Operating the House/Start battery selector

[Udi]

Hi !
Request The forum's advise concerning the operating of the "operating the House/Start battery selector between : "on" and combine batteries meaning: what should be it's position when : 1)on shore power (2 when starting engine. 3) when cruising on engine.4)when cruising on sails.5) when anchoring with no electricity.
Thanks for any help.
*Attached picture

 

[Davidasailor26]

It depends on how your batteries are wired. Generally you’ll want to select the larger bank when sailing or anchored to save the smaller bank for emergencies. It’s an old setup and there are some compromises with it. Many more details at

1/2/BOTH Switch Considerations

1/2/BOTH Battery Switch Considerations - Ever wonder how to make the 1/2/BOTH switch easier to use, let this article explain how to do that.

marinehowto.com

 

[Don S/V ILLusion]

I would trash that switch if, as the label implies, it allows only ‘on or combine’. If you ever depleted whatever is connected to the ‘on’ side, combining them would potentially serve no purpose particularly if it was the ‘start’ battery.

Replacing it would allow independent draw as well as a learning opportunity to figure out how all are wired.

 

[Davidasailor26]

I’m sorry, I completely missed the type of switch and assumed you meant a 1-2-B switch, not a DCP. @Scott T-Bird speaks highly of his DCP and could probably talk about how he uses it. In general I believe what you want is just “on” except you need to combine the banks for some reason, or you have separate shutoffs for each bank allowing the DCP to work as an emergency cross-over.

 

[Stu Jackson]

It depends on how your batteries are wired. Generally you’ll want to select the larger bank when sailing or anchored to save the smaller bank for emergencies. It’s an old setup and there are some compromises with it. Many more details at

1/2/BOTH Switch Considerations

1/2/BOTH Battery Switch Considerations - Ever wonder how to make the 1/2/BOTH switch easier to use, let this article explain how to do that.

marinehowto.com

Correct, except his is NOT a simple 1-2-B switch.

I would trash that switch if, as the label implies, it allows only ‘on or combine’. If you ever depleted whatever is connected to the ‘on’ side, combining them would potentially serve no purpose particularly if it was the ‘start’ battery.

Replacing it would allow independent draw as well as a learning opportunity to figure out how all are wired.

Here's the correct answer:
How to properly wire & switch a DCP switch - Maine Sail's "workaround" explained Replies #28 & 29
What size fuse for automatic charging relay?

Your choice is simple:

1. Figure out if you can figure it out and if you have the additional switches required. If not, add them and learn to use it properly.

2. Replace it with a simpler 1-2-B switch if potential (I say potential) electronics drop outs do not affect you.

Here's another story about those DCP switches:
AGM Battery Issues and the Blue Seas Dual Circuit Switch (from Maine Sail) "DARN AGM Batteries"
Darn AGM Batteries

Your boat, your choice.

 

[Udi]

Thank you very much everybody. I understand that its better to replace the switch but at this time I can't do that so that's the reason I would like (and still don't understand) to understand the exact way to operate it.

 

[Don S/V ILLusion]

Thank you very much everybody. I understand that its better to replace the switch but at this time I can't do that so that's the reason I would like (and still don't understand) to understand the exact way to operate it.

The way to operate it depends on how it is wired. We can’t see that from pictures. For example, some previous owner may have rewired your boat to separate the ‘start’ battery‘ for only engine use independent of the switch which only combines house batteries.

absent more info, no one knows how you should use it.

 

[Scott T-Bird]

Hello @Udi ,
I'm by no means the electrical guru but I do advocate the DCP switch with qualifications. The simple answer is that under all conditions mentioned, you turn your switch On or Off ... that's it. There should not be any reason to use the "Combine" position under normal use. The switch even colors the position yellow with an exclamation point to fortify that understanding.

But there are too many open questions before any more specific information can be discussed. First, define your batteries. What do you have for a house bank? I assume you have a separate start battery, if so, what do you have? How do you charge your batteries? The DCP switch typically is installed with the Blue Sea Automatic Charging Relay (ACR) ... should we assume that you have one? Did you follow all of the wiring instructions for it? Where is your alternator current directed? It seems to me that your question revolves around the charging mechanisms. It will be helpful if you define your charging sources and how they are wired. Wiring diagrams are the best mode of description.

You have a 45' boat, probably with some sophisticated electrics that many don't have. Your panel describes front and rear electric winches, one with a thermal circuit breaker and another with a high-amp buss. Then you also have a high amp buss for a circuit labeled "Anchor". I assume that is a windlass? What batteries power these loads? I have no idea what the differences are between normal circuit breakers, thermal circuit breakers and high-amp busses with these applications. So I would need explanation to understand how they might be affected by the DCP switch.

