Antrepat

OK, OK, 1.9mph at 400W, then! Mph m/s Force (N) Power (W) hp 0.0 0.00 0 0 0.0 0.5 0.22 33 7 0.0 1.0 0.45 130 58 0.1 1.5 0.67 294 197 0.3 2.0 0.89 522 467 0.6 2.5 1.12 815 911 1.2 3.0 1.34 1174 1575 2.1 3.5 1.56 1598 2500 3.4 4.0 1.79 2087 3732 5.0 4.5 2.01 2642 5314 7.1 5.0 2.24 3261 7290 9.8

Well, I don't want to use a toothed belt drive particularly. I just wondered if it would reduce the tension required, but if it's a lot more complicated to fit then I think you're suggesting it's not worthwhile. Understood that a large radial load is going to need a large belt. Balmar information for their large 48v alternators suggests they recommend wide multi-v belts, maximising the surface for friction I suppose. My concern was more about the impact on the engine of a much larger belt-driven load - that is, one where the main power of the engine is not being delivered axially.

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Now that you mention it, I've seen that before. Avoiding salesmens' rose-tinting is definitely one of my objectives. It looks like about 3kw on a canal and less on a river (as I'd have expected). That is, of course, electrical input into the system, so that suggests my estimates are significantly more than practical reality: given 55% propellor fluid-mechanical efficiency and 90% electrical efficiency (perhaps optimistic but assume I've got good kit and really thick wires), you'd get about half that power as actual thrust. Here are my estimates for raw thrust needed to achieve different speeds, based on the mk. 1 horse being able to pull a lightly-laden full-size narrow boat at 2mph: Mph m/s Force (N) Power (W) hp 0.0 0.00 0 0 0.0 0.5 0.22 52 12 0.0 1.0 0.45 209 93 0.1 1.5 0.67 469 315 0.4 2.0 0.89 834 746 1.0 2.5 1.12 1303 1456 2.0 3.0 1.34 1877 2517 3.4 3.5 1.56 2554 3996 5.4 4.0 1.79 3336 5966 8.0 4.5 2.01 4222 8494 11.4 5.0 2.24 5213 11652 15.6 That means about 5kW electrical power to make 3mph, so clearly I'm being too conservative (if that chap's data are correct). Sadly the Horseboating Society have so far ignored my request for the speed at which a good horse can actually pull a lightly-laden boat (they're probably dismissing me as a crank, and they're quite likely right), so I had to guess, and I dare say there are other factors I haven't included in the model. Anyway, to get it to align with 1.5kw at 3mph, the baseline for that horse is about 2.4mph, so maybe it's the mk. 2 horse instead; or maybe it just shows how little I know about horses. Mph m/s Force (N) Power (W) hp 0.0 0.00 0 0 0.0 0.5 0.22 30 7 0.0 1.0 0.45 121 54 0.1 1.5 0.67 271 182 0.2 2.0 0.89 483 432 0.6 2.5 1.12 754 843 1.1 3.0 1.34 1086 1456 2.0 3.5 1.56 1478 2313 3.1 4.0 1.79 1931 3452 4.6 4.5 2.01 2443 4916 6.6 5.0 2.24 3017 6743 9.0 This is very encouraging, as it implies a 400Ah battery, which is what I'd estimated I'd need, would deliver a lot more silent cruising than I thought.

Thinking about my existing engine, this would be the opposite end from the usual location of an alternator pulley. The concerns people are expressing seem to be that a large alternator putting out 7kw or something will have issues with belt drive effectiveness and in any case, "normal" engines are not designed to have such large devices attached in this way and an in-line generator would be much better. As it happens, the cost of one of those is comparable to the large alternators, but my issue with that idea is that I'm not sure I would have space to fit one in. Thinking about the moment of force on the engine crankshaft bearings, the larger the alternator, the more tension is needed, and the more sideways force there is being applied on the shaft. Indeed these engines are intended to be connected to something axially, and to deliver most of their power along that axis and not to something through a belt. So, what is the advantage of a belt drive coming off the flywheel rather than off the other end? Would a toothed belt significantly reduce the tension required, at the expense perhaps of being noisier and wearing out more often?

The Sincro one is currently €1,488.40 - heavily discounted, I notice, which is curious. Thanks to the Natural Party of Government, that's pretty much the same in £ now, but I'd happily pay that for a solid piece of equipment. The issues are: cost of an engine of the appropriate power to attach it to (14hp is nowhere near enough), space to accommodate engine and generator, with a drive motor in the same bay, and control of the rig given the stringent requirements of LFP charge termination. The Wakespeed WS500 is designed to control alternators, and this is not an alternator, at least, not in the conventional sense, and you can't just shut off the power when the termination point is reached, unless a relay signal to an engine auto start/stop makes for a sufficiently graceful shutdown (I doubt it).

