Relay

[Caladh]

I have one of these fitted on the house/start/bow thruster circuit. If it stopped “working” what would happen. I thought it kept the start battery isolated from the house, but my volt meter shows all batteries connected together. The volt meter monitors both house and start battery’s.

 

[wonkywinch]

It's a 75 amp relay so whatever it is switching (trace the thin red wire) doesn't burn out the switch with high current load.

Switch triggers relay, relay supplies high current to device. Undo a wire and see what no longer works. Looks like you could pull the crimped spade off easily to test.

Do you have a remote switch to join house and starter battery?

This is the part - Bosch 0 332 002 156 Relay : Amazon.co.uk: Automotive

Edited to say, I can't see a 0v/negative/black wire there (on pin 85). The relay coil will need that to energise. Does this set up currently work?

 

[Alex_Blackwood]

It's a 75 amp relay so whatever it is switching (trace the thin red wire) doesn't burn out the switch with high current load.

Switch triggers relay, relay supplies high current to device. Undo a wire and see what no longer works. Looks like you could pull the crimped spade off easily to test.

Do you have a remote switch to join house and starter battery?

This is the part - Bosch 0 332 002 156 Relay : Amazon.co.uk: Automotive

Edited to say, I can't see a 0v/negative/black wire there (on pin 85). The relay coil will need that to energise. Does this set up currently work?

Looks like it could connect two units, possibly battery banks. Is the other wire for the coil hidden behind the left hand large red? I would be inclined to start tracing wires, see where the big one go and if the small coil connections are from a switch or possibly connected in the alternator circuit to operate when that is running?? Once again just from the info. (Photo) posted impossible to say with any certainty.

 

[Caladh]

It's a 75 amp relay so whatever it is switching (trace the thin red wire) doesn't burn out the switch with high current load.

Switch triggers relay, relay supplies high current to device. Undo a wire and see what no longer works. Looks like you could pull the crimped spade off easily to test.

Do you have a remote switch to join house and starter battery?

This is the part - Bosch 0 332 002 156 Relay : Amazon.co.uk: Automotive

Edited to say, I can't see a 0v/negative/black wire there (on pin 85). The relay coil will need that to energise. Does this set up currently work?

….well, the bow thruster works, as does the start battery.

 

[Bouba]

...

 

[wonkywinch]

I think it’s a circuit breaker for when the thruster overheats. You can do without it...as long as you remember not to continuously use the thruster

No it's not. Feel free to click my Amazon link in post #2 for the identical part - ie a Bosch 12v 75A Relay part number 0 332 002 156. Heck you can even see the relay pin layout in the OP's picture with pins 30, 85, 86 & 87 which are common or garden bog standard automotive relay pin outs.

 

[Bouba]

No it's not. Feel free to click my Amazon link in post #2 for the identical part - ie a Bosch 12v 75A Relay part number 0 332 002 156. Heck you can even see the relay pin layout in the OP's picture with pins 30, 85, 86 & 87 which are common or garden bog standard automotive relay pin outs.

Ok....all my relays are plug in....but if that’s what it says on the lid, I can’t argue

 

[Caladh]

Can anyone tell me what this relay would do and more to my understanding, what would happen if it doesn’t work ? I think the l/h cable is start battery and r/h cables are house and bow thruster/anchor winch.

 

[S04]

Duplicate?
Link

 

[alahol2]

At a guess it closes when the engine is running and allows the house and thruster batteries to charge along with the start battery. When engine not running and ignition off the house and thruster batteries are isolated from the starter battery.

 

[Caladh]

I’ve had some interesting replies here. I’ve asked again because it seems, according to my Victron battery monitor that ALL the batteries are connected together and I’m sure that I never saw this before on 7 years use. I’ve got engine battery 1 x 90 a/h, bow thruster/winch battery 1 x 90 a/h and 4 x house 90 a/h. The monitor shows exactly the same voltage whatever I’m doing esp at anchor whereby in the morning with 2 fridges running and evening lights on etc the voltage reads the same iro of 12.5/6v for both house and start.

 

[alahol2]

Perhaps that relay is permanently activated, try detaching the thin red wire and see if that makes a difference. If it makes no difference maybe the relay has welded itself shut.

 

[Caladh]

Perhaps that relay is permanently activated, try detaching the thin red wire and see if that makes a difference. If it makes no difference maybe the relay has welded itself shut.

