VSR blowing fuses

simonfraser said:
red top starter and trojan 2x house
VSR between the two
shore charger to both
engine alt connected to red top

i need a 35+A spade fuse in the VSR connection to stop it blowing

fuse rating seems v high ?
Click to expand...

when does it blow?

When shorepower charger is on?
When engine is running?
Only when both are in operation

Even if neither is in operation?

When you crank the engine ?


If the max output of the alternator is greater than 35 amps that might explain it (or if only one of the shorepower charger outputs is working and that is more than 35 A.

Fuse rating seems low to me but the instructions for installing the VSR should advise . Whatever rating you fit ensure the interconnecting cables are appropriately sized
 
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simonfraser said:
red top starter and trojan 2x house
VSR between the two
shore charger to both
engine alt connected to red top

i need a 35+A spade fuse in the VSR connection to stop it blowing

fuse rating seems v high ?
Click to expand...

Does not seem high to me. Connections must be able to take the full charging current and VSR are often rated at 70A or more. Not sure a dedicated fuse for the VSR is needed, provided there is a fuse close to the house bank.
 
simonfraser said:
i need a 35+A spade fuse in the VSR connection to stop it blowing

fuse rating seems v high ?
Click to expand...

It isn't. When the engine's running, the VSR will be carrying all the charging current to your Trojans. You should fuse the connection to match the VSR's current-handling ability. And, of course, ensure the cables connecting the VSR are able to handle that current.
 
Naively - does not the introduction of a fuse to an alternator output introduce a risk of blowing the alternator output diodes when it ruptures?

The output from a car alternator goes straight to the battery (via the starter motor connection).
 
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simonfraser said:
yes, clarification, the alt is connected to the main +ve to the starter battery via the starter motor, red top.
i dont think it has a fuse, but it can't have one ?
Click to expand...

If there was one and there was a short the fuse would blow and probably destroy the alternator diodes.

If there wasn't one and there was a short the alternator would probably be destroyed anyway!

Take your pick!
 
BabaYaga said:
The reason for fusing only the VSR connections and leaving every other wire unprotected escapes me.
Click to expand...

I dont think the diagram ( not mine) is intended to be a comprehensive wiring diagram . Only intended to show the connections for the VSR

Given more time I would have found a better one perhaps.
 
BabaYaga said:
The reason for fusing only the VSR connections and leaving every other wire unprotected escapes me.
Click to expand...

The reason is VSR protection. I fit a minimum of three resettable fuses, one protects the relay coil and feed, the others protect control system for relay, plus positive voltage feeds to display and display electronics.

Brian
 
halcyon said:
The reason is VSR protection. I fit a minimum of three resettable fuses, one protects the relay coil and feed, the others protect control system for relay, plus positive voltage feeds to display and display electronics.
Click to expand...

Interesting. Would that be your general recommendation for others to follow? How do you get at the relay coil feed and control system without opening the relay – I think most VSR's have only 3 connections, 2 for the battery positives and 1 negative?
 
BabaYaga said:
Interesting. Would that be your general recommendation for others to follow? How do you get at the relay coil feed and control system without opening the relay – I think most VSR's have only 3 connections, 2 for the battery positives and 1 negative?
Click to expand...

No, I just design and build to my standard, the connections are integral with the control system, the 4 battery bank unit for example has 8 resettable fuses, 4 protect internal electronics and voltage feed to display, 3 protect shunts and display feed, 1 protects relay drives.

I agree with you, most VSR's cannot have protection fitted for control side, fitting a 1.5 / 2 amp fuse to earth feed will give some protection if not already fitted. As long as the supply cable is the same or larger than main feed and taken from correct point, then the main fuses if itted will provide protection.

Brian
 
Today was instructive,
Red top and two Trojans fully charged from shore charger, all new batteries.
Windlass wired to red top as is the KAD.
VSR with 35A spade fuse between the red top and Trojans, obviously.
Engine ticking over, put the chain down, CLUNK, knot in the chain, that must pull some amps, fuse ok
On the way back, 30m to pull up, that is unusual round here for a lunch stop, anyway, fuse blew whilst pulling it all up, in sections of 10m, as in a short rest.
So, thinking is that the red top and engine ticking over cant supply enough for the windlass so the extra comes in via the VSR and pop goes the fuse.
Bigger, 80A fuse being organized with thicker cables.
Would it be kinder to the batteries to run the engine at higher revs in neutral when the windlass is being used ?
 
simonfraser said:
Today was instructive,
Red top and two Trojans fully charged from shore charger, all new batteries.
Windlass wired to red top as is the KAD.
VSR with 35A spade fuse between the red top and Trojans, obviously.
Engine ticking over, put the chain down, CLUNK, knot in the chain, that must pull some amps, fuse ok
On the way back, 30m to pull up, that is unusual round here for a lunch stop, anyway, fuse blew whilst pulling it all up, in sections of 10m, as in a short rest.
So, thinking is that the red top and engine ticking over cant supply enough for the windlass so the extra comes in via the VSR and pop goes the fuse.
Bigger, 80A fuse being organized with thicker cables.
Would it be kinder to the batteries to run the engine at higher revs in neutral when the windlass is being used ?
Click to expand...

If the windlass was connected to the domestic bank there would not be a tendency to draw power from the other bank. Whilst the VSR is rated at 120a, it would need 20mm cable for that rating and it wasn't really designed to be supplying power to a windlass.

I would put the windlass on the domestic bank, and increase the fuse rating too.
 
simonfraser said:
Today was instructive,
Red top and two Trojans fully charged from shore charger, all new batteries.
Windlass wired to red top as is the KAD.
VSR with 35A spade fuse between the red top and Trojans, obviously.
Engine ticking over, put the chain down, CLUNK, knot in the chain, that must pull some amps, fuse ok
On the way back, 30m to pull up, that is unusual round here for a lunch stop, anyway, fuse blew whilst pulling it all up, in sections of 10m, as in a short rest.
So, thinking is that the red top and engine ticking over cant supply enough for the windlass so the extra comes in via the VSR and pop goes the fuse.
Bigger, 80A fuse being organized with thicker cables.
Would it be kinder to the batteries to run the engine at higher revs in neutral when the windlass is being used ?
Click to expand...

The next thing is to check what volts you get at each battery bank with winch running, this will give a good clue as to where the power is coming from. You can then make a rational choice as to best supply source.

Brian
 
halcyon said:
The next thing is to check what volts you get at each battery bank with winch running, this will give a good clue as to where the power is coming from. You can then make a rational choice as to best supply source.
Click to expand...

But if the batteries are linked by the VSR, wouldn't the measured voltage be fairly similar?
 
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