Power on boats

There are a number of problems in getting power on a boat the major one is the electrolyse. I have looked at many ways around the problem.

Diodes in earth cable
Isolation Transformer
Chargers and Inverters
Special alternators like the Electrolux Travel Power AC Generator

And stand alone generators.

The first two mean one is reliant on being in a marina to be able to use power. But the other methods do not always give a true sine wave and it seems some washing machine do not like the AC supply from inverters.

Diodes are the cheap way out but not sure I like that idea and isolation transformers are not cheap. To buy a 230 volt to 110 volt isolation transformer is not too bad but 230 volt and 230 volt out near double the price of the 110 volt types.

So if spending £250 for an isolation transformer why not pay a little extra and run everything off an inverter?

The inverters at 1500 to 3000VA start to become very expensive and do not produce a true sine wave.

At this point one wonders if the high load items would be better run off a generator and reduce the inverter size to 500VA which should cover TV etc.

If going down generator route then stand alone or powered off main engine? The type which are driven off main engine picture above seem to also use inverter technology so it can produce 230 volt 50 Hz at variable engine speed.

The problem is although one can find limited information on using inverter derived supplies for example recommended to use washing machine with non electronic timers. Information as to what will and will not run on a non sine wave supply seems rather minimal and the method used to get 230 volt 50 Hz will depend a lot on what can be run with the different methods of supply.

At the moment only thing I have tried running off an inverter 150VA which I have in my car is phone charger and PC both run without problem so it seems there is not a problem with anything using switch mode power supplies.

So I would like to hear for anyone who runs equipment off an inverter. Items we will be interested in are microwave, food mixers, coffee peculators, DVD players, TV,s basically the highest draw would be micro wave and for that I would consider 1500VA inverter and then only use washing machine in the marina. Or if using a generator at 3.5KVA then everything can be run of own power.

Running costs are another factor, Items like washing machines and the like do not use full 2.5Kw for whole cycle and that would mean running a generator for a long time light load.

Current switching relays to switch off other supplies when for example the micro wave is used.

I have tried to work out cost effective methods but each thing I look at seems to have some vital information missing.

Anyone with any experience of using inverters I would love to hear from also using generators although I have used and repaired many I was not concerned with running costs.

The main engine runs on mixture of red and white diesel as permitted for canal boats where the government makes allowance for so much of the diesel is used for heating and so much to drive boat.

So it may be cheaper not to use main engine!

Any ideas welcome

Eric

ericmark said:

Diodes are the cheap way out but not sure I like that idea and isolation transformers are not cheap. To buy a 230 volt to 110 volt isolation transformer is not too bad but 230 volt and 230 volt out near double the price of the 110 volt types.

So if spending £250 for an isolation transformer why not pay a little extra and run everything off an inverter?

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You wont find a pure sine inverter that will provide anywhere near enough power for hungry appliances such as washing machines for anywhere near £250, not to mention the load it would put on the boat's electrical system. For large loads, shore power + isolation transformer seems the only sensible option, with a small inverter or genny for offshore use.

ericmark said:

At this point one wonders if the high load items would be better run off a generator and reduce the inverter size to 500VA which should cover TV etc.

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That sounds more sensible, although you need to be careful - cheap and cheerful generators tend to have rather poor Automatic Voltage Regulation, so they aren't really suitable for powering sensitive electronics. Hence, without splashing the cash (pardon the loosely maritime pun!) you still have similar pitfalls to a non-sinusoidal inverter.

ericmark said:

The problem is although one can find limited information on using inverter derived supplies for example recommended to use washing machine with non electronic timers. Information as to what will and will not run on a non sine wave supply seems rather minimal and the method used to get 230 volt 50 Hz will depend a lot on what can be run with the different methods of supply.

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Such information is scarce because it's rather hit-and-miss. Generally speaking, anything involving PWM and/or variable speed drives will not function correctly on square or modified-sine inverters, which rules out a lot of washing machines. Some motors may not take to it very well, nor fluorescent lamps, and other such loads with a high inductive component.

ericmark said:

At the moment only thing I have tried running off an inverter 150VA which I have in my car is phone charger and PC both run without problem so it seems there is not a problem with anything using switch mode power supplies.

