Rishworth_Bridge

The attachment may be of interest. It is a sheet from the spreadsheet I prepared (with the help of our electrical engineer) when specifying Ampère back in 2013. It has proved to be on the generous side, particularly for cruising power where we tend to use only 2.25 kW and that for only about 3 hours/day (getting old!). I have left it in .docx form so that you can change to your own figures or otherwise play around with it. Electrical Boat Calcs for Canal World.xlsx

I'll name Rupert Smedley. Based near Stoke on Trent but travels within reason. 07973 538690. Regards Malcolm

Just because it's signed off doesn't mean it was understood. Subsequent discussions with the guy who signed Ampère off for the first time strongly suggested that he didn't. Since then I have only used the one examiner I know for sure has an electrical engineering background.

How many surveyors know enough to assess an electric-drive boat properly? I'll bet you can count them on one hand.

A very interesting 'discovery', though possibly one I should have made myself years ago. We have a Sevcon 4 which controls to constant shaft speed so was, presumably, set by our motor supplier (TEMA) to Speed Mode. What is very noticeable, particularly as the leaves start to fall, is how much the power is increased by quite minor fouling of the prop, something that probably wouldn't happen in Torque Mode (or in a diesel boat) as the prop would simply slow a little.

200A isn't enough. As you have worked out, you need 300 plus a bit to spare for a 15kW motor - which is the right size for most boats. You also need to consider the location of your batteries - as close as possible to your motor controller to avoid having to buy even thicker copper. We have LA batteries so I'm not across the details of Lithiums but there are people in this group who are.

A few more comments. Ampère's solar panels were bonded to the roof in accordance with the manufacturer's instructions and appeared to fail by delamination - white spots which grew to patches the size of postcards. I'm sure that panels will have improved since then but am pleased, if a little surprised, to learn that IanD has got a 10 year warranty. An Internet search about 12 months ago suggested that a life of 5 years was about average, the longest I found being 8. My understanding is that heat is the principal problem. Panels are mostly black so absorb heat easily and boat roofs (if there is any left that isn't under panels) also get hot so can't dissipate much heat. What appears to be needed is a method of positive cooling. The obvious one would be a double-skinned roof through which cold water could be passed, though I hate to think what this might cost. Ortomarine are mounting panels on thin plastic sheets like that in the photo, something which will certainly allow some ventilation though I doubt that it will offer a complete solution. My current thoughts are to try passing cold water through capillary matting (as used in ceiling heating) attached to the underside of the roof. Anybody fancy trying it? As to use, since taking ownership of Ampère at Crick in May, 2015, we have done something over 5,500 miles and almost 4,000 locks and expect to do about another 100 miles and a similar number of locks before the end of the year. Although we are registered as continuous cruisers and spend more time aboard than at home, we aren't live-aboards, putting the boat into marinas or boat clubs or occasionally leaving it pinned to the bank if we need to be elsewhere. So far this year it has spent 12 weeks in marinas or boat clubs (with another 2 due to start tomorrow) and about 3 pinned to the bank. Doing relatively little cruising for the time spent onboard means that a disproportionate amount of our fuel goes on domestic use rather than propulsion, particularly when our oil stove is running during the winter.

Power usage inevitably depends on both the setup of a boat and how it is used. One of the stupidest examples of the latter I have come across was a boater with whom I once shared the Braunston flight who, in the bottom lock, revealed that he had a parallel hybrid and was going to switch to electric drive so he could "listen to the birds" once he was out of Braunston. How much fuel had he wasted by not using what would have been a minimal amount of electric power through the locks? As to IanD's figures, they look reasonable if a bit higher than ours on Ampère, though I know that we cruise slower than he does and the cube law makes a huge difference. We also have a larger, slower prop than him, probably another plus factor. I don't have the sort of detailed records that he has but did calculate after our first few years that we were saving between 58 and 67% of the diesel we would have used for propulsion with a modern 4-pot. If this seems high consider the following cruder calculation. We usually cruise using 47A off our batteries (2.25kW) and charge at about 85A using about 1.5 litres/hour. Allowing 30% for time spent not under power (locking, etc) that equates to about 0.6 litre for each hour's cruising on a typical 1.1 locks/mile canal. And remember that that is for a boat weighing 23 tonnes and with a draft of 2'6". I usually assume 1.5 litres/hour for a modern diesel in a boat of normal draft while under power and 1 while idling, equivalent to about 1.35 litres for each hour's cruising. That suggests a saving of 56% though comparison with a diesel in a boat with our draft would almost certainly be more favourable. IanD's diesel figures are more sophisticated than mine but as slowing for moored boats is omitted in both my calculations, the difference probably isn't material. Our original 400W of semi-flexible solar panels failed after 3 years and were only replaced (with rigids) when the price of diesel rocketed a couple of years ago. In their first year they produced just under 300 kWh of power, saving about 90 litres of diesel. If that is maintained they will pay for themselves in just over 3 years. Larger installations, if they don't fail prematurely, will obviously contribute more. Turning to domestic matters, electric isn't necessarily more efficient. In fact, it can sometimes be worse than using a primary energy source like gas, though there isn't much in it. We try to maximise our fuel efficiency by making good use of waste heat. After swapping our Bubble for a simpler Kabola oil stove to get rid of incompatible thermostat problems our generator cooling water now passes through a 50 litre domestic hot water calorifier followed by a 120 litre one which runs underfloor central heating. Our horizontal calorifier isn't very efficient and we can only store enough heat for about 4 hours of meaningful heating and the floor area of our (probably any) boat isn't large enough for the heating to be sufficient on its own in cold weather. Nevertheless, it's 4 or 5 kWh that doesn't need to be found from another source. Where we missed out is heat from our Quattro which isn't as efficient as we expected, certainly while charging. If starting again I would include a small fan and a bit of ducting to capture this heat.

