battery 1 or 2 switch

[kalindi]

I know that it is not a good idea to switch the battery off when the alternator is running but is it OK to change from 2 to 1 ? I want to put the engine and domestic battery banks in parallel for a few minutes when manouvering with a bow thruster and then revert to normal. Will change to dedicated battery for the bow thruster in a few months so is a short term measure. Thanks in advance for the help.

 

[macd]

I know that it is not a good idea to switch the battery off when the alternator is running but is it OK to change from 2 to 1 ? I want to put the engine and domestic battery banks in parallel for a few minutes when manouvering with a bow thruster and then revert to normal. Will change to dedicated battery for the bow thruster in a few months so is a short term measure. Thanks in advance for the help.

If it's a 'make before break' switch, changing in this way will be OK since the connection is not interrupted. To be on the safe side I always did it with the engine just ticking over.

Dedicated bow thruster/windlass batteries always seem to attract polarised views. I see little point in lugging about dedicated batteries which cannot be used for general domestic use, not least because the cabling to charge them isn't very much smaller than the cabling needed to use the main batteries for the same purpose. Others will have a different opinion, but I'd think hard before going to all that trouble.

 

[William_H]

With a 1,2,both switch I think it better to make "both" your normal position for when the engine is running. Switch to either battery for operation with out engine or occasionally for engine starts. This latter to ensure both batteries alone will start the engine.
Operation on both will charge both batteries mostly at a rate equal to charging one battery. The alternator may reach its limits on initial start of charge but fairly quickly each battery current acceptance will fall so that alternator is well able to cope with charging 2 batteries at once in parallel.
I agree with macd heavy wires up to the bow thruster would be far better than adding another battery. good luck olewill

 

[pvb]

At the end of the day, it's easier to run cables to the bow thruster than install a dedicated battery. If you're going to buy another battery, simply add it to the domestic bank and wire your bow thruster to the domestic bank.

While you're at it, you might consider ditching the 1-2-Both switch for a much simpler pair of on/off switches, but that's another discussion...

 

[reeac]

At the end of the day, it's easier to run cables to the bow thruster than install a dedicated battery. If you're going to buy another battery, simply add it to the domestic bank and wire your bow thruster to the domestic bank.

While you're at it, you might consider ditching the 1-2-Both switch for a much simpler pair of on/off switches, but that's another discussion...

But the "much simpler pair of on/off switches" will increase the probability of accidentally disconnecting the alternator. I can't see what's wrong with the 1-2-both system.

 

[pvb]

But the "much simpler pair of on/off switches" will increase the probability of accidentally disconnecting the alternator. I can't see what's wrong with the 1-2-both system.

Not at all. One switch for the engine battery; one for the domestic bank. Arrive at boat, turn both on, use boat, turn both off, go home. No need to touch the switches otherwise. Couldn't be simpler. The 1-2-Both switch, in contrast, has endless possibilities for forgetful or careless owners or crew to mess things up.

 

[Storyline]

Not at all. One switch for the engine battery; one for the domestic bank. Arrive at boat, turn both on, use boat, turn both off, go home. No need to touch the switches otherwise. Couldn't be simpler. The 1-2-Both switch, in contrast, has endless possibilities for forgetful or careless owners or crew to mess things up.

I can see the elegance of your solution but when the engine is not running surely there is a risk of the domestic drain flattening both battery banks ? Edit: that is rubbish - I presume the domestics are wired only through one switch. I like your idea and will adopt it when rewiring the boat 'one day'

 

[chewi]

But you do lose the option to start from the domestic unless you addmore switches (or a jump lead).
My 1-2-both takes the field current so it protects the alt. if anyone sets to Off while running.

 

[prv]

Not at all. One switch for the engine battery; one for the domestic bank. Arrive at boat, turn both on, use boat, turn both off, go home. No need to touch the switches otherwise.

I've gone one better, and bought a 500a DPDT switch. So I only have to turn one switch on when I arrive

Pete

 

[prv]

I can see the elegance of your solution but when the engine is not running surely there is a risk of the domestic drain flattening both battery banks ? Edit: that is rubbish - I presume the domestics are wired only through one switch. I like your idea and will adopt it when rewiring the boat 'one day'

You're correct that the domestics are wired only to the domestic battery. However, in a system like this you also need to consider the charging side of the circuit. If you just wired the alternator directly to both batteries, you'd also be wiring them together - electricity can flow either way in a wire!. So you also need either a large diode (not my choice due to volt-drop) or a relay that only makes the connection during charging and then disconnects afterwards. Both are available packaged for this specific purpose.

The resulting system is much more convenient than a manual 1-2-both switch, though.

Pete

 

[Billjratt]

Surely the problem - if there is one, would be overcome by looking at the charging system....
Wire the alternator to the batteries without going through the 1-both-2 switch. This is normally done
via a splitter of your choice so both banks are charged independently.

 

[prv]

But you do lose the option to start from the domestic unless you addmore switches (or a jump lead).

True. On Kindred Spirit my charging relay was controlled by the Smartguage, and that has a button on the front which you can hold down for a couple of seconds to engage "emergency parallel". This closes the relay for 30 seconds, tying both batteries together.

On Ariam I think I'll just bring a jump-lead. When you don't have any way of accidentally running your domestics off the engine battery (say, by leaving a big round switch in the wrong position ), a flat engine battery is an extremely rare event for which there's no need to pre-prepare dedicated wiring.

My 1-2-both takes the field current so it protects the alt. if anyone sets to Off while running.

