Battery Isolator Wiring

[Beagle@Bodymoor]

Hi,

 

I have recently helped my dad replace his domestic battery bank. He has changed from 3 x 110Ah Batteries, to 3 x 225Ah batteries. This has had the desired effect, and the electricity reliability, especially the 240vAC is significantly better.

 

I have noticed however that the 2 battery isolator switches do not fully isolate the batteries.

 

The engine has 2 alternators, one for the engine battery bank, and one for the domestic.

 

Each circuit (engine and domestic) has a battery isolator switch with 2 poles, so effectively te switch either makes, or breaks the circuit between the 2 poles. The alternator and battery both go to one pole, and the load goes to the other pole. However this means that when the switch is turned off, the alternator is still connected to the batteries, so if the engine runs, it is still charging, and if the engine is not running, there is still a 12v feed to the alternator.

 

My question is simple, is this right? Or should the 2 pole isolator, actually be a 3 pole?

 

Many Thanks

 

Andy

[by'eck]

Its normal for the alternator(s) (and battery charger) to be connected directly to the batteries. The reasoning being that even if the isolator is off, if the engine is run without remembering to turn on isolator, no damage will come to the alternators. Ditto for battery charger.

 

Other items bypassing the isolator are bilge pumps and alarm systems since they need to be left active when boat is unattended.

[Beagle@Bodymoor]

Its normal for the alternator(s) (and battery charger) to be connected directly to the batteries. The reasoning being that even if the isolator is off, if the engine is run without remembering to turn on isolator, no damage will come to the alternators. Ditto for battery charger.

 

Other items bypassing the isolator are bilge pumps and alarm systems since they need to be left active when boat is unattended.

 

Thankyou for your reply, good to know its not a problem. You mention battery charger. This is an area my dad and I have been discussing. Currently the batteries only get charged from the alternators, my dad has said that other people where he is moored have controllers to monitor the batteries, and regulate the alternators level of charge. He would also like to look at getting some solar trickle charge into the the batteries.

 

Can anyone advise on whether we really do need any sort of regulator/maintaining device, an how do we go about sizing a solar trickle charger?

 

Thanks again,

 

Andy

[Roger Crown]

Its normal for the alternator(s) to be connected directly to the batteries. The reasoning being that even if the isolator is off, if the engine is run without remembering to turn on isolator, no damage will come to the alternators.

 

Richard you are very wrong and should not be giving advice like this until you better understand the requirements of wiring on boats which come under the requirements of the BSS.

 

If an alternator was connected directly to the batteries, then for it to pass a Boat Safety Scheme examination it would be necessary to fit a suitable fuse in the circuit and also to provide written evidence from the manufacturer of the alternator supporting the decision to by pass the main Isolator.

[Beagle@Bodymoor]

Richard you are very wrong and should not be giving advice like this until you better understand the requirements of wiring on boats which come under the requirements of the BSS.

 

If an alternator was connected directly to the batteries, then for it to pass a Boat Safety Scheme examination it would be necessary to fit a suitable fuse in the circuit and also to provide written evidence from the manufacturer of the alternator supporting the decision to by pass the main Isolator.

 

The boat did pass its BSS examination last Sunday (however we put the 3 x 110Ah batteries back in, because the 225Ah do not fit in the battery tray properly). There is a large fuse (I dont know the rating off the top of my head) connected about 1 inch from the +ve take off point on the domestic battery bank.

 

 

Ok, as there is a mixed opinion already, let me give you the full rundown.

 

the boat is a 60ft canalboat, it now has 3 x 225Ah batteries on the domestic side, and 1 x 110Ah on the engine side.

There is a Victron 3kw inverter fitted which is connected using 70mm² cable to the domestic batteries.

The inverter, when switched on, is used to power a microwave, a washing machine, and an LED tv with dvd player.

There is also a smaller cable that feeds the 12v fuseboard, this is used to power the boat lighting (now all LED bulbs), the fridge, 2 car stereos (one at front, one at back), the shower, the toilet, and the hot water and water pump.

The engine has 2 alternators, a 35A (from memory) for the engine battery bank, and a 110A for the domestic batteries.

