All Electric?

[nicknorman]

Just now, IanD said:

I know -- and every extra hour drinks more fuel...

 

I know you're well aware of this, but an external alternator controller is also a must to get anywhere close to the efficiencies and charge times we've been talking about 😉

I think having an external alternator controller is a must anytime you have LI batteries connected direct to the alternator - otherwise you can expect a very short alternator life, and some not very happy LI batteries.

[IanD]

8 minutes ago, nicknorman said:

I think having an external alternator controller is a must anytime you have LI batteries connected direct to the alternator - otherwise you can expect a very short alternator life, and some not very happy LI batteries.

But a lot of "let's just drop in lithium" proponents don't seem to realise this... 😞

[dmr]

2 hours ago, IanD said:

<sigh> See the graph I posted which shows exactly this, with actual numbers (for an indirectly injected Beta 43). Look, here it is again...

 

But surely this is the absolute efficiency rather than the marginal efficiency that we were talking about?

Why does it have a big kink at 2400 rpm?

I am surprised that the efficiency increases with speed (20kW, 1500-2000rpm for example) as both pumping loss and ring friction will be increasing?

As you are installing a generator which can be run at optimum efficiency then why are you not looking at a slower revving direct injected engine?  or are you? Though a smaller turbocharged unit is probably the best way to go?????

[IanD]

13 minutes ago, dmr said:

 

But surely this is the absolute efficiency rather than the marginal efficiency that we were talking about?

Why does it have a big kink at 2400 rpm?

I am surprised that the efficiency increases with speed (20kW, 1500-2000rpm for example) as both pumping loss and ring friction will be increasing?

As you are installing a generator which can be run at optimum efficiency then why are you not looking at a slower revving direct injected engine?  or are you? Though a smaller turbocharged unit is probably the best way to go?????

Yes this is absolute efficiency, but it's easy to work out marginal efficiency from it -- as I've described several times now 😉

 

Why does it have the kink at 2400rpm? Ask Beta Marine, might be something to do with it being IDI but who knows...

 

Efficiency at constant load generally decreases with speed, follow a horizontal line across the contours. There are many causes of losses in an engine, not all of them obvious ones.

 

These are curves for a Beta 43 which is probably the most common propulsion diesel on the UK canals, so it's most relevant to this particular discussion. Also it's normally well-nigh impossible to get hold of data like this, the only reason these curves are out there is because Hybrid Marine use this as their base engine and provide the data as part of their justification for going hybrid.

 

Generators use whatever engine the manufacturer selects, but from the Victron tests many of them end up around 25% maximum efficiency regardless of this.

 

Smaller turbocharged engines are sometimes used for big generators (they're more efficient) but are far too powerful for the <10kW generator class relevent to the canals; even the 1500rpm ones use pretty small engines because they only need maybe 50bhp or so, a small DI turbo engine (if it exists) is too powerful and too expensive.

Edited November 15, 2021 by IanD

[IanD]

1 hour ago, nicknorman said:

 

I wasn't considering a big alternator solution, just the standard alternator solution (which is quite big!).

 

65% is the quoted figure but no doubt it is their best figure and reality will be worse. But as I said, I am only interested in the marginal efficiency which is much better, especially at lower outputs (when its running cooler)

 

Interestingly if the overall marginal efficiency is 27% and 1 litre of diesel is 80p and contains 10kwh of energy (which apparently it rather conveniently does) then for your additional 1 litre of fuel burned charging the batteries as you cruise, you get 2.7kwh, ie aroud 30p per kwh which is actually pretty good considering household electricity is up to 20p a unit these days. Of course that is massively better than if you were running the engine solely to generate power and using LA batteries!

FYI, some real measurements -- typical alternator rpm on a cruising narrowboat (with standard polyvee pulleys) is about 3500rpm, so about 50% efficiency at 1.5kW/14V output, or 3kW engine load. Even lower using the inbuilt regulator, so allowing for excitation current and regulator losses...

 

Edited November 15, 2021 by IanD

[Tony1]

48 minutes ago, nicknorman said:

I think having an external alternator controller is a must anytime you have LI batteries connected direct to the alternator - otherwise you can expect a very short alternator life, and some not very happy LI batteries.

 

Whilst Ed Shiers was helping me to sort out my electrics, I of course provided moral support by chattering endlessly at him as he worked- and in particular about my previous struggles with a few electricians who didnt really understand what was needed to manage lithium batteries, or who just refused to get involved in lithium work.

But I did also mention that I had gotten a lot of help and advice from yourself on this forum (and of course in a different place), and he said he had come across a CWDF thread about lithiums (I dont think he peruses the site regularly).

At some point he realised that you (the CWDF contributor who had helped me) were very likely the same chap he had done some work for a while ago, and I remember he was extremely impressed with your ability to design your own alternator regulation system.  

