wireing question

[chrishelen]

Hi, I have fitted a 1-2 both, off switch on my boat, the old wireing had a positive cable going to the starter, coming off this cable is two thickish wires going to a relay. Do I connect these to the batt + ? There are two thinner cables going to the alternator from this relay if this helps.

 

[VicS]

Hi, I have fitted a 1-2 both, off switch on my boat, the old wireing had a positive cable going to the starter, coming off this cable is two thickish wires going to a relay. Do I connect these to the batt + ? There are two thinner cables going to the alternator from this relay if this helps.

IF you are adding a second battery and fitting a 1,2,off,both switch in place of a simple isolator:

Take all the wiring feeding the boat circuits (It may only be one wire at this point) off the old isolator and put them (it ) on the "C" terminal of the new switch. Transfer the existing battery + lead to "1" on the new switch . Connect the new battery + to "2"

 

[chrishelen]

Thanks,
The old system had two batts connected to a cut off switch, I have connected all the wires to the new switch but I am left with the re!ay, I don't know where I need to connect this.

 

[VicS]

Thanks,
The old system had two batts connected to a cut off switch, I have connected all the wires to the new switch but I am left with the re!ay, I don't know where I need to connect this.

You mean two batteries originally coneceted in parallel to a single isolator ?

What is this relay for ? Is it a relay ?

Best perhaps if you post a diagram of the old system.

This is how a 1,2, both,off switch should be wired ( two batteries here making up the domestic bank)

 

[chrishelen]

Yes I got that, thanks the relay at the moment is fed off the common cable, can't post a diagram, the small wires coming out of it go to the back of the alternated...sorry I can't be clearer and I can't remember the old wireing set up, even though is was only this afternoon I worked on it.

 

[ghostlymoron]

You seem to be a little uncertain about electrics. Ide be very careful about doing anything until you understand what the components do. (I'm not being superior - I'm still learning and have roped in a friend to help me)

 

[VicS]

Yes I got that, thanks the relay at the moment is fed off the common cable, can't post a diagram, the small wires coming out of it go to the back of the alternated...sorry I can't be clearer and I can't remember the old wireing set up, even though is was only this afternoon I worked on it.

You say this relay has two thickish wires both originally connected to the main + cable going to the starter motor and two thin wires going to the alternator ?

I dont know what it is or what it does. What is it? What is it for ? Are you sure its a relay ?

Therefore leave it connected as previously. The two thicker wires to the main + cable between the 1,2 both off switch and the starter motor and two thinner wires to the alternator.

 

[chrishelen]

You seem to be a little uncertain about electrics. Ide be very careful about doing anything until you understand what the components do. (I'm not being superior - I'm still learning and have roped in a friend to help me)

That's an understatement, although today I fitted a bilge pump with two float switches and and alarm, and it worked, so I am learning.

 

[prv]

Does your new wiring plan need a relay? If so, connect this one where your new plan needs it. If your new plan doesn't need it, put it in the spares box in the shed (or in the bin). If you don't have a plan and are making it up as you go along.... :dejection:

My guess is that it used to parallel the banks for charging when the engine was running, as determined by the alternator producing a voltage. Since you've decided to ditch this automatic system in favour of the antediluvian 1/2/both switch, you don't need it any more.

Pete

 

[VicS]

My guess is that it used to parallel the banks for charging when the engine was running, as determined by the alternator producing a voltage.
Pete

The OP's description of how it was wired does not support that idea.

Perhaps his description is wrong, perhaps the wiring has already been messed about with. As he is unable to post a diagram of the original wiring its difficult to know.

Chrishelen, are there any markings on this "relay" that might identify it.

 

[Jean]

A possibility for the relay perhaps, that's if it's a diesel engine, engine heater plugs?

 

[VicS]

A possibility for the relay perhaps, that's if it's a diesel engine, engine heater plugs?

But that does not tally with the way the OP said it was wired.
My first thoughts were not a relay but an external alternator regulator but that does not fit the described wiring either.

I reckon Pete's suggestion is the most likely but that the wiring has already been messed about with.

 

[chrishelen]

The OP's description of how it was wired does not support that idea.

