Fuse / Circuit Breaker Question

[Brendanpd28]

Hey guys,

    I have started wiring my console and I have all my schematics drawn out etc...  I am using the Blue seas Mini Add-A-Battery setup, A switch panel with built in circuit breakers, and a fuse block for some other non switched accessories. I have it about 90% planned out.....my only issue is figuring out what size in-line fuses or breakers to use on the main battery cables. I know I dont need any on the + side of the outboard starting circuit, but I do on the house side and going into the ACR.  My loads include:  VHF Radio, Stereo, Nav Lights, horn, compass light, voltmeter, bilge. The outboard is a 1990 Evinrude 88 SPL. Below is a wiring diagram from Blue Seas for the add-a-battery kit. There is an in depth diagram and instructions on their website but I still can't figure out the breaker size!!

I greatly appreciate the help on this.....I have read countless articles on this subject but am still a little confused.

Thank you

[wingtime]

Here is a basic drawing of how I did my ACR install.  It's not on the drawing but the main breaker for the house feed on my Explorer is 40 amps.  Of course I have more pumps and other loads than you do.  You can also just add up all the fuse sizes for your circuits and add on to that.  You want to allow for future loads.  Of course if you use a Maxi fuse you can just go to a bigger fuse down the road over a breaker. (just be sure to carry spare fuses)

[Brendanpd28]

Here is a basic drawing of how I did my ACR install.  It's not on the drawing but the main breaker for the house feed on my Explorer is 40 amps.  Of course I have more pumps and other loads than you do.  You can also just add up all the fuse sizes for your circuits and add on to that.  You want to allow for future loads.  Of course if you use a Maxi fuse you can just go to a bigger fuse down the road over a breaker. (just be sure to carry spare fuses)

Thanks wingtime.  What size breaker or fuse did you use between battery+ and the ACR?  The schematic shows them there. I assume its based on the charging amps of your outboard but I dont know how to figure that.

Thanks

[Brendanpd28]

Im also a little confused because I was under the impression you weren't supposed to chain the battery switch to the ACR. It shows separate + cables directly from the battery to both the switch AND the ACR.

" It is recommended that the m-ACR be connected directly to your battery positive terminals through
appropriately sized fuses. Connecting in a different location such as a battery switch may affect
accuracy because of voltage drop along current carrying conductors."

[Capt. Bob]

OK,
Remember first that the function of a fuse is to protect the wire, not the device. With that said, you appear to have the 65amp add a battery system. I take that to mean that the ACR is designed to handle loads approaching 65 amps from your charging system so....
As you stated, you need to first know the output of your engine's charging circuits. That's usually readily available in a service manual that you have.

The schematic that you first show is based on the idea that the ACR is close to the batteries and could use a smaller gauge wire than the feeds to your motor which should be based on the distance from the battery and the amp draw while cranking (hard to find other than actual measurement). Max cable size for your ACR is 1/0 AWG so if your running 2 AWG to the motor, you can use the same gauge for the ACR (assuming 2 AWG is the right size but it is what most use when relocating batts to the console). The disclaimer on voltage drop is to prevent the ACR from overheating. You can CYA by using a larger wire size and the fuse size needed to protect it. Blue Sea probably has a chart showing their recommended fuse size.

The dual circuit switch that comes with the kit is designed to eliminate feedback from your starting circuit to your electronics while still having the ability to combine both batteries in a pinch. Your schematic shows the switch in the combined mode.

I run 2/0 wires for my starting system (I also have the old style battery switch) and my charging system is/was at one time about 35 amps while my cranking amperage is 170 amps (measured).

Good luck.