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

[Tranona]

I'd be interested to hear the sort of power needs boats have. I struggle to draw 10 amps with everything on and that is rare as the power consumption of most kit has been significantly reduced over the last 20 years.

Do a power audit. The single biggest killer is the fridge, typically average 4amps, then basic electronics including autopilot and radar if you have it. Night sailing requires lights and electronics. Nights at anchor, interior lights, water pump, charging devices, using laptop, TV etc. Whatever your mix of activity you are likely to use between 80-100amps in a 24 hour period - that is the usable capacity of a 200Ah house bank. Of course you might get some back by solar during the day or running the engine. While the consumption of individual items has fallen, we just have more of them

On my Bav 33 on my own with a 270Ah house bank I could manage 2-3 days away from shorepower just relying of the 2 hours engine time a day (no solar). However if fully crewed and adding radar and some night sailing that would be inadequate without solar or shorepower stops. With my GH, no fridge, no pressure water, no night sailing, all LED lamps etc, I am quite comfortable with my 190Ah bank just engine charging and no solar.

To answer your question, the needs are a direct function of the amount of gear and the time used running off 12v. Basic like me at one end and full time off grid liveaboard on the other. I cope with simple systems, the latter looks to large buffer banks and as much charge capacity (typically solar) as can be crammed on the boat.

 

[B27]

My boat is typical 'last century'.
It has a 1 Both 2 switch.
1 is 'engine battery', 2 is 'house battery'.

Other than the engine, we have cabin lights, nav instruments, a VHF, nav lights, charging for USB devices and a fridge.
I don't think that laot can draw more than 15A total if it all peaks together.
There's a Chinaspacher hich probalby uses a few A while running and a few more for the glowplug?

So I am thinking I will keep the 1B2 switch but simply add a separate 25A 'main switch' for the domestic stuff.
That will cost about £5.
Then I can add a VSR so both batteries get charged when the engine is running. That wouldn't cost much even if I didn't already have the parts, it doesn't need to be clever or handle starting currents.
The main solar will just do the house battery.
I have a little solar panel which will float the engine battery iin Winter or if the boat doesn't get used much.


Depends what you want from it all.
Back in the day, the battery switches were expected to isolate the batteries fully, it was seen as a safety thing.
These days I don't think people worry about that and most batteries are permanently connected to some solar charging even when 'everything is off'?

If you've ever been in a car or boat with smoke coming from the wiring, you'll understand the desire to be able to simply isolate the batteries!

Also while 'every boat in 1990 had a 1B2 switch' many were more complex, I recall offshore racing rules requiring another little battery to power the VHF?
Maybe it could also feed the Decca?

Then it all started getting complex with splitter diodes and alternator boosters etc etc. At that point it became much harder to go on someone elses boat and know exactly what to expect.

 

[jac]

I'd be interested to hear the sort of power needs boats have. I struggle to draw 10 amps with everything on and that is rare as the power consumption of most kit has been significantly reduced over the last 20 years.

For me Fridge is the big one - just under 5 Amps when running. Time running varies of course on many factors - I assume 40 AH per day
MFD is just under 2 Amps with max brightness - assume day sailing thats 16 AH
Log . Wind. Depth etc - maybe 0.25 A = 4 AH
Autohelm - - Who knows! varies but assume 2A typical - if sailing maybe 1 Ah per day - if motoring - much more!
Lights - Negligible if LED - Assume 1 AH per day
USB Devices 5v @ 2.1A assume 1A @ 12v and 2 hours to charge an item. Personally can end up with 6 items being charged ( 3 simultaneously) so 3 A peak load but 12 Ah from the battery
Radio, etc - negligible on Rx - Assume 1 Ah per day
Other Misc - e.g. pumps 3A max draw - Assume 1 AH per day
Have Radar but rarely used - Quantum radar is 7W Standby and 17 W Tx so maybe 0.5A raising to 1.5A peak.

SO peak draw would be 13-14 Amps if radar on standby and daily demand typical daysailing of maybe 75 AH. That suggests a battery bank of 250 - 300 AH minimum.

