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Old 10-04-2012, 19:22   #46
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His statement is partially true, but only up to the point that the battery reaches its absorption voltage. This voltage is set by the controller, maybe 14.1 for gels, 14.8 for open lead acid. Up to the absorption voltage the current is constant as the battery voltage rises - controlled by the charge acceptance of the battery. At this point the battery stays at this voltage and the charge acceptance of the battery then determines the rate of the falling charge current. After a set time and or current and or other parameters programmed in by the engineer that designed the system, the controller switches to a much lower float voltage.
Most people don't understand how voltage or current sources work, most people don't actually understand how negative feedback regulation works. Most don't understand how a smart charger works.

How could they no manufacturer provides a proper description of what actually happens. So people trot out manufacturers descriptions as if it's the actual science.

Have any of you actually logged on a data logger the actual current and voltage waveforms of a typical LA charge cycle. Have you compared them with the silly stylised IUI drawings that get published by manufacturers.

The terminal voltage of a battery is a function of the division of impedances between the charging sources and the battery. If you draw out a simple equivalent circuit of a battery under charge and power it with a simple imperfect voltage source you'll see what I mean. In fact put the who,e thing into spice and model it.

Yes I find it hard to use words to describe technical things normally I would use drawings and formulae

Let's consider the charging cycle. There is a bulk mode and an absorption mode. ( float mode is somewhat of a construction) there is no abrupt transition between the two modes.

In bulk mode the input impedance of the battery is so low compared to the charging sources that they cannot set the terminal voltage ( look up potential divider circuits) the battery is basically the sole arbiter.

So in bulk mode the charging circuit is faced with a virtual short circuit. It runs as a constant current source. Ie the voltage is determined by the circuit characteristics . It typically uses a current foldbsck to do this.

As the SOC rises an LA battery rases it voltage , the equivalence is it impedance rises. Hence the terminal voltage will rise. Now LA has an unfortunate characteristic that it will Subject to enough power boil its own juices. So a charger manufacturer ensures that the charger regulates the voltage in absorption. This is do e by in essence throttling the current so that the voltage doesn't rise. Ie the charger various it's output impedance to slowly disconnect itself from the circuit as the change cycle finishes.

Yes it's true that some chargers use several "tricks" to determine when the battery is full , many don't they just ensure the voltage doesn't rise too high and eventually the battery stops accepting current. ,

Float mode is merely in effect increasing the output impedance of the charger to allow the battery voltage to settle down at a lower voltage. It's the battery that's lowering the voltage not the charger. ( think about it , no charger is a current sink, it cannot "force" the voltage into float mode. La batteries float when you remove loads from them.

This is where the English gets twisted people talk about the " charger switching to a lower voltage" even EEs use these types of terminology of course wer,e supposed to know what actually happens.. The charger can't " switch to anything" it's a function of battery chemistry what happens. Few chargers are much smarter that that , some use charge current as an indication. Some run a coarse timer some do nothing.


So of you consider multiple charge sources. ( and I specifically exclude bang bang solar regulators. As they are a different technology that takes advantage of the PV constant current idea) they don't interact per say. If the battery needs to stay in absorption mode ( because current is flowing into it) then one of the sources will oblige. The other sources for example can't enforce float mode ( again no current sink) all that happens is the non active sources are in effect high resistance.

As I said one or more sources will contribute it just you cant tell in advance what one. But it will not stop your battery from being charged.

As to manufacturers recommended views , well they have to take the view that on a typical self install product all their customers are technical idiots and that's because most are. They don't want or can't explain the technical issues so they make blanket statements.

The practice is in the eating I've regularly run multiple sources ( two alternators , a big smart charger and before a wind Jenny ) all worked fine together. By fine I mean they didn't explode. It's was just that with the characteristics of the wind unit it tended to want to finish the batteries. So you could wasted running time turning over charge sites that didn't do anything.

I'm sorry if the words are convoluted. Yes there maybe some controllers that do strange things , but in general they all o eh the laws of electrical circuits.

For example one of the stupid things I've seen is delayed switching from float to absorption. Some battery chargers will not return to absorption mode from float unless they go back go bulk mode first. This means that say a wind gen can cause a funny situation where in a gust it takes over absorption mode and then after the gust the other charger will not reengage until it sees bulk level voltages. This is not interfering. It's more the consequence of a particular design feature. The charging sources can still all remain connected. Wind generation in my view is not well suited to finishing a battery absorption mode

Dave

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Old 10-04-2012, 19:29   #47
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Re: Wind Gen Excess to Where?

To my batteries PLS!

;-)
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Old 11-04-2012, 00:35   #48
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Re: Wind Gen Excess to Where?

Quote:
Originally Posted by goboatingnow View Post

This is where the English gets twisted people talk about the " charger switching to a lower voltage" even EEs use these types of terminology of course wer,e supposed to know what actually happens.. The charger can't " switch to anything" it's a function of battery chemistry what happens.

