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Post by tonyqj on Oct 31, 2016 15:22:23 GMT
Calculations for the above (not my work): The reaction is 2H2O -> 2H2 + O2 The bond energies (correct to 3 sf) are H-O : 459 kJMol-1 H-H : 432 O=O : 494 So the total energy is 459*4 - 494 - 432*2 = 478 kJ But that is for two moles of H2O, so the energy per mole is 239kJ You are correct - I forgot the energy released by O+O becoming O2 Β and H+H becoming H2 Β - very embarrassed. Hey, it's not me that's correct, all I did was copy/paste. π
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Post by tonyb on Oct 31, 2016 15:36:41 GMT
Is there not an inconsistent argument there? "Resistive losses within the battery" that manifest itself - how? Would that be heat by any chance. I think it is important to give the less technical something by which to pin the losses on. So far noone seems to have come up with a simpler "pin" than heat and gassing. Tonyb Maybe the thought that the charge has to be pushed/attracted deeper into the plates the more the battery is charged. That means work has to be done, work produce heat etc. A thought But at the start of the discussion it was said that heat did not contribute to the loss of Ah going to actually charge the battery. I thought that I said that it did.
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Post by Graham on Oct 31, 2016 17:00:42 GMT
Tonyb Maybe the thought that the charge has to be pushed/attracted deeper into the plates the more the battery is charged. That means work has to be done, work produce heat etc. A thought But at the start of the discussion it was said that heat did not contribute to the loss of Ah going to actually charge the battery. I thought that I said that it did. I learn a long time ago that sometime to get a point across No one has convinced me that the loses between the energy that goes into a battery, note energy, is not a combination of the work done pushing the charge into the plates and the heat that caused, plus the gassing, electrolysis that produces the hydrogen and oxygen that is the gas. Gibbo is querying N's insistence that Ahs can exist in isolation, something I have never believed. Unfortunately my damaged head lost the necessary information to argue the case but what is left heavily does not agree. But I must leave you to decide it is your article. I think the important thing is the reader gets a good picture of the factors they need to take into consideration when using a battery in every day use. They, in my opinion need an insight not a pure technical thesis.
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Post by Telemachus on Oct 31, 2016 17:24:20 GMT
Phew well that's alright, I don't have any of those! As I said earlier, CEF is a consequence of electrons "lost" to gassing. EEF (energy efficiency factor) is lower than CEF and a consequence of differing charge vs discharge voltage, resistive losses within the battery and of course gassing. However I'm not sure it's necessary to mention EEF since it's not relevant to most folk with an AH gauge (or without one). Is there not an inconsistent argument there? "Resistive losses within the battery" that manifest itself - how? Would that be heat by any chance. I think it is important to give the less technical something by which to pin the losses on. So far noone seems to have come up with a simpler "pin" than heat and gassing. No inconstancy. I am merely drawing a comparison between CEF and EEF. CEF does not manifest itself as heat. EEF does, however this is not relevant to AH counters.
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Post by Gibbo on Oct 31, 2016 17:45:49 GMT
I have to say, there's a fair amount of bullshit being spouted here.
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Post by Deleted on Oct 31, 2016 17:50:10 GMT
No inconstancy. I am merely drawing a comparison between CEF and EEF. CEF does not manifest itself as heat. EEF does, however this is not relevant to AH counters. Do you think at any point you will accept a simple explanation of the subject? If so can you suggest some amendments to the original op that do not need an in depth knowledge of the subject to understand.
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Post by Telemachus on Oct 31, 2016 17:55:26 GMT
No inconstancy. I am merely drawing a comparison between CEF and EEF. CEF does not manifest itself as heat. EEF does, however this is not relevant to AH counters. Do you think at any point you will accept a simple explanation of the subject? If so can you suggest some amendments to the original op that do not need an in depth knowledge of the subject to understand. My suggestion is to change the explanation for CEF being less than 100% from being heat dissipation, to gassing. Is that too complicated?
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Post by Gibbo on Oct 31, 2016 18:01:00 GMT
Do you think at any point you will accept a simple explanation of the subject? If so can you suggest some amendments to the original op that do not need an in depth knowledge of the subject to understand. My suggestion is to change the explanation for CEF being less than 100% from being heat dissipation, to gassing. Is that too complicated? It's not complicated. But it is wrong. Technically CEF covers all losses encountered during charging. All of them. Technically it does not cover losses during discharging. EEF is a figure not used for batteries because in the real world CEF is corrupted to cover all losses during charging and discharging. All of them. Therefore the EEF and what everyone refers to as CEF (and what AH counters use internally as CEF) are identical.
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Post by Deleted on Oct 31, 2016 18:04:08 GMT
My suggestion is to change the explanation for CEF being less than 100% from being heat dissipation, to gassing. Is that too complicated? Not to me. I think it is helpful to the op. I don't know whether you are right or wrong (not my area of expertise), but if others accept you are right then the 'article' can move on. I know I am new here, but I'd rather see some constructive suggestions when someone suggests an 'idiots' guide to something than a discussion that goes nowhere.
