Wiring a relay help

[jps123456]

Hi, could someone tell me how to wire a basic relay switch please.

So I want to power my car stereo from my leisure battery when the ignition is off.

Do I use a 4 pin relay with (30) connected to the leisure battery and (86) connected to the ignition.

Or

Do I use a 5 pin relay with (86) connected to main battery (ignition) and (87A) connected to the leisure battery?

Thanks

 

[Lucien Nunes]

I am trying to understand the need for the relay.
Where do you want the stereo to be powered from when the ignition is on, and why?
Surely when the engine is charging the battery, the VSR or split charge relay will enable the leisure battery to charge as well, in which case the stereo can continue to be powered from the leisure side, there's no reason to switch it back to the vehicle battery.

If you do need to change over (e.g. no split charging) then you need a 5-pin (changeover) relay.

86 (coil feed) + 87 (normally open) both connect to ignition-controlled vehicle feed.
87A (normally closed) connects to leisure battery feed (via fuse).
30 (common) to stereo input
85 (coil return) earthed.

When the ignition-controlled feed is available, the relay will switch to it, otherwise it will default to the leisure battery.

 

[jps123456]

I am trying to understand the need for the relay.
Where do you want the stereo to be powered from when the ignition is on, and why?
Surely when the engine is charging the battery, the VSR or split charge relay will enable the leisure battery to charge as well, in which case the stereo can continue to be powered from the leisure side, there's no reason to switch it back to the vehicle battery.

If you do need to change over (e.g. no split charging) then you need a 5-pin (changeover) relay.

86 (coil feed) + 87 (normally open) both connect to ignition-controlled vehicle feed.
87A (normally closed) connects to leisure battery feed (via fuse).
30 (common) to stereo input
85 (coil return) earthed.

When the ignition-controlled feed is available, the relay will switch to it, otherwise it will default to the leisure battery.

Thanks for that.

Yes the reason to use the changeover relay is to stop the starter battery going flat when camping and engine isn't running.

 

[Lucien Nunes]

That's not quite what I meant. Is the leisure battery not always present on the vehicle and/or does it not charge when the engine is running? Because if so, I can't see a reason ever to power the stereo from the vehicle battery. Although I suppose you might want it to switch on and off with the ignition for convenience, which would occur if you put a switch in the feed from the leisure battery to the relay 87A and switch it off.

 

[jps123456]

That's not quite what I meant. Is the leisure battery not always present on the vehicle and/or does it not charge when the engine is running? Because if so, I can't see a reason ever to power the stereo from the vehicle battery. Although I suppose you might want it to switch on and off with the ignition for convenience, which would occur if you put a switch in the feed from the leisure battery to the relay 87A and switch it off.

Yes leisure battery is always present and it does charge when the engine is running.

And yes I want the stereo to turn on and off with ignition but also I want to use the stereo with leisure battery when camping.

Don't really want to put in a switch as the ignition is just easier

 

[Lucien Nunes]

With the relay present and no switch, the stereo will be powered 24/7. It will never switch off under ignition control, merely switch between vehicle battery and leisure battery.

My initial thinking was that it might as well be powered from the leisure battery 24/7. I can however see the benefit of having the relay to enable it to operate with the leisure battery circuit decommissioned.