The one thing you should do since you have a DCP switch is install 2 isolation switches between the batteries and the DCP switch. One isolation switch should be positioned between the House Batt bank and the House post on the DCP. The other isolation switch should be between the Start Batt and the Start post on the DCP. The isolation switches are simple On-Off switches (use Blue Sea just to be consistent). Both should always be "ON", even when you leave the boat. It is best to put them in a compartment out of view so nobody inadvertently turns one or both OFF. The only purpose of these switches is to isolate a battery bank that has a catastrophic failure (such as a short, or it's dead beyond redemption). With a dead battery (bank) in isolation (by turning the appropriate isolation switch OFF), only then do you use the "Combine" position on the DCP to provide juice to both the Start battery and the House Bank simultaneously using a single source live battery or battery bank.

The advantage of the DCP switch is that the Start and House banks are isolated and "ON" simultaneously under all normal circumstances. However, isolation of a failed battery and simultaneous use of House and Start loads is only possible by adding 2 On-Off isolation switches. But, by doing that, you get the best of both functions. You can do the same thing with (2) 1+2+B switches, btw. It's all in the wiring sequence.

Hope that helps!

 

[Maine Sail]

Thank you very much everybody. I understand that its better to replace the switch but at this time I can't do that so that's the reason I would like (and still don't understand) to understand the exact way to operate it.

You turn it to ON..If you have a dead bank you want to avoid the use of combine unless you have additional switches to isolate the bad bank as below....the additional on-off battery switches are best located In the battery compartment so they cannot be seen by guests. the only time these additionalon-off switches are used in emergency .

 

[Stu Jackson]

Thank you very much everybody. I understand that its better to replace the switch but at this time I can't do that so that's the reason I would like (and still don't understand) to understand the exact way to operate it.

We understand. Here's where you and we are: You asked a question. You were given ALL of the available knowledge this group has about that switch, how it works and the options about how it is wired. That information is ALL that is available simply because it is everything anyone would need to know, and is everything that can be said about it.

So the ONLY thing left for you to do is begin to trace wires and draw a wiring diagram of how it is connected on YOUR boat, and since YOU are the ONLY one of us who are there on YOUR boat, that is work YOU have to do.

Many people are hesitant or simply afraid of drawing diagrams. It is not that hard. Start with paper and pencil, forget about using a computer, for now and maybe forever. Often your owners manual will have a good starting point to build on. Many of us start our wiring diagrams based on a simple floor plan layout of the boat starting with where the batteries are and where the switch is and just connecting them based on how the wires are run by tracing them. Here's an example: Stu's Wiring Diagram Stu's Wiring Diagram & The 1-2-B & Dual Circuit Switches

The previous links also included diagrams, IIRC.

It behooves you to at least get started. Denial is never a good state to be in. Good luck.

 

[Benny17441]

There are different type batteries and batteries may be wired differently by boats. Usage of the switch may vary with different installations. Find out how many batteries do you have and what type is each. Usually you have Deep cycle batteries for house duties and they are rated in Amp/Hours (Ah 90-120), the other type is Starting Battery and they are rated in Cranking Amps (500-700). If you have a Deep Cycle Bank and a Starting Bank do not combine. The functions of the switch are fairly standard, when the pointer is set to one bank it means all power draws from appliances will be served from that Bank and not the other, it will also mean that the alternator will only charge that bank and not the other. In simple two battery systems it is common to have two deep cycle batteries each connected to one position like 1,2 or house, starter. if both batteries are deep cycle they can be combined usually for two purposes 1) emergency power to start the engine or 2) to charge both batteries from the alternator when underway. What many find useful is to alternate the use of batteries for consecutive outings, one time use one and next time use the other. This will allow them to age similarly and also will keep one battery at all times as emergency backup. The inboard charger will likely charge both batteries with shore power irrespective of selector switch position. Whatever you do, DO NOT TURN THE SWITCH TO OFF WITH THE ENGINE RUNNING AS IT COULD DAMAGE YOUR ALTERNATOR. As far as setting the switch when the boat is docked, you could continue to alternate them to feed the lights and appliances or combine them as you wish. Understand that one of the problems of combining them is that if one battery fails or is weak, it will bring down the other. Unless you are running 12V refrigeration you can turn the switch Off when you leave the boat. The battery charger and bilge pump will likely be hardwired and in operation even if the switch is off. If your switch only allows for On and Off you could add a second On/Off switch to one of the batteries. To start the engine select one position or the other if the batteries are the same type. There is plenty of information about this topic in the archives. Some of these basic recommendations may not apply to your switch but hope it gives you a better idea on house to use your batteries.