 

[geem]

A B2B doesn't really put out many amps. They get hot and the output diminishes compared to the actual rated output. If you wanted to go the B2B route, consider using one to charge your engine battery. The alternator output and solar can go to the house battery. That is the battery that will benifit from all the amps available from the alternator. The engine battery can start the engine and the B2B replaces the small amount of charge needed. Once the engine battery is charged, the engine battery sits on float full-time via the B2B. The advantage of this approach is your engine battery is kept in tip top condition with a proper 3 stage charge and permanent float when not in use. The solar keeps both batteries charged when the boat is unattended

 

[seafox67]

I have found the purpose of "1 both 2" switches interesting. Over the years, I have spoken to people with different understandings of what they do! Even putting doubt on my own switch! I guess this maybe be an underlaying reason for me to remove it! I did a rough draft for my future electrics that has 2 isolator switches making understanding a little simpler. As mentioned by B27, it does appear in these modern times that you now have permeant connections to power sources like solar and shore power!

 

[geem]

I'd be interested to hear the sort of power needs boats have. I struggle to draw 10 amps with everything on and that is rare as the power consumption of most kit has been significantly reduced over the last 20 years.

Our average daily draw from our domestic lithium battery, is 230Ah at 12v

 

[PaulRainbow]

I have found the purpose of "1 both 2" switches interesting. Over the years, I have spoken to people with different understandings of what they do! Even putting doubt on my own switch! I guess this maybe be an underlaying reason for me to remove it! I did a rough draft for my future electrics that has 2 isolator switches making understanding a little simpler. As mentioned by B27, it does appear in these modern times that you now have permeant connections to power sources like solar and shore power!

Fuses go next to the power source (batteries).
The B2B is wired incorrectly (is it even a B2B).

I still maintain that you will get little useful benefit (if any) from a B2B. Fit a Victron Cyrix £45 ish and only fit a single output charger, the VSR will take care of the rest.

 

[seafox67]

Fuses go next to the power source (batteries).
The B2B is wired incorrectly (is it even a B2B).

I still maintain that you will get little useful benefit (if any) from a B2B. Fit a Victron Cyrix £45 ish and only fit a single output charger, the VSR will take care of the rest.

How do you mean it's not battery to battery?... I think what i'm trying to achieve is keep the engine side as much independent as possible so that if the house side (with all the electronics) goes to crap... the engine will still work!

 

[LittleSister]

Where's the popcorn emoji?

From my perspective, separate bank switches, an emergency link switch, and a VSR (such as Vic S pictures above - other brands available), is a simple fit and forget solution. You get maximum reliability, and maximum potential charge to the batteries. What's not to like?

A 1-2-Both requires you to operate various times every trip and remember to do so. Forget, or switch too soon or too late, and you won't get get maximum charge to both batteries, and could potentially flatten one or both batteries. (Whether it's worth the cost and hassle of changing If that's what you have already is up to you, but it still doesn't make it an ideal solution.)

Separate switches for each bank, and a diode splitter to distribute the alternator charge means you lose significant charging potential because of voltage drop across the diodes (unless very expensive) at high rates of charge, and if one battery fails or ends up discharged somehow, you need jump leads or to physically swop batteries to start the engine or keep domestic kit/instruments/lights going.

A Dc to DC charger seems to me unnecessarily expensive and complicated. It is a solution to a problem I (and most others, I'm sure) don't have.

 

[Plum]

Paul - I'm not against newer systems ... as I pointed out - I now have boats with old and new setups ...

Of course if 'user' is not careful - problems arise ...

You admit yourself and was my point with OP's boat - simple setup works fine with either .... even that old 1-2-B ...

Agree, for a simple low energy demand system with two matching batteries a 1-2-B switch, with or without a VSR works perfectly for me.

Www.solocoastalsailing.co.uk

 

[B27]

I have found the purpose of "1 both 2" switches interesting. Over the years, I have spoken to people with different understandings of what they do! Even putting doubt on my own switch! I guess this maybe be an underlaying reason for me to remove it! I did a rough draft for my future electrics that has 2 isolator switches making understanding a little simpler. As mentioned by B27, it does appear in these modern times that you now have permeant connections to power sources like solar and shore power!

