1-2-both switch! is it still required!

[vyv_cox]

Paul ... B27 ... and anyone else on their bandwagons .....

You can all come up with scenarios to support your viewpoints ..... that's life.

But I will say this : I have had failure of one battery with the 1-B-2-Off switch couple of times (no fault of the switch system) ... and it has NEVER caused me to have no power on board ... ie start engine.

Can we stop 'sucking at straws' ????

Exactly. I have owned my boat, with its 1-2-Both switch, since 1994. I never run it on both. I switch to 2 in April and switch off in October. Every now and again, maybe once a week or a fortnight dependent upon how often I start the engine I switch to 1, start and run for half an hour, then back to 2. I have never been in a situation where the batteries failed to start the engine, even when my domestic bank (2) was only 220Ah, running a fridge 24/7.

 

[vyv_cox]

Funny that just about all modern (modest) boats are wired exactly like this - I wonder why?

Because every boat builder wants to bring every component down to utterly foolproof. Their aim seems to be for the novice who knows absolutely nothing about boats to jump on and go off on a charter holiday without having to worry about knowledge.

Switch batteries? Don't even know what a battery is. As said many times, car manuals used to tell you how to maintain it, at least on a basic level. (Although the operator's manual for my 1948 MG is almost a workshop manual) Now they tell you not to drink the battery acid

 

[PaulRainbow]

Exactly. I have owned my boat, with its 1-2-Both switch, since 1994. I never run it on both. I switch to 2 in April and switch off in October. Every now and again, maybe once a week or a fortnight dependent upon how often I start the engine I switch to 1, start and run for half an hour, then back to 2. I have never been in a situation where the batteries failed to start the engine, even when my domestic bank (2) was only 220Ah, running a fridge 24/7.

Note the number of people who, in this thread and other similar ones do leave it on both !

 

[jac]

The purpose of a 1B2 switch is to connect one, both, the other or neither to either
a) all the electrics in a simple boat or
b) the engine electrics, starter motor etc

It's that simple. The only subtlety is that it can switch from 1 through Both to 2 without disconnecting the batteries, so the alternator is not stressed by having no battery connected.

EDIT

turn it to 1 to start the engine
when the engine's running turn to to both, to charge both
when you stop the engine, turn it to 2
when you leave the boat long term, turn it to 'off'.

There's probably an app to help younger people with it.

Sorry but b) doesn't happen ( unless you have some odd wiring ) - A typical 12BOff switch has 2 inputs - ( Battery 1 and 2) and a common output to which all loads are ultimately connected. if either battery is on, you can run any electrical load.

And that manual process causes a few challenges. lets assume one has been at anchor overnight, usual load so Battery 2 ( Domestic) is fairly low but Battery 1 ( engine Start) is fully charged. You switch to 1 so the full load goes to the engine start, including instruments etc. You start OK and then switch to Both. AIUI, the batteries will try and equalise the charge between them - You run the engine for say 30 minutes and then shut down and switch to 2. Result is that engine start is discharged to some extent ( maybe 90% SoC) - Theoretically one could repeat the exercise for several days gradually dragging the engine start battery down whilst in B.

The big issue though is the reliance on memory / habit to switch back from B to 2 when the engine is off. That is not possible to guarantee 100% reliability. Separate isolators and two totally separate circuits achieve that. You can then not discharge the engine start battery by leaving it connected to a stray fridge or light etc. Whilst a good practice to isolate when not in use, it is perfectly acceptable to just leave that battery on the whole time and have the engine immediately available with no risk of flattening the start battery

 

[rogerthebodger]

The issue with 1 2 B switches is that generally there is only a single charging source so the need to switch to Both to charge both batteries.

I have 2 off 1 2 B switched as I have 2 banks of Domestic batteries and a second 1 2 B switch for my domestic and engine batteries

I also have 2 alternatives 1 foe Domestic and a smaller for engine batty.

I also have separate solar panels for Domestic and engine start batteries.

 

[Tranona]

Because every boat builder wants to bring every component down to utterly foolproof. Their aim seems to be for the novice who knows absolutely nothing about boats to jump on and go off on a charter holiday without having to worry about knowledge.

Switch batteries? Don't even know what a battery is. As said many times, car manuals used to tell you how to maintain it, at least on a basic level. (Although the operator's manual for my 1948 MG is almost a workshop manual) Now they tell you not to drink the battery acid

There is zero benefit in doing it your way - you have adjusted to what you have (would not start from here...).

So if you are starting from scratch like the OP why not make it simple and idiot proof as far as charging is concerned. Can't see how "knowledge" or lack of makes any difference. It works just the same for novices and experts and both benefit from it. The requirements for house batteries and start batteries are very different, so why have a system that allows mixed use, or requires you to remember to switch for charging?

Builders do it because it is efficient and why make a simple thing complicated?

 

[Refueler]

OK .. limited engine run and BOTH is not always a good idea if one battery is low ... agreed.