 

The reason for my original question about the isolators, is that I am going to modify the battery tray this weekend to fit the bigger batteries, when I do this I will need to re-route/replace some of the cabling so it all reaches nicely. i wanted to rectify any issues with the isolators at that point.

 

I would also appreciate any info on solar charging, and charge manager devices for the setup I have mentioned.

 

As much relevant information is appreciated.

[Roger Crown]

The boat did pass its BSS examination last Sunday (however we put the 3 x 110Ah batteries back in, because the 225Ah do not fit in the battery tray properly). There is a large fuse (I dont know the rating off the top of my head) connected about 1 inch from the +ve take off point on the domestic battery bank.

 

 

Ok, as there is a mixed opinion already, let me give you the full rundown.

 

the boat is a 60ft canalboat, it now has 3 x 225Ah batteries on the domestic side, and 1 x 110Ah on the engine side.

There is a Victron 3kw inverter fitted which is connected using 70mm² cable to the domestic batteries.

The inverter, when switched on, is used to power a microwave, a washing machine, and an LED tv with dvd player.

There is also a smaller cable that feeds the 12v fuseboard, this is used to power the boat lighting (now all LED bulbs), the fridge, 2 car stereos (one at front, one at back), the shower, the toilet, and the hot water and water pump.

The engine has 2 alternators, a 35A (from memory) for the engine battery bank, and a 110A for the domestic batteries.

 

The reason for my original question about the isolators, is that I am going to modify the battery tray this weekend to fit the bigger batteries, when I do this I will need to re-route/replace some of the cabling so it all reaches nicely. i wanted to rectify any issues with the isolators at that point.

 

I would also appreciate any info on solar charging, and charge manager devices for the setup I have mentioned.

 

As much relevant information is appreciated.

 

Hi Beagle@ Bodymoor

 

Welcome to the forum, as you probably already know there is some great information and advise on this forum, unfortunately some advice given in good faith is not always correct.

 

Re the BSS inspection I really can't comment as to why the boat has passed with the alternator/s incorrectly connected, it is very clear in the BSS guide that alternators should be disconnected by the main isolators. It is always possible that the large fuse you mention is in the alternator circuit, though I very much doubt it is and more likely for the Victron.

Btw the mounting position of that fuse does not sound ideal so close to the batteries.

 

I'm sure others will be along soon to help with the solar charging

 

Regards

Roger

 

edited for not reading before posting

Edited May 16, 2012 by Crown Narrowboats Ltd

[Beagle@Bodymoor]

Hi Beagle@ Bodymoor

 

Welcome to the forum, as you probably already know there is some great information and advise on this forum, unfortunately some advice given in good faith is not always correct.

 

Re the BSS inspection I really can't comment as to why the boat has passed with the alternator/s incorrectly connected, it is very clear in the BSS guide that alternators should be disconnected by the main isolators. It is always possible that the large fuse you mention is in the alternator circuit, though I very much doubt it is and more likely for the Victron.

Btw the mounting position of that fuse does not sound ideal so close to the batteries.

 

I'm sure others will be along soon to help with the solar charging

 

Regards

Roger

 

edited for not reading before posting

 

As you have mentioned other things that might be wrong, such as the fuse location, can anyone offer a circuit diagram, or run through of how the system should be wired, as I would be happier just starting again and getting it all wired up correctly. I have been through quite a lot of info on tb-training, but am yet so find a circuit that includes 2 alternators, 2 battery banks, 2 isolators and an inverter (I thought this was a typical installation?)

 

Just thought of one other thing regarding the isolators, if I wired them so the battery was on one pole and the alternator and load on the other pole, that would mean the battery was isolated, but surely if the engine was running and the isolator off, the alternator would try to power the boat??? Surely with a 2 pole isolator you can only wire it one of 2 ways?

Edited May 16, 2012 by Beagle@Bodymoor

[Roger Crown]

Just thought of one other thing regarding the isolators, if I wired them so the battery was on one pole and the alternator and load on the other pole, that would mean the battery was isolated, but surely if the engine was running and the isolator off, the alternator would try to power the boat??? Surely with a 2 pole isolator you can only wire it one of 2 ways?

