something designed to supply a little cig lighter but if you are just using it to turn the relays on that are switching a nice BIG cable you'll be ok.

Coffeelandy · May 14, 2016

Jam1 said:
I have a feeling we've been here before
As said that's a lot of stuff to run off something designed to supply a little cig lighter but if you are just using it to turn the relays on that are switching a nice BIG cable you'll be ok.

And the nice big cable comes direct from battery I'm guessing with a big in line fuse? ??

blue beasty · May 14, 2016

Coffeelandy said:
And the nice big cable comes direct from battery I'm guessing with a big in line fuse? ??

Yes, think of a relay as a big chucky switch in it's own chunky circuit. Instead of throwing it manually you use a small existing circuit to turn it on and off.

It's a way of turning stuff on and off with existing circuits without risking overloading them

jamesmartin · May 14, 2016

Coffeelandy said:
And the nice big cable comes direct from battery I'm guessing with a big in line fuse? ??

or the starter

Coffeelandy · May 15, 2016

blue beasty said:
Yes, think of a relay as a big chucky switch in it's own chunky circuit. Instead of throwing it manually you use a small existing circuit to turn it on and off.

It's a way of turning stuff on and off with existing circuits without risking overloading them

I hate relays!!!

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Leaks an prone to bits dropping off

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