Battery Fault

[WotEver]

4 minutes ago, nicknorman said:

Before my time. Obviously!

Also completely irrelevant. 

1 hour ago, smileypete said:

If discharging a 100Ah battery at 50A for 1 hour removes more than 50Ah of charge, exactly where have the extra electrons over and above the 50Ah of charge gone to?

I have no idea what you mean by ‘extra electrons’ but if you mean why has the charge reduced by more than 50% it’s because some of it has been used to warm the battery due to the rising internal resistance. Just like Battery FAQ state. 

[cuthound]

If the lost, unrecoverable charge is heating up the battery, then it should be possible to measure the increase in plate and electrolyte temperature.

If the ambient tempersture is known, the mass of the battery is known, and the increase in temperature is known, then it should be possible to calculate the energy used in increasing this temperature, should it not?

[WotEver]

1 hour ago, nicknorman said:

You keep reciting that some of the charge is being used to warm the battery up, but you have no suggestion as to the current path of this charge.

Sure I have. The battery’s rising internal resistance. What happens when you pass s currebt through a resistor? It heats up and wastes power. Charge = Power. Hence charge is reduced. 

7 minutes ago, cuthound said:

If the lost, unrecoverable charge is heating up the battery, then it should be possible to measure the increase in plate and electrolyte temperature.

If the ambient tempersture is known, the mass of the battery is known, and the increase in temperature is known, then it should be possible to calculate the energy used in increasing this temperature, should it not?

I’m sure it could be measured that way. I’m told that it can be calculated too (because the US military require it to be). 

[WotEver]

8 minutes ago, WotEver said:

Charge = Power. Hence charge is reduced. 

And before you start arguing that they’re not the same thing, I know that, it’s just simpler to write it the way I wrote it. 

They’re proportional and that’s all that matters. 

1 hour ago, smileypete said:

Just because all the charge cannot be safely removed at a high rate doesn't mean that some charge has 'disappeared into thin air'

Actually, that’s exactly where it goes - in the form of heat. 

3 hours ago, nicknorman said:

none of you can explain where this lost charge went, except to say it went to heat up the battery even though you know fully well that you don’t drop current through a resistor.

You don’t drop current (what an odd phrase) but you do waste power. Where else do you suppose it came from?

[WotEver]

1 hour ago, nicknorman said:

I can’t think of a possible mechanism for it to happen and no such mechanism has been suggested.

I’ve said a dozen times that it heats the battery!

[Tony Brooks]

And I know I have seen heavy gassing under HRD testing so what produced the "energy" required to  brake down the water?

Its seems to me that under high rates of discharge the heating effect and  gassing caused by current flow requires "energy" from somewhere and unless it is magic that "energy" can only come form the charge in the battery. Such charge as is used for this must be non-recoverable.

Now what proportion of the charge that represents I am not clever enough to say, but it must be non-recoverable.

[WotEver]

1 minute ago, Tony Brooks said:

And I know I have seen heavy gassing under HRD testing so what produced the "energy" required to  brake down the water?

Its seems to me that under high rates of discharge the heating effect and  gassing caused by current flow requires "energy" from somewhere and unless it is magic that "energy" can only come form the charge in the battery. Such charge as is used for this must be non-recoverable.

Now what proportion of the charge that represents I am not clever enough to say, but it must be non-recoverable.

Thanks for the sanity Tony

I’ve been waiting for someone to ask what percentage of the Peukert losses are non-recoverable and the answer is an awful lot more than Nick’s ‘negligible’. It depends on the battery and the rate of discharge but it’s anywhere between 12.5% to over 33%.  

[nicknorman]

6 minutes ago, cuthound said:

If the lost, unrecoverable charge is heating up the battery, then it should be possible to measure the increase in plate and electrolyte temperature.

If the ambient tempersture is known, the mass of the battery is known, and the increase in temperature is known, then it should be possible to calculate the energy used in increasing this temperature, should it not?

No, because the battery doesn’t heat up due to lost charge, the battery heats up due to pushing current through finite resistance, simply   I^2R. No current /electrons are “dropped” when passing through a resistor.