 

What you say is true and there is worse that can happen. Never switch off a main isolator with the engine running, you would be lucky to get away not damaging the alternator.

 

The correct way of wiring is through the isolator, I don't make the rules.

 

I would be happy to look at your boat and advise you, it's not something that can be done sensibly without actually seeing the installation first hand.

Where is the boat?

Regards

Roger

[Beagle@Bodymoor]

What you say is true and there is worse that can happen. Never switch off a main isolator with the engine running, you would be lucky to get away not damaging the alternator.

 

The correct way of wiring is through the isolator, I don't make the rules.

 

I would be happy to look at your boat and advise you, it's not something that can be done sensibly without actually seeing the installation first hand.

Where is the boat?

Regards

Roger

 

The boat is at bodymoor heath on the Birmingham and fazeley canal

 

When you say the correct way is through the isolator, can you explain what is connected at each pole of the isolator, for example I have 2 poles on the isolator, lets say A and B, and then I have 3 wires (theres more than 3 but for ease of explanation) Cable 1 is the battery bank positive, Cable 2 is the Alternator Charge, and Cable 3 is the load (the boat). Which way is the best in this situation?

Edited May 16, 2012 by Beagle@Bodymoor

[nicknorman]

What you say is true and there is worse that can happen. Never switch off a main isolator with the engine running, you would be lucky to get away not damaging the alternator.

 

The correct way of wiring is through the isolator, I don't make the rules.

 

I would be happy to look at your boat and advise you, it's not something that can be done sensibly without actually seeing the installation first hand.

Where is the boat?

Regards

Roger

Roger, you are right about the wording of the BSS of course, however the BSS is ultimately some hurdle to be passed, written by committee some of whom will have their own bees in bonnets etc - it was not handed down to Moses by God at the dawn of time! It is not based on any sort of risk assessment nor in some areas, based on any accidents or incidents.

 

It is fairly common practice to connect the alternator directly to the batteries - certainly that seems to work fine in all cars, which vastly outnumber boats and don't seem to have electrical fires as a result. My domestic alternator is connected to the bat side of the isolator. If the BSS man objects in 3 years time, I will move it to the other terminal. But then back again once I have my certificate.

 

The down side of having the alt though the isolator in my opinion outweighs the advantages - inadvertent switching off, voltage drop at high current etc, dodgy connection/ arcing causing and hence alternator death. But that is of course just my choice and I do ensure that the supply bypassing the isolator is well protected with no exposed conductor/terminals etc.

[Keeping Up]

I firmly believe that the isolator should do exactly what the name suggests: it should isolate. Therefore NOTHING should be connected to the battery when the isolator is open. If all my electrics were going up in smoke I would expect the power to be completely disconnected by turning the isolator off, and if it happened that my alternator were to die when I did this, I would consider that to be only a small sacrifice to make in the circumstances.

[Roger Crown]

I firmly believe that the isolator should do exactly what the name suggests: it should isolate. Therefore NOTHING should be connected to the battery when the isolator is open. If all my electrics were going up in smoke I would expect the power to be completely disconnected by turning the isolator off, and if it happened that my alternator were to die when I did this, I would consider that to be only a small sacrifice to make in the circumstances.

Allan I am in agreement with what you say in the main, though some pieces of equipment should not be isolated for good reason BUT the key point is they should be locally fused.

 

regards

Roger

 

 

It is fairly common practice to connect the alternator directly to the batteries - certainly that seems to work fine in all cars, which vastly outnumber boats and don't seem to have electrical fires as a result.

Nick, it seems to me there are many car fires daily, perhaps an isolation switch would aid the fire services. The very first thing they have to do in an emergency is crop the battery wires.

 

Does your boat insurance company know you swap things about to suit yourself?

regards

Roger

[Beagle@Bodymoor]

Im sorry, but despite everything you are all saying, there is no circuit that will isolate everything from the battery using the 2 pole isolator mentioned. ( does this mean the correct answer is a 3 pole isolator?)

 

So in reality, the question is (considering the fact that for 99.9% of the time the isolator will be ON), what side should the alternator cable go, battery or load?

