Jump to content

Advice on installing an inverter


brich

Featured Posts

The reality is that alternator controllers did indeed make a huge difference when most alternators charged at 13.8 volts. This was a common charge voltage for many, many years.

 

Gibbo - I've read your comments on alternator regulators with interest and I have to say that it is difficult to see a flaw in your argument. I'm sure it won't stop others from trying to find one, however. :lol:

 

I've got a (much vilified!) Kestrel controller, which I was going to replace. I've changed my mind now. I've adjusted it down to 14.4 volts cutoff from the factory setting of (from memory) 15.5 volts that tended to fry 12V equipment, and it works fine. My current thinking is that if it (or the alternator) ever packed up I'd replace the alternator with a modern one and throw the Kestrel away.

 

Having said that, is there any merit in the controllers that claim to emulate a four-stage charger?

Link to comment
Share on other sites

Having said that, is there any merit in the controllers that claim to emulate a four-stage charger?

 

This will cause yet more arguments discussions as a result of people believing marketing bullsh*t hype.

 

A normal alternator is already 2 stage. The first stage is the bulk stage ie current limited, this is limited by the rating of the alternator. The next stage is acceptance ie voltage limited, this is set by the regulator.

 

The 3rd stage is float. This isn't really required on an engine driven alternator unless the engine is run for 10s of hours (or even days) at a time.

 

The so called 4th stage is used to mean different things depending upon which manufacturer you ask. Some say it is a manually triggerable equalisation/desulfation cycle (very rare). Others use it to describe an automatic desulfation cycle (a bit more common but still quite rare). Yet others use it to describe a second lower float voltage. This can be useful on mains powered chargers but completely pointless on an engine driven charge source. And finally some use it to describe (as they do with mains powered chargers) what some call "power pack mode" ie where the charger supplies the loads directly. This really is nothing more than marketing speak to describe something that a normal alternator/charger does anyway.

 

So what is a four stage charger?

 

Gibbo

 

Edit: It appears to me that I could bring out a 10 stage charger with each stage being nothing more than marketing speak for something that the existing ones already do and a certain band of naive people would buy it being totally convinced that it is better than a 3 stage charger.

 

Let's try it:-

 

Stage 1 = Bulk

Stage 2 = Acceptance

Stage 3 = Acceptance on a tuesday

Stage 4 = Acceptance on a wednesday

Stage 5 = Float

Stage 6 = Float when it's raining

Stage 7 = Float when it's snowing....

 

Etc. You get my drift. It sounds flippant, but it's really no sillier that "Power pack mode"

Edited by Gibbo
Link to comment
Share on other sites

This will cause yet more arguments discussions as a result of people believing marketing bullsh*t hype.

Where's the "innocent expression" smiley when you need it?

So what is a four stage charger?

 

I was hoping you were going to tell me....

 

Seriously - very interesting, thanks for sharing your thoughts.

 

P

Link to comment
Share on other sites

I wonder if I fitted gas mantles, a gas fridge, gas water heating and get a soss stick I can chuck all this electrical rubbish out except for the starter battery ...

 

What sort of mantles are you considering, Clamond baskets or Welsbach?

 

Richard

 

It's the thorium dioxide that makes the difference...

Edited by RLWP
Link to comment
Share on other sites

Clamond Baskets haven't been used for years, have they?

 

Ummm. I was making a humorous comment with the intention to illustrate that eventually any technology becomes sophisticated and attracts experts who may cause differences of opinion to become disputatious.

 

Richard

 

I'll bet it got really tedious around the fire of an evening when the advocates of bronze and flint spearheads got going...

Edited by RLWP
Link to comment
Share on other sites

Brian

 

At risk of confusing things even more, don't forget the amount of current inverters will pull on the 12v side - a 1500W inverter will translate to 125A at 12v, which means pretty beefy cables.

 

If I was wanting to run an inverter that size, I would be tempted to keep the existing 12v setup to feed the lights, pumps etc and fit a second (24v) alternator and battery bank to run the higher power stuff (fridge, inverter). That way you'll halve the current that the higher power devices are using which means smaller (and hence cheaper) cables and probably less trouble with volt-drop.

