Battery sums please

[PaulRainbow]

Tnx, did not know those existed, would have been good to know.

Won't make any difference, your mains charger will close the VSR anyway.

If you insist on using the battery configuration that you have a VSR probably isn't appropriate for you. You would likely be better off with a low loss splitter to charge both batteries from the alternator and leave the solar just for the domestic bank.

 

[PaulRainbow]

What battery are you recommending that will not pull current from a battery parallel with it during starting?

Brian

One that is suitable for a 3.6 litre, straight 6, 260 hp engine, that also have the windlass wired to it.

My engine battery starts the engine without blowing VSR fuses, as does every boat i have fitted a VSR to.

 

[<152587>]

Won't make any difference, your mains charger will close the VSR anyway.

So why would you start the engine with mains charger connected? The voltage drop on a one way VSR will reduce the threshold to open said device.

 

[<152587>]

One that is suitable for a 3.6 litre, straight 6, 260 hp engine, that also have the windlass wired to it.

My engine battery starts the engine without blowing VSR fuses, as does every boat i have fitted a VSR to.

Well whoopee do dah.

 

[PaulRainbow]

So why would you start the engine with mains charger connected?

I wouldn't, but the OP is attempting to start the engine immediately after disconnecting the charger, whilst the batteries are still at 13.5 volts, read post #1

The voltage drop on a one way VSR will reduce the threshold to open said device.

Maybe, maybe not, depending on the VSR. Will it open quick enough so it doesn't blow the fuse ?

 

[PaulRainbow]

Well whoopee do dah.

So, what are you, 5 years old ?

 

[simonfraser]

The solar connected to the house battery will activate the dual sensor Cyrex at just about any time during the day
Thus causing the fuse to blow, IF the voltage is sufficiently different between the red top and the Trojans
The fuse blows both with starting and or the windlass
So i could as PR suggests connect the windlass to the Trojans, now the trojans may have a voltage drop towards them and again the fuse may blow, but that still leaves me with the starting problem
Conclusion is that there is too much of a capacity diffence between the single red top and the pair of trojans for the dual sensing VSR to work
The single red top starts the KAD just fine in 0C, but may still be too small vs the trojans

 

[pvb]

The solar connected to the house battery will activate the dual sensor Cyrex at just about any time during the day
Thus causing the fuse to blow, IF the voltage is sufficiently different between the red top and the Trojans
The fuse blows both with starting and or the windlass
So i could as PR suggests connect the windlass to the Trojans, now the trojans may have a voltage drop towards them and again the fuse may blow, but that still leaves me with the starting problem
Conclusion is that there is too much of a capacity diffence between the single red top and the pair of trojans for the dual sensing VSR to work
The single red top starts the KAD just fine in 0C, but may still be too small vs the trojans

Jesus, this whole sorry saga is unbelievable. The wretched fuse blows because you've fitted the wrong size fuse. Even you admit that the manual told you to fit a 120A fuse. This isn't rocket science, you know, although you seem to want to turn it into something similar.

 

[PaulRainbow]

Jesus, this whole sorry saga is unbelievable. The wretched fuse blows because you've fitted the wrong size fuse. Even you admit that the manual told you to fit a 120A fuse. This isn't rocket science, you know, although you seem to want to turn it into something similar.

The manual does not say fit a 120a fuse. Victron say that the fuse should be matched to the cable, (with a max rating of 120a) when they supply this as a kit the cable is 10mm, which is rated at 75a max. A 120a fuse would need 20mm cable.

 

[PaulRainbow]

The solar connected to the house battery will activate the dual sensor Cyrex at just about any time during the day

Correct, you wanted the solar panels to keep all batteries charged, this is what it's doing.

Thus causing the fuse to blow, IF the voltage is sufficiently different between the red top and the Trojans

NO !! The fuse will not blow unless the current passing through it exceeds its rating, you solar panel cannot blow the fuse. Voltage difference between the two banks is irrelevant.

The fuse blows both with starting and or the windlass

Becuase both are connected to the Red Top, which isn't meant for big engine or a windlass.

So i could as PR suggests connect the windlass to the Trojans, now the trojans may have a voltage drop towards them and again the fuse may blow,

No, again. Voltage differences between the banks are irrelevant here.

but that still leaves me with the starting problem

Well, you did fit the wrong battery for your installation.

Conclusion is that there is too much of a capacity diffence between the single red top and the pair of trojans for the dual sensing VSR to work

Your conclusion is totally wrong. Capacity difference between the banks is NOT the problem. I have 390ah and about 90ah, no problems. Some people have even greater differences, they are of no relevance.

The single red top starts the KAD just fine in 0C, but may still be too small vs the trojans

NO again. You just don't understand how it all works and seem determined not to take good advice. Here's one last ditch attempt, then i'm done.

Fit the bigger fuse, sized to the cables not the VSR, please pay attention here, or keep the fire extinguisher at hand.

If that cures it, great. If not, you need to make changes to the batteries or the split charging, the two will be mismatched. If you don't want to replace the Red Top, swap the VSR for a low loss splitter, which will charge the batteries from the alternator and keep both banks separate (even when cranking or using the windlass). The solar controller will then only charge the domestic bank.

 

[pvb]

The manual does not say fit a 120a fuse. Victron say that the fuse should be matched to the cable, (with a max rating of 120a) when they supply this as a kit the cable is 10mm, which is rated at 75a max. A 120a fuse would need 20mm cable.

In post 18, the OP said the manual suggested a 120A fuse. The datasheet I've seen for a 120A Cyrix-ct shows a 120A fuse in the wiring diagram. Of course, it may not be a Cyrix-ct which the OP has - only he knows.

 

[VicS]

In post 18, the OP said the manual suggested a 120A fuse. The datasheet I've seen for a 120A Cyrix-ct shows a 120A fuse in the wiring diagram. Of course, it may not be a Cyrix-ct which the OP has - only he knows.

And the manual shows the same ........ but if you read the writing instead of just looking at the pictures you will find the manual says that the fuse must match the wiring . 120 A is the maximum

Rather confusing nevertheless

 

[PaulRainbow]

In post 18, the OP said the manual suggested a 120A fuse. The datasheet I've seen for a 120A Cyrix-ct shows a 120A fuse in the wiring diagram. Of course, it may not be a Cyrix-ct which the OP has - only he knows.

The installation manual supplied with the VSR says

Connect the plus of the batteries to the brass bolts of the Cyrix, marked with no 30
resp. 87. Install a fuse in series (see fig). The fuse should be sized in accordance
with the wire cross section used, but not exceed 120A.

When supplied as a kit, Victron supply 10mm cabling, which is only rated at 75a, so the biggest fuse that can be fitted with the kit is obviously 75a. To use cable rated at 120a would mean 20mm cable, bit big for the 6mm studs, IMO.

I have never fitted one with such a big fuse, never had one blow a fuse either.

 

[pvb]

The installation manual supplied with the VSR says

When supplied as a kit, Victron supply 10mm cabling, which is only rated at 75a, so the biggest fuse that can be fitted with the kit is obviously 75a. To use cable rated at 120a would mean 20mm cable, bit big for the 6mm studs, IMO.

I haven't seen the installation manual. However, I reckon it's rather simplistic to talk about cable ratings with no mention of cable length. The use of larger cross-section cables is normally to avoid excessive voltage drop on longer runs. Smaller cables can safely handle larger currents on short runs.