1-2-Both-Off

[Tim Good]

Ok so I know some of you don’t like these things but it does server a purpose. At the moment I can divert the house bank to the bow or the engine if needed in an emergency by selecting Both. OFF means just everything powers it’s designated thing. House, engine and bow are all separate.

I should be able to then select either bow or engine and divert charge to it. However when I select 2 for example, rather than just selecting Engine, it brings engine and House together.

This prevents me from manually charging the engine on its own from shore power. The only way to charge the engine on shore power is when it is grouped with the house bank.

Without looking at how it is wired, can anyone say where I’d start in order to get what I desire?

 

[vyv_cox]

I think you will have to investigate how it is wired. I do not have a thruster but I do have a windlass. My engine starter is on 1. My domestic and windlass are on 2, along with the battery charger. I only start the engine on 1, maybe twice per week, switch to 2 after 30 minutes. Otherwise the switch stays on 2 for starting and everything else. I have used this method for more than 30 years.

 

[Tim Good]

I think you will have to investigate how it is wired. I do not have a thruster but I do have a windlass. My engine starter is on 1. My domestic and windlass are on 2, along with the battery charger. I only start the engine on 1, maybe twice per week, switch to 2 after 30 minutes. Otherwise the switch stays on 2 for starting and everything else. I have used this method for more than 30 years.

If for some reason you have to turn your engine over a lot. Perhaps to bleed it or something. How do you get it up to charge again other than running it and allowing the alternator to top it up?

 

[oldmanofthehills]

Tim. The switch on its own is intended for a two battery system switching between engine and a n other. But you have 3 batteries one of which is clearly permanently connected and unswitched - and I am fairly sure its the house battery .

To get round such issues our boat for instance which has 3 batteries has individual on off for engine and on off house plus a 3 position switch to enable joining diversion of aux battery(bilge pump& heater) to house or engine, both or none.

So to do what you want you need to add on off switch for house between house battery and main connecting point.

Then you need to ensure charging goes to right spot, and that depends whether you have 2 or 3 outputs from charger. We for instance have only 2 going direct to house and engine battery with no land charging of aux battery.

Either your alternator has multiple outlets also to the various batteries either by voltage sensing relays or splitting diodes, or charging is always by selecting on the rotary switch and commoning up with the house battery - which is always connected

 

[VicS]

Ok so I know some of you don’t like these things but it does server a purpose. At the moment I can divert the house bank to the bow or the engine if needed in an emergency by selecting Both. OFF means just everything powers it’s designated thing. House, engine and bow are all separate.
I should be able to then select either bow or engine and divert charge to it. However when I select 2 for example, rather than just selecting Engine, it brings engine and House together.
This prevents me from manually charging the engine on its own from shore power. The only way to charge the engine on shore power is when it is grouped with the house bank.
Without looking at how it is wired, can anyone say where I’d start in order to get what I desire?

As the oldman above says The 12both switch is intend to select the duty battery in a simple two battery system

I am sure you would be best advised to ditch it and start afresh with separate switches and a suitable ( VSR based ???) charging system

HOWEVER I think the attached diagram will do what you want ( isolator switches and fuses omitted for clarity) but I would not wire my batteries like this

In the OFF position:
The engine battery supplies, and is charged by, the engine.
The house battery supplies the domestic distribution panel and can be charged by the battery charger
The bow battery supplies the bow thruster.

In position 1
The engine and house batteries are paralleled
The engine will charge both when it is running
The battery charger wiil charge both

In position 2 :
The engine and bow batteries are paralleled
The engine will charge both
You will normally have the engine running when using the bow thruster

In the BOTH position
All three batteries are paralleled
The engine will charge all three
The battery charger will charge all three.

 

[jac]

Are you sure about that wiring diagram? I would have expected the ability to isolate the house bank as well. All looks like a creative and complex solution to a problem.

 

[Tim Good]

In the OFF position:
The engine battery supplies, and is charged by, the engine.
The house battery supplies the domestic distribution panel and can be charged by the battery charger
The bow battery supplies the bow thruster.

In position 1
The engine and house batteries are paralleled
The engine will charge both when it is running
The battery charger wiil charge both

In position 2 :
The engine and bow batteries are paralleled
The engine will charge both
You will normally have the engine running when using the bow thruster

In the BOTH position
All three batteries are paralleled
The engine will charge all three
The battery charger will charge all three.

What you describe there is how mine currently is. However in position 2 for example trying to charge the engine battery when the domestic bank paralleled to it, is problematic. The two connected together means they go into float quickly as the large house bank dominates the voltage.

 

[VicS]

Are you sure about that wiring diagram? I would have expected the ability to isolate the house bank as well. All looks like a creative and complex solution to a problem.

I would fit isolating switches. Omitted from the diagram for clarity.

