Battery Fuses

[rrees]

I have notices in the RS catalogue they do fuses that are part of the Battery clamp
Part number CF8
I though it would be a great safety feature to have these in line with the positive of the battery as we are away from the boat quite a lot and use a Stearling battery charger on constantly to charge the batteries.
ratings come in 50A through to 300A
I have a Yanmar 27h engine and 2 battery banks any thoughts on the rating of fuses I should use

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[bedouin]

The correct way to select the fuses is according to the rating of the wire connected to it. So you should measure/work out the size of the wire, find out it's rating from that and use the biggest fuse smaller than that.

Of course this could give you problems if the battery cable itself is underspecified.

Alternatively, it is fairly easy to calculate the capacity for the domestic battery - just add up the loads of all attached items. The starter is harder - since on start up it draws a huge instantaneous current - but fusing it a little above it's rated capacity should be okay

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[rrees]

Thanks for the advice

on the battery issue my battery storage space is ideal on the domestic side for a bank of 3 85A leasure batteries instead of 2 110A
What are people thought on this, as to use 2 I would have to modify the area

Thanks

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[jcr]

The way to select a fuse is to determine the maximum current that the battery cable will carry under normal operation. This will probably be the maximum current that your alternator/charging system will provide if your batteries are deeply discharged or, possibly, the current to supply a windlass or bow thruster plus whatever other loads that will be on. The fuse selected must be able to carry this maximum current comfortably. It is assumed that your system has been properly designed so that your cable sizes and fuses will carry the design currents, at various points in your circuit, comfortably.

The purpose of equipment fuses is to protect the equipment in case a fault in the equipment causes too heavy a current to flow into the equipment. The correct fuse rating should be the design current + a small percentage - say 20%.

The purpose of a battery fuse is to prevent meltdown of the system cables and hence a fire hazard. The rating selected is not, therefore quite so critical. I select a fuse rated at the maximum expected current + 50%.

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