Calling all 12V Dc gurus!

Don S/V ILLusion · Mar 14, 2013

I don't understand your second q. If you are asking how to isolate the start battery, is your query on how to direct wire? This would also obviate the need for a problematic isolator and its inherent voltage drop problem.

As to the need to ventilate wet cells, which if it matters, is preferable unless you have an unstated need or rationale for using AGMs, there is none unless you are prone to out-gassing by overcharging. aGMs can out-gas too if you overcharge them. Lots of mfgs typically locate wet cells inside the boat which is also quite safe under ordinary circumstances.

Paul F · Mar 14, 2013

This is what I advised a new boater the other day on this site.
http://forums.hunter.sailboatowners.com/showthread.php?t=150232

I would recommend using a combiner rather than an isolator to charge both batteries at once. This is what I wrote:

Welcome to the site. You will get a lot of answers to your questions. If you have two 12 volt batteries, you can hook each red positive to the red pinwheel switch. One battery to the number 1 and the other to number 2. When you take the pinwheel switch apart you will find three posts. 1,2 and a middle one to carry the current on to your applications. O.K. so far? You can now use one battery to start the engine. This keeps one battery in reserve. After the engine is started you can place the switch to the both setting and charge both batteries at the same time. Most of us buy a combiner a little smart connection that connects both batteries together when one of them is charged to 13.5 volts. When you have a combiner there is no need to worry about moving the switch to both as the batteries will be connected for charging when one of them is charged.

On my first boat we used the number 1 on odd days and the 2 on even days so that the batteries were used evenly. Kind of a set for the day and forget system. If you get another battery so that you have three batteries a starter and a "house bank" of two batteries then there is more.

For this the addition of another switch works best for me. This new switch is on/off and is dedicated to a single starter battery wired through the switch to the starter motor. The red pinwheel 1,2,Both switch is then used to control the "house" battery bank. I wire this bank to number 2 on the switch. The number one is wired to the starter. When the new on/off switch is on and the pinwheel switch is on Both all batteries send power to the starter. The same combiner is used to keep the batteries charged connecting the starter battery to the "house" bank of two batteries. Don't worry about this now, just hook up the two batteries as first suggested and everything will work fine.

Paul F · Mar 14, 2013

Got it. I would simply add an On/Off switch going from your starter battery to the starter motor/ignition system and bypass all that other stuff. You can then use your house battery - ies to power the DC switch and the DC needs of the boat. Again use a Combiner to automatically connect the batteries when they are being charged by the engine's alternator or an outside AC charger.

kloudie1 · Mar 14, 2013

Interesting, Jim.. Normally the Yanmar panel would be fed from the battery lug on the starter solenoid. A red wire with a 30 ampere fuse in a little holder usually somewhere by the starter. The main battery switch, 1-2-both, connects the battery to the starter and if you turn the key on, the panel gets power. The panel is isolated as long as the key is off. The main battery switch also feeds the power buss for the breaker panel. That is the normal yanmar scheme.. but if someone changed yours up .. then it is whatever ya got.

Don S/V ILLusion · Mar 14, 2013

Paul F said:
Got it. I would simply add an On/Off switch going from your starter battery to the starter motor/ignition system and bypass all that other stuff. You can then use your house battery - ies to power the DC switch and the DC needs of the boat. Again use a Combiner to automatically connect the batteries when they are being charged by the engine's alternator or an outside AC charger.

That's it!

Both of our previous boats were set up exactly that way.
Anything different is overly complicated and prone to operator error.

If you want to get fancy, the only addition might be a cross-over switch but that a is almost always just for feel-good perception.

Stu Jackson · Mar 14, 2013

You;re buying or have already bought the Blue Sea "kit" with the switch and the "isolator." That isolator is NOT a diode, it is a true ACR (automatic combining relay).

What you do is wire the alternator output to the house bank and use the ACR to connect the house and reserve (start) banks. You're done.

If you have a wire between the alternator output and the starter, remove it (see this for why: OEM 1-2-B Switch Wiring History http://c34.org/bbs/index.php/topic,4949.msg30101.html#msg30101).

You seem to be confusing the "ignition" circuit with the power from the switch to the starter. The Blue Seas wiring diagram should show all this, although, IIRC, it only seems to show outboard motors instead of inboards with alternators.

Does this answer your question?

The downside of the system that you bought is that it only combines batteries when the house bank is dead, which is not such a great idea, but if you understand how it works, then it should work for you. Try reading this:

AGM Battery Issues and the Blue Seas Dual Circuit Switch (from Maine Sail) "DARN AGM Batteries"
http://forums.catalina.sailboatowners.com/showthread.php?p=848465&highlight=darn agm

If you think int will work for you, go ahead, or return it (the switch), buy an echo charger or keep the the ACR and use your existing 1-2-B switch.

Like this:

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615

Good luck.

