Doing away with battery switches

[bigwow]

As the current thinking is to do away with the 1/2/both battery switches, and as I suspect one of mine needs replacing anyway, can anyone give me a diagram for rewiring without them. Two alternators, two engine starting batteries and the battery bank. Thanks

 

[gianenrico]

IMHO I would wire one voltage sensitive relais between the alternator and the battery bank; this will ensure that the alternator will ALWAYS top charge the starting battery and, when this is "filled up", it will start charging the bank.


This is the conclusion I draw after mauch researching on forums, suppliers sites and sending an enbquiry to PBO (this latter without results).
Cheers

 

[CPD]

When you say "one of mine needs replacing", that would indicate you have 2 and I dont understand that. You say you have 2 engine start batteries which I presume are both wired in parallel but also individually isolated, so you can use either. If that is the case, then domestic (i think what you refer to as battery bank) is wired into (1) of the 1,2,both,off and the individually selectable engine start betteries are wired into (2). So you only need 1 off 1,2,both,off selector.

I have recently done away with the 1,2,both,off switch and have isolators on the engine and domestic batteries which are wired to the common positive after the selector switch (also on the positive). If you do have 2 engione start batteries, then I would put 1 on 1 alternator and then have what I have running from the other alternator.

Or do I have it completely misunderstood ? /forums/images/graemlins/frown.gif

 

[halcyon]

Try option 3 on following link, allows two independent engine batteries, plus a service bank. Engines are allways connected to there battery, services battery is charged from both alternators, if a alternators fails the good one will charge the other bank, and it has integral link start from other engine battery.

http://kddpowercentre.com/04/sc/page5.html

Sorry odd words, site is starting to fall apart, new one on computor at the moment.

Brian

 

[orizaba]

or you could use one alternator to charge your start batteries and one to charge yuor leisure,straight forward and no relays or voltage drop,probabally the ideal setup,its what i had for 12 yrs on the nb and would have now if i had a bit more room.if you want to fit a boost charger fit it too the alternator feeding the leisure batteries,

 

[Dipper]

Make sure you fit some means of breaking the circuit such as those red isolator keys.

I was wiring my first boat which had no battery switch and stupidly touched a positive and negative wire together. The resulting 'burn' traveled along the wire like a fuse. In my panic I cut the wire further down with a pair of scissors but all this did was start it off again at the cut point. It rapidly traveled to the voltage regulator near the engine, there was a pop and a puff of smoke and it stopped. Rather lucky really as I had a petrol Stuart Turner engine. /forums/images/graemlins/shocked.gif

Before I did anything else, I fitted one of those red keys.

 

[bigwow]

Sorry for the confusion Bigwow is a cat with two engines each with it’s own starter battery and battery switch

 

[William_H]

There is a comparison here with light twin engined aircraft in that they always have one battery used to start both engines and a regulator which balances the charge rate of both alternators. Now these regulators might be a bit hard to find/expensive and perhaps not absolutely necessary. (A plane generally has a much higher load

However it would be worth having decent sized cables from one engine to the other to permit start on the opposite engine. In fact I reckon you only need one engine battery. Which might lead you to run the domestic battery off the gen not connected to the engine battery. If the batteries are identical ie not specialised engine start batteries then just have a battery for each engine and use the same battery one at a time for domestic consumption. Knowing that you can start off the other non discharged battery.

Or just retain the individual batteries for engine start and have a VSR with a changeover switch so you can select charging from either alternator. Note here you won't get more charge into the domestic battery by feeding from 2 alternators unless it is very flat or you have a smart charger. (Which of course would be confused by being connected to 2 alternators.

So I have rattled on and not really helped. It is not so much the wiring diagram you want as to decide exactly what you want to happen. good luck olewill

 

[dedwards]

check out bepmarine.com they make a battery distribution cluster that suits your needs. There is also a pdf on their site that you can download to see how its wired. Essentially, the engines and house system are independantly connected to their respective battery banks via three switches. There is then a voltage sensitive relay connected to each alternator, either of which can independantly charge the house battery. Finally, there is a fourth switch that allows you to join the two engine batteries should you need to start an engine off the other engine's battery.

 

[Jonny_H]

Ditto that - fitted one of their clusters to my boat - very easy to do and a great product IMHO (appears to be well made)

 

[catmandoo]

On my set up the out put from 2 alternators go direct to the batteries via two separate diode splitters. There is therefore no interposing switch between the alternators and the battery/ load . I have a separate line to the starter which does have a selector switch and is fed directly from battery one and battery two . So if I accidentally change the battery selection when the engine is running I don't damage the alternators although there is a slight risk of one battery feeding from another in the 1 and 2 position

 

[Trundlebug]

Last season I completely rewired my twin engined boat's batteries and charging system and I'm now really pleased with it.

Against all "expert" advice I now have one starter battery, serving both engines, and a bank of three leisure batteries. Each battery has its own red isolator switch, enabling complete flexibility, and I used the old / existing 1/2/both switch toenable me to slecet which "bank" is used to start the engines. I hope to fit an old starter solenoid (probably from an old Mini or similar) to replace this in due course, to enable me to carry out this switching remotely.
Under normal circumstances it's switched to 1, the one starter battery. If ever I had a problem I could select to start from the leisure bank (2) or both to have them all in parallel.

To take care of the charging, both simply and most efficiently, I fitted a Sterling Alternator to battery charger, with both alternators connected into the input side.
Whichever engine is running (normally both), will charge all the batteries, with the extra benefit of boosting the charge into the leisure bank.

There's a lot of hocus pocus about "must have a dedicated starter battery for each engine", and frankly it's rubbish. As long as you have the flexibility to be able to switch to another bank if there's trouble, you only need one starter battery to cover both engines. The "experts" seem to forget that any correctly sized battery is capable of starting one engine twice, or two engines at least once, 99.9% of the time, so why waste all that battery capacity by having an extra starter battery that's not required?

