pvb
Well-Known Member
So if the voltage is the same, because the VSR is connecting, what exactly indicates what's supplying the power?
VSR blowing fuses
- Thread starter simonfraser
- Start date
So if the voltage is the same, because the VSR is connecting, what exactly indicates what's supplying the power?
William_H
Well-Known Member
The point is the batteries are only connected by a VSR and wiring which will have a finite resistance. This resistance is not normally noticed until you draw a large current from the system (when winch is working hard). So simplistically if winch power comes initially from house battery then its voltage will drop somewhat lower than that of the engine battery. Perhaps just a fraction of a volt. If the engine alternator is charging at a decent lick and if power comes initially from house battery we would expect the alternator to be trying to maintain voltage of house battery meaning a large current from alternator (to engine battery) then to house battery via VSR hence possibly blowing fuse. I think I would always power winch from engine battery on the basis that engine will be charging when winching. olewill
pvb
Well-Known Member
But that's what the OP says he has done.
PaulRainbow
Well-Known Member
If i remember correctly ;
a) The OP originally had a pair of 12v Trojans, one for engine start and one for domestics. The windlass and alternator were connected to the engine battery. The VSR fuse never blew.
b) A Redflash battery has been fitted as a starter battery and the two Trojans have become the domestic bank, with the alternator and windlass still connected to the engine battery. Now the VSR fuse blows.
It is my belief that when the windlass was connected to a Trojan it could get enough power without pulling a large current from the domestic Trojan, through the VSR. The Redflash isn't really a suitable windlass battery and i doubt very much it can deliver the current needed, so the windlass is now pulling a heavy current from he domestic bank, via the VSR. Neither the wiring or the fuse can handle that level of current, so the fuse blows.
Considering the windlass and batteries are at opposing ends of the boat, connected by 50mm cables, i don't consider the VSR would withstand supplying the necessary current to the windlass, even if wired with 20mm cable and a 120a fuse. The VSR is there for charging purposes, not to run the windlass.
I do usually connect the windlass to the engine battery and have never had a VSR fuse blow before. Never had the VSR fuse blow though. But, i have a heavy duty 700CCA engine battery, i doubt the windlass stresses that too much, with the engine running, so the VSR never has to supply much current at all.
In this case though, i feel the windlass needs connecting to the domestic bank.
a) The OP originally had a pair of 12v Trojans, one for engine start and one for domestics. The windlass and alternator were connected to the engine battery. The VSR fuse never blew.
b) A Redflash battery has been fitted as a starter battery and the two Trojans have become the domestic bank, with the alternator and windlass still connected to the engine battery. Now the VSR fuse blows.
It is my belief that when the windlass was connected to a Trojan it could get enough power without pulling a large current from the domestic Trojan, through the VSR. The Redflash isn't really a suitable windlass battery and i doubt very much it can deliver the current needed, so the windlass is now pulling a heavy current from he domestic bank, via the VSR. Neither the wiring or the fuse can handle that level of current, so the fuse blows.
Considering the windlass and batteries are at opposing ends of the boat, connected by 50mm cables, i don't consider the VSR would withstand supplying the necessary current to the windlass, even if wired with 20mm cable and a 120a fuse. The VSR is there for charging purposes, not to run the windlass.
I do usually connect the windlass to the engine battery and have never had a VSR fuse blow before. Never had the VSR fuse blow though. But, i have a heavy duty 700CCA engine battery, i doubt the windlass stresses that too much, with the engine running, so the VSR never has to supply much current at all.
In this case though, i feel the windlass needs connecting to the domestic bank.
simonfraser
Well-Known Member
A) i initially did have two trojans connected via 1 2 both switch, i had to use both to start the KAD, CCA of one trojan is not sufficient to start the KAD, that showed in my boat and the CCA of one trojan is 500 according to the supplier of the batteries.
the VSR fuse did not blow then cos there was none.
B) correct.
the extra current has to come from the house batteries, else the fuse would not blow.
so does a red top provide better CCA to start, but trojans better longer term amps to wind the windlass ?
remember the fuse did not blow when the windlass jammed on a chain knot, that suggests the red top was ok with that ?
the VSR fuse did not blow then cos there was none.