 

Peter

Link to comment
Share on other sites

Brian

 

At risk of confusing things even more, don't forget the amount of current inverters will pull on the 12v side - a 1500W inverter will translate to 125A at 12v, which means pretty beefy cables.

 

If I was wanting to run an inverter that size, I would be tempted to keep the existing 12v setup to feed the lights, pumps etc and fit a second (24v) alternator and battery bank to run the higher power stuff (fridge, inverter). That way you'll halve the current that the higher power devices are using which means smaller (and hence cheaper) cables and probably less trouble with volt-drop.

 

Peter

 

Hmmmmmm, I can see the logic but:-

 

Fit some thick cables...

 

OR

 

Find somewhere on engine to fit new alternator, make up some new brackets, source and fit a new alternator, find somewhere to fit a new pulley on the engine, find suitable alternator belt, source new 24 volt battery bank, source and install new 24 volt mains powered charger, rewire almost entire system, install new battery isolator. Cables will be a bit thinner thus saving maybe a tenner. I suppose it sort of helps towards the 500 to 1000 quid just spent on the other stuff.

 

I think I'd prefer thick cables.

 

Gibbo

Link to comment
Share on other sites

This ideal charging voltage roughly ties in with what became known as "amp hour law" charging (first proposed by amplepower IIRC) which states that the amount of current that can be returned to the battery at any one time is equal to the number of amp hours missing from the battery. So a 100Ahr battery, completely flat can be charged at 100 Amps. After a short time that battery will now be at 1% SoC, so 99Ahrs are missing. It can now be charged at 99amps, and so on and so on. This, by sheer coincidence, ties in almost exactly with charging at the changing gassing voltage.

 

Gibbo

If this is correct then a 14.8v charge (on wet cells) must be better than a 14.4v charge. Once the battery reaches the regulator voltage. the only parameter controlling the amount of current pushed into the batteries is the regulator voltage irrespective of whether it is the alternator's own regulator or an alternator controller. So the higher the regulator voltage the greater the charge current.

 

When my 405AH bank is down after an overnight mooring (usually about 100AH down) the most that I can push in is initially limited by the battery's terminal voltage and not the charging voltage. I can now get about 100A into the bank with the alternator's paralleled, but that drops as the battery terminal voltage rises.

 

As the alternator controller takes over and allows the battery terminal voltage to rise to 14.8v, I get 50A of charge current which, according to your rule, is ideal as the bank is then about 50AH down.

 

This current then drops off very much in line with your AH rule.

 

If I charged at 14.2v the current would be way below that rule by almost 50% at the start of acceptance and still significantly low (compared to your rule) throughout the majority of the whole acceptance cycle.

 

Chris

Edited by chris w
Link to comment
Share on other sites

If this is correct then a 14.8v charge (on wet cells) must be better than a 14.4v charge. Once the battery reaches the regulator voltage. the only parameter controlling the amount of current pushed into the batteries is the regulator voltage irrespective of whether it is the alternator's own regulator or an alternator controller. So the higher the regulator voltage the greater the charge current.

 

When my 405AH bank is down after an overnight mooring (usually about 100AH down) the most that I can push in is initially limited by the battery's terminal voltage and not the charging voltage. I can now get about 100A into the bank with the alternator's paralleled, but that drops as the battery terminal voltage rises.

 

As the alternator controller takes over and allows the battery terminal voltage to rise to 14.8v, I get 50A of charge current which, according to your rule, is ideal as the bank is then about 50AH down.

 

This current then drops off very much in line with your AH rule.

 

If I charged at 14.2v the current would be way below that rule by almost 50% at the start of acceptance and still significantly low (compared to your rule) throughout the majority of the whole acceptance cycle.

 

Chris

 

You've made the same mistake that you keep making. You make it over and over again. No matter how many times you are told otherwise, you continue to make the same mistake.

