Electrical Wiring Diagram Help

[albinalaska]

I'm looking to rewire a new (to me) vessel to seperate and protect our new AGM batteries and would really appreciate some guidance on this current diagram I've been working on.

I can't take full credit for this diagram, it's from a sailboatowners forum (link below) but I modified it to fit my needs as I've yet to see diagrams that includes twin engines.

As stated in the artical below the "on/off" switches would be mounted by each bank in the engine room and would normally turned "on" except for in the event of a bank failure. During that time the Dual Circuit switch would be turned from "on" to "combine" to pull from the remaining good bank to still be able to crank over the engines.

My electrical understanding is only slightly better than my drawing skills so any advice or input would be very much appreciated.

Information I forgot to include in the diagram:

Charger: Blue Sea P12 runs at 40A
Alternator: Leece 51A
Solar: 30A
House Bank: 480Ah
Start Bank: 390Ah
Bus Bars: Blue Sea 600Amp

original link:
(https://forums.sailboatowners.com/threads/1-both-2-off-switches-thoughts-musings.137615/)

 

[pjtemplin]

Take a look at the YouTube channel from Pacific Yacht Systems, and find his "design" videos. Do a few things to streamline your diagram (based on what he says):


Eliminate the negative wires from your diagram - we know you're going to have them, everything needs to tie back to them, but if you eliminate them from the diagram it already becomes a bit cleaner. While you're at it, use that neutral bus bar and tie EVERYTHING to it. I'm speaking about your DC panel - run it to the NBB, not to the battery. You want those terminals to be as simple as possible, and you want to have the cleanest option to insert a shunt to be able to utilize a battery monitor.


Watch his videos for a description of switched versus unswitched distribution. Several things do NOT belong behind a switch, and the alternator is the biggest offender I see. Starter is probably next, and review his recommendations on fuses for the starter. I think you're going to have tons of nuisance tripping with a 150A fuse on the starter, as well as from the house battery to the ACR.


I don't like how you have the DC panel fed. That switch up top seems to almost bypass the ACR.



Consider what you want that ACR to do. Is it there in case the start bank is dead and you want to use the house bank to get one engine started? It seems like the switch up top can easily bypass the ACR, which seems "wrong" to me. Also consider if you would be better off with a battery isolator unit, which would allow the alternator to charge both banks while NOT tying both banks together, and/or a DC-DC converter so that you have a controlled current flow from one bank to the other (tying the banks together with one bank in a sad state will result in a HUGE current flow, apt to blow that 150A fuse).

 

[albinalaska]

I appreciate the input- I’m a visual learner so I added everything necessary but thank you for your clarification on cleaning up the diagram. I’m looking to evolve this so the 150A fuse is certainly negotiable. I had assumed that was for the ACR which is only rated at 120A so it gave some room with the 150A. What fuse size would be recommended instead?

My theory was exactly as you mentioned: With both switches next to the ACR set to “On” the alternator would charge the house bank first (since its larger) then hit the Starter bank. The ACR would separate them and in the situation a bank failed you’re correct- I would just turn off that switch associated with that bank- set the Dual Circuit switch to “combine” and the good bank to turn the engines over.

There is currently two sure isolators wired in in some very confusing manner amongst just to the two starter batteries. Everything in wired in parallel which is a big mess and we really just want to clean it up and redo it the right way.

 

[albinalaska]

Regarding the Dual Circuit switch - it’s my understanding it just activates the two separate banks at the same time. The ACR - performing as expected - splits the banks when drawing power, combines them when charging but nothing can bypass it. It’s either on or off.

 

[Comodave]

The thing to remember about ACRs is when you are on shore power and use a battery charger as the voltage rises the ACR will activate and connect the banks. That is probably not what you want so you need to open the ground on the ACR so it won’t combine the banks when on a battery charger. We just have an on/off switch in the ground wire and turn it off when on shore power.

 

[albinalaska]

The thing to remember about ACRs is when you are on shore power and use a battery charger as the voltage rises the ACR will activate and connect the banks. That is probably not what you want so you need to open the ground on the ACR so it won’t combine the banks when on a battery charger. We just have an on/off switch in the ground wire and turn it off when on shore power.

Thanks COMODAVE- Ive actually seen that on other diagrams but forgot it. Does it matter if the charger sends different loads to multiple banks? Or maybe that makes it all the more important to turn off the ACR.