 

He was strongly in favour of installing a proper solution for my charging, which would have been an upgraded poly V crank pulley (my 38hp engine doesnt have this as standard) plus an external Mastervolt regulator, and if I could turn back the clock I would go that route every time, and not use B2Bs.

But given how much I had already expended on the B2Bs and other gubbins, he accepted that it would be more cost effective to just get my existing equipment running safely, which he very kindly did. 

I just wish I had known of his existence and his skillset and knowledge regarding the charging of lithiums a year ago. If I had consulted him at the start, I would have a much better charging system now.

 

[nicknorman]

11 minutes ago, Tony1 said:

 

Whilst Ed Shiers was helping me to sort out my electrics, I of course provided moral support by chattering endlessly at him as he worked- and in particular about my previous struggles with a few electricians who didnt really understand what was needed to manage lithium batteries, or who just refused to get involved in lithium work.

But I did also mention that I had gotten a lot of help and advice from yourself on this forum (and of course in a different place), and he said he had come across a CWDF thread about lithiums (I dont think he peruses the site regularly).

At some point he realised that you (the CWDF contributor who had helped me) were very likely the same chap he had done some work for a while ago, and I remember he was extremely impressed with your ability to design your own alternator regulation system.  

 

He was strongly in favour of installing a proper solution for my charging, which would have been an upgraded poly V crank pulley (my 38hp engine doesnt have this as standard) plus an external Mastervolt regulator, and if I could turn back the clock I would go that route every time, and not use B2Bs.

But given how much I had already expended on the B2Bs and other gubbins, he accepted that it would be more cost effective to just get my existing equipment running safely, which he very kindly did. 

I just wish I had known of his existence and his skillset and knowledge regarding the charging of lithiums a year ago. If I had consulted him at the start, I would have a much better charging system now.

 

Yes he supplied me with a new freewheel pulley for our Travelpower (it had started slipping) mail order at a good price. And then when I failed to get the old one off, he offered to turn up with his impact wrench and get it off for me (he was at Streethay which was only about 10 miles away) AND THEN declined any money for his trouble. I did eventually manage to force £10 on him for fuel, but it was a struggle!

Edited November 15, 2021 by nicknorman

[Tacet]

4 hours ago, IanD said:

LiFePO4 should really be part of the solution though; using LA you not only have the low round-trip efficiency but the need to run for at least a couple of hours regularly to get to 100% SoC. I'd be surprised if these don't put the cost per unit up by al least 50%, probably more than that...

I've never really bought the economics of running an engine (or generator) for several hours each week solely to extend the life of lead acid batteries.  At maybe £2 per running hour or thereabouts, it feels like dodgy maths.  And I don't like the noise.

[IanD]

13 minutes ago, Tacet said:

I've never really bought the economics of running an engine (or generator) for several hours each week solely to extend the life of lead acid batteries.  At maybe £2 per running hour or thereabouts, it feels like dodgy maths.  And I don't like the noise.

That running cost looks very high; at light load for equalising LA batteries the fuel consumption should be no more than 1l/hour which costs about 80p at the moment, so maybe £2 extra per charge cycle not per hour. Do this once a week and it costs about £100 per year -- more if you do it more often and vice versa.

 

With a fairly expensive decent size battery bank (600Ah or more, like we've been talking about for a gas-free boat) this should more than pay itself back in increased battery life.

 

Even though they're cheap, LA batteries are still not a good solution for a power-hungry boat though...

Edited November 15, 2021 by IanD

[dmr]

5 minutes ago, IanD said:

That running cost looks very high; at light load for equalising LA batteries the fuel consumption should be no more than 1l/hour which costs about 80p at the moment, so maybe £2 extra per charge cycle not per hour. Do this once a week and it costs about £100 per year -- more if you do it more often and vice versa.

 

With a fairly expensive decent size battery bank (600Ah or more, like we've been talking about for a gas-free boat) this should more than pay itself back in increased battery life.

 

£2 per running hour is about right or even a bit optimistic if you factor everything in. This would include servicing and also an estimate of up to £10,000 to replace or rebuild an engine after 10,000 - 15,000 hours.

I appreciate that not many boaters actually put 10,000 hours on an engine...but a few do 😀

[Tacet]

4 minutes ago, IanD said:

That running cost looks very high; at light load for equalising LA batteries the consumption should be about 1l/hour which costs about 80p at the moment, so maybe £2 extra per charge cycle not per hour. Do this one a week and it costs about £100 per year.

 

With a fairly expensive decent size battery bank (600Ah or more, like we've been talking about for a gas-free boat) this should more than pay itself back in increased battery life.