 

1. The measured current going into the battery is not the same as the current that is actually charging the battery. To you they are clearly one and the same. That is totally incorrect.

 

2. If you reduce the charge voltage down to the gassing voltage the charge current will increase. It takes somewhere between about nothing and 20 minutes for this to happen depending upon the type and condition of the batteries. It is a test that you simply cannot do on a boat because you have to run the exact same tests under controlled conditions and compare the results from one test to the other.

 

How long is it going to take for this to sink in?

 

I suspect it is simply never going to happen.

 

If your batteries are 50Ahrs down from 405Ahrs then the gassing voltage will be much lower than 14.8 volts. Probably closer to 14.0 volts. That being the case, then at that stage, charging at 14.0 volts will (not might) result in a faster recharge. I'm not guessing at this, and you simply do not have the experience or equipment to test it. You might have some great maths, but as you recently found out, if you base it on incorrect assumptions you get incorrect answers.

 

The first time I saw this effect (about 20 years ago) I thought I was seeing things. A large charger accidentally set to equalise (at 16.5 volts) connected to a semi flat battery. The voltage and current were being logged. As the voltage rose the current increased. When it got to about 14.5 volts the increase in current slowed down. By the time it reached 15.0 volts the current was actually decreasing with increasing charge voltage. Reducing the charge voltage saw an increase in current. That's what prompted the research. That's what led to correspondence with several others who were working on amp hour law charging.

 

You have to remember that I have researched this subject for many years. I have worked with some of the leading experts in the field. I still correspond regularly with current researchers in the field. You have played with a few batteries and a PDAR on your boat. There is simply no comparison.

 

And I now officially give in. There is absolutely no point in debating this subject with you any longer.

 

Gibbo

Link to comment
Share on other sites

If you are correct then your "ampere-hour" rule can't apply in practice. The current from most practical alternator installations will be way below that required to fulfill that rule at 14.2v. You can't have it both ways.

 

Further, if a battery is 100AH down in charge, it will require more than 100AH (maybe as much as 140AH) to recharge it, due to battery inefficiencies. So should one charge at 100A or 140A?

 

Chris

Link to comment
Share on other sites

Sorry, I copied the detail of the RoadPro website spec where it said the average hourly consumption was 19W (1.6A at 12V) and forgot to put the H afterwards.

 

I'm sorry I asked about the alternator controller - didn't mean to stir up an argument!

 

Brian

 

Don't worry about it. Just sit back and enjoy the battle. Read all the posts and try to understand the science behind what they are saying. You will learn a lot about the art of battery charging.

 

Nick

 

 

May I just, very tentatively, see if I have got it right. This is my interpretation of what Gibbo says:

 

Charging above the gassing point is not much use because the extra energy that goes into the battery is not providing useful storage. It is dissociating the hydrogen and oxygen which are then lost to the atmosphere.

 

Have I got it approximately right?

 

Nick

Edited by Theo
speeling
Link to comment
Share on other sites

I know I said I'd given in but I'll just answer these points. Trust me Chris, if, instead of saying to yourself "that can't be right because I've never heard of it before" (do a bit more research and you will hear of it), try saying to yourself "I wonder if this is indeed correct, I'll run some maths on it" and you will finally accept it. Quite simply because it is reality.

 

If you are correct then your "ampere-hour" rule can't apply in practice. The current from most practical alternator installations will be way below that required to fulfill that rule at 14.2v. You can't have it both ways.

 

That isn't relevant. The fact that the alternator cannot pump in the maximum current that the batteries can accept doesn't alter anything. We pump in what we have available. We can't put any more in whatever method we try to use. Where the rule comes into play is where we apply the regulation voltage ie where the batteries have reached a state of charge so that the charge source does have sufficient to meet the rule (prior to this stage it makes no difference what rule we try to apply - the charge is limited and stuck at the maximum current of the alternator/charger - it will always be this charge current - it can't be anything else). Once this stage is reached, if the regulation voltage is too high then the maximum charge current isn't being applied. Ditto too low. The ideal is to adjust the charge voltage throughout the charge cycle to match the changing gassing voltage of the batteries. That just happens to roughly coincide with the "amp hour law" charging idea.

