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8 minutes ago, IanD said:

And they also don't want to be told that stuff shipped from China should be more expensive to pay for the CO2 burden of container ships.

 

There's more to this than that. Never mind the container ships, if we produced those goods we are consuming here in the UK, our CO2 emissions would be way higher. What the west is doing by buying from China is exporting our own CO2 emissions so those should really be loaded back into our own CO2 statistics, rather than blaming them on China. 

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38 minutes ago, MtB said:

 

There's more to this than that. Never mind the container ships, if we produced those goods we are consuming here in the UK, our CO2 emissions would be way higher. What the west is doing by buying from China is exporting our own CO2 emissions so those should really be loaded back into our own CO2 statistics, rather than blaming them on China. 

I wasn't blaming China, a large part of their emissions are due to making stuff bought by consumers in the West. This ought to be reflected in CO2 emissions statistics, but isn't...:-(

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A lot of very good info there -- and thanks for the comment at the beginning, the cheque's in the post 😉

 

Your power use estimates are quite close to mine, I had 1.75kW average over an 8h day (14kWh/day) -- of course this depends on day length as I said earlier, it's only 7kWh for a 4 hour day. As said again and again it does depend on how fast you travel, boats going slower will use less and vice versa. I deliberately left the domestic system out so as to not confuse the issue, this also depends very much on what electric appliances you have on the boat and how much you use them, and again different people have very different ideas (washer/dryer, dishawasher, induction hob, aircon...) so it's impossible to generalise. Heating is another can of worms entirely...

 

I also think rigid solar panels are the right choice for all the reasons you say, including much lower cost, higher efficiency and longer lifetime -- many of the "new electric boat" suppliers are pushing flexible ones because they're less obtrusive and some claim long lifetimes, but there's no field data to back these claims up and many people (including you) have found they don't last. When I looked at this the rigid panel power came out cheaper than a generator when you also included shorter running times, but this does depend on the cost of the generator -- if this is cheap then this changes the balance.

 

The CANbus control was specifically for LiFePO4 batteries -- are you using these or lead-acid? By far the best way to deal with these is to either have an intelligent BMS inside the battery (e.g. BYD) or one added on and matched to them (e.g. Finesse, Ortomarine) which is the master controller and tells the Quattro/MPPT what to do (using software assistants over CANbus), not just for charging and discharging but also deals with cell balancing, cell temperature and so on. These systems often also log the data and allow remote diagnostics to be run by the supplier, typically in exchange for a 10-year guarantee. It's this part that I meant really needs to come from one supplier, to get all the control and limits set up correctly and make sure that the batteries are treated as well as possible, because if they're not replacing them is *very* expensive.

 

Once you do this it's best if the generator is AC and plumbed into the Quattro rather than DC and connected to the batteries -- as you say, any decent generator with a remote start/stop will do. If you really want an ultra-quiet solution the best one -- though not the cheapest -- is a cocooned generator which is then installed inside a second soundproofed enclosure, the bow locker in my case.

 

The drive system is another separate system which can come from another supplier, but again the motor/controller/display really needs to come as a package -- the controller needs correctly configuring for the motor including protection limits, and you need a display which talks to the controller and BMS so it can display things like motor speed/power/temperature as well as battery charge and status.

 

If you're doing all this yourself and have the knowledge about how to connect up and configure everything and control it from a PLC then that's great, but then you're responsible for doing all this and maintaining it in future. This is also the route that Ortomarine are taking (custom display/controller) which has the advantage of being purpose-built for the job and supported by them; there's a downside which is that if they ever go bust nobody else will have a clue about it.

 

Not many boaters have the knowledge to do this themselves so they need to be able to buy in gear that is known to work and preferably already configured, for example battery/BMS/inverter/MPPT and motor/controller/display. Victron have a list of certified LiFePO4 BMS that are known to work with their gear, which is the route a lot of suppliers go -- if the display/controller is standard Victron (Cerbo/Touch50) then this is not only supported by Victron but there's a community with useful software add-ons as well as advice, and it will be maintainable in future.

 

All this makes for a system which is much more complex to design/control than a traditional engine/alternator/battery/inverter, but delivers a lot of benefits -- as it should, given the cost. The issues of integration/protection/control/faultfinding should not be overlooked if this is being bought in -- with your DIY system it's all your problem, but who finds and fixes problems when they go wrong with a multi-supplier system? Most marine electricians would run a mile when confronted with something like this...