Ok thanks I’ll try that over the next few weeks.

 

[Stemar]

FWIW, I had something similar on my previous boat as a split charge relay, connecting start and domestic batteries, and energised by the field (charge warning light) connection on the alternator. It worked well, but I'd use a VSR now, as they've become a lot less expensive.

 

[Caladh]

I have now traced the cables attached to the Bosch relay. The l/h red wire goes to start battery switch (live side). One red on r/h side goes to the house battery switch (live side), the other red goes to the alternator. Both the thinner black and red cables goes to the alternator. Am I any the wiser as to what the relay does ? Well I’m guessing the alternator charges the start battery first before switching in and doing the house as well - I could be wrong.

 

[PaulRainbow]

I have now traced the cables attached to the Bosch relay. The l/h red wire goes to start battery switch (live side). One red on r/h side goes to the house battery switch (live side), the other red goes to the alternator. Both the thinner black and red cables goes to the alternator. Am I any the wiser as to what the relay does ? Well I’m guessing the alternator charges the start battery first before switching in and doing the house as well - I could be wrong.

You are

When you start the engine the relay closes and parallels the engine and domestic batteries, thereby charging them all. It was a common thing before the advent of sensibly priced VSR's.

 

[Refueler]

I have now traced the cables attached to the Bosch relay. The l/h red wire goes to start battery switch (live side). One red on r/h side goes to the house battery switch (live side), the other red goes to the alternator. Both the thinner black and red cables goes to the alternator. Am I any the wiser as to what the relay does ? Well I’m guessing the alternator charges the start battery first before switching in and doing the house as well - I could be wrong.

I have same in my boat .. and that is what it does .... engine starts and once charging starts - relay closes so that both banks get charged. Engine stops - relay opens and banks separate. But I do not have the extra connection (the smaller gauge red wire) ....

 

[PaulRainbow]

I have same in my boat .. and that is what it does .... engine starts and once charging starts - relay closes so that both banks get charged. Engine stops - relay opens and banks separate. But I do not have the extra connection (the smaller gauge red wire) ....

View attachment 201397

The two fat wires go to the batteries, from terminals 30 and 87. 85 and 86 are the coil terminals, if you don't have a positive wire going to the alternator (or somewhere else) what energises the coil to close the relay ? Without that connection it cannot work as you describe. Perhaps there is a wire going to the coil from terminal 30 or 87 (whichever goes to the engine battery) that becomes live when the engine isolator is turned on ?

 

[Refueler]

The two fat wires go to the batteries, from terminals 30 and 87. 85 and 86 are the coil terminals, if you don't have a positive wire going to the alternator (or somewhere else) what energises the coil to close the relay ? Without that connection it cannot work as you describe. Perhaps there is a wire going to the coil from terminal 30 or 87 (whichever goes to the engine battery) that becomes live when the engine isolator is turned on ?

I sat thinking about it after posting ... and I agree with your questioning ... There must be a wire/s behind that are not clear in the photo .. looking at the photo .. it may be the black smaller diameter wire running behind ...

What I do know is that it works as described ... if engine is not running ... battts show typical voltage levels ... start engine and both banks voltages rise showing charge going in.

Its not easy to get a photo of it .. its tucked under the bunk base and I'm not supple enough to bend into the battery locker !! I have one of the domestic bank batts out at present - that's in the 25ft boat as temporary till lift out.
Today I have to check the boat as tomorrow breakfast time - we let go - to sail down coast to lift out for winter ... I will try get another lok at that unit.

 

[PaulRainbow]

I sat thinking about it after posting ... and I agree with your questioning ... There must be a wire/s behind that are not clear in the photo .. looking at the photo .. it may be the black smaller diameter wire running behind ...

What I do know is that it works as described ... if engine is not running ... battts show typical voltage levels ... start engine and both banks voltages rise showing charge going in.

Its not easy to get a photo of it .. its tucked under the bunk base and I'm not supple enough to bend into the battery locker !! I have one of the domestic bank batts out at present - that's in the 25ft boat as temporary till lift out.
Today I have to check the boat as tomorrow breakfast time - we let go - to sail down coast to lift out for winter ... I will try get another lok at that unit.

Looking again, there is a thinner black wire at 1-o-clock and another at 7-oclock, that would account for it Nigel.