37 minutes ago, WotEver said:

Sure I have. The battery’s rising internal resistance. What happens when you pass s currebt through a resistor? It heats up and wastes power. Charge = Power. Hence charge is reduced. 

I’m sure it could be measured that way. I’m told that it can be calculated too (because the US military require it to be). 

Wow, this is such a basic error. Charge is not “dropped” or “lost” when passing through resistance. Power is dissipated because voltage is dropped. Power is lost, but not charge.

[cuthound]

1 minute ago, nicknorman said:

No, because the battery doesn’t heat up due to lost charge, the battery heats up due to pushing current through finite resistance, simply   I^2R. No current /electrons are “dropped” when passing through a resistor.

I know, I was why I started the question with "if". 

[nicknorman]

23 minutes ago, WotEver said:

I’ve said a dozen times that it heats the battery!

But you haven’t explained how charge is lost, except by your amazing suggestion that charge is dropped due to passing through the battery’s resistance. Power is lost, voltage is lost. But charge isn’t lost - Kirchov’s first law.

15 minutes ago, Tony Brooks said:

And I know I have seen heavy gassing under HRD testing so what produced the "energy" required to  brake down the water?

Its seems to me that under high rates of discharge the heating effect and  gassing caused by current flow requires "energy" from somewhere and unless it is magic that "energy" can only come form the charge in the battery. Such charge as is used for this must be non-recoverable.

Now what proportion of the charge that represents I am not clever enough to say, but it must be non-recoverable.

Heating effect is caused by current passing through resistance. No current or charge is “lost”, only voltage and power. Gassing does “use up” electrons unrecoverably, but only a very small amount relative to the high currents we are talking about.

[Dr Bob]

1 hour ago, WotEver said:

You quoted a simple binary reaction earlier in this thread, in an attempt to justify your mistaken belief that Peukert losses are all recoverable. That reaction results in a fixed voltage. It can’t alter as the reaction doesn’t alter. So why is a ‘full’ 12V battery at about 12.7V and a flat one at 10.5V (or whatever)?

If the reaction happens it happens. If it doesn’t then it doesn’t. So how can that reaction that you quoted result in a varying off-load voltage?

Both Tony and Nick are not understanding the chemistry.

The binary reaction happens only at the molecular level. For every 2 electons made the voltage is increadibly small. I think this needs to be looked at as a 'Molar' property, ie you need 10 to the power 23 double electons to get the 2.1V that each cell can potentially produce. Yes it is a binary reaction but 10 to the power 23 of them have to happen to get the full voltage. The difference between 12.7V at rest and the 10.5 "fully depleted' (not quite!) is because you have less than 10 to the power 23 of molecules to react. The overall battery chemisty is not binary.

There is no doubt that some sites are lost during a discharge and cant be got back probably due to gassing or increased temperature but it is not clear to what extent this happens and how much is just 'inaccessible sites' as my previous posts. I think Tony and Nick are saying the same thing with the exception that they cant agree on the amount truly lost (which I think is small).

It should be straightforward to anyone who knows battery chemistry to identify these side reactions where charge is lost (and there must be lots of reactions that could take place with all the other metals doped into the plates.

One othe key point is that no electrons transfer out of the battery. They do not move out of the atom they are in. The mechanism is that they transfer their charge to the next atom and so the the 'next' electron is energised. This is how current flows down a conductor. It is not a flow of electrons, it is a flow of charge down a conductor via electrons (which stay with their atoms).

 

[nicknorman]

2 minutes ago, Dr Bob said:

Both Tony and Nick are not understanding the chemistry.

The binary reaction happens only at the molecular level. For every 2 electons made the voltage is increadibly small. I think this needs to be looked at as a 'Molar' property, ie you need 10 to the power 23 double electons to get the 2.1V that each cell can potentially produce. Yes it is a binary reaction but 10 to the power 23 of them have to happen to get the full voltage. The difference between 12.7V at rest and the 10.5 "fully depleted' (not quite!) is because you have less than 10 to the power 23 of molecules to react. The overall battery chemisty is not binary.

There is no doubt that some sites are lost during a discharge and cant be got back probably due to gassing or increased temperature but it is not clear to what extent this happens and how much is just 'inaccessible sites' as my previous posts. I think Tony and Nick are saying the same thing with the exception that they cant agree on the amount truly lost (which I think is small).