And 10,000 hours from a £10,000 engine adds another £1 per hour; might be a bit high but add some additional servicing all depending.

 

So, splitting the difference, maybe £150 a year for a couple of hours per week.  Which means, roughly speaking, you will need to double the life of the batteries to break even, which I doubt.  And I would willingly pay something not to have the irritation of the engine running when stationary.

 

 

[IanD]

1 minute ago, Tacet said:

And 10,000 hours from a £10,000 engine adds another £1 per hour; might be a bit high but add some additional servicing all depending.

 

So, splitting the difference, maybe £150 a year for a couple of hours per week.  Which means, roughly speaking, you will need to double the life of the batteries to break even, which I doubt.  And I would willingly pay something not to have the irritation of the engine running when stationary.

 

 

 

If you don't ever equalise LA batteries (get to 100% SoC by running down to a tail current of a couple of percent of capacity) then you'll certainly lose at least half of the lifetime, maybe more.

 

I'd also suggest that the engine replacement costs quoted are high, since that's more than a brand new engine and gearbox cost, and many people report longer life than that too.

 

Whether the noise for extra running is a big problem depends on how noisy the engine is -- it's not as if it won't have to run for recharging anyway, it's the extra time that's being objected to.

 

Of course if people want to avoid the noise, don't equalise, and kill their batteries off before their time to save the engine, that's their choice -- as is doing the reverse... 😉

 

And going by all that, LiFePO4 probably work out cheaper in the long term as well as avoiding the charging problem completely 🙂

[MtB]

50 minutes ago, Tacet said:

And I don't like the noise.

 

You're buying the wrong sort of engine then....

 

I get complaints from neighbouring boaters when I turn the Kelvin off!

[Tacet]

6 hours ago, IanD said:

You can't have "60W an hour". 60W is already a rate of energy consumption (it's 60 joules per second).

 

11 minutes ago, IanD said:

 

If you don't ever equalise LA batteries (get to 100% SoC by running down to a tail current of a couple of percent of capacity) then you'll certainly lose at least half of the lifetime, maybe more.

 

 

You can have 60W an hour.  But a rate can never be any proportion of a capacity😉

 

On the other points, it is going to be a compromise between battery charging and battery life; there are some that exhort an extra 8 hours at the weekend.  My own experience of living aboard on a well-equipped boat was that battery charging whilst tied-up was rarely (maybe once a month) needed and the battery life was fine.  Again, it depends on the cruising patterns.

 

Things have come a long way; I recall boating with (only) zinc-carbon batteries - and we were happy

4 minutes ago, MtB said:

 

You're buying the wrong sort of engine then....

 

I get complaints from neighbouring boaters when I turn the Kelvin off!

That's a fair point.  Would you like me to bring my motorcycle around one evening for a comparison?

[MtB]

11 minutes ago, Tacet said:

That's a fair point.  Would you like me to bring my motorcycle around one evening for a comparison?

 

Is it a single cylinder diesel?

[Tacet]

5 minutes ago, MtB said:

 

Is it a single cylinder diesel?

The number of cylinders depends on the mood of the magneto.

 

 

[MtB]

17 minutes ago, Tacet said:

The number of cylinders depends on the mood of the magneto.

 

 

Ooo a petrol-start diesel. Cool!!

[Alan de Enfield]

17 minutes ago, MtB said:

 

Ooo a petrol-start diesel. Cool!!

 

We had a couple of tractors that were started that way - had two fuel tanks - start on petrol and once they heated up switched over to TVO (Tractor Vapourising Oil)

[IanD]

13 hours ago, Tacet said:

 

You can have 60W an hour.  But a rate can never be any proportion of a capacity😉

 

 

You don't have 60W per hour in any normal usage -- the only way this would be true is if your power use went up from (say) 40W to 100W in one hour, then you could say that your "rate of power increase was 60W per hour" -- but this is really stretching a point, and would never be used in practice, as I'm sure you're aware. Or you're still misunderstanding what power (and watts) actually mean...

 

And I think you know exactly what I meant -- tail current to confirm 100% SoC is normally defined as something like "2% of capacity", meaning that a 500Ah battery is fully charged when tail current drops to 10A. I could have said "LA are considered fully charged when tail current in A falls to 2% of the Ah rating of the battery", but what I said was shorter and widely understood -- and BTW a current isn't a rate either... 😉

[LadyG]

I'm cc, with nominal 600ah, all fairly new, all AGM, I take note of the numbers every day, assuming my solar looks after them 6 months, and I use engine as appropriate in the cold months. How do modern AGM s differ from LA s?

[IanD]

16 minutes ago, LadyG said:

I'm cc, with nominal 600ah, all fairly new, all AGM, I take note of the numbers every day, assuming my solar looks after them 6 months, and I use engine as appropriate in the cold months. How do modern AGM s differ from LA s?

