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Please explain how this works


pelicanafloat

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This is the product: http://www.shop.sterling-power.com/acatalog/VSR_CVSR.pdf

 

I stress, I don't have this fine beast. A friend has one fitted on his boat ... typically as shown on page 2 in basic 90% application drawing ...

 

The fuse between the device and the bow thruster battery bank blew. It was replaced. Now it appears that the led's on the unit don't light up. The unit is supposed to reset and reboot automatically upon be powered up again ..... I can't tell you why, it doesn't appear to work, its not mine, I haven't tested anything ...

 

What I would like to know is just what does this device actually do or protect. Does it prevent the positive feed going right to the other end of the boat overloading? I notice that the size of the cable going off to the battery bank seems no bigger than about 6-8mm in diameter (bare). I wondered if the device limited the amount of load current going through the device, and hence cable, but it just seems a wierd way to go about it. What I can't get my head around is that the total possible alternator output could be as high as 175amps yet the fuses each side of the device are 80amp? ...and it been ok for last 3 years from new??

 

Anyway, I'm not involved, so my asking is sheer curiosity (and as friend asked if I could help, it would be nice to be able to explain what is actually happening). I like things to be KISS.. ty for reading

 

Stewart

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I could be wrong but I could be something to do with volt drop.

 

Its not volt drop it looks like the unit detects when the primary battery off the alternator if full and sends the charge to another battery bank.

Edited by leeco
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The link explains how it works. Its a voltage sensitive relay, ie it joins up 2 battery banks when one is being charged. For example if your engine is running and the starter battery is charging, it joins it to the domestic battery bank. And if you have shoreline with a battery charger charging the domestic bank, then it will join up the engine/starter battery too.

 

As I see it, there's no current/limiting function over & above the fuses which are external to the unit, except on the "current limiting" model - does your friend have this one or the standard one?

 

Then there's a bunch of other functions which complicates things but are things which people might want to do, like the override switch, etc.

 

Of course, these days, boats may have more than one alternator; or a mains battery charger with more than one output - thus making it superfluous.

Edited by Paul C
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I thought the cable a bit small for a 60' run .... comparing to the size of the standard battery cables, I would have expected a much larger cable to limit the voltage drop.

 

I can't get into look or inspect the unit. It is very conveniently screwed to the wall with a girder supporting the battery cut-off switch running about 2" in front thereby limiting access to the working bits. I am told it is a current limiting device as well. I assumed the current limiting aspect was one of a dead short occuring somewhere, or a basic high current failure in the battery bank ... The fuses are intact, and it maybe that the unit is working ... but I rather suspect that the blowing of the fuse infers a melting of the relay ..perhaps??

 

The boat has 2 alternators, a travel pack, and 'maybe' an adverc though it is only a maybe :) I wasn't intending to be too precise because I really wanted to know what a current limiting device does in this situation. I must be bored lol

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It is with great sadness that I will have to leave this thread while I make a visit to Narrowboat World ........

 

..... nothing but delusions of expectation were harmed in the making of this thread ...... was it something I said?

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Reading the link in the original post, it appears as if it SHOULD limit current over a sustained period of time over 70amps, to something like 6 amps. If it senses this, it also opens the relay ie cuts it off so its obviously 0 amps flowing. And it allows short peaks of over 70 amps (because the overload device is a thermal one).

 

Anything much more than 70 amps, would rely on a conventional fuse either side blowing, to protect it.

 

Unfortunately for some reason I suspect the 80 amp fuse didn't blow, despite a current more than that (dead short created in the wiring somewhere? Bow thruster had something jammed in its propeller and drew 300-400 amps?) and the resulting overcurrent "cooked" the device, despite its overcurrent protection feature, and quicker than the 80A fuse could blow.

 

Personally the thing seems more complicated than it needs to be and the bin is probably the best place for it.

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Thanks for all the replies, especially Pretty Funked Up's not quite pointless yet very erudite reply :-)

 

I understand the idea of putting in this particular item in the circuit was because the fitter was concerned by the inadequate size of the supply cable. Ah well......

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