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Electronics with Switch Mode Power Supplies such as computers and the like will usually work fine, as the incoming AC is rectified before being chopped and fed into a high frequency transformer.

A cheap inverter solution may be for you to purchase a UPS and modify to suit your needs. You will need to check first, but a significant portion of APC units have sinusoidal output. You will be limited as to size, though, as the larger, more powerful models run on higher DC voltages than you'll find on a boat.

A engineering colleague of mine lived on a narrow boat in London ( Grand Union Canal ) using shore supplies. I recall that after some problems with hull corrosion he opted for an isolation transformer and an active system to reduce corrosion. He had the obligatory zinc (?) blocks bolted to the hull but it seemed these were not able to counter the corrosion if the hull was earthed to the shore. He experimented with a DC offset between shore earth and the hull to reduce the electrolytic corrosion. Did it work ?. I do not know but he thought it did.

In the past a DC offset was often used to protect lead telecommunication cable sheaths from electrolytic corrosion. Electrolytic corrosion of cable sheaths was often a problem in the vicinity of electrified railway lines. Something of the order of half a volt was often sufficient.

IIRC with the various ferrous and cuprous alloys used in a boat, a metal from much further up the periodic table, something like magnesium, is the usual choice for a sacrificial anode.

electronicsuk said:

Such information is scarce because it's rather hit-and-miss. Generally speaking, anything involving PWM and/or variable speed drives will not function correctly on square or modified-sine inverters, which rules out a lot of washing machines. Some motors may not take to it very well, nor fluorescent lamps, and other such loads with a high inductive component.

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Not sure what PWM is. As to lights they are all switch mode 12V models. I have been talking about the batteries to my son at the moment he has 4 x 120AH traction batteries all in parallel one with starts the engine is isolated from other three. And it seems the three batteries supplying boat need replacing.

Since he already has a large charging unit designed for this type of installation and engine alternator only at this time produces 12 volt keeping to a 12 volt system does seem to make some sense. But running lead acid batteries in parallel does not and I think some relays or blocking diodes will make some sense so if one battery becomes faulty it does not drag down the rest. Even a forklift type plug and socket so they can be disconnected and reconnected safely may be better idea.

Tickly and bernardgreen yes he is also worried about electrolyse but if he uses a large inverter the charger is already double insulated and isolates so he would not need an isolation transformer so until he decides what to do about power when shore power is not available he can't really make any decision as to how to protect his boat from shore power earth problems.

Buying an inverter than seeing what will work does not seem a good idea he would much more like to find out problems before he buys inverter hence this post.

We are both electricians and I have also done auto electric and even worked on pipe lines with cathodic protection but a long time ago and as with most big jobs just did as told and really like a fish out of water with this problem.

The main thing is every solution to each of the problems will affect how the others are cured. So until he decides on whole plan nothing is being done.

Yes I have also seen how small generators seem unreliable on last job we hired 7.5KVA generators to run two bulbs on the cranes overnight as the smaller ones kept failing and being on an airport that was not acceptable. Hence why also looking at add on type generator driven by main engine as yet no price. Bet they are not cheap though! Anything called marine doubles in price!

PWM = pulse width modulation. Turn a 12 volt supply and chop it on and off many times second with equal on and off times and it can look like it is only 6 volts average. Make it an on / off ( mark space) ratio of 1/4 and 3/4 and it looks like 3 volts average. Not quite that simple but that is the basic idea.

Invertors vary the mark space ratio to create a "sine wave" voltage which is then smoothed ( averaged ) to create something like a sine wave. This works OK for resistive loads such as heaters and lamps. But motors and other equipment with coils can react badly to the chopped voltages.

I would keep the 12 volt lighting and up grade the battery management. TV's and a lot of other equipment will work on 12 volts. That way what ever happens there will be lights. ( handy when the boat slips it moorings in the middle of the night and snaps the shore mains feed )

If you have gas on the boat keep the battery management equipment above the ventilation in case of gas leaks. Use Schottky diodes as they only drop 0.2 of a volt compared to normal diodes which drop around 0.6 of a volt.