I'm surprised that IanD uses as much as 3kW for normal cruising in what is almost certainly a lighter, and thus shallower, boat than Ampère (23 tonnes). I suspect that a factor is a missing from the discussion - speed. We usually cruise using 2.25kW. This gives us 430 rpm which, in turn, gives 3.3 mph in open water, 3 mph in wide and reasonably deep canals (think Paddington Arm or parts of the Bridgewater) and 2.25-2.75 in most other canals. However, as power required (strictly speaking for a sphere) goes up as the cube of the speed (a very good graph for Firecrest is closer to a 5th power), there doesn't need to be much difference in speed to produce a big difference in power consumption, possibly enough to outweigh the effects of motors and propellers, though better choice of those will still pay dividends.

I suggest that you don't go above 48V, principally because your choice of other equipment, including inverters, will be limited. I flirted with both 72V and 96V when we were having Ampère built, because, having been let down by our preferred motor supplier, we needed to find something which would fit in the space left in a by then almost finished boat. In particular, I found a range of higher voltage motors from a German company called Perm (since taken over), most of which were available in both air- and water-cooled versions, for which latter I had (and still have) a fairly strong preference. They were not only smaller that the only other water-cooled 48V unit I could find but would also have needed thinner cables, a useful bonus. Fortunately, I was persuaded by our (excellent) electrical engineer to stick to 48V and we finally found our air-cooled TEMA motor, with which we have been very happy, even if going air-cooled did leave us a year late taking to the water and with a redundant skin tank. Despite my ready acknowledgement of IanD's much greater engineering knowledge I would caution against taking VicProp at face value (a point made in the Introduction to Electric Boating). If I put in the figures for Ampère using the continuous power rating for our motor it suggests 18.2" x 11.4", even less than the 19" x 12" originally supplied by Crowthers and with which we were clearly under-propped. When Crowthers re-visited it with the aid of some further calculations from our engineer it was increased to 20" x 14". With this we are technically over-propped, as we can only reach about 850 rpm rather than the nominal 1,000 (a point brought to my attention by IanD to give him the credit due), but we use less power while cruising at normal canal speeds (though I can't quantify it as I don't have sufficient data for the original prop) while still being able to reach 6 mph, which I consider to be an adequate maximum for a canal boat. Discussion with the owner of another electric-drive boat at Electrika revealed that, having discovered that his boat under-performed relative to another of the early electric-drive boats, Firecrest, he re-propped (don't know the details), improving his speed by 10% while using 20% less power (his figure). To return to VicProp, if you put in your instantaneous power rather than the continuous you will almost certainly get a better recommendation, though one which is likely to be slightly over. For Ampère it suggests 20.9" x 13.7", probably slightly more demanding than our actual 20" x 14". I have heard from a number of motor suppliers that instantaneous power is a matter of fact, limited by the amount of current that can be pushed through the windings, but that continuous power is a matter of opinion - what can be produced without cooking the motor. This leads me to wonder whether the torque isn't dependent on the instantaneous power rather than the continuous, though it may well have a lot to do with how the motor controller is set up. IanD will no doubt explain where I am wrong. As I said, he's an engineer and looks for things to perform to spec; I'm a boat owner who just wants my boat to perform efficiently under normal operating conditions while having sufficient reserves of power to cope with more demanding situations. Finally, I have been given some curves for the Engiro motors which suggest that they just have the edge on the Mothership one, though I don't think you will go far wrong with either as long as you don't under-prop.

