Economic Generation

[nb Innisfree]

I do think that it's more useful to construct an imaginary model such as this to keep referring to so that you don't miss something basic before using maths and formulas to compound that mistake.

 

I think that's a great description

 

To add to it, as the battery gets old and tired, that's the equivalent of a load of muck in the bottom of the tank, reducing the tank's capacity and causing the ball cock to come into action much sooner.

 

Tony

 

 

And provided that the head of water or pressure (voltage) is higher than that in the tank it will eventually fill up.

Edited November 30, 2010 by nb Innisfree

[Gibbo]

But bear in mind that the alternator will not produce its full output if it is not running fast enough regardless of how much the battery could take.

 

You KEEP missing the pertinent point.

 

If the alternator is not spinning fast enough then, as far as the batteries are concerned, that is exactly the same as having a smaller alternator. The batteries will be in bulk charge (current is limited by the charge source) and the voltage will be less than the acceptance voltage.

 

I'm confused why you're having a hard time understanding this.

 

Am I right in thinking that if you have a smaller-than-the-batteries-can-pull alternator (say a 45A on a 600Ah bank) which will therefore lengthen the bulk phase, this in turn will then shorten the acceptance time?

 

Or did I dream that somewhere?

 

Tony

 

Spot on. Likewise if you have an enormous alternator that will instantly get the batteries up to acceptance voltage as soon as it starts spinning then the required acceptance time will be very long. A simple graph can be drawn between these two extremes.

 

Note that this is exactly the opposite of what adaptive charging does which is why the idea doesn't (and can't ever) work.

[blueprince]

Oh, goodie ,goodie, gibbo,

 

You know I had a lot more to say before I had a poke at gibbo, Erm, batteries are flat ionic exchange plates, you need an electrolyte, preferebly an infinite amounte, charging is dependant on a whole load of stuff, voulume and area, oh sorry, I'm a bit too pissed for this. You're wrong gibbo, a multiple bank in a low amp charging situation is better than a big one. I'm having probelms typing this, so I'll argue with you later, or preffin person, ammeteres at dawn!

[nb Innisfree]

You KEEP missing the pertinent point.

 

If the alternator is not spinning fast enough then, as far as the batteries are concerned, that is exactly the same as having a smaller alternator. The batteries will be in bulk charge (current is limited by the charge source) and the voltage will be less than the acceptance voltage.

 

I'm confused why you're having a hard time understanding this.

 

 

 

Spot on. Likewise if you have an enormous alternator that will instantly get the batteries up to acceptance voltage as soon as it starts spinning then the required acceptance time will be very long. A simple graph can be drawn between these two extremes.

 

Note that this is exactly the opposite of what adaptive charging does which is why the idea doesn't (and can't ever) work.

 

Is that shorter bulk charge actually totally cancelled out or is it still an advantage to have a quick bulk charge (assuming of course it doesn't exceed the 1 amp per 1 percent rule)

[Gibbo]

Oh, goodie ,goodie, gibbo,

 

You know I had a lot more to say before I had a poke at gibbo, Erm, batteries are flat ionic exchange plates, you need an electrolyte, preferebly an infinite amounte, charging is dependant on a whole load of stuff, voulume and area, oh sorry, I'm a bit too pissed for this. You're wrong gibbo, a multiple bank in a low amp charging situation is better than a big one. I'm having probelms typing this, so I'll argue with you later, or preffin person, ammeteres at dawn!

 

Edited because I can't be bothered arguing with someone ill-equipped to fight back.

 

Is that shorter bulk charge actually totally cancelled out or is it still an advantage to have a quick bulk charge (assuming of course it doesn't exceed the 1 amp per 1 percent rule)

 

No it's not cancelled out. The full charge will still be quicker (but not as much as some would believe).

 

But the point is that with adaptive charging it will cut short the acceptance cycle (regardless of the remaining charge current) because the bulk stage was completed quickly. That's what adaptive charging does.

Edited November 30, 2010 by Gibbo

[nb Innisfree]

 

No it's not cancelled out. The full charge will still be quicker (but not as much as some would believe).

 

But the point is that with adaptive charging it will cut short the acceptance cycle (regardless of the remaining charge current) because the bulk stage was completed quickly. That's what adaptive charging does.

 

Cheers

Edited November 30, 2010 by nb Innisfree

[Robin2]

Robin2, on 30 November 2010 - 05:23 PM, said:

But bear in mind that the alternator will not produce its full output if it is not running fast enough regardless of how much the battery could take.

 

 

You KEEP missing the pertinent point.