There are 12 volt refrigerators. For the heavy stuff like washing machines an isolation transformer would be cheaper than looking for 12 ( or maybe 24 volt machines ) with gas heating of the water. ( there was a German or Austrian company that made these 1980's )

Not all invertors and UPS have isolated outputs and some so called UPS are direct to the mains while mains are available and switch quickly to invertor when the mains fails. These are strictly a SPS ( Standby Power Supply ) A true UPS ( Un-interuptable Power Supply ) runs on the invertor all the time with the mains feeding DC power to the invertor and battery. Mains failure does not result in any glitches on the output as there is no switch over. Only if the invertor fails is there a switch of the output to run from the mains.

bernardgreen said:

Use Schottky diodes as they only drop 0.2 of a volt compared to normal diodes which drop around 0.6 of a volt.

There are 12 volt refrigerators. For the heavy stuff like washing machines an isolation transformer would be cheaper than looking for 12 ( or maybe 24 volt machines ) with gas heating of the water. ( there was a German or Austrian company that made these 1980's )

Not all invertors and UPS have isolated outputs and some so called UPS are direct to the mains while mains are available and switch quickly to invertor when the mains fails. These are strictly a SPS ( Standby Power Supply ) A true UPS ( Un-interuptable Power Supply ) runs on the invertor all the time with the mains feeding DC power to the invertor and battery. Mains failure does not result in any glitches on the output as there is no switch over. Only if the invertor fails is there a switch of the output to run from the mains.

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The experience I have had to date is that although in theory blocking diodes work trying to balance current through them and modifying the voltage regulator unless the old CAV 440 is just too much hassle and I would go for relay. And if you are referring to diodes used in earth cable then we need 1.2 volt so need the volt drop of two diodes anyway.

As to 12 volt fridges I have had problems with them as often there is no thermostat when running off 12 volt. Although there are 12 volt freezers they use a semi-conductor some French invention used a lot in cool boxes etc. I have not seen many for sale and those I have are very small. I think he has gas fridge not sure and I did find in the past they were expensive to run but 12 volt type draw somewhere around 8 amp and the method of cooling is very inefficient compared with a heat pump.

But thanks for pointing out because I had forgot to talk to him about that. I lived for 3 years in a touring caravan on a construction job and I found with nothing else running fridge alone could empty a gas bottle in just over 3 weeks.

The water and central heating is done with the 35 sec gas oil not sure of spelling something like Evenspacker again I have used them before in buses. Although they were hot air and this one is water it circulates.

The UPS and SPS I had forgotten about and would have been an easy mistake to make. Thanks for the reminder.

Personally I think I would go for a small inverter and an isolation transformer plus a small generator for the odd time they need high current away from base.

I am sure I have seen an isolation transformer in same type of case as 110 volt ones but all I seem to be able to find on the net are double the price of the 110 volt ones. Also there seems to be not info about them. I know with 110 volt in little yellow case they draw quite a bit of current with Fe losses etc where the larger units with same output have much lower losses but non of the adverts seem to publish what those losses are. So hard to decide which to get when there is no info published on them.

I am logging all points raised and when he pops in again we will go through them all.

The diodes would be between battery and load switching to ensure a flat battery connected to a charged battery during change over would not take charge from the charged battery.

The anti electrolysis system was a DC voltage power supply at about 2 volts with the positive side to the earth ( I recall he tried a metal plate in the water for this ) and the negative side to the hull.

The 12 volt fridges I have seen used the ammonia cycle. Some were dual fuel and could be run on either electric or gas. The ones using the Peltier effect ( solid state heat pump ) are in-efficient but nice and quiet and very reliable.

Site safety transformers are expensive compared to an open frame dual bobbin isolation transformer that you then mount and case in a safe area.

I have bought standard and custom transformers from
http://www.sigaelec.co.uk/index.htm and their technical department has always been very helpful when designing a custom transformer.