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.

It's everything else that's complicated and open to opinions about what is 'right'.
Your diagram is a little confusing, you have some red lines which it's unclear whether they cross or connect.


Personally I think B-to-B charging is generally an expensive low power option, but sometimes people want that, e.g. to charge a windlass/thruster battery at the from of the boat without using a massive cable, or to trickle charge a battery from one which may be being bulk charged at a higher voltage.

In general, I want my engine battery to be charged as simply as possible, and I want the house battery to get as many amps as it will take from the alternator.
The way we sail, often we only run the engine for say 20 minutes, in that time the alternator can pump in a fair few amp hours.

My engine battery only ever gets used to start the engine, so it never needs much charging.
Mostly it needs to be either left in peace or floated at 13.5V
So, I'm not keen to have it over charged by the solar, which should be charging the house battery at 14.4V a lot of the time.

Yes you can connect the alternator to the house battery then B2B to charge the start battery, but what happens if the house battery develops a fault?

I'd suggest if you do anything complex, be very clear what it does and understand what happens if any part fails.
A 1B2 switch does need some human input, but it's nothing you can't explain to my Mum,
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.

 

[Refueler]

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.

It's everything else that's complicated and open to opinions about what is 'right'.
Your diagram is a little confusing, you have some red lines which it's unclear whether they cross or connect.


Personally I think B-to-B charging is generally an expensive low power option, but sometimes people want that, e.g. to charge a windlass/thruster battery at the from of the boat without using a massive cable, or to trickle charge a battery from one which may be being bulk charged at a higher voltage.

In general, I want my engine battery to be charged as simply as possible, and I want the house battery to get as many amps as it will take from the alternator.
The way we sail, often we only run the engine for say 20 minutes, in that time the alternator can pump in a fair few amp hours.

My engine battery only ever gets used to start the engine, so it never needs much charging.
Mostly it needs to be either left in peace or floated at 13.5V
So, I'm not keen to have it over charged by the solar, which should be charging the house battery at 14.4V a lot of the time.

Yes you can connect the alternator to the house battery then B2B to charge the start battery, but what happens if the house battery develops a fault?

I'd suggest if you do anything complex, be very clear what it does and understand what happens if any part fails.
A 1B2 switch does need some human input, but it's nothing you can't explain to my Mum,
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.

I love it ...

Regardless of the reasons of one or other system ... what always strikes me is the advice to have 3 switches instead of the one ??

My 25 has the single switch job and on entering boat - I select position 1 or 2 ... (I use two HD car batterys so it makes no difference which does what) ... I can then start engine ... run all gear on board ....
Once started - I usually switch to both ... when I stop engine - I then switch to the other battery that did not start engine ...

My 38 has two switches ... one engine .. one domestic. Nuff said !!!

 

[Stemar]

A 1-2-Both requires you to operate various times every trip and remember to do so. Forget, or switch too soon or too late, and you won't get get maximum charge to both batteries, and could potentially flatten one or both batteries.

Not necessarily - see how it worked on Jissel in my previous post. I'd have to turn to 1 to start the engine, but it stayed like that until we turned of off as part of the boat's bedtime routine. I had to turn it to 2 once in 15 years, when the engine battery didn't want to play any more. The only reason I did things differently on Jazzcat is the twin engines.

 

[PaulRainbow]

How do you mean it's not battery to battery?... I think what i'm trying to achieve is keep the engine side as much independent as possible so that if the house side (with all the electronics) goes to crap... the engine will still work!

Your diagram shows a DC-DC converter, not a DC-DC charger.

From your domestic bank run a cable to the domestic busbar, fused close to the battery, cable and fuse both rated for the engine starting current, to allow emergency started. Each load or charging source then comes off of that busbar, fused close to the busbar. Connect the solar controller and mains charger here too.

Connect the alternator to the engine battery, via its isolation switch. Rarely is the alternator fused, but ensure the cable cannot chafe etc.

The Victron VSR connects between the domestic and engine batteries.

Fit a 3rd, emergency, switch. This switch connects between the load terminals of the domestic and engine batteries.