But this then brings in the factor of type of boat ... lets go back to SR25 ... its a motor-sailer ... so usual scenario is engine runs for about 40 - 50% of passage time unless wind is strongish and passage speed is not important.
My 4-107 has the standard car based alternator its usually supplied with - likely 45A ... Lets say one of my 90A/hr batts is very low .. and other is in good charge state .... I have on BOTH while engine is running ....
The high charge state battery will basically not take any significant charge ... but the low battery will take all it can get ... lets say it gets 25 - 30A ...
If I'm on route to Gotland 16 - 18hrs .... I'm full charged on both batts within 3hrs of departure ...........

Even if I do a river jaunt in afternoon with friends ... my batts will be near or full easily ...

Think we need to stop the sneaky scenarios to prove a point ... usage and battery state / charge is dependent on boat type and its use.

 

[[70521]]

What I see often is that the modest requirements of a pocket cruiser are often overshadowed by advice to rip out and replace with systems more suited to higher demand applications.

Forgive me for being so - but that's my opinion.

What is your consumption?

The question posed was about the amps consumed not how they are moved about the system.

 

[fisherman]

My last boat had two switches, for start and service banks. There was a blocking diode between alt and battery banks, to ensure one bank could not drain the other. Two voltmeters, showing battery level, and one ammeter showing alt output. All very simple. However, If I ever needed a start boost I would have needed jump leads, or rather, a jump lead for the pos.
I had no sensing issues, as soon as I switched stuff on the alt would step up output, even though the sense lead was on the start side. Only a 40A alt, the maximum draw with everything switched on was 28A. Nav lights, fishing lights, accomodation lights, deck floods, two VHF, two GPS, radar, PC, bilge pump, jabsco pump clutch. The only extra draw would be VHF transmit, another 3A.
I considered a bigger alt, but none of them reach max ouput until 3000 revs (of the alt, about 1000 on the engine), so no point.
The previous boat had two separate batteries separately switched, each running everything, blocking diode as well.,

 

[Tranona]

OK .. limited engine run and BOTH is not always a good idea if one battery is low ... agreed.

But this then brings in the factor of type of boat ... lets go back to SR25 ... its a motor-sailer ... so usual scenario is engine runs for about 40 - 50% of passage time unless wind is strongish and passage speed is not important.
My 4-107 has the standard car based alternator its usually supplied with - likely 45A ... Lets say one of my 90A/hr batts is very low .. and other is in good charge state .... I have on BOTH while engine is running ....
The high charge state battery will basically not take any significant charge ... but the low battery will take all it can get ... lets say it gets 25 - 30A ...
If I'm on route to Gotland 16 - 18hrs .... I'm full charged on both batts within 3hrs of departure ...........

Even if I do a river jaunt in afternoon with friends ... my batts will be near or full easily ...

Think we need to stop the sneaky scenarios to prove a point ... usage and battery state / charge is dependent on boat type and its use.

That is not like a typical small cruising boat (such as the OP) where the challenge is to have enough reliable and easily charged domestic capacity and an easily started small diesel auxiliary which is also a potential source of charge through its alternator. Commonly now though (again like the OP) this is insufficient and is supplemented by solar and shore power. The start battery is just that and it is only necessary to have one large enough to start the engine - so why link it to the house at all? except in an emergency.

What you are describing works for you on your motor sailor because you have a continuous supply (well at least 50% of the time) of power from the alternator and minimal house requirements. You will find when you go cruising in your new boat you will have completely different requirements and will benefit from the simple split systems described here.

 

[Ammonite]

Exactly. I have owned my boat, with its 1-2-Both switch, since 1994. I never run it on both. I switch to 2 in April and switch off in October. Every now and again, maybe once a week or a fortnight dependent upon how often I start the engine I switch to 1, start and run for half an hour, then back to 2. I have never been in a situation where the batteries failed to start the engine, even when my domestic bank (2) was only 220Ah, running a fridge 24/7.

That's how I used my previous boat and the current one before I fitted seperate switches and a third to link them if needed. The problem I had with the 1-2-Both-Off was whenever I started the engine it would restart the plotter when starting from the domestic bank (even after fitting new batteries and rewiring the whole thing) which was a right PITA on both boats. Maybe the kit I had was overly sensitive or there was an issue with the old switch but there is no chance of that happening with my new set up.

 

[Refueler]

That is not like a typical small cruising boat (such as the OP) where the challenge is to have enough reliable and easily charged domestic capacity and an easily started small diesel auxiliary which is also a potential source of charge through its alternator. Commonly now though (again like the OP) this is insufficient and is supplemented by solar and shore power. The start battery is just that and it is only necessary to have one large enough to start the engine - so why link it to the house at all? except in an emergency.

What you are describing works for you on your motor sailor because you have a continuous supply (well at least 50% of the time) of power from the alternator and minimal house requirements. You will find when you go cruising in your new boat you will have completely different requirements and will benefit from the simple split systems described here.

You concentrate on one aspect of the post and miss the point being made ... which you then allude to yourself :

It depends on the type of boat and what use is made of it.

As to my later addition to my fleet ... it has TWO batts as Engine start and ONE batt for domestic .... ????????? Logic in my view went out the window there !!