Thank you again for your help. I have used the multi-voltage plus gas fridge and I know they have changed thou the years. The early ones had a pilot flame which increased in size when the thermostat called for more cold. But latter ones used an electric ignition system instead of pilot flame but from outside looked the same. Electrolux I seem to remember. There was a void where one could put a heating element on early ones then on latter ones they came ready fitted and then the larger ones had both 12 and 230 volt elements. But on the ones I have used in the past the 12 volt element was a lower wattage than 230 volt element and there was no thermostatic control. I will have to investigate to see if they are still made this way or if that also has now been up dated.
Interesting what you say about the Peltier effect being in-efficient I was not aware of that I am learning.
I will pass on information about transformer supplies and see if they are any better or cheaper than what we have found to date.
Again interesting what you say about active cathodic protection not sure how it would work while he still has zinc sacrificial anodes?
I did a lot of work with blocking diodes and in theory they do seem better than using split charging relays but I also did some tests to see what current could flow when a fully charged and nearly discharged battery were connected together as it did worry me that it could be quite high. But I used 50 amp fuses in all the charge cables and found they never ruptured even when using very large batteries. The first time I experimented with them was on mobile library's with trailer and towing wagon and the trailer batteries were not gaining enough charge. Using relays did help but the only real cure was to change the type of depot biased charger from a float charge to a fork lift constant current charger with voltage sensor to reduce to float charge once 80% charged.
Also used in caravans and the whole idea of plug in and be charged while towing was really a failure and only method was to have a portable battery which could be placed in the car for charging with as a result less cable and more chance of being charged as could be transferred with days out as well. With a service van using two batteries arranged in parallel for charging and series for jump starting again it was found blocking diodes would not allow it to charge enough so three things were done. One a suppressed zero volt meter was fitted. Two the existing diode pack had the same size diodes for the excitation as for charging so this was utilised to charge both batteries and an additional three diodes were added to power the excitation. This worked well as no extra volt drop also a switch was included to short out the regulator so one could boost charge the battery on the vehicle being repaired.
On some boats on the 7 Bridge project we had problems as to take the 80 amp supplied by the alternator two blocking diodes were required and the guy who had wired them had not insured all cables were same length so the diode with shorter cables kept burning out. Silly fault really but the only way the system worked was because the AC5 alternator used a 440 regulator which had high med and low setting so the output voltage could be boosted.
Some Japanese alternators did have external mechanical control boxes and with these the output voltage could be adjusted but today most alternators have a built in control box and the output can't be boosted so I am thinking the caravan type duel contact split charging relay is the best option.

While at the marina the float charger is OK but once he starts to move around the constant current charger would be a better option. However as yet I can't see a way to do this for the traction type battery used for day to day living yet keep to standard float charge for the starting battery.

We have been considering two alternators but there is a limit and if the special like shown when I first posted is used then can't really fit three alternators. So then it would need a new charger building or acquiring like those used to charge fork light batteries.

Which is why as I said we need to consider all options then use an integrated system as no single option can be undertaken without effecting another one.

Not sure on prices of Schottky diodes they are worth looking into at 12 volt 0.4 volt gained is quite a lot.

Of course one big factor is how much he is going to travel? It seems in last two months only 8 hours has been away from maria he wants to go into Llangollen at Easter which is likely to be first time boat will spend any time without either engine or shore power and once that has been completed then he will have much better idea of what is required.

I would love a holiday on it but as to living in a tin box I think I'll pass on that and keep to living in a house!

I have a cheap inverter to use when we have a powercut and i have run my tv on it,But i noticed that SMPS in the set was making a loud buzzing sound which i was a bit worried about anyway it worked ok.
So the buzzing sound is obviouly down to the modified sine wave (square).
To be honest i would be worried if i running a set full time on a cheap inverter.

I also have a standby UPS for the computer for my security system i have run the tv off that and there's no buzzing sound from the psu so presumibly it has a better designed inverter than the cheap one.
We have 5 short power cuts this month and the pc has worked ok on the UPS.

andy

He needs to change his TV anyway the Plasma one he had will not fit in boat. I have noted many small ones are 12 volt with power supply like those used on Lap tops.