It should be straightforward to anyone who knows battery chemistry to identify these side reactions where charge is lost (and there must be lots of reactions that could take place with all the other metals doped into the plates.

One othe key point is that no electrons transfer out of the battery. They do not move out of the atom they are in. The mechanism is that they transfer their charge to the next atom and so the the 'next' electron is energised. This is how current flows down a conductor. It is not a flow of electrons, it is a flow of charge down a conductor via electrons (which stay with their atoms).

 

I’m puzzled by your comment about the voltage of electrons. Electrons don't have any intrinsic voltage, only charge surely? Where does the 10^23 come from? 

Also whilst we know that current flow isn’t a stream of electrons like a line of ants, I don’t see how your description can be right. An electron has a fixed amount of charge, a quantum property, it can’t give it up to some other atom.

[Dr Bob]

49 minutes ago, WotEver said:

Thanks for the sanity Tony

I’ve been waiting for someone to ask what percentage of the Peukert losses are non-recoverable and the answer is an awful lot more than Nick’s ‘negligible’. It depends on the battery and the rate of discharge but it’s anywhere between 12.5% to over 33%.  

This to me is the key question to which we have not had an answer. I said in my above post that it is likely small - as we do see some heat and gassing (as Tony B said). Tony (Wotever) says 12.5-33%. Is this 12.5-33% of the Peuket losses or is it the % of the total charge? If it is the % of the Peuket losses then I would probably agree with something of that nature (which to me is small). All we need is a paper on the side reactions etc. The fact internal resistance goes up means heat will be generated and surely there are some papers on how much that is.

[Dr Bob]

Just now, nicknorman said:

I’m puzzled by your comment about the voltage of electrons. Electrons don't have any intrinsic voltage, only charge surely? Where does the 10^23 come from? 

Also whilst we know that current flow isn’t a stream of electrons like a line of ants, I don’t see how your description can be right. An electron has a fixed amount of charge, a quantum property, it can’t give it up to some other atom.

This is where my chemistry knowledge is being challenged. I did my PhD in 1976 so it is a bit hazy. In a 1 molar solution, you have 10 to the power 23 molecules - I think it is the 'Avagadro number'. Therefore you can estimate the number of molecules that will react by measuring the weight of the total molecules (ie the weight of the plates) divided by the molecular weight of the material, all multiplied by avagadro's number.

Yes, it is charge only ie potential so lots and lots and lots *10 to the power 23 electrons will have the potential of 2.1V ish.

Yes, electrons attached to one atom can transfer charge to the electron on the next atom. That's how it happens. It would be impossible for electons to move down a copper wire. Wasnt this what you were taught on you course?

[nicknorman]

7 minutes ago, Dr Bob said:

This is where my chemistry knowledge is being challenged. I did my PhD in 1976 so it is a bit hazy. In a 1 molar solution, you have 10 to the power 23 molecules - I think it is the 'Avagadro number'. Therefore you can estimate the number of molecules that will react by measuring the weight of the total molecules (ie the weight of the plates) divided by the molecular weight of the material, all multiplied by avagadro's number.

Yes, it is charge only ie potential so lots and lots and lots *10 to the power 23 electrons will have the potential of 2.1V ish.

Yes, electrons attached to one atom can transfer charge to the electron on the next atom. That's how it happens. It would be impossible for electons to move down a copper wire. Wasnt this what you were taught on you course?

Hmmm well I have no chemistry PhD but a few things seem wrong.

Firstly electrons only have a fixed charge. There is no voltage associated with them so I don’t see what Avagadro’s number has to do with it. The reaction “pumps” the electrons up a potential gradient to create voltage. Just one electron can be at a potential of 2.1v.

Secondly with the current flow thing, I still don’t see how electrons can transfer their charge to an adjacent electron. The charge of an electron is a fixed fundamental property. Current does flow due to electrons moving, but they move quite slowly. The movement propagates at near the speed of light by each “nudging” the next. Semiconductors work only because electrons “move” and you get “holes” etc.

If you are adamant on your two points above, can you point us to any reference material supporting them?