F
There have been a few posts about this. I don't see anything technically wrong with saying the charger controls ( or switches) to the float voltage. It's much easier to understand that way.
I can press a few buttons on the charger and change the float voltage. There is nothing I can change on the battery that will change the float voltage. Even if I substitute a different battery, with different chemistry, the float voltage will remain at the level set by the charger, providing it can supply enough current to stay on the float cycle.
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Old 11-04-2012, 01:22   #49
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Re: Wind Gen Excess to Where?

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Originally Posted by goboatingnow View Post
Most people don't understand how voltage or current sources work, most people don't actually understand how negative feedback regulation works. Most don't understand how a smart charger works ......................

Dave
Please stop your ranting - you are spoiling this thread!

You've described in 897 words what I described in 110 - and 800 of your words are incomprehensibable to most of us - that's my engineers spelling. Next you'll be posting in CAPITALS so that we can all hear.

We don't care how the chargers work - the fact is that a charger sits at its pre-determined float voltage despite the impedance of the battery, or which battery is connected. An AGM has a very different impedance to a wet lead acid battery, so there must be another mechanism within the charger to control voltage. If there is I ain't bovvered, probably none of us are bovvered - so please don't try and confuse us anymore.
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Old 11-04-2012, 02:43   #50
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Re: Wind Gen Excess to Where?

Exclude me from the "we" please. I have learned a lot from the posts, and appreciate the time people have taken to write in detail.
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Old 11-04-2012, 06:28   #51
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Re: Wind Gen Excess to Where?

Have to agree with gscriba's post above regarding the "Royal We".

I'm going through the research process (total novice) at the moment and I know the following question shows my ignorance on the subject but I would like to know if there is such a thing as a sequential charge controller that will allow inputs from solar and wind and then distribute the power in sequence to different battery banks then to the water heater mentioned above.

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Old 11-04-2012, 08:14   #52
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Re: Wind Gen Excess to Where?

To gsrciba and Ancient Marina and others:

Sorry for the "Royal We" in my posting. I did go back to "I" later in the para.

I'm sure goboatingnow has contributed many good ideas in his 3,768 postings, but this thread is not one of them. He keeps trying to make the same point, and then contradicts himself:

" So a charger manufacturer ensures that the charger regulates the voltage in absorption."

This is exactly what I, and others say is happening - how it does it is not important, yet all of his other posting say it's the battery that controls the voltage.

If you are new to all this "electrickery" then you don't need postings that will confuse you.



You've got to admire his signature at the bottom:

"logic" - A way of going wrong with confidence.

So I'll add mine:

Ignorance isn't what you don't know, but what you think you know that isn't true.
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Old 11-04-2012, 20:57   #53
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Re: Wind Gen Excess to Where?

Let go of the hostility gentlemen. You don't need to prove to everyone that you know more or best. I benefit from everyone's posts; long and short. A good debate over technical issues is helpful and interesting, and sometimes writing things in a different way does clarify.

Thanks.
Your mother.
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Old 11-04-2012, 21:15   #54
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Re: Wind Gen Excess to Where?

Agree with Mother - less hostility is better.

Dave, "goboatingnow", makes a good point about the battery voltage, although it may be more nuanced than necessary. The voltage is a result of the state-of-charge of the battery and the net current through the battery (both instantaneous and historical). However, that current is limited by the regulator in absorption and float modes to achieve the desired voltage. Properly speaking the voltage is a function of both the battery and the regulator.

Edit: And, of course, it is a function of the other loads and sources attached to the battery, but we are just talking about the battery and charger here for simplicity.
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Old 11-04-2012, 21:17   #55
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Originally Posted by sailinglegend
To gsrciba and Ancient Marina and others:

Sorry for the "Royal We" in my posting. I did go back to "I" later in the para.

I'm sure goboatingnow has contributed many good ideas in his 3,768 postings, but this thread is not one of them. He keeps trying to make the same point, and then contradicts himself:

" So a charger manufacturer ensures that the charger regulates the voltage in absorption."

This is exactly what I, and others say is happening - how it does it is not important, yet all of his other posting say it's the battery that controls the voltage.

If you are new to all this "electrickery" then you don't need postings that will confuse you.

You've got to admire his signature at the bottom:

"logic" - A way of going wrong with confidence.

So I'll add mine:

Ignorance isn't what you don't know, but what you think you know that isn't true.
I find it hard to handle personal denouncement. It's very unbecoming on a forum that prides itself on a "be nice" rule. or to count my posts over the years and throw them back at me.

As to my contradicting myself. I will refrain from pointing out that regulation is what happens. But the charger is not in series with the battery , it's in parallel. You might want to examine how such regulation works at a science level, and how a device that cannot sink current can "set" a voltage


Yes using just words its hard to describe the process. It's why textbooks use picture tables and graphs. But I understand if simplicity is more important them truth.

The fact is argue against me on the science is one thing., just telling me I'm wrong because you think so is hardly valid.

My point was trying to deal with the mis understandings about charging processes and how a charger interacts with a battery and also how multiple charge sources react.