I do wish these firms would just publish a price list rather than get you to ask - it's just a way of getting you talking to a salesman. I've asked FP anyway and got quoted £15,600 for their AGT-48v generator. I haven't asked PM yet but is it likely to be much different?

Well, it all depends on the generator: Maybe £5k for LFP (EVE cells from Fogstar) £2k for control equipment (BSS etc.) £3.5k for drive motor, controller, etc. (specific quotation, adjusted for inflation) £0 for solar - already have another two panels and the electrics are already set up. £1k for wiring, switches, relays, breakers, etc. £? for the generator rig

I know it's not going to be easy, nor did I expect it to be - if it were, people wouldn't be forking out £40k+ to firms to do it for them. £57k for an electric conversion reported in one of the magazines a while ago, if I recall, and they only had LAs (goodness knows why given the weight and the limited DOD) and eschewed solar on their 60ft boat because "it wouldn't contribute anything significant". Hmm, so my two cheap Chinese panels gave me 350W on a beautiful sunny West Yorkshire autumn day today, and I could fit four on at a push, so maybe 6 on a 60ft boat with plenty of room to spare, that's over a kilowatt in October. I wouldn't call that "not significant" but I'm sure it was worth every penny of that £57k to lug about a ton of batteries from which you can never draw half the charge whilst basking in the kilowatts of uncaptured sunshine. Perhaps I'm being unfair but I read that article and wondered about some of the professional advice people are buying. I enjoy a challenge, particularly when it might allow me to save £0000s on professional services and will mean I know my own system inside out. At least I can have fun learning and working out whether it is feasible, anyway. Regarding solar, I could probably come up with over 800W with four panels on a great day, which is also not insignificant in my opinion. My possibly-wrong-and perhaps-a-bit-potty reckoning, based on the guess that a mk. 1 horse (746W) can move a lightly-laden 72ft narrow boat at about 2mph (thus allowing me to estimate the drag coefficient), is that about 2.2kw of thrust is needed is needed for 3mph in a narrow boat - quite possibly an overestimate - so with 55% propellor efficiency and 90% electrical efficiency (former from advice on here, latter quoted for real motor drive products), that's 4.5kw of electrical power. If someone has some data to show this is indeed a significant under- or overestimate, I'm all ears. I'd especially like to hear from someone who has an electric boat and knows how many kw they draw at 3mph. Yes, I am understanding the on-the-side belt solution is a problem. The Sincro DC generator is indeed in-line - I read the docs the other day. It's about 60cm in addition to the length of the engine, and of course it has to go at the bottom which, if the engine were aligned with the propellor shaft like at present, there wouldn't be room for with a drive motor as well. Of course, it doesn't need to be aligned with the propellor shaft at all, so I wonder if it could go sideways, with a redesigned engine bay.

I like crazy projects. If it's not feasible, it's not feasible, but I'm not yet convinced it isn't.

It's not in their online catalogue, at least. I'm not going to use the engine for propulsion at all. That's the whole idea, to cruise electric and just use the engine for charging. I can't afford £20k for a "marine generator", hence the DIY talk about modifying alternators and whatnot. If I have to compromise to a lower power generator to have an engine that will fit in my boat, so be it!

Oh. That's unfortunate, because a 180A alternator putting out, say, 58v, that's about 10kw (which I doubt would be practically achieved), and even if it were only 50% efficiency that would be, what, 26hp? A 43hp engine would barely have to tick over, and I'm pretty sure I don't have room for one anyway I'll see what Beta say.

Very much noted. My engine actually appears to be some years older (early 80s) than the boat (early 90s) so I don't know if it was second hand when it went in. In any case, it has problems (air getting in somewhere, coolant frothing in expansion tank, coolant loss, wild fluctuations in coolant level), which may be just gaskets but may be a cracked block. If I replaced, different ball game, it seems. Maybe I should have a word with Beta...

Just saw this, which happens to be exactly the one I was just talking about. I'm not sure that alternator is still made, but a similar setup with the Mahle is what I'm trying to explore.

Found this one as well: https://www.dfjauto.com/product/electrodyne-brushless-alternator/ but it doesn't seem to be listed in the manufacturer's catalogue anymore: http://www.electrodyneinc.com/ge-series. They do have a different 48v one but the information isn't really there. Isn't brushless better? I'm not sure if this one can be externally regulated, though - I see a "voltage adjust" which presumably is a screw in a hole. It does say "full field", indicating another mysterious hole.