[Dr Bob]

2 minutes ago, nicknorman said:

Hmmm well I have no chemistry PhD but a few things seem wrong.

Firstly electrons only have a fixed charge. There is no voltage associated with them so I don’t see what Avagadro’s number has to do with it. The reaction “pumps” the electrons up a potential gradient to create voltage. Just one electron can be at a potential of 2.1v.

Secondly with the current flow thing, I still don’t see how electrons can transfer their charge to an adjacent electron. The charge of an electron is a fixed fundamental property. Current does flow due to electrons moving, but they move quite slowly. The movement propagates at near the speed of light by each “nudging” the next. Semiconductors work only because electrons “move” and you get “holes” etc.

If you are adamant on your two points above, can you point us to any reference material supporting them?

I can't point you to any reference materials as it was very basic stuff taught early on.

On the 2nd point first. Electrons spin around the proton in the atom. When charged they move into a different higher orbital (and that is truly complicated and I have forgotten all the details of energy levels of electrons) but yes....they nudge the atom next to them and transfer the charge to that atoms electron and that is how current moves. The movement of electrons around an atom and the different orbitals an electron can occupy is incredibly complex and to understand it you need to understand Schrodingers wave equation viz

https://plus.maths.org/content/schrodinger-1

I suggest we dont go there!

On the first point. Avogadro's number which I have just checked is 6 * 10^23 tells you how many molecules in a mole of material. A mole is basically the molecular weight (in grams). Therefore you can estimate the number of molecules able to react in a battery. That total number of molecules will make up the capacity. I think I learnt that you need these 10^23 numbers of electrons with a charge to give you voltage level potential. You may be right and an individual electron has a potental of 2.1v but I am not sure - I thought you need 10^23 of them or at least a lot of them . What is certain though is to get the capacity of a 110Ahr battery, you need lots and lots of reactive molecules so 10^23 of them. If some of them arent available ie too cold so steric hinderance on sites deep in the plates, or not enough acid ions due to fast depletion (so it is almost pure water next to the sites) then you havent got your 10^23 anymore and so the capacity is lower and the voltage at rest is lower (which is why I think you need lots and lots of molecules to get 12.7V and not just one).  Again we really need a good battery chemist here.

[Chewbacka]

27 minutes ago, nicknorman said:

Hmmm well I have no chemistry PhD but a few things seem wrong.

Firstly electrons only have a fixed charge. There is no voltage associated with them so I don’t see what Avagadro’s number has to do with it. The reaction “pumps” the electrons up a potential gradient to create voltage. Just one electron can be at a potential of 2.1v.

Secondly with the current flow thing, I still don’t see how electrons can transfer their charge to an adjacent electron. The charge of an electron is a fixed fundamental property. Current does flow due to electrons moving, but they move quite slowly. The movement propagates at near the speed of light by each “nudging” the next. Semiconductors work only because electrons “move” and you get “holes” etc.

If you are adamant on your two points above, can you point us to any reference material supporting them?

It's a long time ago, bit my memory is that electrons are a fixed charge and they can not pass on the charge because if they did they would no longer be electrons.  My understanding is that where there is an equal number of electrons and protons then the charge is balanced, but electrons do drift about moving from atom to atom.  Maybe it's time to dig out my old course books.

 

Electrons do drift and that is the basis of current flow - http://www.schoolphysics.co.uk/age16-19/Electricity and magnetism/Current electricity/text/Free_electron_motion/index.html

Too tired to read up any more.

Edited November 28, 2017 by Chewbacka

[Dr Bob]

11 minutes ago, Chewbacka said:

It's a long time ago, bit my memory is that electrons are a fixed charge and they can not pass on the charge because if they did they would no longer be electrons.  My understanding is that where there is an equal number of electrons and protons then the charge is balanced, but electrons do drift about moving from atom to atom.  Maybe it's time to dig out my old course books.