If I'm confusing people I'm sorry that's not my intention. , but I will not be just shouted down.

Dave
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Old 11-04-2012, 21:36   #56
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Agree with Mother - less hostility is better.

Dave, "goboatingnow", makes a good point about the battery voltage, although it may be more nuanced than necessary. The voltage is a result of the state-of-charge of the battery and the net current through the battery (both instantaneous and historical). However, that current is limited by the regulator in absorption and float modes to achieve the desired voltage. Properly speaking the voltage is a function of both the battery and the regulator.
Yes that's close except chargers can't sink current, and since they are in parallel all the charger can do is vary its output current. It can decrease its current and LA batteries then float down to a steady state. Or it can increase its current and assuming its not forced into constant current mode the output voltage will rise. But depending on the SOC and the relative input and output impedances, the battery dominates for the most part the terminal voltage ( its simply a better voltage source then the charger)

Take for example this case. The battery is in float mode ( as some would see it by the charger). Lets say for argument thats 13.5v The charger is supposed to be regulating the voltage. , say I connect a powerful voltage source of 14v to that battery. Does the charger " regulate" the voltage back to 13.5v ( as that is the definition of regulation) no it doesn't , why because it can't. It has no electrical mechanism ( no current path) to do so. All it does is in effect reduce its current to zero in an attempt to get the battery to return to float. At zero current , it has an effective infinite output impedance. So what's happened, all it's done is disconnect itself. To effect proper regulation in a parallel circuit , in that case the charger would have to "load " the battery and the other voltage source to try and actively pull the output voltage down. That would require massive current sink ability. This effective disconnect of the charge source is why you can have many charge sources. (with provisos) if the charge sources in a parallel circuit had current sink ability ( ie true regulation ) you couldn't connect multiple chargers as each would seek to regulate the output of the other.

So who is in charge of the terminal voltage , why the strongest voltage source. ( in simplistic terms) or perhaps a better approximation. Is the battery and the charger, but only so long as the battery allows it to be. ( the you're in charge until i decide otherwise type of managemt control)

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Old 11-04-2012, 22:33   #57
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Re: Wind Gen Excess to Where?

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Yes that's close except chargers can't sink current...
I believe what I wrote is precisely correct. I never mentioned the charger sinking current from the battery because that is not needed in this application. (The charging current is another matter: it is either shunted to a sink or interrupted.) The current sink is not required for the battery because the voltage will always drop when the charging current is removed - down to approx. 12.5V once the electrolyte reaches equilibrium. And no harm is done to the battery as the voltage drops through the range of 14.2V to 13.5V. Thus stable regulation is accomplished without a sink.

Personally, without going back and trying to nit-pick your posts, I see no problem with your accuracy. But sometimes your attempts to get things precisely correct are more confusing than enlightening. Your discussion, including the current sink and the 'stiffness" of the voltage source, is appropriate for a discussion of generalized regulator design with electronics techs and engineers, but less so a group of cruisers.
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Old 12-04-2012, 06:32   #58
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Re: Wind Gen Excess to Where?

I just appreciate that members take the time and effort to educate the like of me.
Not a matter of who is right or wrong, but gives us an inkling on how all the electrickery works, and points me in the right direction to do more research, and more importantly, will let me ask the right questions when I come to hand over my hard earned cash to the likes of Blue Sky
Cheers and thanks
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Old 12-04-2012, 07:13   #59
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Re: Wind Gen Excess to Where?

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Originally Posted by Ancient.Mariner View Post
Have to agree with gscriba's post above regarding the "Royal We".

I'm going through the research process (total novice) at the moment and I know the following question shows my ignorance on the subject but I would like to know if there is such a thing as a sequential charge controller that will allow inputs from solar and wind and then distribute the power in sequence to different battery banks then to the water heater mentioned above.

Bill
I would have to go back through my research but i believe Blue Sky or Outback had one.Dont remember whitch it was.I do remember i decided against it because it was not a ...guess sealed unit is what i'm thinking of....have to put it in a perfectly dry place.That and stepping down 24v to 12v so wanted dual chargers so i have some charge capacity when one goes down.
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Old 12-04-2012, 07:48   #60
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Re: Wind Gen Excess to Where?

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I would have to go back through my research but i believe Blue Sky or Outback had one.Dont remember whitch it was.I do remember i decided against it because it was not a ...guess sealed unit is what i'm thinking of....have to put it in a perfectly dry place.That and stepping down 24v to 12v so wanted dual chargers so i have some charge capacity when one goes down.
Mark
I'm 99% sure I'll be purchasing the Blue Sky 3024DiL. It's an MPPT controller for the solar, but from what I can see, it does quite control wind, but will divert it when it senses the battery is near charged. Has a diversion function, but you will also need a means to dump the excess power from the wind geny.
There are some issues regarding float charge when if using the divert function, Blue Sky recommend that the float charge facility is disabled if the wind geny is connected. Their manuals available online explain the issues
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