 

Remember, we can only pump what is available. That is the maximum we have. But if the charge source has the ability to put in more than is required then that actually results in a reduced charge rate not an increased charge rate because it will simply raise the battery voltage above the gassing voltage.

 

Further, if a battery is 100AH down in charge, it will require more than 100AH (maybe as much as 140AH) to recharge it, due to battery inefficiencies. So should one charge at 100A or 140A?

 

This might be partly where you're going wrong.

 

I've told you about this before aswell but you clearly didn't accept it (or even hear it).

 

What causes the charge efficiency to be lower than 100%? There are many factors including breaking and making nuclear bonds, battery internal resistance wasting power etc. But the biggest single contributor is wasted energy from splitting the electrolyte in hydrogen and oxygen. If this is avoided (ie by not going above the gassing voltage) then a huge part of the inefficiency is avoided. The result being that by charging at, or just very slightly below, the gassing voltage, the charge efficiency can actually approach 100%. I said "approach", not "be".

 

So if the battery is 100Ahrs down and we are charging according to this rule we might have to actually put back in (say) 105Ahrs.

 

Remember, it is precisely the process of charging above the gassing voltage that is almost solely responsible for the apparent low charge efficiency.

 

Now in post #60 you wrote:-

 

As the alternator controller takes over and allows the battery terminal voltage to rise to 14.8v, I get 50A of charge current which, according to your rule, is ideal as the bank is then about 50AH down.

 

ie, when your alternator reaches acceptance (at 14.8 volts) your batteries are 50Ahrs down.

 

Yet in another post you wrote that when your alternator reaches acceptance your batteries were at about 80% SoC. Meaning they were 80Ahrs down.

 

So which is it? Are you misremembering things? Is it that you don't actually have a way of measruing the charge status and are therefore taking an educated guess? Or is it that you are just picking numbers out of the air to suit whichever argument you are having at the time?

 

The reason I ask is that a change from 50Ahrs to 80Ahrs is one hell of a difference and it therefore makes a huge difference to your argument above.

 

Gibbo

Link to comment
Share on other sites

Charging above the gassing point is not much use because the extra energy that goes into the battery is not providing useful storage. It is dissociating the hydrogen and oxygen which are then lost to the atmosphere.

 

Absolutely spot on.

 

And this has one major effect: Obviously it causes the electrolyte to bubble profusely. This (again obviously) fills the electrolyte with bubbles. This raises the bulk internal resistance of the battery quite dramatically (gas is quite an attrocious conductor) because the plates are covered in bubbles instead of electrolyte and therefore this high resistance path now replaces a large part of the low resistance path (ie directly between electrolyte and plates) that would otherwise exist at the interface. In effect the bubbles have been put in series with the battery internal resistance. This (obviously) reduces the actual charge current. So some people think "simple, wack the charge voltage even higher, that will force more current in". It doesn't, it increases bubbling even more and makes the internal resistance even higher!

 

Because of the (now) high internal resistance the current that is actually charging the battery (as opposed to the measured current into the battery - they are obviously not the same thing) is actually less than it would be by avoiding all that gassing. To clarify, one can actually increase the charge rate by reducing the charge voltage.

 

The problem Chris seems to be having is that he can't (or won't) accept that the gassing takes some considerable time to stop and start so simply reducing the charge voltage will result in an immediate decrease of (both measured and actual) charge current. So simply switching an external controller on and off and watching the immediate change in measured current is a naive and pointless excercise.

 

Taken to its extreme (as I showed in a previous post with a very large charger/battery size ratio) as the voltage is increased above the gassing voltage even the measured current into the battery drops, let alone the portion that is actually doing any useful charging.

 

Gibbo

Link to comment
Share on other sites

What causes the charge efficiency to be lower than 100%? There are many factors including breaking and making nuclear bonds, battery internal resistance wasting power etc.