Post a diagram showing how you would do it.

 

[VicS]

What you describe there is how mine currently is. However in position 2 for example trying to charge the engine battery when the domestic bank paralleled to it, is problematic. The two connected together means they go into float quickly as the large house bank dominates the voltage.

Isolating switches would solve that problem .............. but then you would be 3/4 of the way to being able to ditch the 1,2 both switch

 

[Tranona]

This is the problem with these old style systems which were state of the art when new but inflexible in practice. On a modern boat like my old (2015) Bavaria with the same 3 battery banks, they were kept separate with individual isolators and charged from the alternator with a 3 output Cristec splitter (other makes are available) and from the mains by a 40A Cristec 3 output mains charger. A refinement (which it did not have) that could be useful is an additional switch that would link the house battery to the engine start circuit in an emergency. The mains charger works independently of the isolators - that is it will charge irrespective of whether a bank is switched on or not.

With your current system the best way of charging the engine battery on its own is to use a free standing charger as I assume your current charger has only one output to the house (which is the one that actually needs it most).

As VicS says it really needs updating to the kind of system I described which is essentially automatic. You switch on which bank you want to use, the charge from the engine is automatically balanced to each bank with priority to the start bank and the mains charger again balances the charge across the 3 banks. No need to remember which number to select and the mains charger switches on as soon as you plug into shorepower (although you can have an independent switch for it) and keeps all 3 banks on float once it gets them up. In reality you probably don't need a shorepower charge for the start because if you only use it for that purpose it should always be fully charged after running the engine. If your single output charger is good and has a decent output I would not bother buying a 3 output, just use it for the house as you will be running the engine when using the bow thruster and the splitter will take care of topping up what little of the capacity of your bow battery you use.

 

[oldmanofthehills]

As the oldman above says The 12both switch is intend to select the duty battery in a simple two battery system

I am sure you would be best advised to ditch it and start afresh with separate switches and a suitable ( VSR based ???) charging system

HOWEVER I think the attached diagram will do what you want ( isolator switches and fuses omitted for clarity) but I would not wire my batteries like this

In the OFF position:
The engine battery supplies, and is charged by, the engine.
The house battery supplies the domestic distribution panel and can be charged by the battery charger
The bow battery supplies the bow thruster.

In position 1
The engine and house batteries are paralleled
The engine will charge both when it is running
The battery charger wiil charge both

In position 2 :
The engine and bow batteries are paralleled
The engine will charge both
You will normally have the engine running when using the bow thruster

In the BOTH position
All three batteries are paralleled
The engine will charge all three
The battery charger will charge all three.

Not a bad solution but leave the Bow on 1 where it already is. Then swap the wire from C (which is currently house etc) to 2 and move Engine from 2 to C. Thus only need to swap two wires.

(I had forgotten that in ancient system like that there is probably only single output on battery charger and single output on alternator.

However it does not enable that vital engine battery can be charged by battery charger on its own, which Tim wanted, and I cannot see how that could be done without isolators added between commoning point of charger and domestic panel and actual house battery

 

[vyv_cox]

If for some reason you have to turn your engine over a lot. Perhaps to bleed it or something. How do you get it up to charge again other than running it and allowing the alternator to top it up?

Not something that happens but the domestic bank of 3 x 110Ah will easily cope with starting a small engine for long periods.

So far as the starter battery is concerned it can recharge either by the alternator or by solar panel via a dual battery controller.

 

[Tim Good]

Not something that happens but the domestic bank of 3 x 110Ah will easily cope with starting a small engine for long periods.

So far as the starter battery is concerned it can recharge either by the alternator or by solar panel via a dual battery controller.

Yeah I have a similar setup. One smaller panel which can roam on a longer lead dual chargers bow and engine. Alternator also engine. I suppose there are occasions where I’d like to equalise or charge the engine battery alone.

Once instance yesterday it took a while to bleed the engine after being laid up for 2 years and I feel perhaps I used 25% of the battery capacity in doing so. I’d liked to have them charged it given the solar won’t do much at the moment when the boat is ashore.

 

[PaulRainbow]

Pushed for time, so i'll have to be brief.....

Bin the switch and fit three separate switches, engine, domestics, bow.
Fit an emergency parallel switch between the engine and domestics.
If you think it's warranted, fit another emergency switch between the domestics and bow.

A three output shore charger will charge all three, as will a Victron Argofet connected to the alternator. A dual battery solar controller takes care of the solar charging.
or
A three output shore charger will charge all three, a dual output Argofet, dual output solar controller and a Victron Cyrix VSR between the domestics and bow battery, so the solar charges it.
or
You fit a couple of Victron Cyrix VSRs.