The Sterling system was easy to install and charges the batteries quickly and very efficiently, making the most of what both alternators have to offer. I monitor all this with a NASA BM1 battery monitor. I'd recommend my system to anyone.

Good luck with whatever you choose

Martin

 

[halcyon]

[ QUOTE ]
Note here you won't get more charge into the domestic battery by feeding from 2 alternators

[/ QUOTE ]

For years we supplied Sealine with a system that charged service bank from both alternators. They then changed to a two battery system, with one engine charging the service bank, and there was a loss of battery capacity.
This was due to the service load on the battery holding down the alternator output volts, so limiting the recharge level. With two alternators running, there was enough output to supply service loads, and reach alternator regulation voltage. We fitted one boat with split charge relay, allowing both alternators to charge the service bank, and capacity came back up. It is only when you reach regulation volts do you start lossing the benefits.
It also gives alternator redundancy, allowing one alternator to charge all three battery banks if one alternator fails. Also allowing a solar panel connected to service bank to charge both engine batteries as well.

Brian

 

[robavery]

Martin

Am considering adding a Sterling Battery to Alternator system to our yacht. Have noted your comments but would be grateful of any other you may have about the product

 

[bigwow]

[ QUOTE ]

There's a lot of hocus pocus about "must have a dedicated starter battery for each engine", and frankly it's rubbish. As long as you have the flexibility to be able to switch to another bank if there's trouble, you only need one starter battery to cover both engines. The "experts" seem to forget that any correctly sized battery is capable of starting one engine twice, or two engines at least once, 99.9% of the time, so why waste all that battery capacity by having an extra starter battery that's not required?



[/ QUOTE ]

My engines are 15-16 feet apart, so having just 1 starter battery would require some long wire runs, at the moment each engine battery is within 2 feet of it's engine so there are no long runs with the risk of voltage drop.

 

[halcyon]

[quote The "experts" seem to forget that any correctly sized battery is capable of starting one engine twice, or two engines at least once, 99.9% of the time, so why waste all that battery capacity

[/ QUOTE ]

The norm is a minimum of 10 engine starting cycles on a 40% discharged battery at -5 degrees C.
A seperate battery for each engine saves the builder altering new engine wireing, minimises cable run, cost and volt drop, thus time and build cost, plus warranty issues with engine maker. There is a big differance between building a new boat, and refitting your own second hand boat.

Brian

 

[bigwow]

I built the boat in 1993 and then it seemed logical to have a separate battery for each engine and the 1/2/both switches were the norm. Engine wiring would not have needed altering anyway as all that needed to be done was connect a pos and neg to each. I intend too keep separate starting batteries but wanted to do away with the battery switches as one of them is starting to play up. I thought I’d do a battery rewire while I was at it.
John

 

[halcyon]

We once supplied switch gear to a cat that had a switch panel in each hull, complete with a service and engine batteries in each hull. Simplified wiring, and power feeds no end.
PM me if you want any info on charging systems.

Brian

 

[William_H]

High Halcyon. My point that you won't get any more charge into a bank of batteries with 2 alternators was on the assumption that both or just one alternator was delivering a regulated voltage. This will be the normal situation provided batteries are not very flat or really huge capacity or tiny alternator and usually that situation only lasts until the batteries get some charge. (quite quickly)

Alternators do fail to deliver regulated voltage when the load is approaching the rated current of the alternator. this is usually only achievable with a high load (as in lights etc) as battery charging as a load tends to be self limiting. ie lower current with less voltage at a rate of reduction much greater than eg a lamp.

I can imagine the voltage limiting situation in some cases but would not think it likely in a pleasure boat.

I remember an old Piper Aztec twin aircraft which originally had a 12v system with one generator (a commutator type about 30 amps flat out) which could actually land with a flat battery after traffic control brought in the requirement to operate with landing lights on for identification. I think they were all modified eventually to twin alternator type generators.

so yes in some extreme cases two alternators can help but in most cases where battery charging is the primary load if the alternator can deliver 14 volts then the current into the battery is dictated by the discharge state of the battery and the battery size. The battery inherent voltage rises to near 14 fairly quickly compared to the actual charge % so your charge current reduces and it takes a long time to fully charge a battery. 2 batteries will take twice as much current making the engine run for charging more useful which works well if they are only partially discharged.

This ten becomes the case for a smart charger or stepped charger to get the voltage up for a period to get more current in.

You probably know all this but I think it useful to reiterate to others.

Back to the original poster. It should be easy to replace each 1,2,both switch with 2 individual on off switches without major changes to the electrical arrangement. good luck olewill

 

[halcyon]

It depends on a particular boat, but for example one mobo pulls 65 amps with all cabin lights on, has two fridges, central heating, radar, nav equip, water pumps, vhf, auto pilot, in boat entertainment system, etc. All adding up to a high normal running load on the alternator.
Assuming this owner only has a small percentage of this for the normal motoring load, has standard the alternator on the engine, has been at anchor for a time giving a low battery bank as well, the battery will not shoot up in seconds. So if you have two alternators why not use them, it's free. I normally try and cover the worst normal case, not the best.
As you say why not fit two switches, all I said was why not fit two relays, linked to one control box.
Why?, it allows both alternators to charge all batteries until one can cope with the charge load, the low set one will shut down due to it inbuilt regulator. But it also allows you to have link start from alt engine battery from a remote switch, alternator redundancy as both alternators can charge all batteries, plus your solar panel can charge all batteries, all using the same equipment with no extra switching or cost.

But the bottom line is it's a boat not a aircraft.

Brian