Battery switch

[Yamanx]

I have recently bought a narrow boat.

 

Please can anyone describe breifly how the battery switch may work. For instance, there are 4 positions. Off, 1, both and 2. Now 1 appears to be starter therefore 2 would probably be leisure and both, well, both.

 

However in what position should they be in for charging?

 

 

Thanks

 

David

[John Orentas]

David.

 

The switch should be used to control the charging of your batteries. You will no doubt have 2, 3 or more batteries fitted in your boat. One will be dedicated to starting your engine (it will probably have heavier cables connected to it), the others will be connected together and power the domestic circuits, lighting, pumps etc.

 

The idea is that your engine battery is always in a fully charged condition, even if you have gone to sleep the night before with the TV and all the lights on.

 

The OFF position should be used when you leave the boat, the position should isolate all the batteries, like the main switch in your house.

 

Position BOTH should be used when the engine is running, all batts' are connected together and therefore all charging, but you must change to ONE or TWO when you stop the engine unless your boat is fitted with a 'Split charge relay', in which case you may leave the switch on BOTH. Never switch to OFF before the engine is stopped.

 

Positions ONE and TWO determines that only the indicated batteries recieve the charge from the alternator. All domestic and engine systems will continue to function off their own batteries.

 

The above is the 'normal' way it should work, there can be numerous variations by design or accident.

 

On more modern boats automatic systems are used to control the systems, they ensure you cannot accidentally flatten your engine battery and that all your batteries are charged without your intervention.

 

John Squeers

 

Is that you in the photo ?

Edited October 13, 2004 by John Orentas

[Bernie]

Our battery switch is the same, therefore 1 for starting, both when engine running and 2 for domestic batteries when the engine is stopped and you want to use the 12V domestic supply and Off when leaving the boat for any length of time.

[Yamanx]

Thanks for that

[stuart]

Am I right in assuming that there is only 1 altenator installed in this situation as well?

 

With a double alternator, one charges leisure, other starter battery?

[John Orentas]

Stuart.

 

There was a thread about twin alternators not long ago.

 

The electrical system is much simplified, one alternator for the engine battery and one for the domestics. Two totally seperate circuits.

 

John Squeers

[alan_fincher]

The switch should be used to control the charging of your batteries.  You will no doubt have 2, 3 or more batteries fitted in your boat.  One will be dedicated to starting your engine (it will probably have heavier cables connected to it), the others will be connected together and power the domestic circuits, lighting, pumps etc.

 

The idea is that your engine battery is always in a fully charged condition, even if you have gone to sleep the night before with the TV and all the lights on.

 

The OFF position should be used when you leave the boat, the position should isolate all the batteries, like the main switch in your house.

 

Position BOTH should be used when the engine is running, all batts' are connected together and therefore all charging, but you must change to ONE or TWO when you stop the engine unless your boat is fitted with a 'Split charge relay', in which case you may leave the switch on BOTH.  Never switch to OFF before the engine is stopped.

 

Positions ONE and TWO determines that only the indicated batteries recieve the charge from the alternator.  All domestic and engine systems will continue to function off their own batteries.

 

The above is the 'normal' way it should work, there can be numerous variations by design or accident. 

 

On more modern boats automatic systems are used to control the systems, they ensure you cannot accidentally flatten your engine battery and that all your batteries are charged without your intervention.

 

John Squeers

 

 

This thread comes closest to a situation I have on my newly acquired (second hand) boat "Chalice", but as you say's in his post "The above is the 'normal' way it should work, there can be numerous variations by design or accident", and I have one of those !

 

I'm now looking for advice from those more experienced than I.

 

I also have a rotary switch exactly as described, (with positions "Off", "1", "BOTH" and "2)", and what I assumed to be a starting battery (Unspecified "Fulmen", and seems to be knackered), and two paralleled batteries, (which you might have reasonably assumed were for on-board lights and services). The latter are "Numax" appear to have been supplied only last year, seem in good shape, but are labelled Starting AND Deep Cycle.

 

HOWEVER, in my case the single battery connects solely to the "1" terminal on the back of the switch, and the bank of 2 to the "2" terminal - nothing else comes from either of these terminals but the heavy duty lead to the battery. There is just one further terminal, to which both the heavy duty connector to the starter, and the positive feed to the distribution box for cabin lights and services are connected, (and the alternator…)

 

So in position "1" or "2" one set of batteries is completely disconnected, can't be charged, nor supply anything. But in "BOTH", I simply have 3 batteries all wired in parallel, and being charged or discharged together.

 

Currently I can't start the engine on what appears to be the starter battery, due to it's poor condition, and am assuming that with "BOTH" selected the "bad" battery is dragging down the good ones.

 

If I accept the argument that switching the switch with the engine running may damage the alternator due to a momentary open circuit bon the change-over, then I can't start on the good (pair of) batteries, and switch to the poor one with the engine running to see if it will then charge.

 

Currently I'm thinking I probably need to...

 

1) get the bad battery to somewhere where I can try and mains charge it, (no 240V on board).

2) Replace it, if it will not recover.

and

3) Look for a better arrangement on the switching and charging.

 

I'm not really ready to move up to some expensive charge management system, (and my elderly BMC has only a low current output, I assume).

 

So how about

 

4) Ditch the single rotary switch

5) Provide separate isolation switches for each battery, using the single battery for starting & the bank for all other services.

6) Use a charge splitting relay so that both batteries charge when engine is running, but so that the two circuits are separated when not.

 

But I'm not sure what else I need to consider, and how easily this can be achieved, (..it doesn't sound too hard, but perhaps I'm naive!)

