Catastrophic Fuses

[harojs]

Do you use an add-on Catastrophic Fuse on your battery terminal(s) for typical V8 sterndrive? If so, what size, mfg, layout, pictures?

 

[Scott Danforth]

No, not needed and wont work. inrush current from the starter is like 400 amps any fuse big enough to survive in-rush current would be too big to handle a short that would cause a fire.

proper maintenance of your battery terminals and all connections is to clean the connections to shiny metal, make a good tight connection (if you have wingnuts, throw them away and get real nuts and a wrench). then after you make your connections, seal with marine electrical varnish.

 

[harojs]

Thanks. I keep hearing the per ABYC spec any circuits directly off the battery need to be fused within one foot. Maybe that is any circuit other than the starter mains, i.e., bilge pump.

 

[harojs]

I'm getting conflicting opinions on if CFs can be used on starter cable terminal. This below from the Hull Truth forum:

"Starter probably draws 100-200 amp. the blue sea MRBF fuses blow about 300% at one sec and at 200% at 10 secs so 900a for the first sec for a 300a fuse."

https://www.bluesea.com/products/5190/MRBF_Terminal_Fuse_-_300A

Any non-theorists out there? How are new boats fused to ABYC battery specs for starter cables??

 

[bruceb58]

http://assets.bluesea.com/files/resources/reference/2010_ABYCexcerpts.pdf

Note that wire intended to carry engine starting currents between the batteries, the switch, and the starter, is not required to have main circuit protection devices installed.

 

[harojs]

Super! Thanks bruceb58 - that diagram is exactly what I am looking for! I must have missed it on the Blue Sea site. It does look like the starter mains are exempt from fusing, but good to know how the other circuits should be fused. -John

 

[harojs]

[Q] Quick follow on question - How to you charge your START and HOUSE battery at the same time? Start engine on START Battery and then switch to BOTH ?

 

[alldodge]

Start engine on START Battery and then switch to BOTH ?

That will work, but best way is to install a ACR (automatic charge relay)