 

(I haredly dare ask about the other things I mentioned now ! ;0) )

Edited May 16, 2012 by Beagle@Bodymoor

[nicknorman]

 

Nick, it seems to me there are many car fires daily, perhaps an isolation switch would aid the fire services. The very first thing they have to do in an emergency is crop the battery wires.

 

Does your boat insurance company know you swap things about to suit yourself?

 

There are car fires daily but how many are due to unisolated alternators going short circuit?. If it was an issue I think designs would be changed. Car fires are generally caused by peripheral circuits and/or fuel in contact with hot engine bits. To say that because cars go on fire, the alternators must be protected by an isolator is the sort of illogic that drives some BSS requirements.

 

My boat is new, built by a reputable builder, and the domestic alt. was wired direct to battery pos. Complete with RCD certificate. I have modified the installation to add a Mastershunt which includes a built in 500A fuse so that probably satisfies the BSS but I am aware of many boats who have passed BSS despite alt being connected to bat pos - the OP's boat is not unusual in that respect. It is very easy to say "what would...(an insurance company, court of law etc) say" if you are the glass half full type, but the reality is that many boats are as I say and I believe it is pretty much industry standard, even if deviating from BBS doctrine.

[Chris Pink]

Im sorry, but despite everything you are all saying, there is no circuit that will isolate everything from the battery using the 2 pole isolator mentioned. ( does this mean the correct answer is a 3 pole isolator?)

 

So in reality, the question is (considering the fact that for 99.9% of the time the isolator will be ON), what side should the alternator cable go, battery or load?

 

(I haredly dare ask about the other things I mentioned now ! ;0) )

 

2 poles; battery one side everything else t'other.

 

This is a storm in a teacup because you have to switch the isolator on to start the engine so all you really have to do is remember not to turn it off while the engine's on.

 

Hardly difficult.

[nicknorman]

Im sorry, but despite everything you are all saying, there is no circuit that will isolate everything from the battery using the 2 pole isolator mentioned. ( does this mean the correct answer is a 3 pole isolator?)

 

So in reality, the question is (considering the fact that for 99.9% of the time the isolator will be ON), what side should the alternator cable go, battery or load?

 

(I haredly dare ask about the other things I mentioned now ! ;0) )

No you only need a 2 pole isolator to comply with BSS dogma. One pole for battery pos, the other for everything else. That does mean that with an electrical fire and opening the isolator, the alternator can continue to feed the fire until you stop the engine. My Iskra 175A alternator is capable of putting out 2kw or so of electrical heat which would be plenty to sustain an electrical fire. The BSS does not consider this scenario, maybe the assumption is that the engine can be cut, but clearly there are circumstances when that would be undesirable ie river or tidal navigation. Like I said, some elements of BSS are someone's bonnet bee and don't stand logical analysis!

[Chris Pink]

to join in with da buoys. It is considered by many examiners to be fairly daft and I have known discretion to be applied.

 

Personally I'd go back to the old fashioned way and wire the engine alternator to the starter motor positive.

[nicknorman]

2 poles; battery one side everything else t'other.

 

This is a storm in a teacup because you have to switch the isolator on to start the engine so all you really have to do is remember not to turn it off while the engine's on.

 

Hardly difficult.

 

Apart from the many boats that have 2 isolators and 2 alternators, one for engine and 1 for domestic! I am inclined to agree that inadvertent switching off can be addressed by sensible location of the isolator (ie ignoring another BSS requirement that the isolator is highly accessible) - for me it is more about the voltage drop, heating and degradation of your average isolator whose design often seems pretty stone age. (Stone not being a good conductor!)

Edited May 16, 2012 by nicknorman

[Roger Crown]

Nick

I got involved on this thread due to some thing Richard Hula said and I felt he was misleading the OP.

I am assuming your reputable builder is the same one he has currently commissioned.

Richard has on other threads stated that it is industry standard to directly connect batteries to the domestic alternator.

If you are both quoting from the same builders methods, this is hardly industry standards.