Are you sure your alternator doesn't energise its own coils, once it's up and running?

Pete

 

[halcyon]

I agree with macd heavy wires up to the bow thruster would be far better than adding another battery. good luck olewill

One consideration is bow thruster loading on cables from the batteries, plus alternator loading, the bow thruster could pull a lot more than the starter motor. Running on all banks you can see a lot of spikes etc, from contactor and bow thruster motor on electronics plus a low voltage as well.

Using VSR's or diodes to charge a bow battery is a cleaner option, but the bow thruster will still try and draw it's power through the bow battery charge circuit as this is higher voltage than drawing power from the bow battery.

Brian

 

[The Dogs Pollacks Brother]

Get yourself a Bluesea Off-On-Combine switch and ditch the stone age 1-2-both.
Off...........isolates both batteries
On...........turns on both batteries, but independent of each other so a low battery can't drag down a good battery
Both........combines them both in parallel if you need it.

Works an absolute dream for us. Rock up to the Grumpy Uncle,turn to ON,start engine and toys,go fishing,catch fish(sometimes),come back,park Grumpster,turn to off!

 

[ditchcrawler]

There is nothing wrong with a 1/2/both switch.I have had them on my boats for 16 seasons now.Why should you forget what you are doing with a 1/2/both switch.Do you forget to open your sea cock or pick up your car keys.Why should a 1/2/both switch be particularly forgettable more than anything else.The 1/2/both does let you choose which battery you want to charge at any given time.I tried a VSR and the drawback can be that it charges the priority battery first (usually the starter battery) and then switches to charge both lots of batteries together.With mine it kept switching in and out something which I understand is called "chatter".With my antiquated system I have a dedicated AGM Red Flash starter battery which I use only for starting on No1,charge it for 10/15 minutes or so and then switch no2 to charge my domestic bank on its own.My AGM sits there fully charged waiting for it's next use.I am not saying that other systems do not have their merits, just that the old 1/2/both switch does not deserve to be maligned as it does it's job faultlessly (in my case) without resorting to extra cost.

 

[vyv_cox]

There is nothing wrong with a 1/2/both switch.I have had them on my boats for 16 seasons now.Why should you forget what you are doing with a 1/2/both switch.Do you forget to open your sea cock or pick up your car keys.Why should a 1/2/both switch be particularly forgettable more than anything else.The 1/2/both does let you choose which battery you want to charge at any given time.I tried a VSR and the drawback can be that it charges the priority battery first (usually the starter battery) and then switches to charge both lots of batteries together.With mine it kept switching in and out something which I understand is called "chatter".With my antiquated system I have a dedicated AGM Red Flash starter battery which I use only for starting on No1,charge it for 10/15 minutes or so and then switch no2 to charge my domestic bank on its own.My AGM sits there fully charged waiting for it's next use.I am not saying that other systems do not have their merits, just that the old 1/2/both switch does not deserve to be maligned as it does it's job faultlessly (in my case) without resorting to extra cost.

I agree totally. I have only ever had 1-2-both switches, on four boats, going back to around 1987. Never had a single problem with any of them. I have recently completely rewired the motorsailer and bought a new 1-2-both switch for that too. Simple, versatile and foolproof. WYSIWYG.

 

[pvb]

I agree totally. I have only ever had 1-2-both switches, on four boats, going back to around 1987. Never had a single problem with any of them. I have recently completely rewired the motorsailer and bought a new 1-2-both switch for that too. Simple, versatile and foolproof. WYSIWYG.

Sadly, they're not foolproof, and there are countless instances of people setting the switch wrongly and then finding they have a flat start battery. There are much better alternatives these days.

 

[rob2]

There are much better alternatives these days.

It depends on what you want and can accept... I have a 1-2-both switch, a cheap Chinese one which relaced the second Plastimo which fell apart. It is not absolutely foolproof, but I can disassemble it and get it working again. Compared to the Plastimo, it's built like a brick outhouse.

If I had one of the electronic versions and it malfunctioned, I'd be fubarred!

Rob.

 

[halcyon]

It depends on what you want and can accept... I have a 1-2-both switch, a cheap Chinese one which relaced the second Plastimo which fell apart. It is not absolutely foolproof, but I can disassemble it and get it working again. Compared to the Plastimo, it's built like a brick outhouse.

If I had one of the electronic versions and it malfunctioned, I'd be fubarred!

Rob.

The battery switches are mechanical, the engine is connected directly to the engine battery, and if the relay electronics fail just swap over the cable to the other terminal to charge service battery.

Brian

 

[ghostlymoron]

The Bluesea Off-On-Combine switch certainly sounds like an ideal solution for those of us who tend to be forgetful which is the main drawback with the 1-2-B-O switch. BUT it seems to share one disadvantage with it - in the 'both/combine' position, if you use it when the engine battery is flat, you're combining a charged battery with a discharged battery to start the engine. You'll only get a reduced voltage from the combination which may be insufficient to start the engine a re-commence chargine your batteries. If you attempt to start your engine with the 'good' battery alone you'll get the full whack from your 'good' battery which is much more likely to start the engine. I'd prefer to have each battery seperate and an 'emergency start' switch to connect the 'house' battery alone to the starter.
The other advantage of a vsr/combiner is that you always get useful charge into the 'house' battery as soon as the 'start' battery is up to voltage whereas with a manual system, this doesn't happen until someone decides to switch from '1' to 'B' (if you are still motoring).