TLW · Mar 14, 2013

Round teak vents:

Thaiteakmarine.com Catalog Page 37

Bill Roosa · Mar 14, 2013

Why do you want to isolate the engine electrical? You typically isolate batteries not parts of the rest of the boat. It will not hurt the engine ignition switch to be on all the time. Since when it is off the regulator and all the instruments that it powers are also off. not sure what you are trying to accomplish by isolating the engine?
Another way of saying this is the ignition switch IS your ON/OFF engine switch others have suggested.

Maine Sail · Mar 14, 2013

On most every boat out there the engine panel is powered directly off the starter lug. When you flip the battery switch on the engine panel can then be powered by turning the key on. If you are wiring in a dual circuit plus switch the engine panel should just pull power off the starter lug, properly fused of course.

Tom J · Mar 14, 2013

puddlejockey said:
Thanks for the quick feedback, guys!

To possible better clarify my question: There are 2 wires ( about size 8 AWG) that run from the engine compartment now to feed the entire Panel, and the current ignition system is tied through the "DC Main" feedswitch....so to power the ignition system, the DC main must be on, which also feeds the house batteries.

All connections of the battery cables themselves aside, how do you reroute/ eliminate/ or permanently connect those lines now feeding the DC panel, so that the ignition power is an isolated circuit?

I could be over complicating things; since I'm stuck with decoding the wiring that other folks have done over the years, much of which is counter intuitive and pretty "half arsed.."

It sounds like you are installing the same system I have on my C310. You are describing an isolating circuit battery switch with an ACR. The battery switch has 4 terminals. The start battery cable goes to a terminal on one side of the switch, and the engine start cable goes to the other terminal on that side. Then the house battery cable goes to one terminal on the other side of the switch, and the feed to the DC panel goes to the second terminal on that side. You are in effect replacing the "DC Main" switch. The ACR is then installed between these circuits, to parallel them for charging purposes. The sensing circuit for the ACR can be calibrated to the house battery or the starting battery. The idea is to isolate any voltage surges in the starting circuit from the electronics in the house circuit. The battery switch is labeled "OFF", "ON" and "BOTH", no "1" or "2". Correct?
As Maine Sail explained, the ignition circuit is still energized from the start circuit.

Stu Jackson · Mar 14, 2013

The battery switch has 4 terminals.

I'm sorry but it simply can't be if the switch only has three positions. Even a simple 1-2-B switch has only three terminals, but four positions.

mitiempo · Mar 14, 2013

Stu Jackson said:
The battery switch has 4 terminals.

I'm sorry but it simply can't be if the switch only has three positions. Even a simple 1-2-B switch has only three terminals, but four positions.

Yes it can Stu. The switch in the "Add A Battery" package from Blue Seas is unique in that it closes 2 separate circuits when in the "on" position. The 2 circuits are kept separate when in the "on" position and there is a "combine" position that parallels the house and start batteries when selected. You already noted that the Blue Seas diagrams (including the one below) only show outboards. That is because this switch is intended for battery banks of equal size. This applies to smaller powerboats that have a single house battery and a start battery. I have installed it on this type of boat, mostly small sportfishing boats and it is ideal for this. It is not intended to be used when one bank (house) is appreciably larger than the start battery. If the start battery is discharged and unable to start the engine the only option with this switch is to combine the banks. If the house bank discharged to 50% and the start is dead combining can leave you with the inability to start the engine. A discharged battery should never be combined with a good battery as the current will flow to the dead battery - if the house is discharged enough - as it might be after a weekend at anchor - you can end up with a start battery that has little charge and a house bank with less capability than before combining.

I love the ACR but this switch really doesn't belong on a cruising boat with unequal bank sizes. One is better off to keep the 1/2/both/off switch that is already installed and add the ACR by itself. This gives you the option of starting with each bank individually without using the "both" position. And it costs less.

Stu - Blue Seas also makes switches that are simple on/off with 3 studs on the back - one source and dual outputs.

Maine Sail · Mar 15, 2013

Stu Jackson said:
The battery switch has 4 terminals.

I'm sorry but it simply can't be if the switch only has three positions. Even a simple 1-2-B switch has only three terminals, but four positions.

Yes it has FOUR terminals and is OFF, ON & COMBINE

Bill Roosa · Mar 15, 2013

Still don't know why you are isolating a specific electrical component. You isolate batteries not the things that have switches on them. If you power the engine electricals off the ignition switch that would seem to be sufficient. What does completely isolating the engine electricals from the batteries accomplish? You don't need the instriments or regulator when the engine is off and the ignition switch would seem to accomplish that.

Stu Jackson · Mar 15, 2013

Maine Sail said:
Yes it has FOUR terminals and is OFF, ON & COMBINE

Thanks, I was wrong.

http://www.bluesea.com/products/7650/Add-A-Battery_-_120A

Calling all 12V Dc gurus!

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