 

[VicS]

What you describe there is how mine currently is. However in position 2 for example trying to charge the engine battery when the domestic bank paralleled to it, is problematic. The two connected together means they go into float quickly as the large house bank dominates the voltage.

Perhaps the simplest solution is another battery charger for the engine start battery. It need not be any larger than necessary to recharge the engine start battery and need not be a "smart" multistage charger. It need not be permanently wired in either.

However the real solution is to ditch the 1,2 both switch and completely redesign the battery selection and charging arrangements.

 

[Tim Good]

Perhaps the simplest solution is another battery charger for the engine start battery. It need not be any larger than necessary to recharge the engine start battery and need not be a "smart" multistage charger. It need not be permanently wired in either.

However the real solution is to ditch the 1,2 both switch and completely redesign the battery selection and charging arrangements.

Yes well perhaps that’s a good idea. Just use a mobile charger when I really need to charge it independently from shore power.

It’s all well and good when people on this thread say redesign the entire system but that’s not going to happen when I have multiple other boat jobs, a toddler and too many other hobbies. The system works but I just want to tweak it.

 

[Refueler]

As many know already - I am a O-1-B-2 (3 pos switch) user and have used for many years. My needs are simple and I get along very well with it.

I am always amazed at the systems some people setup with this simplest of switches. Some that it was never designed or suitable for. Lets be honest - it was a switch designed for the 60 - 70's just to allow a 2 battery setup ... an extension of the old single battery Key cut-off ... maybe some here are too young to remember the red plastic key and mount that switched the +ve lead.

OK ... lets look in steps and excuse me for the simple text ... I'm trying to break it down into parts to better appreciate problem ...

"At the moment I can divert the house bank to the bow or the engine if needed in an emergency by selecting Both."

That tells me that Engine and Bow are connected in in effect parallel when BOTH selected.

"OFF means just everything powers it’s designated thing. House, engine and bow are all separate."

mmmm OFF would be disconnecting all power OUTS that it controls. So now we have items are connected outside of the switch .... so question is - how can switch disconnect those parallel power lines without some kind of relay to switch off and only have switch power connected out ?

"I should be able to then select either bow or engine and divert charge to it. However when I select 2 for example, rather than just selecting Engine, it brings engine and House together.

This prevents me from manually charging the engine on its own from shore power. The only way to charge the engine on shore power is when it is grouped with the house bank."

Off course it would - because you have BOTH and the outside parallel power lines defeating the object of the 3 pos switch.

Much as hate the idea of independent switches and VSR as many todays boaters advise - I think to achieve what OP wants - it may be the only sensible / practical solution. It could be done by adding relays and extra switches to present 3 pos ... but what a mess !!

My biggest worry as systems get more complicated is the risk of switching off batterys from alternator while engine running .... as more switches and combinations are added ... the easier it is to have a brain-fart moment !!

IMHO of course ....

 

[Refueler]

In fact there is a simple solution to this part :

"I should be able to then select either bow or engine and divert charge to it. However when I select 2 for example, rather than just selecting Engine, it brings engine and House together.

This prevents me from manually charging the engine on its own from shore power. The only way to charge the engine on shore power is when it is grouped with the house bank."

There are many split charge solid state units designed to monitor 2 batterys and divert charge to whichever requires it ..... primarily designed for caravans and RV vehicles. They accept 12 - 18v charge in ... The charge supply is connedcterd to the unit and then the outputs to the batterys .... they monitor and feed whichever battery or both as required. Not expensive .... my Kemo was about 10 quid ... is over 30yrs old and still works as good as the day I bought it. There are higher rated ones now that can take full whack of alternator ... and when batts full - alternator still actions in its designed way. BUT remember they are only there for CHARGE ... not to have power services through them.
Google RV or Caravan Split Charge relays ...........

 

[oldmanofthehills]

Yes well perhaps that’s a good idea. Just use a mobile charger when I really need to charge it independently from shore power.

It’s all well and good when people on this thread say redesign the entire system but that’s not going to happen when I have multiple other boat jobs, a toddler and too many other hobbies. The system works but I just want to tweak it.

Your switch is designed for a different era. For the first 25 years of my sailing boats were in muddy creeks or pulled up on the foreshore for winter. No electricity for battery chargers except to take battery home. But just maybe perhaps shore supply if you visited foreign parts ie anywhere outside eastern Bristol Channel, where there might be that odd innovation "A marina".

Your simplest solution is leave switch alone but add a single isolator between the house battery and the rest of the system - or just disconnect the positive terminal while charging engine battery

 

[Tranona]

Yes well perhaps that’s a good idea. Just use a mobile charger when I really need to charge it independently from shore power.

I use something similar to this as I now only have a single output mains charger for house bank. Halfords Smart Battery Charger 8A | Halfords UK
I use it for keeping the bow battery up during the winter. Could equally be used for the engine start.