 

This is why I think the "hybrid kit" market -- especially using a pick'n'mix approach -- probably won't succeed. At one end there are the "true DIY" solutions like yours where you design/build/maintain everything, at the other end are complete systems/boats from suppliers like Finesse/Ortomarine/Mothership who also put everything together and guarantee that it all works. In both cases there's only one place to point the finger of blame if something goes wrong, or changes/additions are needed. Maybe a "complete kit" solution from such a supplier could work, but then this would probably cost as much or more as getting them to install it -- always assuming they want to shoot their own boat market in the foot by helping other people build boats to compete with them.

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2 hours ago, Rishworth_Bridge said:

An interesting discussion with the usual mixture of informed and wildly eccentric comments. As the owner of an electrically-propelled narrowboat for over 6 years now I think I can safely say that the contributions from IanD are, without exception, sound.

 

A narrowboat with a well-designed electric drive system should need only 1-5-2.5 kW to maintain a reasonable canal cruising speed. (There's a whole debate to be had about what "well-designed" means but I don't intend to pursue that.) Allowing for locking time that means an average of 1.0-1.7 kWh/hour. That's 6-10 kWh for a 6 hour day, the longest that most of us will usually do. Ampère is deep-drafted (30") and we almost invariably use 2.25 kW, accepting whatever speed that gives us, typically doing about 4 hours/day. We therefore use about 6 kWh except when the lack of dredging means that we are ploughing rather than cruising, when it goes up sharply.

 

As most boats with electric drive will also have an electric domestic system, provision then needs to be made for that. Our use is quite variable, depending on whether we run the washing machine or not and have a roast dinner, a salad, or eat out. Including fridge & freezer and system losses (a big battery bank has significant internal losses before inverters, droppers, etc, are even considered) we find that we use a bit more for that than for cruising so tend to be in the 15-20 kWh/day range overall. (Hot water and some heating comes from waste heat from our generator so isn't included.)

 

As to input, solar can be a bit of a distraction. If you cover the whole roof of a 50-60' narrowboat with (flexible) panels you will get about 10 kWh on the best few days of the year. That's enough to eat or cruise but not both. For most of the year you won't even have that choice. And where are you going to put your pole(s), ropes, etc? Moreover, it's not 'free' power; it's distinctly expensive. If you assume that panels will last 10 years (questionable for flexibles; ours only managed 3) and work out the lifetime cost/kWh you will probably get an answer around the 50 p/kWh mark. That's about double the marginal cost of power off a generator and three times what you will pay for mains power, though adding in the £10-20 for a night's mooring to access this last makes it the most expensive option. The economics of rigid panels are much better as they are simultaneously cheaper, more efficient and more durable but you can't get as many on the roof and, to my mind, there are safety issues (ropes snagging, etc) if the installation is big enough to be useful. Even doubling the current 20% efficiency won't make the sun shine for longer in December. And don't bother with wind turbines. One small enough to be carried on a narrowboat will barely be noticed by an electric boat's battery bank.

 

The cost of electric drive is undoubtedly the biggest barrier to its widespread adoption. At the moment I reckon that going to a single supplier for a 'system' will set you back about £40K. Mixing and matching components from different suppliers (as we did) will knock that down to about £30K and, as has already been pointed out, you can knock it down further by buying components that aren't sold as 'marine'. Marine generators, in particular, are extraordinarily expensive. The current version of ours is over £15K while industrial equivalents (skin tank-, not air-, cooled for the benefit of the contributor who talked about large fans) can be bought from reputable manufacturers for about £5K. It won't be cocooned so you will have to do some soundproofing but not £10K's worth!

 

The suggestion that it is necessary to buy from a single supplier to ensure compatibility and particularly the reference to needing a BUS control system is equally wide of the mark. As long as you match the voltages correctly, the components of an electric drive system will look after themselves quite happily. Any generator giving a half-decent 230V AC sine-wave output will be compatible with pretty much any battery charger (or inverter/charger). The output from our generator is far from perfect but our Quattro is quite happy (which is more than can be said for the washing machine). I'm less familiar with DC generators but, as far as I know, they should be straightforward providing their voltage is right for the battery bank. That said, if you have significant AC circuits, you probably should be using an AC generator to minimise charging losses. The only difference I would make to our system if I were to repeat our build would be to use a £200 PLC (industrial computer) instead of the £1,000-worth of battery monitors and generator controllers we have. It would be another useful saving while also giving greater flexibility.