 

Finally, what I've read seems to say that a good old mechanical relay is often less problematic than solid state charge splitting diodes. (Sounds odd, doesn't it!...)

 

Any advice please ?

 

Alan Fincher

 

"Chalice"

[dor]

I would go for the relay.

 

Switches rely on you remembering to put them in the right position.

Diodes are not so much unreliable as they give rise to a significant voltage drop, which can restrict the amount of charge going into the batteries.

Relays are reliable and automatic in operation, but if you have a reasonable size alternator, make sure it is a proper one for the job rather than a typical automotive one.

 

Also, make sure it is energised off the alternator charge light circuit to ensure it is open when you start the engine (unless you are sure that the ignition switch isolates the current-supplying pole when the starter is engaged). Otherwise, if the start battery is relatively flat, a very large current can be drawn through the relay from the service batteries which is likely to blow it.

[Alan Saunders]

This thread comes closest to a situation I have on my newly acquired (second hand) boat "Chalice", but as you say's in his post "The above is the 'normal' way it should work, there can be numerous variations by design or accident", and I have one of those !

23571[/snapback]

I think yours is the 'standard arrangement', could be your start battery is knackered but it may be a defective switch. If you shop around you should be able to get a replacement start battery for about £50. Leisure batteries with a starting rating are intended for boats that only have one battery (bank). They are a compromise.

 

Unless you have an electric refrigerator or other power hungry devices you can probably manage with just one 110A leisure battery. Take out the existing start battery and temporarily replace it with one of the start/leisure batteries. If you cannot remove the links between the batteries completely make sure they are well insulated.

 

If the switch is well designed and not faulty it will 'make before break' - so long as you do not go via the off position all should be well. On the other hand, perhaps the switch is faulty? I would first check the resistance of the switch in each position, it should be less than 1 ohm and then check the voltage drop across the switch in each position with say the tunnel light on, probably less than 200mV. It may be possible to dismantle the switch and clean the contacts. Or spray it with switch cleaner and operate several times.

 

As Dor says, diodes are more reliable than relays but they drop 0.6V. A corroded or under-rated relay may drop the same or more. I originally fitted the blue Lucas automotive (not marine) relay. It was tucked away in the battery box in the engine compartment but after a few years the operating spring corroded through. I replaced it with a Durite relay rated at 12V, 180A. This picked as soon as the 'ignition' circuit was live. It took less than 4V to pick it! I increased the armature gap and strengthened the spring so that it needs 10V to pick.

 

I bought a second hand alternator controller a few months back. I rate it a better investment than an additional battery. Not only can I recharge the batteries faster, their capacity has increased, I assume they have been 'de-sulphated'. Voltage drop in cables and relay is taken care of by remote sensing but I now need to fit a diode to reduce the charge voltage to the start battery.

 

I am not sure what the output of your alternator may be but I am sure it exceeds the minimum of 10% of the battery capacity. Without remote sensing you will be lucky to push more than 10A into the batteries, half of the manufacturers recommendation.

 

Alan

[alan_fincher]

Many thanks, both.....

 

In theory, as Alan says, the switch seems to be designed as "make before break", but I have read in a number of places, (including the "Reading College course notes), that this cannot be relied upon in an elderly switch.

 

I haven't yet tried detailed measurements on it, or removing to see if dismantling / cleaning is possible. But, I think that you are right that this is probably worth a try, (......visions of springs popping out that will not go back !!....).

 

Thanks for the comments on diodes versus relays, but you have now got me wondering if the extra expense of a controller might be worth it, if it significantly increases battery capacity, and (probably) overall life. I need to look at costs, I guess.

 

There is a 12 volt capable fridge aboard, by the way, though only having had "Chalice" about 3 days, (most of it spent trying to remove much heavily contaminated water from the bilges !), it's one of the things I have yet to try out to see if it is working.... I've heard that 3-way ones, (which this seems to be), can be very thirsty when run on 12V.

 

Alan

[DHutch]

In theory, as Alan says, the switch seems to be designed as "make before break", but I have read in a number of places, (including the "Reading College course notes), that this cannot be relied upon in an elderly switch.

The switch you describe sounds very like the vetus one we have,

- It is of cause make-before-break going via 'both'.

- And break-before-make going via the 'off'.

 

 

 

Daniel

[Alan Saunders]

There is a 12 volt capable fridge aboard, by the way, though only having had "Chalice" about 3 days, (most of it spent trying to remove much heavily contaminated water from the bilges !), it's one of the things I have yet to try out to see if it is working....  I've heard that 3-way ones, (which this seems to be), can be very thirsty when run on 12V.Alan

23626[/snapback]

The Electrolux or similar 'three way fridge' is an absorption type, using heat to provide cooling, clever! The heating coil needs around 100W, insignificant from a shoreline or whilst the engine is running, intended for caravans whilst towing, but 100W at 12V = 8 amps, your two leisure batteries will barely run it for 24 hours, whereas a 12V compressor fridge might average only 2A. It will run for a month on a 13Kg bottle of propane gas. So long as it is properly installed with an unobstructed, external flue and adequate ventilation there is little safety hazard. Still, in this current heatwave, mine is adding a few degrees to the cabin temperature (80F+)!

 

When you have pumped out most of the bilge water I suggest cat litter spread over the baseplate and vacuumed up a week or two later leaving only the grind of scrape, chip, rust-treat and paint. Meanwhile you need to find the source of the water incursion and fix it! Water in the bilges makes for a generally 'damp' boat with mildew and all the associated problems. Window seals and corrosion under them are prime candidates followed by the shower compartment and shower tray.

 

(yet another) Alan