When adding an auxiliary powered fuse block should you fuse the positive cable going to it from the battery? I’m helping my dad with a project adding some lights and other goodies to his truck. We are going to add a 100 amp breaker to the positive wire as the max amperage of the fuse block is 100 amps. Dad also wants to be able to open the breaker to turn off the power to the accessories to work on them instead of having to disconnect the battery cables. I know adding a fuse or breaker won’t hurt anything but is it recommended or just something extra.

 

Yes any source off the battery that will be constant hot should be protected as close to the battery as possible. I would use a 100amp circuit breaker.

 

While the Max Rated Amperage of the Box may in fact be 100A as you state, Actually a 100A breaker may be too large for your needs... just because you can add the values of all the fuses in the box does not give you an Accurate Total Current Draw.

your best bet would be to temporarily install an Ammeter inline with the Battery and new Fuse box or use a Clamp On Ammeter and see what your actual Current draw is with all the accessories turned on, then you can realistically determine the best size breaker to use.

Using the 100A breaker while you folks are installing everything and getting all the things to work wouldn't hurt anything.

 

I've used these types of circuit breakers with combined off switching capability: Circuit Breakers In fact that entire site has a lot of high quality parts for adding, repairing or replacing vehicle electrical distribution components.

They're not cheap which is exactly what I want when dealing with something as important as electrical distribution and protection.

 

yeah our local West Marine carries Blue Sea products too, and there is nothing cheap about Boat (Bring Out Another Thousand)
Power Products, LLC now owns Blue Sea Systems since 2014 ... I saw a hike in cost shortly after that and saw much coming from China, but still good Quality.
I have done a lot of Marine work so I know a little bit about Marine products

 

As blasphemous as this might sound I'm not so much against anything made in China as I am those who move production of their once valued high quality items and lower the design specs to achieve lower costs. The Chinese are very capable of producing top quality IF their customers demand it. Whether good or bad the Chinese simply seize upon an opportunity to manufacture things exactly to the spec's they're provided.

I hate that USA jobs are disappearing but its those who sell us stuff who're to blame. I'm sure Blue Seas stuff will still be very good quality but probably less well-made as in years past.

 

Amen to that...........

EDIT: when we source a part to a China Manufacture, it also often ends up being cloned either/or much stock sneaks out the back door and a wise shopper can buy it for pennies on the dollar from Aliexpress ...... just saying
Aliexpress is almost as much fun as FleaBay.... Oh they have Crap items too, but you can find Quality at a reasonable price.
you just gotta have patience as shipping is on the Slow Boat as they say