See my earlier post regarding use of and benefits of, the emergency switch.

 

[B27]

I love it ...

Regardless of the reasons of one or other system ... what always strikes me is the advice to have 3 switches instead of the one ??

My 25 has the single switch job and on entering boat - I select position 1 or 2 ... (I use two HD car batterys so it makes no difference which does what) ... I can then start engine ... run all gear on board ....
Once started - I usually switch to both ... when I stop engine - I then switch to the other battery that did not start engine ...

My 38 has two switches ... one engine .. one domestic. Nuff said !!!

It's not just '3 switches', it's 3 new expensive switches, instead of the one people already have which is doing the job fine, and the woodwork has been made for.

After a while, switching the 1B2 switch becomes as natural as turning the gas off after making a cuppa.

 

[PaulRainbow]

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

The 12B typically connects everything on the boat to one battery or the other.

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.

It's everything else that's complicated and open to opinions about what is 'right'.
Your diagram is a little confusing, you have some red lines which it's unclear whether they cross or connect.

What do you find complicated or confusing about turning 2 switches on and just leaving them until you go home ?

Should i write you a little app' to explain how to turn a switch on, or can you get your Mum to show you

In general, I want my engine battery to be charged as simply as possible, and I want the house battery to get as many amps as it will take from the alternator.
The way we sail, often we only run the engine for say 20 minutes, in that time the alternator can pump in a fair few amp hours.

You must have a very big alternator. A 60a alternator could only put 20ah into your batteries in 20 mins. That's at a theoretical max that you never likely to see.

My engine battery only ever gets used to start the engine, so it never needs much charging.
Mostly it needs to be either left in peace or floated at 13.5V
So, I'm not keen to have it over charged by the solar, which should be charging the house battery at 14.4V a lot of the time.

Yes you can connect the alternator to the house battery then B2B to charge the start battery, but what happens if the house battery develops a fault?

With your 1-2B you're screwed. With my suggested system, no problemo.

I'd suggest if you do anything complex, be very clear what it does and understand what happens if any part fails.
A 1B2 switch does need some human input, but it's nothing you can't explain to my Mum,
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.

Amazes me every time when people claim that 2 switches, requiring no more user input than turning them on/off (same as you would a light switch).

By the way, whilst you're running the engine with your 1-2-B switched to both, what happens if a) someone forgets to change it over or b) there is a failure that drains all of the batteries (because you have connected them in parallel using the 1-2-B switch ?

 

[PaulRainbow]

It's not just '3 switches', it's 3 new expensive switches, instead of the one people already have which is doing the job fine, and the woodwork has been made for.

After a while, switching the 1B2 switch becomes as natural as turning the gas off after making a cuppa.

Expensive my backside.

BEP 1-2-B switch cost the same as 3 separate BEP switches.

A 1-2-B has 3 sets of internal contacts, so effectively 3 switches anyway. 3 separate switches givee options if one fails. A failed 1-2-B is a real pain.

 

[Refueler]

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' ????

 

[Tranona]

How do you mean it's not battery to battery?... I think what i'm trying to achieve is keep the engine side as much independent as possible so that if the house side (with all the electronics) goes to crap... the engine will still work!

You are just making everything too complicated. either wire as Paul says or use a switch cluster. That achieves the objective of keeping the 2 banks separate. A B2B is a waste of time and money for what you are trying to achieve. I have one, but as B27 says for charging the bow battery from the start battery. I don't see any need to have a mains charge or solar to the start battery. The engine charges this instantly and if you do have a problem with it you can always use the house battery to start with the emergency switch. Solar through a controller and mains to the house bank.

 

[Tranona]

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' ????

It is not sucking at straws.

The old saying " if i wanted to achieve that (whatever it is) I would not start from here."

So, if you have a 1,2,B and it works for you then fine, but it does not achieve the Ops objectives

The OP says his is knackered and he wants to achieve specific objectives with his new system. so ditch the 1,2,B idea as the objectives (and more) can be achieved by the systems proposed at similar cost and without any manual choices apart from switching 2 circuits on at the start, and off when you finish.

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