 

Finally, be careful with the EBA. I am a member and would encourage others to join. I can also vouch that there are some very knowledgeable people within it but, in my opinion, commercial interests exert too much influence meaning that, again in my opinion, it isn't the ideal place to go for impartial advice. The IWA's Sustainable Boating Group, of which I am also a member, may lack a little of the EBA's expertise but its still quite knowledgeable members will always try to offer impartial, fact-based advice.


 

0161-627-8933

 

At last we have a "real world" narrowboat account - very interesting.

 

It certainly challenges the notion that you can move a narrowboat at "normal" cruising speeds with less than 1kw.  And with the state of many of our narrow canals, lack of dredging etc. means that most of the time you are going to be travelling in less than optimal conditions.

 

The economics of solar panels is equally thought provoking.  

 

 

 

 

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1 hour ago, Neil2 said:

 

At last we have a "real world" narrowboat account - very interesting.

 

It certainly challenges the notion that you can move a narrowboat at "normal" cruising speeds with less than 1kw.  And with the state of many of our narrow canals, lack of dredging etc. means that most of the time you are going to be travelling in less than optimal conditions.

 

The economics of solar panels is equally thought provoking.  

 

 

Certainly the economics of flexible ones are distinctly iffy -- here's a comparison from Bimble...

 

Rigid 450W (2150x1060mm) £160 inc VAT ==> £355/kW ==> £118/kWh/day ==> about £1/kwh over 1 year lifetime

Flexible 270W (2080x990mm) £669 inc VAT ==> £2480/kW ==> £830/kWh/day ==> about £7/kWh over 1 year lifetime

 

So the flexible ones have 60% of the output per m2, and cost 7x as much per kW as rigid ones.

 

If the rigid panels last 10 years, the electricity cost is 10p/kWh -- which is cheaper than mains power. If the flexible panels last 5 years, the cost is 140p/kWh (70p/kWh if they last 10 years, which seem unlikely).

 

A generator putting out 7kW uses about 2.7l/hr of diesel, depending on what VAT rate you pay (propulsion? heating? 50:50?) this costs between 35p and 60p per kWh.

 

Which means rigid panels are definitely a lot cheaper than running a generator, but flexible ones are definitely a lot more expensive (depending on lifetime).

 

Apart from cost, a big (for a narrowboat) rigid solar panel setup (7kWh/day average in summer) probably halves the required generator running time when cruising -- Ampere uses lead-acid cells so the saving will be less than this, his consumption is 15-20kWh/day, would expect less than this for lithium because of much lower round-trip losses. When moored in summer (domestic loads only) the generator should hardly ever be needed with LiFePO4 batteries.

 

But unless you can fit a big array in (over 2kW) the generator running time saving will matter less, so then it's only the power savings that matter.

 

Small area flexible panels : pointless (this was the conclusion for the Finesse boat tested recently, could only fit 2 panels in)

Big (max 1.5kW) flexible panels : save genny time (30% or more saving) but you pay a lot more for the power, doesn't make economic sense

Small area rigid panels : cheap electricity, what's not to like?

Big (2kW or more) rigid panels : cheap electricity and shorter generator running times (~1hr/day saving in summer), maybe zero when moored in summer

Edited by IanD
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4 minutes ago, IanD said:

 

A generator putting out 7kW uses about 2.7l/hr of diesel, depending on what VAT rate you pay (propulsion? heating? 50:50?) this costs between 35p and 60p per kWh.

If you are going to amortise the cost of a solar panel over its life, shouldn't you do the same with the cost of the generator, in addition to the fuel cost - and then add in other ongoing costs - oil, filters etc.

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8 minutes ago, David Mack said:

If you are going to amortise the cost of a solar panel over its life, shouldn't you do the same with the cost of the generator, in addition to the fuel cost - and then add in other ongoing costs - oil, filters etc.

No, because you have to have the generator to have a usable hybrid propulsion system, like you have to have a motor and batteries -- here we're trying to decide whether adding solar panels is worth it or not, or just run the generator for longer.