 

If the alternator is not spinning fast enough then, as far as the batteries are concerned, that is exactly the same as having a smaller alternator. The batteries will be in bulk charge (current is limited by the charge source) and the voltage will be less than the acceptance voltage.

 

I'm confused why you're having a hard time understanding this.

 

 

 

I don't know where you got the idea that I keep missing the point. A - this was the first and only time I made this comment and B I was trying to be helpful in relation to an earlier post by someone else who, I thought, may have been wondering why his battery was not taking all the output from his 75A alternator in the bulk charge phase. You (correctly) said that the battery would not be in the bulk charge phase but your answer assumed the alternator was giving full power which might not have been the case. So back off!

[Gibbo]

I don't know where you got the idea that I keep missing the point. A - this was the first and only time I made this comment and B I was trying to be helpful in relation to an earlier post by someone else who, I thought, may have been wondering why his battery was not taking all the output from his 75A alternator in the bulk charge phase. You (correctly) said that the battery would not be in the bulk charge phase but your answer assumed the alternator was giving full power which might not have been the case. So back off!

 

Your post was in response to mine. It quoted my post.

[WotEver]

Fit that analogy to all the ways you can abuse a battery, and a super-useful meme has been born.

How's this then? I'm stretching the original analogy somewhat here, because my 'addition' isn't actually true to the process, whereas the original description was. However the results are similar even if the process isn't.

 

The water feeding the tank flows through a dirty tube. That's where the muck comes from that gradually fills the bottom of the tank. If it flows gently then it doesn't disturb too much muck, so the tank will retain a good capacity for a long time. If you draw loads of water from the tank on a regular basis so that the filler is really gushing then you'll pass loads more muck into the tank, and its capacity will be reduced far quicker.

 

Where this falls down as an analogy is that sulphation and shedding have nothing to do with the charge source in reality, so maybe I should have left the original analogy alone - I don't want to murky the waters.

 

Tony

 

And provided that the head of water or pressure (voltage) is higher than that in the tank it will eventually fill up.

And if you raise the head far higher than normal on occasion, it will pass by the valve and increase the tank's capacity a little (equalisation charge).

 

Tony

[nb Innisfree]

How's this then? I'm stretching the original analogy somewhat here, because my 'addition' isn't actually true to the process, whereas the original description was. However the results are similar even if the process isn't.

 

The water feeding the tank flows through a dirty tube. That's where the muck comes from that gradually fills the bottom of the tank. If it flows gently then it doesn't disturb too much muck, so the tank will retain a good capacity for a long time. If you draw loads of water from the tank on a regular basis so that the filler is really gushing then you'll pass loads more muck into the tank, and its capacity will be reduced far quicker.

 

Where this falls down as an analogy is that sulphation and shedding have nothing to do with the charge source in reality, so maybe I should have left the original analogy alone - I don't want to murky the waters.

 

Tony

 

 

And if you raise the head far higher than normal on occasion, it will pass by the valve and increase the tank's capacity a little (equalisation charge).

Tony

 

Yes, by stirring up the surface of the sediment and thereby making it more liquid allowing more water/electricity in - not strictly true as the sediment is still there in suspension so this needs to be ignored i.e. think of the sediment as solid, but liquid whether clear or cloudy as electricity.

 

Much more interesting than electricity as electrons and stuff

[WotEver]

Much more interesting than electricity as electrons and stuff

"Charging for Dummies" I can see the book on the shelf now

[Robin2]

"Charging for Dummies" I can see the book on the shelf now

 

You'll need a different title. The legal profession already has that one

[WotEver]

... the sediment is still there in suspension...

I told you I was muddying the waters

[Gibbo]

I told you I was muddying the waters

 

Robert Johnson was much better.

[Robin2]

I have been digesting all the information I have gleaned from this thread and elsewhere and I have a question for the experts.

 

It seems that no matter what size of battery (within reason) I have there will be a substantial number of hours when the alternator is charging the battery but the battery cannot accept all of the alternator's output. In effect there is energy going to waste because the engine would use virtually the same amount of fuel to produce more amps.

 

My question is:

 

How can I usefully store that "waste" energy and get value from it?

[ymu]

I have been digesting all the information I have gleaned from this thread and elsewhere and I have a question for the experts.

 

It seems that no matter what size of battery (within reason) I have there will be a substantial number of hours when the alternator is charging the battery but the battery cannot accept all of the alternator's output. In effect there is energy going to waste because the engine would use virtually the same amount of fuel to produce more amps.

 

My question is:

 

How can I usefully store that "waste" energy and get value from it?