I'm afraid that I only became aware of this discussion when it had already grown to 16 pages which, with the best will in the world, I can't read in full so apologies for any duplication. If you haven't already, can I suggest that you read the IWA Sustainable Boating Group's Introduction to Electric Narrowboating, https://waterways.org.uk/wp-content/uploads/2024/05/An-Introduction-to-Electric-Narrowboating-Reviion-2.pdf, of which I was the lead author. This covers most of the points that have been discussed about propulsion and related issues though, because of its nature, doesn't name manufacturers, something I can do here. One point which has certainly already been mentioned is the need for the largest possible propeller (subject to any limits imposed by draft) turning at the lowest possible speed to maximise propulsion efficiency. As well as the names Finesse and Engiro I should like to throw in another one, that of Mothership Marine who now have a high torque, 15 kW motor capable of swinging a 20" prop, comparable to the TEMA unit in Ampère so possibly the best on the UK market at the moment. The availability of heat pumps suitable for use on boats has been questioned. I don't know the details but Cadalcraft (https://cadalcraft.co.uk/) have a demonstrator with a water-source heat pump which was working impressively when the SBG took a trip on a frosty morning last January and a quick Internet search shows that Kensa have compact 3 and 6 kW models. These are sold as ground-source pumps but are the same animal. There is a bit more about heat pumps in the attachment. Canal boats don't need pukka marine generators so don't waste money on them. Any decent quality, water-cooled unit costing about half as much will do the job, though you will have to arrange your own soundproofing. On the topic of the adequacy of mains power supplies, there seems to be some confusion about the rating of shore connections. Any electrically-propelled boat will have a large battery bank and an inverter which can provide short-term power; the shore line simply recharges the batteries over a much longer timescale. The popular Victron Quattros (as we have on Ampère) will mix and match. The SBG hasn't yet published anything yet on the domestic side of narrowboating but I attach a file that I have been using to assemble ideas for when we do. Be aware that this is a working document which is updated quite frequently as I get new ideas or information and that some of it is off the wall and hasn't been discussed with my colleagues so may simply be crazy. Boat heating ideas.pdf

Certainly didn't, though I can see that it might be an issue for canal-side properties. (The only property I know of using such a system is on CRT's Kennet) Can you quote chapter and verse for boats, please?

Thanks for that Alan. Presumably you have to have dedicated EV chargers to make differentiation possible. At the moment marinas seem to be covered so it's probably something that hasn't received much thought - yet. I don't expect to get the use of charging facilities for free as I recognise that there are costs involved to the provider but should prefer that to take the form of a reasonable mooring charge (£2-5 per night rather than the £15-20 which seems to be the norm in marinas nowadays) with the actual power still supplied at cost. Referencing Magnetman's comments on the Thames. There doesn't seem to be a single system. Some places charge a fixed amount with power included while others charge for it separately. Overall, cost tends to be £10-15, which isn't bad compared with using marinas but equally isn't really competitive with using the generator, though we do it to be that bit greener. We try to arrange to plug-in when we want to float the batteries as doing so using the generator is very inefficient.

Perhaps I can throw a couple of curved balls relating to boat heating and a comment about batteries/charging. Is it possible to address the problem of icing of water-source heat pump sources by using a propeller (think gentle bow thruster) to blow canal water continuously over (internally-mounted) input coils? In a boat equipped with a heat pump would it be simpler to recover heat from stale warm air by passing it through an air/water heat exchanger in the heat pump input system? The next big step in electric propulsion, long promised but yet to arrive, is the solid electrolyte battery. These are said to be in an advanced stage of development, with Toyota in particular, suggesting for some years that they would have them in their cars by now. This hasn't happened but, if projected figures are correct, when they do the energy density should be high enough for the battery volume we have in Ampère (about a cubic metre) to support our (fairly gentle) regime for a week, making managing without a generator at least a theoretical possibility. However, this is a 2-edged sword. Currently, a 16A overnight plug-in is sufficient for a couple of days, meaning that a 32A one should suffice for 4 days. Both of these would be possible using our existing inverter/charger with power at sensible prices governed by the electricity resale regs. However, if it becomes necessary to double this charging rate again we get into fast chargers, to which the regs do not apply, so could finish up paying more for our power (as with cars) than we would burning HVO in our generators. Incidentally, the Thames has, in theory, enough charging points (at locks) for a boat like ours to manage without using the generator, though about half were out of action when we were last there.

... and flattens your battery alarmingly fast! It's more than you would use for cruising. If the weather isn't excessively cold we often run a couple of fan heaters in the morning instead of lighting our oil stove but do so at the same time as running the generator to avoid charging losses.