Battery Switch Help

[Scott T-Bird]

With a 1-2-B-OFF switch and an engine battery disconnect you can connect anything to anything, and isolate either the house bank or the engine batt if there is a fault with either. I frankly don't "get" the DCP switch. Seems like BSS is just trying to create some new, exclusive thing.

I leave my 1-2-B-OFF in "1" always, and the engine batt disconnect closed, and just turn off the house main breaker when I leave the boat. When I'm on the boat the echo charger keeps the engine batt charged, and the alternator is connected to the house bank.

So, basically you are saying that the 1-2-B-OFF switch is inadequate when it is a stand-alone battery selector switch. I agree that with the engine battery disconnect switch added, you can increase the functionality of it. That seems to be what you are saying - that's fine, I agree. What you aren't saying is that you never find it acceptable to use the B position, even though it is available and is mis-used by many sailors (exactly the same way that a DCP switch can be mis-used in a stand-alone installation with the "COMBINED" position).

If you don't "get" the DCP, it's probably just because you don't want to. I recognize the limitations of it as a stand-alone switch, too. When the system is supplemented with 2 hidden ON-OFF switches, it basically rectifies the weakness. That was the point of Maine Sail's article, as I was saying. I'm not sure what your closing sequence is all about, leaving the selector switch on 1, turning off the batt disconnect, turning off the main breaker. Ok, that's fine.

When I go to my boat, I simply turn the DCP Selector ON, when I leave the boat and I want to charge when I'm away, I simply turn the selector switch OFF and I turn my AC charger ON at the AC panel, leaving the shore power cord plugged in. The ACR manages all charging. Simple, done (no need for echo charger). The 2 hidden switches are always ON and only need to be turned OFF (the appropriate one) when there is an emergency battery failure. What is there not to "get"? All situations covered, no need for distress. What situation do you think would not be covered?

 

[jviss]

What you aren't saying is that you never find it acceptable to use the B position, even though it is available and is mis-used by many sailors (exactly the same way that a DCP switch can be mis-used in a stand-alone installation with the "COMBINED" position).

This was a tough sentence to parse, with the multiple negatives. But, no, the "B" position is used, in two of the four modes: when there's an engine battery fault and you want to start using the house bank, and if there's an echo charger or ACR fault, and you want to charge the engine battery by manually combining it with the house.

Mode:​	1-2-B-OFF	Engine Disconnect
Normal Operation	1​	Closed​
House Bank Fault - Use Engine Battery	2​	Closed​
Engine Battery Fault - Start Using House Bank	B​	Open​
Echo Charger Fault - Combine House and Engine to Charge Engine	B​	Closed​

Note that this isolates the battery or bank that has a fault.

If you don't "get" the DCP, it's probably just because you don't want to.

Hardly.

2 hidden ON-OFF switches

Why "hidden?"

What is there not to "get"?

Three switches instead of two.

 

[Scott T-Bird]

This was a tough sentence to parse, with the multiple negatives. But, no, the "B" position is used, in two of the four modes: when there's an engine battery fault and you want to start using the house bank, and if there's an echo charger or ACR fault, and you want to charge the engine battery by manually combining it with the house.

No, you missed the point. You obviously needed to add the Engine Disconnect switch to make the system as functional as DCP, that is house bank isolation and start batt isolation. Standing alone 1+2+B doesn't have that function. Standing alone, you would not use the "BOTH" position, although many sailors do use that position without knowing any better.

Mode:​	1-2-B-OFF	Engine Disconnect
Normal Operation	1​	Closed​
House Bank Fault - Use Engine Battery	2​	Closed​
Engine Battery Fault - Start Using House Bank	B​	Open​
Echo Charger Fault - Combine House and Engine to Charge Engine	B​	Closed​

Note that this isolates the battery or bank that has a fault.

DCP performs each of these situations (as simply) when the system is designed correctly.