Use a generator for absorption charging. It won't be doing any more work than it needs to (thanks, I think, to Innisfree, for pointing this out to me).

[Chris Pink]

 

 

How can I usefully store that "waste" energy and get value from it?

 

How about "charge another battery bank"?

[WotEver]

Robert Johnson was much better.

Oh, good old McKinley Morganfield... yes he was

[Tony Brooks]

Use a generator for absorption charging. It won't be doing any more work than it needs to (thanks, I think, to Innisfree, for pointing this out to me).

 

 

Absolutely - 746 watts in 1 hp multiplied by some horrible inefficiency in the alternator so say you were absorption charging with an alternator (say) 30% efficient. (if I can still do % calculations )

@20 amps = 20 x 14.4 (say) / 30 * 100 = 960 watts = 1.3 hp

@10 amps = 10 x 14.4 /30 * 100 = 480 watts = 0.64 hp

 

The load on the engine will try to slow the engine down or allow it to speed up but the governor in the fuel pump will increase/decrease the fuel to ensure that whatever the load the revs remain fairly constant after allowing for inertia in the governor assembly. (Except on my VW 3 pot diesel car with electronic control this does not seem to hold true!)

 

The engine will work no harder than it needs to but it will still be overcoming its own internal friction so on low loads it may well be less efficient than at higher loads. This is why I advise that you set your charging revs to the point where an ammeter no longer rises with revs AND you keep on checking and adjusting the revs down as the current falls.

 

You could always use the wasted energy (which there always will be) in heating you domestic water or radiators, but that is heat that is wasted in stopping the engine melting, not the charging.

 

At the risk of starting another highly technical thread how about arranging a load of thermo-couple things in the exhaust to generate electricity to heat the immersion

[Robin2]

Use a generator for absorption charging. It won't be doing any more work than it needs to (thanks, I think, to Innisfree, for pointing this out to me).

 

I suspect the generator would cost more than the fuel it saves.

 

How about "charge another battery bank"?

 

Did you not notice earlier in this thread how I was blown out of the water for suggesting that

[nb Innisfree]

Use a generator for absorption charging. It won't be doing any more work than it needs to (thanks, I think, to Innisfree, for pointing this out to me).

 

Our main diesel engine uses approx just under 1 lph at tickover when charging at about 44amps @24v, our petrol 2kva digital genny uses the same amount at rated output of 1600watts which equals 44amps charge but consumption drops to about a quarter of this when at or near 100% SoC. So for us the break even point is at 44amps charge rate but as diesel is cheaper it pays to stay on main engine for a while longer.

[Chris Pink]

I suspect the generator would cost more than the fuel it saves.

 

 

 

Did you not notice earlier in this thread how I was blown out of the water for suggesting that

 

That, if I read it right, is because you are what they call the 'OP' and didn't say that you had another device, alternator, battery charger with which to charge another bank. The main thrust of the argument against is that you can't do it with one alternator without isolating the sensing to each bank. But with 2 battery chargers you can have one bank in bulk and one in absorbtion, though the argument Gibbo ventures above about leaving the bank in absorption less than fully charged will shorten battery life means that the maths of the economics is still not simple.

[Gibbo]

That, if I read it right, is because you are what they call the 'OP' and didn't say that you had another device, alternator, battery charger with which to charge another bank. The main thrust of the argument against is that you can't do it with one alternator without isolating the sensing to each bank. But with 2 battery chargers you can have one bank in bulk and one in absorbtion.....

 

Absolutely.

 

I thought about this earlier.

 

A device would be possible to allow this to happen with a single alternator by having the alternator feeding directly into the batteries in acceptance, then, using a switching controller to feed the balance of the spare power to the other battery (the one that should be in bulk) at the maximum possible without dragging down the voltage of the battery in acceptance. This is a perfectly feasable electronic device. The problem is, I just don't see a market for it. And it wouldn't be a cheap device.

 

"Of course!", I thought, it can be done with two alternators, but then I realsed that one of the alternators would be running at less than maximum all the time and people would want to use that available power. Which puts one back to square one of not using all the available alternator power, just with different numbers.

[ymu]

Why wouldn't there be a market for it? It looks like it would save over a third on diesel costs compared to doubling the size of a single battery bank. We spend £1800/year on diesel. It'd have to be pretty expensive not to pay for itself pretty quickly, at least for liveaboards who aren't able to rely on shoreline most of the time.

[Nickhlx]

Why not cut out all the "thermocouples and high-tech electrickery" needed to covert hot waste exhaust gases into electricity, and plumb them through another calorifier coil ?

 

Nick