 

[Udi]

You turn it to ON..If you have a dead bank you want to avoid the use of combine unless you have additional switches to isolate the bad bank as below....the additional on-off battery switches are best located In the battery compartment so they cannot be seen by guests. the only time these additionalon-off switches are used in emergency .

Thanks. that's clarifies the picture and make sense as I understand the system.

 

[Udi]

There are different type batteries and batteries may be wired differently by boats. Usage of the switch may vary with different installations. Find out how many batteries do you have and what type is each. Usually you have Deep cycle batteries for house duties and they are rated in Amp/Hours (Ah 90-120), the other type is Starting Battery and they are rated in Cranking Amps (500-700). If you have a Deep Cycle Bank and a Starting Bank do not combine. The functions of the switch are fairly standard, when the pointer is set to one bank it means all power draws from appliances will be served from that Bank and not the other, it will also mean that the alternator will only charge that bank and not the other. In simple two battery systems it is common to have two deep cycle batteries each connected to one position like 1,2 or house, starter. if both batteries are deep cycle they can be combined usually for two purposes 1) emergency power to start the engine or 2) to charge both batteries from the alternator when underway. What many find useful is to alternate the use of batteries for consecutive outings, one time use one and next time use the other. This will allow them to age similarly and also will keep one battery at all times as emergency backup. The inboard charger will likely charge both batteries with shore power irrespective of selector switch position. Whatever you do, DO NOT TURN THE SWITCH TO OFF WITH THE ENGINE RUNNING AS IT COULD DAMAGE YOUR ALTERNATOR. As far as setting the switch when the boat is docked, you could continue to alternate them to feed the lights and appliances or combine them as you wish. Understand that one of the problems of combining them is that if one battery fails or is weak, it will bring down the other. Unless you are running 12V refrigeration you can turn the switch Off when you leave the boat. The battery charger and bilge pump will likely be hardwired and in operation even if the switch is off. If your switch only allows for On and Off you could add a second On/Off switch to one of the batteries. To start the engine select one position or the other if the batteries are the same type. There is plenty of information about this topic in the archives. Some of these basic recommendations may not apply to your switch but hope it gives you a better idea on house to use your batteries.

Many thanks Benny you sure gave me a better idea on using my system.

 

[Udi]

Hello @Udi ,
I'm by no means the electrical guru but I do advocate the DCP switch with qualifications. The simple answer is that under all conditions mentioned, you turn your switch On or Off ... that's it. There should not be any reason to use the "Combine" position under normal use. The switch even colors the position yellow with an exclamation point to fortify that understanding.

But there are too many open questions before any more specific information can be discussed. First, define your batteries. What do you have for a house bank? I assume you have a separate start battery, if so, what do you have? How do you charge your batteries? The DCP switch typically is installed with the Blue Sea Automatic Charging Relay (ACR) ... should we assume that you have one? Did you follow all of the wiring instructions for it? Where is your alternator current directed? It seems to me that your question revolves around the charging mechanisms. It will be helpful if you define your charging sources and how they are wired. Wiring diagrams are the best mode of description.

You have a 45' boat, probably with some sophisticated electrics that many don't have. Your panel describes front and rear electric winches, one with a thermal circuit breaker and another with a high-amp buss. Then you also have a high amp buss for a circuit labeled "Anchor". I assume that is a windlass? What batteries power these loads? I have no idea what the differences are between normal circuit breakers, thermal circuit breakers and high-amp busses with these applications. So I would need explanation to understand how they might be affected by the DCP switch.

The one thing you should do since you have a DCP switch is install 2 isolation switches between the batteries and the DCP switch. One isolation switch should be positioned between the House Batt bank and the House post on the DCP. The other isolation switch should be between the Start Batt and the Start post on the DCP. The isolation switches are simple On-Off switches (use Blue Sea just to be consistent). Both should always be "ON", even when you leave the boat. It is best to put them in a compartment out of view so nobody inadvertently turns one or both OFF. The only purpose of these switches is to isolate a battery bank that has a catastrophic failure (such as a short, or it's dead beyond redemption). With a dead battery (bank) in isolation (by turning the appropriate isolation switch OFF), only then do you use the "Combine" position on the DCP to provide juice to both the Start battery and the House Bank simultaneously using a single source live battery or battery bank.

The advantage of the DCP switch is that the Start and House banks are isolated and "ON" simultaneously under all normal circumstances. However, isolation of a failed battery and simultaneous use of House and Start loads is only possible by adding 2 On-Off isolation switches. But, by doing that, you get the best of both functions. You can do the same thing with (2) 1+2+B switches, btw. It's all in the wiring sequence.

Hope that helps!

Hi Scotty
It helps, and I'll have to consider steps ahead!
Many thanks.