I dont think it is easy to find a simple reference - as most stuff on electrons will be about ions in aqueous solutions. Here molecules dissociate into positively charged (proton minus electon) and negatively charged (electon rich) ions so yes you do get electrons 'drifiting'. It is this ionic dissociation that happens in a battery and the HSO4- anion goes to the plates and reacts releasing an electron. It all happen s in aqueous solution - except with ionic liquids which are too complex for here. The conduction of current in a conductor is  different as you do not get +ve and -ves but just conduction of current down a wire. In this case electrons are launched into a higher orbit by accepting a charge and nudge the next one passing on the energy so the new electron goes to a higher orbit and the old one drops back to where it was. I think that is the 'simple' explanation. The treatment of electrons is totally different from aqueous solutions to conducting a current in a wire.

Edited November 28, 2017 by Dr Bob

[nicknorman]

1 minute ago, Dr Bob said:

I can't point you to any reference materials as it was very basic stuff taught early on.

On the 2nd point first. Electrons spin around the proton in the atom. When charged they move into a different higher orbital (and that is truly complicated and I have forgotten all the details of energy levels of electrons) but yes....they nudge the atom next to them and transfer the charge to that atoms electron and that is how current moves. The movement of electrons around an atom and the different orbitals an electron can occupy is incredibly complex and to understand it you need to understand Schrodingers wave equation viz

https://plus.maths.org/content/schrodinger-1

I suggest we dont go there!

On the first point. Avogadro's number which I have just checked is 6 * 10^23 tells you how many molecules in a mole of material. A mole is basically the molecular weight (in grams). Therefore you can estimate the number of molecules able to react in a battery. That total number of molecules will make up the capacity. I think I learnt that you need these 10^23 numbers of electrons with a charge to give you voltage level potential. You may be right and an individual electron has a potental of 2.1v but I am not sure - I thought you need 10^23 of them or at least a lot of them . What is certain though is to get the capacity of a 110Ahr battery, you need lots and lots of reactive molecules so 10^23 of them. If some of them arent available ie too cold so steric hinderance on sites deep in the plates, or not enough acid ions due to fast depletion (so it is almost pure water next to the sites) then you havent got your 10^23 anymore and so the capacity is lower and the voltage at rest is lower (which is why I think you need lots and lots of molecules to get 12.7V and not just one).  Again we really need a good battery chemist here.

Hmmm well electrons moving to different energy levels around the nucleus all have the same charge. As I said, an electron can only have one charge, the elementary charge or 1.6... 10^-19 coulombs. They have different energy levels at different orbits, not different charge. We do seem to be struggling with dimensions again. Charge and Energy are entirely different things!

And thus an electron can’t transfer charge without itself moving since it can only have 1 value of charge.

Avagadros number is just the number of atoms/molecules in a mol. You can have a battery with fewer than a mol’s worth - or of course more normally with a lot more. I don’t see it’s significance here.

1 minute ago, Dr Bob said:

I dont think it is easy to find a simple reference - as most stuff on electrons will be about ions in aqueous solutions. Here molecules dissociate into positively charged (proton minus electon) and negatively charged (electon rich) ions so yes you do get electrons 'drifiting'. It is this ionic dissociation that happens in a battery and the HSO4- anion goes to the plates and reacts releasing an electron. It all happen s in aqueous solution - except with ionic liquids which are too complex for here. The conduction of current in a conductor is  different as you do not get +ve and -ves but just conduction of current down a wire. In this case electrons are launched into a higher orbit and nudge the next one passing on the energy so the new electron goes to a higher orbit and the old one drops back to where it was. I think that is the 'simple' explanation. The treatment of electrons is totally different from aqueous solutions to conducting a current in a wire.

When electrons move to higher and lower energy levels, energy is transferred (eg by emitting a photon) but not charge.

[nicknorman]

Every hit on Google’s first page talks about free electrons moving in a metal.

[Dr Bob]

2 minutes ago, nicknorman said:

Hmmm well electrons moving to different energy levels around the nucleus all have the same charge. As I said, an electron can only have one charge, the elementary charge or 1.6... 10^-19 coulombs. They have different energy levels at different orbits, not different charge. We do seem to be struggling with dimensions again. Charge and Energy are entirely different things!

And thus an electron can’t transfer charge without itself moving since it can only have 1 value of charge.

Avagadros number is just the number of atoms/molecules in a mol. You can have a battery with fewer than a mol’s worth - or of course more normally with a lot more. I don’t see it’s significance here.

I am not going to argue the point around energy levels or charge, or around how current moves as we will be at it all night. It is not really important to your discussion.