He gave up on sky he did have 12 volt unit but he kept losing signal when he rocked the boat!

Battery charging is something which needs some thinking about. It very much depends on how much time is spent away from the maria but if he needs to charge in a limited time the float charge method is not really good enough and the constant current system used with Fork Lift batteries would be better option. However with a standard motor vehicle alternator which he needs to charge engine battery there is not real way he can use a constant current charger. So then one looks at the type I showed on first post and a 230 volt charger.

Eric

I do electrical installs on yachts and have found a great book called 'Electrics Afloat' invaluable.

http://www.amazon.co.uk/gp/product/...e=UTF8&n=266239&s=books&qid=1235427580&sr=1-2



To stop electrolyse galvanic isolators seem to be the low cost solution.

At least with a metal hulled narrow boat you don't have to worry about bonding all underwater metalwork as long as all the DC -ve is connected to it.

bernardgreen said:

A engineering colleague of mine lived on a narrow boat in London ( Grand Union Canal ) using shore supplies. I recall that after some problems with hull corrosion he opted for an isolation transformer and an active system to reduce corrosion. He had the obligatory zinc (?) blocks bolted to the hull but it seemed these were not able to counter the corrosion if the hull was earthed to the shore. He experimented with a DC offset between shore earth and the hull to reduce the electrolytic corrosion. Did it work ?. I do not know but he thought it did.

Click to expand...

The problem with Shore Power is that the Protective Conductor (old name "Earth") will be connected to an Electricity Board copper earthing rod somewhere. When you connect the "Earth" to your steel boat you have effectively made a battery with one plate made of copper and the other plate (your boat) made of steel. One solution would be to have a boat made from copper but this would be rather costly! The isolation transformer route is a good one although the transformers are heavy, costly and are apt to hum.

A cheaper way is to buy two, four or six bridge rectifiers and build up a diode box. The rectifiers are wired with + and - in the earth wire and the other one wired - and +. How it works is that the turn-on voltage for a silicon rectifier is about 0.6 volts so the bridge rectifiers will give 1.2 volts of blocking ability. If one buys four bridge rectifiers the blocking ability rises to 2.4 volts. It is even possible to use six bridge rectifiers to give 3.6 volts of stand-off. 25 amp or 35 amp bridge rectifiers are fairly cheap and they will easily pass enough current to blow a trip if an appliance fault should occur. The AC terminals of the rectifiers (often marked ~) are not used.

Please do not attempt to build up such a box unless you are 100% confident and know exactly what you are doing.

At the time of writing four 25 amp metal cased bridge rectifiers can be bought for less than £10. The working voltage is unimportant as the diodes will not be stressed to any extent.

It is possible to buy diode blocker boxes ready made but the cost of about £100 seems excessive.

Good luck!

Dear Retirednow

As you have some time on your hands, it would be useful if you could look at the date of threads before you respond. This topic was from 4 years ago. I rather think the problem is now solved?

The boat was sold some years ago it is very unlikely that the earth on any marina will be provided by the DNO likely it will be a TT system with a hundred boats all steel there would not be big problem it will just eat away the zinc of the cathodic protection, but if any of the boats are aluminium there is a big problem. If you look at the Standard electrode potential of steel, copper, zinc and aluminium −0.44 +0.159 −0.7618 −1.662 as you say it is the copper and aluminium which is the problem. One would hope a marina would not use copper coated rods but some mass of iron.

As to diodes my worry is how often they are tested? All it needs is some one to used an insulation tester or an earth loop impedance tester and the diodes can pop we all hope those electricians working on boats are careful but problem is those not use to boats may very well test as they would with a house and be unaware of the damage which could result.

As a result I wanted to go down the isolation transformer route but the cost of a 230 to 230 3KVA transformer was silly. In fact I could by a 230 to 110 and a 110 to 230 volt pair of transformers for less than single 230 to 230 volt.

But all now history decided bringing up small child on a narrow boat was not the best idea so they now live in a house.