 

Costs per extra hour of generator running time (oil, filters...) should be added in, but I didn't include these because service intervals are typically 250hours and it will have burned at least £500 worth of fuel (maybe 700l) in this time, so the fuel cost completely dominates.

Edited by IanD
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1 hour ago, IanD said:

 

Certainly the economics of flexible ones are distinctly iffy -- here's a comparison from Bimble...

 

Rigid 450W (2150x1060mm) £160 inc VAT ==> £355/kW ==> £118/kWh/day ==> about £1/kwh over 1 year lifetime

Flexible 270W (2080x990mm) £669 inc VAT ==> £2480/kW ==> £830/kWh/day ==> about £7/kWh over 1 year lifetime

 

So the flexible ones have 60% of the output per m2, and cost 7x as much per kW as rigid ones.

 

If the rigid panels last 10 years, the electricity cost is 10p/kWh -- which is cheaper than mains power. If the flexible panels last 5 years, the cost is 140p/kWh (70p/kWh if they last 10 years, which seem unlikely).

 

A generator putting out 7kW uses about 2.7l/hr of diesel, depending on what VAT rate you pay (propulsion? heating? 50:50?) this costs between 35p and 60p per kWh.

 

Which means rigid panels are definitely a lot cheaper than running a generator, but flexible ones are definitely a lot more expensive (depending on lifetime).

 

Apart from cost, a big (for a narrowboat) rigid solar panel setup (7kWh/day average in summer) probably halves the required generator running time when cruising -- Ampere uses lead-acid cells so the saving will be less than this, his consumption is 15-20kWh/day, would expect less than this for lithium because of much lower round-trip losses. When moored in summer (domestic loads only) the generator should hardly ever be needed with LiFePO4 batteries.

 

But unless you can fit a big array in (over 2kW) the generator running time saving will matter less, so then it's only the power savings that matter.

 

Small area flexible panels : pointless (this was the conclusion for the Finesse boat tested recently, could only fit 2 panels in)

Big (max 1.5kW) flexible panels : save genny time (30% or more saving) but you pay a lot more for the power, doesn't make economic sense

Small area rigid panels : cheap electricity, what's not to like?

Big (2kW or more) rigid panels : cheap electricity and shorter generator running times (~1hr/day saving in summer), maybe zero when moored in summer

You are correct flexible panels are useless which is why I have the rigid ones. If I was doing this again I would fit 500 watt ones which I can get for just over 100 squids it would be a neater job, but as we know we fit what's available at the time.

As you know I had the whispergen for domestic power and central heating, but that has been replaced by the 6kw vetus genny because it came at such a good price with only 4 hours on the clock! Which shows how expensive gennys are in comparison to shoreline (it was on a Dutch barge on the Thames) willing use it much? Who knows but it's a great backup and is one of the reasons for HVO, 10 year life makes sense plus no seals issues 

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Some good points. I'm not going to get into detailed discussion of BUS requirements for Li batteries except to say that they seem to work perfectly well with their own BMS and some sort of black box to interface them to the charger.

 

I did a calculation some time ago which suggested that rigid solar panels could produce power at about mains cost so were a very good option for static and minimal movement boats. However, I'm not happy with the safety (let alone aesthetic) aspects of rigids on cruising boats so we are currently without. I note that flexibles are currently being advertised as having aluminium backs "to dissipate the heat". To where when the roof itself is hot enough to fry an egg?

 

The fuel consumptions quoted for the 7 kVA generator look rather high. We seem to use about 1.5 litres/hour for 5+ kVA. Doesn't fall much below 1 even with virtually no load so, rather than running the generator very inefficiently to float our batteries we try to arrange plug-ins every 7-10 days. Even with mooring charges this is reasonably economical if we let the batteries get a bit lower than usual first. While I understand the case for amortising the cost of a generator I'm not sure that it is valid as it is going to be there anyway, unlike solar panels. By all means include oil changes, etc, (which is in my 25 p/kWh estimate).

 

If you are looking to improve overall efficiency without breaking the bank completely, look at supercapacitors. 40 years/1 million cycles, 100% dod and no charging losses at a cost that I believe to be between Lead-acid and Li batteries. The problem is that the energy density is only about half that of Lead-acids. Because they don't have charging losses a smaller 'battery bank and more frequent charging runs should suffice.