What is important is that the capacity of a battery will be dependent on the number of moles of reactive sites and you can estimate the number of sites using the weight of sites available, the molecular weight and avogadros number. The number of sites will be proportional to the capacity. The current you will get out of the battery will be totally dependent on the number of sites. I have my own vision of how this affects voltage and my thoughts do fit the chemistry mechanism but lets not argue that one either as we will never get a clear answer.

All we really need to do to solve your argument with Tony is to identify the side reactions that 'loose' charge.

3 minutes ago, nicknorman said:

Every hit on Google’s first page talks about free electrons moving in a metal.

I think that is because to explain it otherwise would be to require the reader to understand atomic orbitals and energy levels which is just too complex. Far easier to say the electron travels down a wire. When you do a PhD, you get into far more detail - but it was 40 years ago.

[Chewbacka]

7 minutes ago, Dr Bob said:

I dont think it is easy to find a simple reference - as most stuff on electrons will be about ions in aqueous solutions. Here molecules dissociate into positively charged (proton minus electon) and negatively charged (electon rich) ions so yes you do get electrons 'drifiting'. It is this ionic dissociation that happens in a battery and the HSO4- anion goes to the plates and reacts releasing an electron. It all happen s in aqueous solution - except with ionic liquids which are too complex for here. The conduction of current in a conductor is  different as you do not get +ve and -ves but just conduction of current down a wire. In this case electrons are launched into a higher orbit by accepting a charge and nudge the next one passing on the energy so the new electron goes to a higher orbit and the old one drops back to where it was. I think that is the 'simple' explanation. The treatment of electrons is totally different from aqueous solutions to conducting a current in a wire.

As I added to my post above, Electrons do drift and that is the basis of current flow - http://www.schoolphysics.co.uk/age16-19/Electricity and magnetism/Current electricity/text/Free_electron_motion/index.html

Energy states of atoms - electrons moving up and down orbit levels is not the same as current flow.  Voltage can cause electrons to drift and recombine with 'holes' and emit photons  - hence LED lights, or just drift about and manifest as current flow.

[nicknorman]

5 minutes ago, Dr Bob said:

I am not going to argue the point around energy levels or charge, or around how current moves as we will be at it all night. It is not really important to your discussion.

What is important is that the capacity of a battery will be dependent on the number of moles of reactive sites and you can estimate the number of sites using the weight of sites available, the molecular weight and avogadros number. The number of sites will be proportional to the capacity. The current you will get out of the battery will be totally dependent on the number of sites. I have my own vision of how this affects voltage and my thoughts do fit the chemistry mechanism but lets not argue that one either as we will never get a clear answer.

All we really need to do to solve your argument with Tony is to identify the side reactions that 'loose' charge.

I think that is because to explain it otherwise would be to require the reader to understand atomic orbitals and energy levels which is just too complex. Far easier to say the electron travels down a wire. When you do a PhD, you get into far more detail - but it was 40 years ago.

I agree with the central section of your post. But sorry, if when you do a PhD you don’t get to know that an electron has a fixed and fundamental charge, something is wrong! Or that electron charge and energy aren’t the same thing!

[Dr Bob]

2 minutes ago, Chewbacka said:

As I added to my post above, Electrons do drift and that is the basis of current flow - http://www.schoolphysics.co.uk/age16-19/Electricity and magnetism/Current electricity/text/Free_electron_motion/index.html

Energy states of atoms - electrons moving up and down orbit levels is not the same as current flow.  Voltage can cause electrons to drift and recombine with 'holes' and emit photons  - hence LED lights, or just drift about and manifest as current flow.

I'll read this tomorrow. My battery is about to expire. Too many electrons!

Still stand by all the stuff on 10^23 and its effect on charge ...

[nicknorman]

Start at page 9, section 28-4 conduction in solids: Electrical conduction in liquids and solids.

Ok it’s from 1958 but did thinking on electrical conduction through solids changed entirely between then and when you did your PhD in ~ 1970s? I doubt it.

And this one: Conduction in solids a bit more recent.

Current in solids is definitely by means of electrons moving between atoms, albeit fairly slowly.

Edited November 28, 2017 by nicknorman