B) correct.
the extra current has to come from the house batteries, else the fuse would not blow.
so does a red top provide better CCA to start, but trojans better longer term amps to wind the windlass ?
remember the fuse did not blow when the windlass jammed on a chain knot, that suggests the red top was ok with that ?
halcyon
Well-Known Member
From memory winch is connected to engine battery, if you blow fuse in VSR link, you are pulling power from service battery. This means that alternator and engine battery are not supplying enough power and you are pulling a lot from the service battery bank, enough to blow 35 amp fuse.
We do not know amps drawn by winch, or amps supplied by alternator, is alternator output collapsing and power supplied by engine and service batteries, hense blown fuse.
You need some facts to make a judgement.
Brian
simonfraser
Well-Known Member
hm, 'is alternator output collapsing'
so could the alternator be able to supply power for a short amount of time and then decrease power even thought it is needed ?
this a sign of it wearing out ? or the belt slipping, it does not squeak / produce dust.
how would i test for that ?
so could the alternator be able to supply power for a short amount of time and then decrease power even thought it is needed ?
this a sign of it wearing out ? or the belt slipping, it does not squeak / produce dust.
how would i test for that ?
PaulRainbow
Well-Known Member
The belt was recently tightened !!
Even without the engine running the battery that is designated for the windlass should be capable of operating the windlass, without heavy current draw from the other bank.
My original advice was to fit a 3rd battery in the available space and have the two Trojans as a domestic bank. I specifically advised against a Red Top battery. I stand by both of those recommendations. Easy to test the Red Top with the windlass, next time you're out, try and recover the anchor without starting the engine.
I'll say it one more time, the VSR is not designed to carry windlass loads, it will not do it. A loaded windlass is perfectly capable of tripping heavy duty thermal breakers, so what chance does the poor little VSR stand ?
Additionally, if you are pulling the boat forwards with the windlass you are going to have problems. You need to slowly motor forward and only use the windlass to retrieve the slack rode.
Advice moving forward, get the windlass onto the domestic bank. You have room for a third battery, which you started a thread about recently, so i'd suggest fitting it. You'll still get some help from the alternator, as the VSR will close when you start the engine, but the Trojans should be able to cope with the windlass without trying to pull a big current from the engine battery.
halcyon
Well-Known Member
The alternator generates watts not volts, as the amps go up the voltage comes down, nothing to do with regulation.
You need data, in your case volts, unless you have a clamp ammeter. Volts will indicate state of alternator, battery volts will indicate what is supplying the power.
You can spend a fortune trying different things, without data you are lost.
Brian
simonfraser
Well-Known Member
yep, it was recently tightened, i was just asking .....
perhaps it still slips under a heavy load ? does the type of belt matter ? its a is a Volvo OEM replacement.
or do alternators wear out and possibly cant cope with the longer strain on them b4 they fail completely, its just a question
obviously the VSR is not designed to carry a full windlass loads.
the Q is why can the red top and the running alternator not provide enough.
no i am not pulling the boat forward with the windlass.
so, what do other furomites recon re red top (the third battery) and windlass, ok or not ?
perhaps it still slips under a heavy load ? does the type of belt matter ? its a is a Volvo OEM replacement.
or do alternators wear out and possibly cant cope with the longer strain on them b4 they fail completely, its just a question
obviously the VSR is not designed to carry a full windlass loads.
the Q is why can the red top and the running alternator not provide enough.
no i am not pulling the boat forward with the windlass.
so, what do other furomites recon re red top (the third battery) and windlass, ok or not ?
PaulRainbow
Well-Known Member
It is an absolute must. Without it a heavy load can be applied to the VSR and its wiring, damaging the VSR or the wiring, even resulting in a fire.
simonfraser
Well-Known Member
k, 'You need data, in your case volts, unless you have a clamp ammeter'
which i now do have. and a remote for the windlass so i can run it and see the amps produced at the same time.
which i now do have. and a remote for the windlass so i can run it and see the amps produced at the same time.
halcyon
Well-Known Member
Okay, run it, check amps at winch, batteries and alternator, plus volts at same points. Do you know alternator rating and winch motor loading.
Brian
lw395
Well-Known Member
when the windlass draws current, as soon as it pulls the combined might of the alternator and 'red top' below the voltage of the other bank, current will start to flow through the VSR, if the VSR is closed.
The VSR will be closed because the starting point is that the engine is running and the alternator is bringing the red top to say 14V.
The VSR will usually only open after a set period from the time when the volts drop below say 13V
The current which flows through the VSR will be dictated by the health and state of charge of each of the batteries, the output impedance of the alternator (depends on RPM), and the resistance of the interconnections.