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By volume As they have a 100% dod while Lead-acids are 50%-ish they are more or less equivalent, the problem being that there is no 'reserve' with the supercapacitor. If you want to know more try Googling "Sirius". This will bring up a US outfit called Kilowatt Labs which likes to claim that they developed them though I believe they were actually developed - and are still produced - in the UAE. I have a direct contact if anyone is interested.

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2 hours ago, Rishworth_Bridge said:

By volume As they have a 100% dod while Lead-acids are 50%-ish they are more or less equivalent, the problem being that there is no 'reserve' with the supercapacitor. If you want to know more try Googling "Sirius". This will bring up a US outfit called Kilowatt Labs which likes to claim that they developed them though I believe they were actually developed - and are still produced - in the UAE. I have a direct contact if anyone is interested.

Supercapacitors are great for really high charge/discharge rate applications i.e. many times C rate. But for a given capacity their cost and energy density are terrible compared to batteries, that's physics for you. A million cycles would be useful if you intend to keep your boat for several thousand years...

 

All boat applications are fractional-C where they're just not the right solution.

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4 hours ago, Rishworth_Bridge said:

Some good points. I'm not going to get into detailed discussion of BUS requirements for Li batteries except to say that they seem to work perfectly well with their own BMS and some sort of black box to interface them to the charger.

 

I did a calculation some time ago which suggested that rigid solar panels could produce power at about mains cost so were a very good option for static and minimal movement boats. However, I'm not happy with the safety (let alone aesthetic) aspects of rigids on cruising boats so we are currently without. I note that flexibles are currently being advertised as having aluminium backs "to dissipate the heat". To where when the roof itself is hot enough to fry an egg?

 

The fuel consumptions quoted for the 7 kVA generator look rather high. We seem to use about 1.5 litres/hour for 5+ kVA. Doesn't fall much below 1 even with virtually no load so, rather than running the generator very inefficiently to float our batteries we try to arrange plug-ins every 7-10 days. Even with mooring charges this is reasonably economical if we let the batteries get a bit lower than usual first. While I understand the case for amortising the cost of a generator I'm not sure that it is valid as it is going to be there anyway, unlike solar panels. By all means include oil changes, etc, (which is in my 25 p/kWh estimate).

 

If you are looking to improve overall efficiency without breaking the bank completely, look at supercapacitors. 40 years/1 million cycles, 100% dod and no charging losses at a cost that I believe to be between Lead-acid and Li batteries. The problem is that the energy density is only about half that of Lead-acids. Because they don't have charging losses a smaller 'battery bank and more frequent charging runs should suffice.

Agreed about batteries -- LiFePO4 need to be the boss and in control of what happens to them, how this is done is an exercise for the designer...

 

Also agree that rigid panels are a pain to mount, but they're still a better solution than flexibles -- about which there is much BS, as you point out. There's also misunderstanding by some boaters about "bifacial panels" claiming to offer higher efficiency -- which they do, but if you dig into the small print they have to be angled and spaced apart so the sunlight which misses the panels reflects off the surface underneath, which should be painted white or silver. Fine for a large-scale solar array with big gaps between the panels, completely irrelevant for boats where they have exactly the same yield as cheaper standard panels. As usual, the devil is in the details.

 

Generator fuel consmption figure was for 7kW not 7kVA, because when charging batteries the inverter looks like a resistive load.

-- Beta Marine BetaSet 10 : 2.7l/hr @ 8.5kVA / 0.8PF = 6.8kW

-- Kohler 7EFKOZD : 2.6l/hr @ 7kW

All the other generators I looked at are similar, they're all about 25% thermal efficiency at maximum load which agrees with the Victron generator tests -- diesel is 38.6MJ/l, 7kW is 25.2MJ/hr, so 25% efficiency is 2.6l/hr.

 

If you think you can do much better than this then you should contact all the generator manufacturers, they'll probably beat a path to your door and pay you a fortune 😉

Edited by IanD
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The Sirius supercapacitors I mentioned seem to be quite widely used for off-grid applications - virtually identical to the requirement for boats. I don't understand how they achieve the performance they do but there is a lot of electronics involved. I suspect that the voltage is boosted hugely on storage and vice versa. I have corresponded with a director of Infusion Energy, the company I believe to be the actual developer and manufacturer of them, and have been assured that they are compatible with standard inverter/chargers like our Quattro. (The advertising at the time suggested that they would need a lower charging voltage.) Indeed, there are pictures of them linked to Quattros on the Internet. Try https://www.getgreen.energy/product/sirius-super-capacitor-kilowatt-labs/.

