Should I swap Starter and Leisure battery connections to my VSR?

PaulRainbow

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View attachment 123551

The switches are shown and on the side are the VSR and a thermal circuit breaker.

The alternator is connected to the starter solenoid and I think the Start switch ties the starter battery to the solenoid. The Emerg. parallel switch has 2 inputs to the VSR so I assume it shunts across the relay.

Looks that way, which is poor design and incorrectly rated cabling. The emergency parallel switch should be wired using cable with the same current rating as the starter isolator switch. The tow cables should be connected to the load side of the respective isolator switches, as shown in the two schematics i previously posted. This allows emergency "jump starting" in the event of a flat engine battery. It also allows for a faulty engine battery to be isolated by turning its isolator switch off and then turning the emergency switch on, allowing the engine to share the domestic batteries. You can, of course, isolate the domestic batteries and use the engine battery in the event of domestic battery failure.

One way to stop the clicking would be to go into emerg parallel mode but that would discharge the starter battery into the leisure battery so I don't want to do that.

Indeed, that's defeating the point of the redundancy of separate circuits.

See post #2
 

PaulRainbow

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Paul: I did not see schematics attached to your second post. It may be because I am not so familiar with attachments to this forum so do not know what I'm looking for.

If you are outside of the UK my website firewall might be blocking the pictures, i'll upload them here:

Charging-2-banks-VSR.png

Charging-2-Batteries-One-Engine-with-ArgoFET.png
 

PaulRainbow

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It seems like I should make a simple change here (using the correct gage of cables)

The two cables that go to the VSR (from the isolators) are lighter gauge than the main battery cables, which is fine, they only need to carry charging current. The two from the parallel switch are the same gauge and it's these that need to be heavier gauge and relocated. So, remove the two cables from the parallel switch and make a new pair of cable, same gauge as the battery cables and connect one from the parallel switch to the common terminal of the domestic isolator and another from the parallel switch to the load side of the engine battery isolator.
 

PaulRainbow

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Easier, move the VSR wire to the other side of the present start switch? No heavy cables involved

So, the engine battery is totally flat, or knackered. You turn the isolator off and close the emergency parallel switch, will the engine start when it's connected to the domestic batteries with 10mm cables ?

The VSR and the emergency parallel switch are there for two different purposes and should be treated as such. The VSR is a split charge device and the wiring to it only needs to be rated for the maximum charging current. The emergency parallel switch and its associated wiring may have to carry the full current required to start a cold engine, so should be rated accordingly and that doesn't include sections of 10mm cable.
 

VicS

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and the VSR should be protected by a fuse no greater than its max rating. or the max rating of the wiring if less
 
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Argold57

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The two cables that go to the VSR (from the isolators) are lighter gauge than the main battery cables, which is fine, they only need to carry charging current. The two from the parallel switch are the same gauge and it's these that need to be heavier gauge and relocated. So, remove the two cables from the parallel switch and make a new pair of cable, same gauge as the battery cables and connect one from the parallel switch to the common terminal of the domestic isolator and another from the parallel switch to the load side of the engine battery isolator.

I agree. But am not sure which side of the start switch the VSR should attach to. If the alternator/solenoid side, ( per my proposed schematic) then I can disconnect the start battery when the domestic battery is flat and charge from the alternator. Will the alternator regulator keep the voltage high enough to keep the VSR closed if the start battery is disconnected? If not, can I charge the domestic battery by closing the emerg parallel and opening the start isolator so as not to draw down the starter battery?
 
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SlowlyButSurely

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So, the engine battery is totally flat, or knackered. You turn the isolator off and close the emergency parallel switch, will the engine start when it's connected to the domestic batteries with 10mm cables ?

The VSR and the emergency parallel switch are there for two different purposes and should be treated as such. The VSR is a split charge device and the wiring to it only needs to be rated for the maximum charging current. The emergency parallel switch and its associated wiring may have to carry the full current required to start a cold engine, so should be rated accordingly and that doesn't include sections of 10mm cable.
So, the engine battery is totally flat, or knackered. You turn the isolator off and close the emergency parallel switch, will the engine start when it's connected to the domestic batteries with 10mm cables ?

The VSR and the emergency parallel switch are there for two different purposes and should be treated as such. The VSR is a split charge device and the wiring to it only needs to be rated for the maximum charging current. The emergency parallel switch and its associated wiring may have to carry the full current required to start a cold engine, so should be rated accordingly and that doesn't include sections of 10mm cable.


Paul, we have a Victron VSR connected in the normal way. If the starter battery is completely flat and you plug in the shorepower cable the battery charger will activate the VSR. If you then start the engine (without closing the emergency parallel switch) the starter motor will draw from the domestic bank via the VSR. For this reason I have used the same size cable for the VSR connections as the main cable. It's unlikely but it did happen.
 

PaulRainbow

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I agree. But am not sure which side of the start switch the VSR should attach to. If the alternator/solenoid side, ( per my proposed schematic) then I can disconnect the start battery when the domestic battery is flat and charge from the alternator. Will the alternator regulator keep the voltage high enough to keep the VSR closed if the start battery is disconnected? If not, can I charge the domestic battery by closing the emerg parallel and opening the start isolator so as not to draw down the starter battery?

Leave the VSR as it is and wire how i said in post post #45, which matches my schematic, apart from the VSR being connected to the 1-2-B switch.

With the engine running, turn the emergency switch on and then the engine switch off. The engine and all domestic loads will now be running from the domestic batteries and alternator charge will go straight to the batteries, the VSR will be irrelevant.

It feels like a bit of a bodge to get around the VSR chatter though.
 

PaulRainbow

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Paul, we have a Victron VSR connected in the normal way. If the starter battery is completely flat and you plug in the shorepower cable the battery charger will activate the VSR. If you then start the engine (without closing the emergency parallel switch) the starter motor will draw from the domestic bank via the VSR. For this reason I have used the same size cable for the VSR connections as the main cable. It's unlikely but it did happen.

Do you have any fuses in the cables going to the VSR, if so, what size ?
 

PaulRainbow

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No, there are no fuses. What would you recommend?

At least one cable should be fitted with a fuse, rated no greater than the VSR rating, or the cable if it's a lower rating. Without this fuse the relay can be damaged by exceeding its rated current. If there is a chance the other cable could chafe and short, it too should be fused.
 

SlowlyButSurely

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At least one cable should be fitted with a fuse, rated no greater than the VSR rating, or the cable if it's a lower rating. Without this fuse the relay can be damaged by exceeding its rated current. If there is a chance the other cable could chafe and short, it too should be fused.

Just checked the spec for the Cyrix 120, it says cranking capacity is 180A for 5 seconds. Our starter motor draws 250A so you are absolutely right, it needs a fuse. Thanks.
 
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