When any boat leaves a builders yard it should be in fit condition to pass any BSS inspection, even the ones that won't be bullied and turn a blind eye.

[nicknorman]

Nick

I got involved on this thread due to some thing Richard Hula said and I felt he was misleading the OP.

I am assuming your reputable builder is the same one he has currently commissioned.

Richard has on other threads stated that it is industry standard to directly connect batteries to the domestic alternator.

If you are both quoting from the same builders methods, this is hardly industry standards.

When any boat leaves a builders yard it should be in fit condition to pass any BSS inspection, even the ones that won't be bullied and turn a blind eye.

Well you are right in that both of us have/are having a boat built by the same builder, however we both have our own ideas based on previous boats, knowledge of electrics, understanding the concepts of risk analysis and the ability to apply logical thought. We have both substantially modified the builder's normal electrical installation in accordance with our own ideas. It would therefore be incorrect to think that our views on this subject come from our builder. I did not ask for the alternator to battery wiring to be modified but was not concerned when the way the alt was to be connected transpired. There has been plenty of discussion on this forum that reveals that not isolating the alternator is quite commonplace if not perhaps "industry standard" - but then bear in mind there isn't really an "industry standard" with much of narrowboat construction!

 

I suppose you are right that a new boat should be able to pass a BSS but bearing in mind that to make it comply involves moving the cable from one stud to the adjacent one, it is not really a big deal.

 

I notice that you haven't responded to the BSS's failure to consider that with the "approved" method the electrical system remains powered when the isolator is turned off with engine running. To my mind, fro a safety point of view an electrical fire is far more likely to occur somewhere else in the electrical system, and very unlikely to occur in the wiring to the Alt or the Alt itself.

 

Finally, I doubt any BSS examiners allow themselves to be bullied, it is more likely that they understand the fallacy of this requirement.

Edited May 16, 2012 by nicknorman

[bizzard]

Due to the fact that the position of battery isolator switches on many boats ARE in an inacessible position,''In rear engine compartments''its prudent just to run for it if a fire breaks out in there, no matter how the components are wired up.

Cruiser stern type boats are the worst offenders especially w/beam boats most of which have that ridiculously unwealdly and heavy steel or plywood engine cover deck board abortion.By the time you've fought with this,tamed it, got it under control and raised it''all in a panic'' without chopping your toes or fingers off and so further fanning the flames into an inferno at the same time,''remember its not advised to open a vehicles engine bonnet with an engine compartment fire''found the dreaded switches amongst all the acrid smoke and flames I reckon there's a good chance you'll become the Guy on the top of your very own electrical bonfire. So if your unfortunate enough to have one of these engine space electrical fires break out on November the 5th, the flames and all would just blend in with all the other pyrotechnics around and about and so probably go unnoticed.

No i think, just run for it.

[Roger Crown]

Well you are right in that both of us have/are having a boat built by the same builder, however we both have our own ideas based on previous boats, knowledge of electrics, understanding the concepts of risk analysis and the ability to apply logical thought. We have both substantially modified the builder's normal electrical installation in accordance with our own ideas. It would therefore be incorrect to think that our views on this subject come from our builder. I did not ask for the alternator to battery wiring to be modified but was not concerned when the way the alt was to be connected transpired. There has been plenty of discussion on this forum that reveals that not isolating the alternator is quite commonplace if not perhaps "industry standard" - but then bear in mind there isn't really an "industry standard" with much of narrowboat construction!

 

I suppose you are right that a new boat should be able to pass a BSS but bearing in mind that to make it comply involves moving the cable from one stud to the adjacent one, it is not really a big deal.

 

I notice that you haven't responded to the BSS's failure to consider that with the "approved" method the electrical system remains powered when the isolator is turned off with engine running. To my mind, fro a safety point of view an electrical fire is far more likely to occur somewhere else in the electrical system, and very unlikely to occur in the wiring to the Alt or the Alt itself.

 

Finally, I doubt any BSS examiners allow themselves to be bullied, it is more likely that they understand the fallacy of this requirement.

