Electrical Wiring Dreams

Bill Roosa · Feb 18, 2014

Hey Apex
there are two schools of thought for wiring a boat; keep is simple and manually control the circuits with switches or automate it so you don't have to do anything. There are an almost infinite mixture between those two extremes.
So there is no ultimate layout till we know which camp you are in.

As to adding an charger you have to consider the following:
how long will the charger have to bring the batteries back up to full charge:
how big is the battery bank?
Do you want to be able to control which bank(s) get charged or do all the banks get charged every time.
Will the banks be at different states of charge when you turn the charger on.
Is it acceptable that you can manually configure the system so it does not work? ie you accept some risk if you screw up and/or forget to do something.

All this gets to how you use the boat.

My weekend/vacation sailing needs are answered thusly:
Big haunkin battery bank (6- 6 volt Trojan T105s) broken into two (4 and 2) banks controlled by a 3-way switch. The charger attaches all the + leads to the common post on the 3-way so if I need to I can just charge or concentrate the charging of one bank. I leave the 3-way on "both" almost all the time so I'm working the entire set of batteries. I only switch to House (4) when my reading from the volt meter indicate that the whole set will not make it through till the next engine start. I have a 150 amp alternator deregulated to 50 amps (belt issues, don't ask). A 40 amp battery charger and no genset. I practice finding snug anchorages when possible so I have the motor on while we move up the river. This practice allows the batteries to get charged back up to the 80%ish SOC level and I have hot water for a shower and dish washing. I do not routinely isolate the separate start bank (2) unless the voltmeter indicates that is needed. I also understand how much energy I use during a night with random cabin lights and the anchor light, bilge pump...... running so I'm manually estimating based on past experience. Now if something changed like the prop shaft gland started leaking and running the bilge pump more. I'd notice that at some point in the night and get up and isolate the starter battery bank......There are thousands of different combinations of events and situations that would require this but those don't happen much, so this setup REQUIRES the Captain to stay on top of things. This is not acceptable to a lot of folks however so this "ultimate setup" that is simple and does not break easily is viewed as a "billy bob solution".
FWIW

Maine Sail · Feb 18, 2014

Are you starting from scratch?

Will you have solar?

How many Ah's per day do you use?

Is the boat at a dock after each use?

Is there already a battery switch installed?

Is it the typical O'Day location with the switch in the panel under the companionway?

How do you use the boat? Day sails, over nights, multiple week trips?

What do you have for an alternator?

What size batteries are you thinking?

Designing a system that works for you and your use will be the best system. What may work for one boater may be financial overkill or too complex for another....

dlochner · Feb 18, 2014

On my Sabre 30, with a 2 Group 24 battery bank, the house and start battery were separated using a Blue Seas System switch. Both batteries are connected with a Blue Seas ACR and charged with the stock alternator. At the time that I installed the system the thinking was to run the alternator to the start battery and let the ACR charge the house battery. My understanding of current thinking is to connect the alternator to house battery and let the ACR charge the start battery.

Separating the batteries in this way is pretty simple and inexpensive and helps to ensure that the start battery is always charged. System worked well, the last set of batteries lasted 9 years.

Maine Sail · Feb 18, 2014

dlochner said:
On my Sabre 30, with a 2 Group 24 battery bank, the house and start battery were separated using a Blue Seas System switch. Both batteries are connected with a Blue Seas ACR and charged with the stock alternator. At the time that I installed the system the thinking was to run the alternator to the start battery and let the ACR charge the house battery. My understanding of current thinking is to connect the alternator to house battery and let the ACR charge the start battery.

Separating the batteries in this way is pretty simple and inexpensive and helps to ensure that the start battery is always charged. System worked well, the last set of batteries lasted 9 years.

If the banks are of unequal size it is best to route charging to the larger house bank. If the banks are of equal size, eg; two group 24 batteries one for start and one for house then it really does not matter.

For two small banks like yours it should work fine either way but as you get into larger and larger house banks or AGM or GEL batteries it can cause relay cycling to occur and slow charging to the house bank...

NorthStar · Feb 18, 2014

Apex said:
... Is there a general consensus on the whole system and it's wiring diagram? I would like to add a charger to a two battery bank, to augment my alt charging.

I realize there are many ways to wire, but what would be your ultimate layout.

So there are also different level of electrical needs as well. I am interested in my 2batt layout, but others are welcomed.

House battery
Starting battery (If you have two batt, would you reserve one solely as starting battery?)
Battery Switch
Charger,
Fusing,
panels,
ACT......???

What I have learned and implemented is; one large house bank (3x4D) and one engine start battery(group 27). All charging is tied to the house bank; alternator, shore power 3 stage charger, solar, wind..... an echo charger (15A) is connected to the engine start battery so what ever the charging source at the moment is applied to the start battery as needed. Then I added a battery switch that connects the starter to the house bank in case the engine start battery fails.

Bill Roosa · Feb 19, 2014

Apex
sounds like you don't have a reefer/freezer so you electrical loads while at the dock are probably in the 0-5 amp range on average. A small to medium (20-30 amp) charger connected to the (DC side of things) common post of the 3-way switch and a standard AC plug for connecting to the AC side of things is the easiest (but requires you to get the switch in the right location) setup to install. I believe they have the chargers that already have the AC plug (and associated fuses mounted internally I would think) in the new west marine catalog
Then you just need to find a place that is close enough to the battery 3-way and an AC outlet so you can run all the wires.
You do not have to buy a charger that will meet your total highest electrical load BTW as the batteries will take up the load if you exceed the chargers capability. You do have to size the charger for the "averaged out" load however. Since you will not be running a tiller pilot, instruments, nav lights....etc at the dock your electrical use probably is just the computer, phone charging and stereo and lighting.
Good luck