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which goes first? fuse or switch

vinthewrench

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Jun 25, 2021
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Quick question of practicality..

Assume an array of batteries in a outdoor battery box, going to an inverter.
which should be closest to the battery in current flow, the fuse or the battery disconnect switch?

I am tending towards the disconnect switch (big Blue Sea SPST) first and then the fuse.

what say you all?
 
The fuse should be as close as possible to the battery, otherwise if a short occurs at the switch (in your case) the fuse does nothing.

Edit - this is a good example of this (fuse before the switch):

 
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An MRBF fuse (also sold by Blue Sea) mounts directly to the battery and is most convenient in many installations.
 
In common wiring the breaker comes first. Actually I would try to skip the switch unless you have a compelling and consistent need to cut power from the inverter. Mine has been connected continuously for years at a time. I remove the fuse or a cable for service.
 
Midnite Solar has a DC circuit breaker that may be big enough to combine the functionality of a breaker and a switch. There's a forum member that is using one.
 
Quick question of practicality..

Assume an array of batteries in a outdoor battery box, going to an inverter.
which should be closest to the battery in current flow, the fuse or the battery disconnect switch?

I am tending towards the disconnect switch (big Blue Sea SPST) first and then the fuse.

what say you all?

A fuseholder can be a battery disconnect switch too.
For bigger packs I like the NH1 fuses and fuse holder / disconnector:

Also is better to fuse and disconnect both cables !
 
Those NH1 fuses look nice, any idea where they may be available for a reasonable price in the US?

I'm building a few LiFePo4 batteries and will be running a shunt followed by fuse off the battery negative, and a 250A remote trip DC breaker on the battery positive. My theory is keep all the safety stuff as close to the energy as possible. :)
 
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