Split Charge Relay and the Yellow Wire

[Bigplumbs]

This is most likely only applicable with a small boat with a starter battery and a single or double leisure battery 12v set up. If you do have this kind of set up it is well worth using the split charge relay that has the yellow wire (many dont) to get you out of trouble should your starter battery be flat for any reason

 

[jakew009]

If you tried to use that to start most boat engines with a dead starter battery it would immediately blow the fuses protecting it.

Might get lucky if the engine battery was just a bit weak.

If your going to do it might as well do it properly with an isolator switch rated for the current and wired with the same size cable as feeding the starter motor.

 

[Bigplumbs]

If you tried to use that to start most boat engines with a dead starter battery it would immediately blow the fuses protecting it.

Might get lucky if the engine battery was just a bit weak.

If your going to do it might as well do it properly with an isolator switch rated for the current and wired with the same size cable as feeding the starter motor.

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You will see that I said this was for smaller engines. The wires to the second battery are sized for at least 80 plus amps and the yellow wire is just in effect a switch. The system I detailed is used in many cars, Motor homes and Camper vans and works well.

Very often space is at a premium in smaller vehicles and having huge switches is not possible. I say again this works well for smaller sized boats.

The issue generally here is that when I say smaller boats many people think 33 footer. I am talking about maybe a 19 footer.

 

[jakew009]

You will see that I said this was for smaller engines. The wires to the second battery are sized for at least 80 plus amps and the yellow wire is just in effect a switch. The system I detailed is used in many cars, Motor homes and Camper vans and works well.

Very often space is at a premium in smaller vehicles and having huge switches is not possible. I say again this works well for smaller sized boats.

The issue generally here is that when I say smaller boats many people think 33 footer. I am talking about maybe a 19 footer.

Possibly, but boats are a bit different to a caravan in terms of risk if things go wrong.

If you had a totally dead starter battery even on a 19 foot boat, 80amps ain’t gonna be enough to spin the starter motor and start it from cold. Looking on eBay most of the fuses supplies with the kits are only 60A.

If a jobs worth doing it’s worth doing properly…

 

[Bigplumbs]

Possibly, but boats are a bit different to a caravan in terms of risk if things go wrong.

If you had a totally dead starter battery even on a 19 foot boat, 80amps ain’t gonna be enough to spin the starter motor and start it from cold. Looking on eBay most of the fuses supplies with the kits are only 60A.

If a jobs worth doing it’s worth doing properly…

This is doing it Properly. It is very easy to way over do things, Add Weight, Add complication and fill up space. I do many projects and firmly believe in the just enough approach. On all of my many projects over 45 years the sky has not fallen on my head yet.

We could debate this point till the cows come home there honestly is not point to doing that as I will never agree with you and you the same I suspect.

 

[stelican]

This is doing it Properly. It is very easy to way over do things, Add Weight, Add complication and fill up space. I do many projects and firmly believe in the just enough approach. On all of my many projects over 45 years the sky has not fallen on my head yet.

We could debate this point till the cows come home there honestly is not point to doing that as I will never agree with you and you the same I suspect.

So are you saying that you would run cranking amps through that yellow wire?or does the relay parrallel the engine and domestic batterys aswell as routeing the charge?

 

[Bigplumbs]

So are you saying that you would run cranking amps through that yellow wire?or does the relay parrallel the engine and domestic batterys aswell as routeing the charge?

The main wires connecting the Split Charge relay between the engine battery and the leisure battery are capable of running cranking current up to about 120 amps. with the relay in normal operation it only switches on at 13.3 volts and when at rest the connection between the engine battery and the leisure battery is switched off. If you ground the little yellow wire it switches the relay so it allows cranking current from the leisure battery to the Engine battery. It works very well and I had to use it this morning on my Camper because the main engine battery was low and would not start the car. All I did was earth the little yellow wire and it started fine.

This is a typical split charge kit that generally comes with a relay without the Yellow wire. Which was the point of my video. See link below.

Split Charge Ready Made Battery Relay Kit 12V 140A Digital VSR Sense Camper Van | eBay