Perhaps his description is wrong, perhaps the wiring has already been messed about with. As he is unable to post a diagram of the original wiring its difficult to know.

Chrishelen, are there any markings on this "relay" that might identify it.

I will have a look in the morning, and take some pics..

 

[andygc]

Why would anybody want to connect their start battery to "all boat circuits"? Mine's a 1-both-2-off switch, but the principle is the same - the C terminal takes the starting/charging cable from the engine and the switch selects which battery starts the engine and then selects which battery gets charged (both if selected). The "all boat circuits" feed comes off the domestic bank and has a separate isolator. On mine it's actually taken off the no 2 terminal on the 1-both-2 because it's convenient to have done it that way.

 

[prv]

Why would anybody want to connect their start battery to "all boat circuits"?

Dunno, but it is the conventional way these things are wired. I've sailed on lots of boats done that way.

My preference is to have engine and service batteries completely separate, except for some shared charging mechanism. This has generally involved a relay, so emergency use of the service bank to start the engine is possible that way. If not, I'd carry a single jump-lead for the very rare occasions that the engine battery won't do its job.

Pete

 

[symondo]

Hi, I have fitted a 1-2 both, off switch on my boat, the old wireing had a positive cable going to the starter, coming off this cable is two thickish wires going to a relay. Do I connect these to the batt + ? There are two thinner cables going to the alternator from this relay if this helps.

im gonna take a punt at this....

sounds like an older style split charge system with using the relay as a switch which is controlled by the output from the alternator?
I'd say with the 1/2 switch you shouldnt need this if you use the switch correctly

 

[prv]

sounds like an older style split charge system with using the relay as a switch which is controlled by the output from the alternator?

That was my guess too, in post #9.

As Vic says, this doesn't strictly match what the OP describes, but what he describes doesn't make any sense anyway - both wires to the relay coming from the "positive cable going to the starter", the relay would achieve nothing.

My advice to the OP remains the same. If what you want to do with your electrics requires a relay, then you could probably reuse this one. If what you want to do doesn't require a relay, then don't use this one. Nothing at all says you have to wedge it into the system somewhere just because it was there before.

Pete

 

[symondo]

That was my guess too, in post #9.

As Vic says, this doesn't strictly match what the OP describes, but what he describes doesn't make any sense anyway - both wires to the relay coming from the "positive cable going to the starter", the relay would achieve nothing.

My advice to the OP remains the same. If what you want to do with your electrics requires a relay, then you could probably reuse this one. If what you want to do doesn't require a relay, then don't use this one. Nothing at all says you have to wedge it into the system somewhere just because it was there before.

Pete

i found with the wiring in our boat - simply make it do what it needs to do - additional wires - probly remove. ive had a handful of redundant cables out that someone has obviously put in there for something which is no longer relevant but couldnt be bothered to remove the wires.

Can take time to trace random cables to find they are just wraped up at the end but dud wiring is best taken out of any equation, just leaving clear wiring that you understand and that works.

 

[VicS]

Why would anybody want to connect their start battery to "all boat circuits"? Mine's a 1-both-2-off switch, but the principle is the same - the C terminal takes the starting/charging cable from the engine and the switch selects which battery starts the engine and then selects which battery gets charged (both if selected). The "all boat circuits" feed comes off the domestic bank and has a separate isolator. On mine it's actually taken off the no 2 terminal on the 1-both-2 because it's convenient to have done it that way.

It's what happens when you start off with a simple single battery system. Then add a second battery with a 1,2 both, off switch as a battery selector switch.

Its simple to use and for the electrical numpty to wire up without touching any of the rest of the boat's wiring.

 

[prv]

i found with the wiring in our boat - simply make it do what it needs to do - additional wires - probly remove. ive had a handful of redundant cables out that someone has obviously put in there for something which is no longer relevant

Quite agree. I've had several bin-bags of rotten old cabling out of ours this winter. The only original stuff left is part of the lighting circuit, as it snakes all through the boat in various inaccessible places. All the rest is now new, tinned, properly fused, and according to a sane and well-understood scheme. And I didn't try to reuse random parts from the old arrangement for no good reason.

Pete