 

Looks like Gibbo has sorted cold fusion! That should solve all our power problems :lol:

 

MP.

Link to comment
Share on other sites

Absolutely spot on.

 

And this has one major effect: Obviously it causes the electrolyte to bubble profusely. This (again obviously) fills the electrolyte with bubbles. This raises the bulk internal resistance of the battery quite dramatically (gas is quite an attrocious conductor) because the plates are covered in bubbles instead of electrolyte and therefore this high resistance path now replaces a large part of the low resistance path (ie directly between electrolyte and plates) that would otherwise exist at the interface. In effect the bubbles have been put in series with the battery internal resistance. This (obviously) reduces the actual charge current. So some people think "simple, wack the charge voltage even higher, that will force more current in". It doesn't, it increases bubbling even more and makes the internal resistance even higher!

 

Because of the (now) high internal resistance the current that is actually charging the battery (as opposed to the measured current into the battery - they are obviously not the same thing) is actually less than it would be by avoiding all that gassing. To clarify, one can actually increase the charge rate by reducing the charge voltage.

 

The problem Chris seems to be having is that he can't (or won't) accept that the gassing takes some considerable time to stop and start so simply reducing the charge voltage will result in an immediate decrease of (both measured and actual) charge current. So simply switching an external controller on and off and watching the immediate change in measured current is a naive and pointless excercise.

 

Taken to its extreme (as I showed in a previous post with a very large charger/battery size ratio) as the voltage is increased above the gassing voltage even the measured current into the battery drops, let alone the portion that is actually doing any useful charging.

 

Gibbo

Bubbles are by their nature discontinuous so that will mean that the battery plates are are covered with liitle spots of insulating gas. My reading of the situation is that there will be a very much more wear on the plates between the bubbles so the plates will pit and be damaged quite rapidly. This is no more than speculation on my part backed up by precisely no research.

 

N

Link to comment
Share on other sites

Absolutely spot on.

 

And this has one major effect: Obviously it causes the electrolyte to bubble profusely. This (again obviously) fills the electrolyte with bubbles. This raises the bulk internal resistance of the battery quite dramatically (gas is quite an attrocious conductor) because the plates are covered in bubbles instead of electrolyte and therefore this high resistance path now replaces a large part of the low resistance path (ie directly between electrolyte and plates) that would otherwise exist at the interface. In effect the bubbles have been put in series with the battery internal resistance. This (obviously) reduces the actual charge current. So some people think "simple, wack the charge voltage even higher, that will force more current in". It doesn't, it increases bubbling even more and makes the internal resistance even higher!

 

Because of the (now) high internal resistance the current that is actually charging the battery (as opposed to the measured current into the battery - they are obviously not the same thing) is actually less than it would be by avoiding all that gassing. To clarify, one can actually increase the charge rate by reducing the charge voltage.

 

The problem Chris seems to be having is that he can't (or won't) accept that the gassing takes some considerable time to stop and start so simply reducing the charge voltage will result in an immediate decrease of (both measured and actual) charge current. So simply switching an external controller on and off and watching the immediate change in measured current is a naive and pointless excercise.

 

Taken to its extreme (as I showed in a previous post with a very large charger/battery size ratio) as the voltage is increased above the gassing voltage even the measured current into the battery drops, let alone the portion that is actually doing any useful charging.

 

Gibbo

BATTERY BOILER.

Link to comment
Share on other sites

Absolutely spot on.

 

And this has one major effect: Obviously it causes the electrolyte to bubble profusely. This (again obviously) fills the electrolyte with bubbles. This raises the bulk internal resistance of the battery quite dramatically (gas is quite an attrocious conductor) because the plates are covered in bubbles instead of electrolyte and therefore this high resistance path now replaces a large part of the low resistance path (ie directly between electrolyte and plates) that would otherwise exist at the interface. In effect the bubbles have been put in series with the battery internal resistance. This (obviously) reduces the actual charge current. So some people think "simple, wack the charge voltage even higher, that will force more current in". It doesn't, it increases bubbling even more and makes the internal resistance even higher!