Normal Operation: DCP Position: "ON" House Bank Switch: Closed Start Batt Switch: Closed
House Bank Fault - Use Engine Battery: DCP Position: "COMBINED" House Bank Switch: Open Start Batt Switch: Closed
Engine Batt Fault - Use House Bank: DCP Position: "COMBINED" House Bank Switch: Closed Start Batt Switch: Open
ACR Fault - Combine to charge both: DCP Position: "COMBINED" House Bank Switch: Closed Start Batt Switch: Closed

Why "hidden?"

Because they almost never, if ever, need to be opened. They are always closed and don't need to be accessed by anybody unless there is a very unusual event.

Three switches instead of two.

So what? Only the DCP switch needs to be used on a regular basis. Your system needs 1 additional switch to make it work like a DCP. I need 2 additional switches to provide emergency isolation with combined loads. What is the difference? You could put your Engine Connect switch in a hidden location, I suppose - if it is normally closed all the time. You only seem to turn off the house panel breaker when you leave the boat. I only turn the DCP switch from "ON" to "OFF" when I leave the boat (I don't have a main breaker for the house panel). In both cases, the functionality is the same. I think the DCP is more intuitive & less inclined to be used incorrectly.

 

[jviss]

No, you missed the point. You obviously needed to add the Engine Disconnect switch to make the system as functional as DCP, that is house bank isolation and start batt isolation. Standing alone 1+2+B doesn't have that function. Standing alone, you would not use the "BOTH" position, although many sailors do use that position without knowing any better.

The 1-2-BOTH-OFF switch is a legacy piece of equipment. They have been used on boats for 50 or more years, and boatbuilders still put them on boats. Clever people figured out how to reconfigure them to achieve the functionality I have, and it doesn't require changing out the switch. I disagree that the DCP is more functional than the 1-2-B-O, as it, too, requires more switches to isolate things. And, if my switch was standing alone, I would use "B" to charge my starter battery and house battery at the same time; think of it as a manual ACR.

DCP performs each of these situations (as simply)

No, not as simply. There are three "inputs" to your system, only two on mine.

Your system needs 1 additional switch to make it work like a DCP. I need 2 additional switches to provide emergency isolation with combined loads. What is the difference?

1 switch.

 

[Scott T-Bird]

The 1-2-BOTH-OFF switch is a legacy piece of equipment. They have been used on boats for 50 or more years, and boatbuilders still put them on boats. Clever people figured out how to reconfigure them to achieve the functionality I have, and it doesn't require changing out the switch.

Exactly … it is not really a very good selector switch. It is only the one that most boats end up with.

No, not as simply. There are three "inputs" to your system, only two on mine.

The DCP switch is simpler, more functional and it requires only two inputs to isolate a bad battery or bank. What you consider a 3rd input is really just a matter of making the proper choice between 2 available inputs. The actual selector switch positions are more intuitive than the 1-2-B switch. I guess I see it this way because I changed out the 1-2-B switch almost immediately and never really understood any logic behind its design. I mean, 2 poles, only 3 posts? What sense does that make? I'm thinking that the only reason it is still in use is because it is a legacy piece of equipment.

 

[Tim Mills]

I have had it both ways on different boats. I much prefer to have separate switches also. Keep the starting battery switch OFF when the engine is off. Also; you are less likely to turn all "OFF" accidentally with a 1 2 B OFF switch when the engine is running possibly burning up the diodes in the alternator, no?

 

[Scott T-Bird]

I have had it both ways on different boats. I much prefer to have separate switches also. Keep the starting battery switch OFF when the engine is off. Also; you are less likely to turn all "OFF" accidentally with a 1 2 B OFF switch when the engine is running possibly burning up the diodes in the alternator, no?

No, not when the alternator (& other) charging goes directly to the battery banks. The wiring diagrams show that the alternator link to the starter is removed so charge does not go thru the selector switch. But turning the selector switch off when running the engine wouldn't seem to be a difference maker between the switches.