AGMs are basically better quality lower-maintenance LAs, they have longer lifetime but are still prone to sulphation (though less so) so need taking to 100% SoC regularly (but less often) to maximise lifetime.

 

Whether the extra fuel cost and engine wear/time justify spending the time getting them all the way to 100% SoC regularly depends on the battery cost and lifetime and how much this reduces if you don't do it. With small cheap battery banks it's probably cheaper in the long term to not do it and replace the batteries more often, with big expensive battery banks it's definitely cheaper to do it.

 

The debate here is where the crossover point is, because battery manufacturers quote lifetime under "ideal" conditions (including charging to 100% SoC) but are very coy about what happens if you don't do this -- for sure if you treat batteries badly the life can be disastrously short, but what happens if you do something in between badly and ideal? Very little real useful information...

Edited November 16, 2021 by IanD

[Tacet]

22 minutes ago, IanD said:

 

You don't have 60W per hour in any normal usage -- the only way this would be true is if your power use went up from (say) 40W to 100W in one hour, then you could say that your "rate of power increase was 60W per hour" -- but this is really stretching a point, and would never be used in practice, as I'm sure you're aware. Or you're still misunderstanding what power (and watts) actually mean...

 

True enough; it would express a rate of change and is not commonly used. Although, to an extent, it is referred to when it is said that charging should continue until the tail current is 2%......  

22 minutes ago, IanD said:

 

And I think you know exactly what I meant -- tail current to confirm 100% SoC is normally defined as something like "2% of capacity", meaning that a 500Ah battery is fully charged when tail current drops to 10A. I could have said "LA are considered fully charged when tail current in A falls to 2% of the Ah rating of the battery", but what I said was shorter and widely understood -- and BTW a current isn't a rate either... 😉

I did know what you meant - and it is commonly used by many.  But it is a horrible mixture and if it is to be used, the units should really be stated.

 

I'll confess to thinking that an ampere was one coulumb per second - but maybe that doesn't make it a rate?  It's getting a bit complicated for me!  Wh or kWh is really a better way of expressing battery capacity although the Ah reigns.

 

 

[IanD]

35 minutes ago, Tacet said:

True enough; it would express a rate of change and is not commonly used. Although, to an extent, it is referred to when it is said that charging should continue until the tail current is 2%......  

I did know what you meant - and it is commonly used by many.  But it is a horrible mixture and if it is to be used, the units should really be stated.

 

I'll confess to thinking that an ampere was one coulumb per second - but maybe that doesn't make it a rate?  It's getting a bit complicated for me!  Wh or kWh is really a better way of expressing battery capacity although the Ah reigns.

 

An amp is indeed one coulomb per second (because current is rate of change of charge), just like a watt is one joule per second (because power is rate of change of energy). The ampere (and the second/metre/kilogram) are actually the SI base units, all the others are derived from them.

 

https://en.wikipedia.org/wiki/SI_base_unit

https://en.wikipedia.org/wiki/SI_derived_unit

 

Agreed that kWh is better than Ah -- but of course MJ is better still, being an SI unit of energy (like is used for fuel), not a rate (J/s) multiplied by a time (s)... 😉

Edited November 16, 2021 by IanD

[Tacet]

13 hours ago, Alan de Enfield said:

 

We had a couple of tractors that were started that way - had two fuel tanks - start on petrol and once they heated up switched over to TVO (Tractor Vapourising Oil)

Petrol-paraffin engines were reasonably common at one time on boats.  Cressy was converted and, for a short time, we had a Morris Vedette engine.  You had to remember to switch back 

to petrol before stopping the engine so that the carburettor was filled for the next start.  Less advantage now that paraffin is not freely available and is more expensive.

 

A low compression engine was necessary to avoid pinking -so side valves were helpful

[nicknorman]

On 15/11/2021 at 10:47, IanD said:

https://sterling-power.com/products/alternator-open-circuit-protection-device

 

Just got my boards back from China, soldered on the transient absorb diodes and the connector. Hmmm, I think I went rather overboard on the connector!

 

The diodes are by no means huge but the spec say each one can absorb 1.8kw for 10mS and clamps at 24v max with 205 amps going through it. I have 4 in parallel so theoretically I suppose it should be able to absorb the full alternator output for 40mS and keep the voltage closer to 20v. In reality the output will be tailing off as the field current subsides so perhaps it could cope with an 80mS event? That is, if the PCB tracks (which are on both sides) don’t fry first.

 

The problem is I have no idea what the rotor inductance is, ie how long it takes for the current to subside once the regulator shuts down. Anyway, it’s a valiant effort and of course the alternator’s own zener diodes will limit to about 36v if my board fries. Which is within the tolerance of the Empirbus system.