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Post by Telemachus on Oct 31, 2016 18:06:02 GMT
My suggestion is to change the explanation for CEF being less than 100% from being heat dissipation, to gassing. Is that too complicated? It's not complicated. But it is wrong. Technically CEF covers all losses encountered during charging. All of them. Technically it does not cover losses during discharging. EEF is a figure not used for batteries because in the real world CEF is corrupted to cover all losses during charging and discharging. All of them. Therefore the EEF and what everyone refers to as CEF (and what AH counters use internally as CEF) are identical. No. CEF is the ratio of AH taken out vs the AH put back in to get back to the same state. Since AH doesn't have dimensions of energy, the AH ratio cannot reflect loss of energy due to conversion to heat etc. There is no such thing as "current drop" or electrons just disappearing. The electrons either go to pumping the electrochemical reaction, or to gassing (and yes of course gassing occurs during discharge as well as charge, although typically much more in the latter). HaHa I was going to quote your own website on the definition of CEF but I see you have removed the text, so in fact it seems like you don't actually know what CEF is!
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Post by tonyqj on Oct 31, 2016 19:41:12 GMT
I did this for someone on the other side and thought it might do for the Advice section. Please comment so I can edit it and may be get it moved once it is approved by the members. Such meters usually have 5 display modes. Amps, Volts, Amp hours into the battery (but note this - NOT Amp hours actually converted into chemical energy and stored within the battery), Amp hours out of the battery, percentage of charge, and finally maybe time left before charging. In the case of the first two (amps & Volts) they are accurate so would agree with an ammeter and voltmeter or a multi-meter but just because they are accurate does not mean the other are although pure Amp hours in and Amp hours out will be but they are somewhat problematical, as for the percentage of charge and time left they are often a work of fiction. The percentage of the Amp hours into a battery that is converted to stored chemical energy alters hour to hour and day to day as the temperature, charging voltage, and battery condition but it will NEVER be 100%. It will also vary from battery type/design to battery type. Just to substantiate this feel some batteries that have been on charge for a while, they will be warm or hot. Where did this heat come from? The answer is the charging current so from that you can deduce that some charge went to make heat, not convert chemicals. Batteries that are on charge tend to vent hydrogen and oxygen so once again the question is where did the energy come form to break down the electrolyte? The answer is still the charging current. Just to complicate things further the actual capacity of the battery reduces over time means that the meter can not know how much electricity is actually stored in the battery - even if it is 100% charged. Within days or at the most a few weeks it WILL be less that the number on the label. The upshot of the above paragraph is that any display that results from Amp hour counting will over record the amount of charge put into the battery and once that is wrong the percentage of charge and time left must also be wrong. The makers try to compensate for this by putting "fiddle factors" into the algorithms the gauges use to work out the percentage charge and time left. If you have understood some of the topics that are around concerning battery charging you will know that when the charging current drops to a very low level - often quoted as 1% of bank capacity - the battery can be CONSIDERED as fully charged. It probably won't be but it will be near enough for practical use. The meterβs electronics knows this and at that point resets itself to 100% charged. All that sounds fine and dandy but the meters are not usually set at 1% by the factory. Probably more like 2% to 3% so they resynchronise early. This causes them to overstate the degree of charge and that in turn persuades many boaters to destroy their batteries by constant and ongoing undercharging. The problems get worse if users do not continue charging until the current drops to such a low percentage. This is why solar charging has such advantages, it provides many hours at a low charge rate to get the final few percentage of charge back in. If you really understand the limitations in such meters, reset them to synchronise at a very low percentage (known as tail current) AND very regularly charge for long enough to cause them to resynchronise then they will be fairly accurate on all scales. If you do not all you can rely upon is the amps and volts. Even so as the battery capacity has dropped over time the percentage of charge and the time left might still be incorrect. The basic rule for most boaters with this type of meter is to only use the amps scale while charging and keep going at least once a week until the charge drops to 1% of bank capacity or less, then manually resynchronise the meter. Then you can note the Amp hours out and percentage of charge and calculate the current capacity of the bank. e.g. 50Ah out that takes it to 75% of charge tells you the battery bank capacity is 200Ah because 50Ah is 1/4 of the bank capacity. Such meters usually have 5 display modes. Amps, Volts, Amphours into the battery (but note this - NOT Amphours actually converted into chemical energy), Amphours out of the battery, percentage of charge, and finally maybe time left before charging. In the case of the first two (amps & Volts) they are accurate so would agree with your multi-meter but just because they are accurate does not mean the other are although pure Amphours in and Amphours out will be but they are somewhat problematical, as for the percentage of charge and time left they are often a work of fiction. Tony - I think this works just fine. It offers good advice to real world boaters. However, could you edit your first para into shorter sentences to make it easier to read?
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Post by tonyqj on Oct 31, 2016 19:46:08 GMT
Like...
Such meters usually have 5 or 6 display modes: 1. Amps 2. Volts 3. Amp hours into the battery (but note this - NOT Amp hours actually converted into chemical energy and stored within the battery) 4. Amp hours out of the battery 5. percentage of charge 6. and finally maybe time left before charging (or time left until flat)
In the case of the first two (amps & Volts) they are accurate so would agree with an ammeter and voltmeter or a multi-meter. Just because these two are accurate however does not mean the others are. Although pure Amp hours in and Amp hours out will be accurate they are somewhat problematical, and as for the percentage of charge and time left they are often a work of fiction.
