12v wiring questions...survey suggestions...

[MoonlightSailor]

Aloha,

My most recent survey suggested installing single circuit switches (on/off) at the starter battery and the two aft 8D batteries. The survey did not mention how I should remedy the lack of a second 300A fuse for the two forward 8D batteries, like the one installed for the two aft 8D batteries. Any thoughts on this or what the ABYC standard is?

The two aft 8D batteries were installed with a 300A BUSS fuse but without a single circuit switch for situations needing a quick disconnect, i.e. arcing.

In 2012 I installed two more 8D batteries forward in the vessel. I did install a single circuit (on/off) switch for these two batteries. However, I did not install a 300A BUSS fuse like the one installed on the two aft 8D batteries. I connected the two forward 8D batteries to the positive and negative busbar as seen on the schematic.

My ultimate question is whether or not I should install another 300amp fuse for the forward 8D batteries like the one installed for the aft 8D batteries? Suggestions?

The two aft 8D batteries are connected to the shunt (-) and the positive house busbar. Bypassing the shunt for the two forward 8D Batteries isn’t an issue at this point unless I wanted to measure the voltage of the forward 8D batteries separately.

Your thoughts, questions and/or suggestions are most welcome!

Matt

[CharlieJ]

If you adhere to the ABYC and/or ISO Standards, every B+ conductor on the boat except the engine starting circuits require an over current protection device (OCPD). The over current protection is generally a fuse or circuit breaker. The OCPD is required to be within 7 inches (there are exceptions) of its attachment to the power source, have adequate ampere interrupt capacity (AIC) and be sized to protect the conductor.

[SailingHarmonie]

You are asking if you should have a fuse protecting the wiring attached to the forward batteries?

The answer to that is ALWAYS going to be not just "Yes", but "Hell, Yes!!!!". It has nothing to do with "ABYC" or "ISO" or any other rule. It is simply the only safe way to do it. If your surveyor did not call out the lack of a fuse, he failed quite badly at exactly what it is you pay a surveyor to do.

I have no idea what the size of the fuse should be, and I have no idea if the fuse installed in line with your old batteries is the correct size. The size of the fuse is dictated by the ampacity of the smallest wires attached to the battery that are not otherwise protected.

[Kettlewell]

Yes, you need a fuse very close to the forward batteries. In addition, unless I am reading the wiring diagram incorrectly, it doesn't look to me like there is any sort of switch to completely disconnect the aft batteries, so I agree with the surveyor you need some switching there too. Basically, you want to have an appropriate fuse very close to any power source and you want to be able to disconnect with a switch any power source.

[MoonlightSailor]

Thanks for the feedback everyone! Makes sense to me. Have to get it done now.

Mahalo!

[MoonlightSailor]

Update:

I installed a single pole on/off switch just before the existing 300 amp BUSS fuse. Mr Frosty installed that 300amp fuse before the house BUSS bar. I have no idea how he calculated or determined that 300amp is what the system needs.

Thought: The auto-charging relay combines the batteries when voltage reaches the determined amount. If a short should occur, I would have to disconnect both the house and the starter battery with the single pole switches because the relay has them combined. Am I thinking correctly about this?

I'm trying to place the disconnect switches as close to the batteries as possible. They are not within 7 inches of the battery. I do understand the reasoning for putting them as close to the battery as possible. Trying to put the switches in a location where they are readily accessible when needed and not have to remove anything cumbersome to get to them.

The windlass has its own dedicated in-line 200 amp fuse.

Starter battery: I need to put a single pole switch and a BUSS fuse close to the (+) of the starter battery with an in-line switch. I just don't know what fuse capacity I need.

If the batteries are always combined with the relay...how does this affect my fuse size...if at all?

It was stated above that The size of the fuse is dictated by the ampacity of the smallest wires attached to the battery that are not otherwise protected. The smallest wires attached to the batteries are just 12G (I think...) which are the voltage indicator wires. All the other wiring is 2/0. Oh, one of the house batteries has the bilge pump direct connect with in-line fuse.

Matt

[CharlieJ]

Fuses are required to be within 7" (with exceptions) of the battery B+. Battery switches are to be readily accessible.

As the system moves away from the 2/0, each B+ has to be protected with an appropriate fuse/circuit breaker.

Recommend Nigel Calder's "Boatowner's Guide to Mechanical and Electrical Systems." Written for the average, handy, boat owner.