Let me check I understand. It's possible to cap the engine effort by capping the field current, and hence reduce the risk of overtaxing a slightly puny engine (mine is 14hp)?

It only seems to be scarce within the UK. Can't imagine why. Who? Actually there's a chap here in Scarborough who does motor rewinds and suchlike. He refurbished a motor for me about six years ago. If he's still in business, maybe I could ask him - ACR Rewinds, that's him.

This makes a lot of sense to me. Having two regulators fighting each other surely would be bad, and anyway the whole point of using something as fancy as the Wakespeed is because it is capable of charging LFPs properly (until absorption is properly complete and current has fallen right off and those pesky memories are erased and whatever the other reason is to be able to charge them properly fully when required). I recently got a quote for £3052 plus VAT for the 100A one from RJS Marine, which is the best price I've found in the UK. I can see you share my excitement about the Mahle.

About £1000-£1200, but no uk supplier has stock (wonder why). If it's 75% efficient then that's about 15hp, but that's at full tilt. Me either. The only 48v alternators I've found are the ones I listed, but I think there is a 100A Mahle one too. Two Balmar 60A ones...but I expect that'd cost even more. I'm very open to posters here pointing out other 48v alternators on the market. This was my understanding to: the internal regulator needs to be discarded altogether and its function replaced with the external device.

For electric propulsion, 12v is no good unless you like using steel ingots as conductors. 48v seems to be the minimum advisable, and for me LFP chemistry is the way to go. That means a charging source that is powerful enough to charge something like 400Ah in a reasonable time (say 0.3C) and which can be regulated for LFP rather than LA chemistry. The Wakespeed WS500 or the Mastervolt Alpha Plus seem to be the off-the-shelf devices of choice for regulation - pricey but if you've just spent £4k+ on a battery, I reckon you should have the best management and protection equipment you can afford. Alternators to charge at 48v, though? Not so easy. I haven't found anyone who recommends stringing two 24v ones together in series (after rectification). The Wakespeed can control dual alternators but I bet that means parallel ones, not in series. I have found only three 48v alternator products available: the Balmar ones, very expensive; these monsters, designed to mate in line with the engine shaft; and this Mahle model, which as far as I can see is used on lawnmowers, presumably big ride-on ones and the alternator provides the power to spin multiple sets of blades. I stumbled across this post by @nicknorman. He mentions Ed Shires of Four Counties Marine Services, who I read is clear that there's no need for the expensive alternators (thought he doesn't seem to be talking about propulsion supply or 48v) and that any standard alternator should be able to be controlled by an external regulator. The Mahle doesn't appear to be inherently unusual - I'm no expert on alternators but as far as I can tell it has what's needed to work with external regulators like the Wakespeed WS500. Using this reference, I spy R(W), which appears to be the stator AC, and DF for the rotor field current. According to the Wakespeed docs, these are the connections that the WS500 needs to control an alternator. BUT DF is behind the internal regulator, so presumably it'd be necessary to bypass that or remove it altogether so the Wakespeed does the job instead. So, who knows anything about modifying standard alternators to control them with an external regulator?

OK, I've read the Wakespeed WS500 docs and my impression is that it's the bee's knees. Then there's the alternator. Different topic, different thread.

Yes, I've been reading the Wakespeed docs and it has to support numerous different proprietary comms over CAN. In other words, I'll only link up with one of the BMSs that are compatible, which includes REC but not, it seems, the Overkill Solar BMS I had been looking at.

I suppose I have an advantage in that I am starting from a clean slate. I put in an entirely new "house bank" side of things last year, based on 48v in anticipation of moving to a large 48v LFP propulsion system in the future, so I've already got the switchboard, solar MPPT, DC-DC converter for 12v, breakers, and whatnot set up and it'd just need to take its feed from the LFP instead of the four 105Ah sealed LA I put in last year. I might consider keeping both and just feeding the solar into the house bank as an entirely separate system - it's not a big boat and I might be lucky to get 800W on a really good day, which isn't much into a 400Ah battery.

The REC Q indeed has a CAN interface, which seems to be a fairly common comms protocol that it shares with (at least) the Wakespeed device and I think at least some Victron kit.

Very much sounds like a false economy to me too. I actually just did remortgage my house, thankfully just before everything went mad the other week (thanks, guys, doing a brilliant job, can't wait for the next two years and the sunlit uplands that surely await us all), but the cost of LFPs from any reputable UK/EU/US source remains eye-watering.