 

Because of the (now) high internal resistance the current that is actually charging the battery (as opposed to the measured current into the battery - they are obviously not the same thing) is actually less than it would be by avoiding all that gassing. To clarify, one can actually increase the charge rate by reducing the charge voltage.

 

The problem Chris seems to be having is that he can't (or won't) accept that the gassing takes some considerable time to stop and start so simply reducing the charge voltage will result in an immediate decrease of (both measured and actual) charge current. So simply switching an external controller on and off and watching the immediate change in measured current is a naive and pointless excercise.

 

Taken to its extreme (as I showed in a previous post with a very large charger/battery size ratio) as the voltage is increased above the gassing voltage even the measured current into the battery drops, let alone the portion that is actually doing any useful charging.

 

Gibbo

And, one would suppose, the waste of energy is even greater because pushing current against that resistance is going to do no more nor less than produce heat.

 

N

Link to comment
Share on other sites

Well Gibbo, if so much current is being lost owing to electrolysis, because you say I am beyond the gassing voltage of my wet cells, then where is all that electrolysed water going? It is extremely rare that I ever have to top up my batteries with water. I check them every two months but it's actually months and months before I need to add any water and even then it's only a small amount. A number of other forum members have experienced the identical situation in this regard using 14.8v external regs, and have expressed the same on similar threads.

 

Further, my increase in measured current owing to the increase in charging voltage follows a typical internal resistance curve from 14.2v (internal reg) to 14.8v (external reg) meaning that these apparent second-order effects are non-existent or negligible.

 

Yet I always charge at 14.8v. So, I shall not be changing my charging regime because my batteries charge beautifully, have great terminal voltages and SG's and use virtually no water.

 

Chris

Link to comment
Share on other sites

Well Gibbo, if so much current is being lost owing to electrolysis, because you say I am beyond the gassing voltage of my wet cells, then where is all that electrolysed water going?

 

Try to keep up at the back. We've done this one once (or 9 times). We've already been here.

 

It takes a ridiculous amount of energy to electrolyse just 1cc of water.

 

If it didn't then we would all be running hydrogen powered cars. It's called the conservation of energy.

 

Gibbo

Link to comment
Share on other sites

Heating anything from battery power is the closest thing to insanity that it is possible to get on a boat.

 

Apart from our beloved heated towel rail which we got on Ebay and is 240 volt / 36 watt.

 

Bob

Link to comment
Share on other sites

Try to keep up at the back. We've done this one once (or 9 times). We've already been here.

 

It takes a ridiculous amount of energy to electrolyse just 1cc of water.

 

If it didn't then we would all be running hydrogen powered cars. It's called the conservation of energy.

 

Gibbo

I would say that it is because it takes a ridiculous amount of energy that the energy density of hydrogen/oxygen makes such cars possible.

 

Nick

Edited by Theo
Link to comment
Share on other sites

Try to keep up at the back. We've done this one once (or 9 times). We've already been here.

 

It takes a ridiculous amount of energy to electrolyse just 1cc of water.

 

If it didn't then we would all be running hydrogen powered cars. It's called the conservation of energy.

 

Gibbo

"Conservation of energy" is a totally different principle to the one we were discussing earlier, and addresses the impossibility of "perpetual-motion" machines. Even if electrolysis used only a tiny amount of energy, it would still have to follow the law of conservation of energy so that, in itself, is not an argument against charging at 14.8v.

 

Chris

Link to comment
Share on other sites

"Conservation of energy" is a totally different principle to the one we were discussing earlier, and addresses the impossibility of "perpetual-motion" machines. Even if electrolysis used only a tiny amount of energy, it would still have to follow the law of conservation of energy so that, in itself, is not an argument against charging at 14.8v.

 

Chris

 

Of course it is. Hydrogen contains a huge amount of potential energy. In order to make that energy available we are electrolysing water. In order to do so requires a huge amount of energy. This we know because we can get a huge amount of energy back by burning the hydrogen. Therefore conservation of energy is intimately related.

 

Gibbo

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.