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Post by Graham on Oct 31, 2016 19:49:29 GMT
I did this for someone on the other side and thought it might do for the Advice section. Please comment so I can edit it and may be get it moved once it is approved by the members. Such meters usually have 5 display modes. Amps, Volts, Amp hours into the battery (but note this - NOT Amp hours actually converted into chemical energy and stored within the battery), Amp hours out of the battery, percentage of charge, and finally maybe time left before charging. In the case of the first two (amps & Volts) they are accurate so would agree with an ammeter and voltmeter or a multi-meter but just because they are accurate does not mean the other are although pure Amp hours in and Amp hours out will be but they are somewhat problematical, as for the percentage of charge and time left they are often a work of fiction. The percentage of the Amp hours into a battery that is converted to stored chemical energy alters hour to hour and day to day as the temperature, charging voltage, and battery condition but it will NEVER be 100%. It will also vary from battery type/design to battery type. Just to substantiate this feel some batteries that have been on charge for a while, they will be warm or hot. Where did this heat come from? The answer is the charging current so from that you can deduce that some charge went to make heat, not convert chemicals. Batteries that are on charge tend to vent hydrogen and oxygen so once again the question is where did the energy come form to break down the electrolyte? The answer is still the charging current. Just to complicate things further the actual capacity of the battery reduces over time means that the meter can not know how much electricity is actually stored in the battery - even if it is 100% charged. Within days or at the most a few weeks it WILL be less that the number on the label. The upshot of the above paragraph is that any display that results from Amp hour counting will over record the amount of charge put into the battery and once that is wrong the percentage of charge and time left must also be wrong. The makers try to compensate for this by putting "fiddle factors" into the algorithms the gauges use to work out the percentage charge and time left. If you have understood some of the topics that are around concerning battery charging you will know that when the charging current drops to a very low level - often quoted as 1% of bank capacity - the battery can be CONSIDERED as fully charged. It probably won't be but it will be near enough for practical use. The meterβs electronics knows this and at that point resets itself to 100% charged. All that sounds fine and dandy but the meters are not usually set at 1% by the factory. Probably more like 2% to 3% so they resynchronise early. This causes them to overstate the degree of charge and that in turn persuades many boaters to destroy their batteries by constant and ongoing undercharging. The problems get worse if users do not continue charging until the current drops to such a low percentage. This is why solar charging has such advantages, it provides many hours at a low charge rate to get the final few percentage of charge back in. If you really understand the limitations in such meters, reset them to synchronise at a very low percentage (known as tail current) AND very regularly charge for long enough to cause them to resynchronise then they will be fairly accurate on all scales. If you do not all you can rely upon is the amps and volts. Even so as the battery capacity has dropped over time the percentage of charge and the time left might still be incorrect. The basic rule for most boaters with this type of meter is to only use the amps scale while charging and keep going at least once a week until the charge drops to 1% of bank capacity or less, then manually resynchronise the meter. Then you can note the Amp hours out and percentage of charge and calculate the current capacity of the bank. e.g. 50Ah out that takes it to 75% of charge tells you the battery bank capacity is 200Ah because 50Ah is 1/4 of the bank capacity. Such meters usually have 5 display modes. Amps, Volts, Amphours into the battery (but note this - NOT Amphours actually converted into chemical energy), Amphours out of the battery, percentage of charge, and finally maybe time left before charging. In the case of the first two (amps & Volts) they are accurate so would agree with your multi-meter but just because they are accurate does not mean the other are although pure Amphours in and Amphours out will be but they are somewhat problematical, as for the percentage of charge and time left they are often a work of fiction. Tony - I think this works just fine. It offers good advice to real world boaters. However, could you edit your first para into shorter sentences to make it easier to read? Can I ask one thing that the tail current is measured for 30 minutes and checking there is no further reduction. And that the charger is checked that it has not gone to float and is actually in absorption mode.
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Post by tonyqj on Oct 31, 2016 19:54:17 GMT
Tony - I think this works just fine. It offers good advice to real world boaters. However, could you edit your first para into shorter sentences to make it easier to read? Can I ask one thing that the tail current is measured for 30 minutes and checking there is no further reduction. And that the charger is checked that it has not gone to float and is actually in absorption mode. I completely missed both points. Yes, well caught. I'd even say '30 to 60 minutes' (in fact I believe I already did in my 'Charger Primer' post.)
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Post by IainS on Oct 31, 2016 21:45:20 GMT
My Amp Hour counter (Merlin Powergauge)doesn't show AmpHours into the battery, only Amphours out, which is really Amphours out minus AmpHours in with a bit of a "fiddle factor", designed to overcome the fact that you need to put more in than you get out. The "time to go before recharge" is the time the current current (!!) would take to discharge the battery to a pre-set level (Default is 50%), assuming that the bank size is accurate.
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