 

[Tranona]

What is your consumption?

The question posed was about the amps consumed not how they are moved about the system.

You have had some examples of different patterns of usage and sizes of boats, but there is no definitive answer. Anyway most people don't know and have never tried to measure it. Perhaps why they get obsessed with defending systems of circulation rather than using the basic data such as you are asking after to construct a system appropriate to meeting their demands!

 

[Tranona]

That's how I used my previous boat and the current one before I fitted seperate switches and a third to link them if needed. The problem I had with the 1-2-Both-Off was whenever I started the engine it would restart the plotter when starting from the domestic bank (even after fitting new batteries and rewiring the whole thing) which was a right PITA on both boats. Maybe the kit I had was overly sensitive or there was an issue with the old switch but there is no chance of that happening with my new set up.

Another benefit of keeping engine and start totally separate except in an emergency.

 

[Refueler]

That's how I used my previous boat and the current one before I fitted seperate switches and a third to link them if needed. The problem I had with the 1-2-Both-Off was whenever I started the engine it would restart the plotter when starting from the domestic bank (even after fitting new batteries and rewiring the whole thing) which was a right PITA on both boats. Maybe the kit I had was overly sensitive or there was an issue with the old switch but there is no chance of that happening with my new set up.

Voltage drop due to engine starting is a common reason for plotters etc. dropping out at engine start. You have choice - start on both avoiding such large voltage drop - or have large capacitor to momentarily maintain plotters supply - or switch on plotter after engine start.

TBH - if that is only reason to change system ... sorry not enough for me.

 

[PaulRainbow]

Voltage drop due to engine starting is a common reason for plotters etc. dropping out at engine start. You have choice - start on both avoiding such large voltage drop - or have large capacitor to momentarily maintain plotters supply - or switch on plotter after engine start.

TBH - if that is only reason to change system ... sorry not enough for me.

Or fit a decent system, fit for purpose.

 

[PaulRainbow]

Paul ... B27 ... and anyone else on their bandwagons .....

You can all come up with scenarios to support your viewpoints ..... that's life.

But I will say this : I have had failure of one battery with the 1-B-2-Off switch couple of times (no fault of the switch system) ... and it has NEVER caused me to have no power on board ... ie start engine.

Can we stop 'sucking at straws' ????

Might it be possible at some point in the future, for you to take part in a thread without being rude and facetious ?

Just because you, one person, has never had a failure, does not mean it's a good system. A single battery failure with a 1-2-B switch should not cause power loss, that's the point of the switch. Of course, people leave them on both while the engine is running, yourself included, this does have the potential for total power loss.

Plenty of other reasons to fit modern systems to boats with more than a candle and compass, as detailed previously in this thread. Problem is, you seem unable to read and digest any of the information.

 

[Aquanaught]

I had a marine electrician 'sort' the electrics on my 1999 Bavaria when we re-engined - he replaced most of the old cables and removed the old 1-2-B switches simplifying the system. Now have alternator connected to engine start batt with a Bluesea ACR to supply the domestic bank. No switches to worry about (other than main domestic bank isolate) and forget to close/open and both batteries are independent unless ACR senses current from alternator and is charging them. In the unlikely event the engine start battery fails I carry a pair of battery jump leads (never used). This system works well for me and removes old diode systems which drop the charge current. Main solar is connected just to domestic bank with a small (30W) panel to the engine battery (via regulators) for float charging when not on boat.

 

[Refueler]

Might it be possible at some point in the future, for you to take part in a thread without being rude and facetious ?

Just because you, one person, has never had a failure, does not mean it's a good system. A single battery failure with a 1-2-B switch should not cause power loss, that's the point of the switch. Of course, people leave them on both while the engine is running, yourself included, this does have the potential for total power loss.

Plenty of other reasons to fit modern systems to boats with more than a candle and compass, as detailed previously in this thread. Problem is, you seem unable to read and digest any of the information.

Rude and facetious ? Who's being that ?

Sorry Paul ... forgot it was you !!

I do read and I take OP's question / basis as the foundation for replies. Unlike some - yourself included.

Too often threads divert away from the core of OP's ...

My premis was to ask if it was really necessary to rip out and change for OP's boat ... plus I had also stated clearly that I now have two boats with the 'opposing' systems ...

 

[geem]

Everybody looks at these issues from their own perspective. There is no right or wrong. We used a 1,2, both switch for many years and we're quite happy with the set up. We didn't forget to switch it. We never flattened the engine battery. Somebody forgetful may deem a VSR an essential upgrade. Not being forgetful or distracted, I never saw the benefit of a piece of additional electrickery that could fail. VSRs are great for some people but not everybody. It's a shame people cannot see the perspective of others.
If we ever had a small simple boat again, I would not hesitate to keep a 1,2 both switch. If I wanted something more sophisticated, I would use a B2B such that the engine battery was given a perfect 3 stage charge. I don't like VSRs as they are an imperfect solution that takes no account of battery state of charge. They are just an electronic switch that does the same as a 1,2 both when switched. But that is just my personal opinion and shouldn't effect others decisions about how you wire YOUR boat