If the resistances are all nice and low, you might expect something like:
The alternator will contribute a large fraction of its design current at that RPM
The batteries will share the remainder of the load very roughly in proportion to their size and/or CCA.
So for a 700W windlass (guess), you might guess a surge current of maybe 200A.
Alternator might do anything from 40 to 80A at fast idle? WE'd need to check that.
Leaves 100-odd amps to share.
The resistance of the wiring might keep the VSR current below 30A, but only while the red top is happy and healthy.
In reality the surge current to pop the fuse could be 2x rating. Fuses are designed to cope with a short surge.
This sounds like a common case of a system that will work fine while all the batteries are new and perfect, but may not be robust for batteries that are not new.
I have apocryphal stories of red tops have short lives when float charged a lot, but as most of this mythology contains LandRovers, winches and nutters, take it or leave it.
So the options are:
Ensure the VSR can take the load
Make sure the VSR is open when the load happens
or design the system rigorously to tolerate a certain worst case level of battery health.
I agree with the need for data, but most of this issue is probably not steady-state, so good luck with that. But have a go, as you may rule out a few things.
HTH, but I have a sweepstake running here about who will say what, refuting kirchoff, thevenin and ohm.....
The VSR will be closed because the starting point is that the engine is running and the alternator is bringing the red top to say 14V.
The VSR will usually only open after a set period from the time when the volts drop below say 13V
The current which flows through the VSR will be dictated by the health and state of charge of each of the batteries, the output impedance of the alternator (depends on RPM), and the resistance of the interconnections.
If the resistances are all nice and low, you might expect something like:
The alternator will contribute a large fraction of its design current at that RPM
The batteries will share the remainder of the load very roughly in proportion to their size and/or CCA.
So for a 700W windlass (guess), you might guess a surge current of maybe 200A.
Alternator might do anything from 40 to 80A at fast idle? WE'd need to check that.
Leaves 100-odd amps to share.
The resistance of the wiring might keep the VSR current below 30A, but only while the red top is happy and healthy.
In reality the surge current to pop the fuse could be 2x rating. Fuses are designed to cope with a short surge.
This sounds like a common case of a system that will work fine while all the batteries are new and perfect, but may not be robust for batteries that are not new.
I have apocryphal stories of red tops have short lives when float charged a lot, but as most of this mythology contains LandRovers, winches and nutters, take it or leave it.
So the options are:
Ensure the VSR can take the load
Make sure the VSR is open when the load happens
or design the system rigorously to tolerate a certain worst case level of battery health.
I agree with the need for data, but most of this issue is probably not steady-state, so good luck with that. But have a go, as you may rule out a few things.
HTH, but I have a sweepstake running here about who will say what, refuting kirchoff, thevenin and ohm.....
simonfraser
Well-Known Member
'So for a 700W windlass (guess), you might guess a surge current of maybe 200A'
yes agree, but the fuse blew when winding in 30m relatively easy, vs coming to a complete stop on a knot in the chain which would draw a major amount of amps for a sec ?
yes agree, but the fuse blew when winding in 30m relatively easy, vs coming to a complete stop on a knot in the chain which would draw a major amount of amps for a sec ?
halcyon
Well-Known Member
Doing random search, Lofrans 700W working load amps 110 A, working pull 125 Kg.
If the OP has two people should not e to ad, only looking or guide values.
Brian
Plum
Well-Known Member
That is completely understood, Paul, but why do all the VSR wiring diagrams show a fuse on BOTH sides of the VSR? Surely just one will protect the VSR.
www.solocoastalsailing.co.uk
lw395
Well-Known Member
I'm not sure what diagrams you are referring to, but possibly it allows for a long cable between the fuses (with the VSR in it somewhere).
Such a cable should be fused at both ends, as it has power source at both ends, if you feel the need to protect that cable from being shorted to GND/-ve/earth.
halcyon
Well-Known Member
The fault could be in either side of the VSR cabling, so you protect either battery supply in case VSR is open circuit, you protect cable not VSR.
Brian
PaulRainbow
Well-Known Member
As said, a single fuse will protect the VSR from current overload. In cases where the VSR is mounted in a position where it might be possible to short the wiring, there needs to be a fuse at the battery end of each cable, these then protect both cables from short circuit and the VSR from current overload.
The Victron wiring schematic only shows a single fuse.