Just to put this to bed as far as I'm concerned ( I have sent PM to the OP offering help)

I didn't actually think a reply necessary to the "BSS's failure etc etc" because it is not a failure to consider as you put it. To comply with the BSS the domestic system remaining powered by the alternator after opening the isolator are all protected by fuses or circuit breakers. There really are some underlying issues of basics going on here.

[nicknorman]

Just to put this to bed as far as I'm concerned ( I have sent PM to the OP offering help)

I didn't actually think a reply necessary to the "BSS's failure etc etc" because it is not a failure to consider as you put it. To comply with the BSS the domestic system remaining powered by the alternator after opening the isolator are all protected by fuses or circuit breakers. There really are some underlying issues of basics going on here.

It is true that circuits SHOULD be protected by CBs, fuses etc, but the reality is that fuses protecting cable, and fuses protecting equipment, are sometimes not correctly installed / replaced by one of the wrong value etc. And even with correctly installed equipment fusing, that fuse has to be rated at the peak demand, and a fault resulting in abnormally high continuous current can result in heat build p and eventual fire after a while. Also the wiring from the alternator to fuse board remains unprotected by any fusing.

 

So in an ideal world you are correct, and also in an ideal world with a well installed system there would not be an electrical fire with or without an isolator in the first place. However it is not an ideal world and that is why an isolator is a good idea, that's also why in reality electrical fires occur in peripheral wiring and not in the wiring from alt to battery. Unfortunately the BSS tends not to consider the real world in this respect.

[Roger Crown]

It is true that circuits SHOULD be protected by CBs, fuses etc, but the reality is that fuses protecting cable, and fuses protecting equipment, are sometimes not correctly installed / replaced by one of the wrong value etc. And even with correctly installed equipment fusing, that fuse has to be rated at the peak demand, and a fault resulting in abnormally high continuous current can result in heat build p and eventual fire after a while. Also the wiring from the alternator to fuse board remains unprotected by any fusing.

 

So in an ideal world you are correct, and also in an ideal world with a well installed system there would not be an electrical fire with or without an isolator in the first place. However it is not an ideal world and that is why an isolator is a good idea, that's also why in reality electrical fires occur in peripheral wiring and not in the wiring from alt to battery. Unfortunately the BSS tends not to consider the real world in this respect.

 

Sorry Nick, read this gobbledegook tomorrow and admit you haven't got the first clue, I think this is where I came in on the thread, somebody giving advice with no real knowledge.

Regards

Roger

[by'eck]

Richard you are very wrong and should not be giving advice like this until you better understand the requirements of wiring on boats which come under the requirements of the BSS.

 

If an alternator was connected directly to the batteries, then for it to pass a Boat Safety Scheme examination it would be necessary to fit a suitable fuse in the circuit and also to provide written evidence from the manufacturer of the alternator supporting the decision to by pass the main Isolator.

 

Roger, ironically on my own boat I do plan for all battery connections to be routed via isolators, such that they do what it says on the box & completely isolate the batteries concerned. If you care to check previous threads on this forum you will find there are two camps on this subject although I suspect with my installation I'm in the minority one.

 

When I asked for this to be done by my boatbuilder he pointed out it was not normal practice with alternators and chargers for the reasons already mentioned i.e. potential damage to these devices it they are run with isolator open. Since he builds up to ten boats a year each of which necessarily come with a BSC, I view your comments regarding such practice as cause for BSC failure with some suspicion.

 

Apologies if I wasn't clear when I suggested connecting directly to batteries since you correctly point out such items should be fused, but the OP was just asking if it was normal for such devices to be not connected through an isolator.

 

I suspect there would be very many blown up alternators if they weren't regularly wired to bypass the main isolator particularly on hire boats. I would go as far to suggest that there are more boats with current BSC's and alternators/chargers wired outside isolators than not. If you care to check Combi manufacturers fitting instructions you will find that rarely is an isolator mentioned just an appropriate fuse and correct cabling.

 

Certainly my last sailboat built to Lloyds specification by a very prolific boat builder had the Combi wired direct to the batteries as was the alternator.

 

Finally please explain how an automatic bilge pump is of any use whilst isolated from the batteries, and if not how leaving the isolator closed with switch panels active improves safety when the boat is unattended.