 

We have off-peak power at home and I am hoping to install a single unit to evaluate overnight charging and daytime use as a proxy for a boat system, though we will be away so much that it may have to wait another year.

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43 minutes ago, Rishworth_Bridge said:

The Sirius supercapacitors I mentioned seem to be quite widely used for off-grid applications - virtually identical to the requirement for boats. I don't understand how they achieve the performance they do but there is a lot of electronics involved. I suspect that the voltage is boosted hugely on storage and vice versa. I have corresponded with a director of Infusion Energy, the company I believe to be the actual developer and manufacturer of them, and have been assured that they are compatible with standard inverter/chargers like our Quattro. (The advertising at the time suggested that they would need a lower charging voltage.) Indeed, there are pictures of them linked to Quattros on the Internet. Try https://www.getgreen.energy/product/sirius-super-capacitor-kilowatt-labs/.

 

We have off-peak power at home and I am hoping to install a single unit to evaluate overnight charging and daytime use as a proxy for a boat system, though we will be away so much that it may have to wait another year.

 

The Sirius supercapacitors make sense at extremely high cycle counts, for example off-grid (daily use 365 days a year) over more than 10 years.

 

Since I doubt that any non-commercial boat will ever even get close to the lifetime of LiFePO4 batteries before the boat (or the drive system) is scrapped, the only reason for using supercapacitors instead would be if they're smaller, cheaper or lighter -- and right now they're bigger, heavier and more expensive.

 

If this changes in future (and no better battery technology for boats than LiFePO4 comes along) then they'll have a market.

Edited by IanD
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Depends how you use your boat. We probably spend about 200 days a year on ours so our batteries get through a lot of cycles, albeit only partial ones. And the batteries have now been installed for just shy of 7 years and used regularly for 6 1/2. We bought them in the expectation of getting 10 years so may need to be considering replacements within the next few years. As discussed earlier, the principal (only?) barrier to the widespread adoption of electric propulsion is cost, a barrier that Lithiums, whatever their technical benefits, make bigger. Despite claims of large price reductions, a functionally equivalent (smaller) bank of Lithiums costs about three times as much as one of Lead-acids. Given the control intricacies that you obviously understand and I don't, that makes them a poor choice in my book, except in one particular situation (below).

 

I have to admit that I have come across conflicting price information for supercapacitors but believe that a 7 kwh unit will (maybe already does) cost about £1,500 in the UK. 6 or 7 of them will be needed to make an electric boat viable so that's £9-11K. If that's correct, that's about 50% more than Lead-acids but about half that of Lithiums. As to weight, they work out at about 1/5 that of Lead-acids which, ironically, adds to the cost as more ballast will be needed. Except where space is critical I see them as preferable to any type of battery - though watch out for Iron-air!

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57 minutes ago, Rishworth_Bridge said:

Depends how you use your boat. We probably spend about 200 days a year on ours so our batteries get through a lot of cycles, albeit only partial ones. And the batteries have now been installed for just shy of 7 years and used regularly for 6 1/2. We bought them in the expectation of getting 10 years so may need to be considering replacements within the next few years. As discussed earlier, the principal (only?) barrier to the widespread adoption of electric propulsion is cost, a barrier that Lithiums, whatever their technical benefits, make bigger. Despite claims of large price reductions, a functionally equivalent (smaller) bank of Lithiums costs about three times as much as one of Lead-acids. Given the control intricacies that you obviously understand and I don't, that makes them a poor choice in my book, except in one particular situation (below).

 

I have to admit that I have come across conflicting price information for supercapacitors but believe that a 7 kwh unit will (maybe already does) cost about £1,500 in the UK. 6 or 7 of them will be needed to make an electric boat viable so that's £9-11K. If that's correct, that's about 50% more than Lead-acids but about half that of Lithiums. As to weight, they work out at about 1/5 that of Lead-acids which, ironically, adds to the cost as more ballast will be needed. Except where space is critical I see them as preferable to any type of battery - though watch out for Iron-air!

If you're right about the UK price of the supercapacitors then they would be a good solution for narrowboats. However the KW Labs price in the UK is £3800 each for the 7.1kW unit, so 4 of these would be £15k, though prices outside the UK are much higher than this (almost double) -- it's also not clear if this includes VAT, if it doesn't the cost would be £18k.

 

Your prices for lithiums look off though -- two BYD 15.4 48V batteries (600Ah, 31kWh usable) cost about £12k inc. VAT. From the quotes I got an 800Ah lead-acid traction bank (hybridmarine) was about £6k and a 1000Ah lead-carbon one (Waterworld) was about £9k, so for the same usable capacity lead-carbon are 1.5x the cost of traction batteries, lithium is 2x, and the supercapacitors might be 2.5x--3x.

 

Lithium lifetime is becoming specified in MWh now, since so long as you stay within 10%-90% SoC the DoD*cycles is roughly constant. The BYDs are rated at 48MWh (and this is guaranteed since they're remotely logged), which is 3200cycles at 100% DoD, 6400 at 50% DoD and so on. If you use 50% DoD every day they'd last about 30 years, so the fact that supercapacitors might last you 1000 years isn't really much of an advantage... 😉

Edited by IanD
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We can probably debate prices ad infinitum. The Sirius price I quoted was converted from dollars and came from a 'when available' UK list about 2 years ago. At that time, Infusion Energy (not KWL) were anticipating having stock in the UK by the end of the year (2019). Unfortunately, I have lost the link so can't check. You may well be right that it didn't include VAT and are certainly right that prices, particularly in Australia and NZ, are much higher. I got the impression that the relationship between Infusion and KWL might be a bit strained. KWL didn't reply to my enquiry and took 3 months to pass it to Infusion. I shall go back to my Infusion contact rather than KWL if/when I am ready to move.

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28 minutes ago, Rishworth_Bridge said:

We can probably debate prices ad infinitum. The Sirius price I quoted was converted from dollars and came from a 'when available' UK list about 2 years ago. At that time, Infusion Energy (not KWL) were anticipating having stock in the UK by the end of the year (2019). Unfortunately, I have lost the link so can't check. You may well be right that it didn't include VAT and are certainly right that prices, particularly in Australia and NZ, are much higher. I got the impression that the relationship between Infusion and KWL might be a bit strained. KWL didn't reply to my enquiry and took 3 months to pass it to Infusion. I shall go back to my Infusion contact rather than KWL if/when I am ready to move.

Just be warned -- I also found articles/reviews on the web saying that these are not supercapacitors at all but just packaged LTO batteries, that the KW labs claims to use graphene are fraudulent, and that even graphene supercapacitors can't get anywhere near the energy densities they claim.

 

LTO cells do have very long lifetime, also lower energy density and higher cost than LiFePO4, and the numbers KWL claim do stack up with what you'd expect if they were LTO cells.

 

Whether you believe KWL or these claims is up to you, but I certainly can't find any reliable independent test/review/technical analysis of them anywhere...

 

Their patent application also suggests it's an LTO battery pack, possibly with some series supercapacitors to provide extra peak current capability, see attached snapshot.

KWlabs.png

Edited by IanD
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Ecological wise Lithium is not good, and at the moment there is no way of disposing of them at the end of their life, though that will be sorted by that time - necessity is the mother of invention ... In Argentina most of the available water in the desert areas is used for extraction, followed by tourist hotels. Some indigenous cultures are dying out with agriculture not feasible. Brings another dimension to going green ... 

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5 minutes ago, OCM said:

Ecological wise Lithium is not good, and at the moment there is no way of disposing of them at the end of their life, though that will be sorted by that time - necessity is the mother of invention ... In Argentina most of the available water in the desert areas is used for extraction, followed by tourist hotels. Some indigenous cultures are dying out with agriculture not feasible. Brings another dimension to going green ... 

You should Google before you post, there are lithium batteries recycling companies in the UK. I have a load of secondhand LifePo4s that are repurposed which is recycling, however companies do recycling as it's to valuable a product to waste 

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Thanks didn't know that. Lithium is expensive.

There are lots of companies out there now that say 100%, big business recycling.

Percentage of battery that can be recycled is 5% (BBC News Business 26/4/21).

Maybe they haven't checked Google recently.

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