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Battery Meter
Is it normal for the battery gauge to read 16 when the boat is in
operation? The gauge only goes up to 18. The battery will be a year old next month. Should I be concerned? |
Battery Meter
On Tue, 18 May 2004 12:20:59 GMT, "Ernie"
wrote: Is it normal for the battery gauge to read 16 when the boat is in operation? The gauge only goes up to 18. The battery will be a year old next month. Should I be concerned? ======================================== Normal voltage while underway is in the range of 13.8 to 14.2 |
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16 Volts is overcharging, and continued use will quickly destroy the battery.
The first guess would be bad wiring to the regulator, or maybe a bad regulator. Before you do anything, check the water level in the battery - if you've been running like this its likely down. If everything looks OK, you should check with a digital meter to verify the voltage. Normally, regulators are set for 14.2 to 14.5 volts, and anything over 14.7 is considered overcharging. If it really is 16 Volts, don't continue running it. BTW, at 16 volts you should be able to smell the battery "cooking." "Ernie" wrote in message . .. Is it normal for the battery gauge to read 16 when the boat is in operation? The gauge only goes up to 18. The battery will be a year old next month. Should I be concerned? |
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Ernie wrote:
Is it normal for the battery gauge to read 16 If the 16 volts displayed is accurate it is a bit too high for continuous charging of a lead acid battery, that is the "equalizing" voltage. Check the charging voltage with a good quality voltmeter before you start changing things because the cheap panel meters supplied with consumer grade boats are not known for their accuracy. If you have access to the battery while running and the battery is a wet cell with removable cell covers (where you add water) look and see if the cells are bubbling. If there are a lot of bubbles and/or you have been adding a lot water then your charging voltage is probably high. Rick |
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Ernie wrote:
Is it normal for the battery gauge to read 16 when the boat is in operation? The gauge only goes up to 18. The battery will be a year old next month. Should I be concerned? You should get an accurate measure of what the charging voltage is that the alternator is putting out. It sounds like your gage is showing 16 volts, but dashboard gages are notoriously inaccurate. Can you put a multimeter on the battery terminals when in operation? As somebody else posted, the voltage should not be more that 14 or 14.2 tops. Fair Skies Doug King |
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Here you go
http://www.solectria.com/products/amphrm.html DSK wrote in message ... Ernie wrote: Is it normal for the battery gauge to read 16 when the boat is in operation? The gauge only goes up to 18. The battery will be a year old next month. Should I be concerned? You should get an accurate measure of what the charging voltage is that the alternator is putting out. It sounds like your gage is showing 16 volts, but dashboard gages are notoriously inaccurate. Can you put a multimeter on the battery terminals when in operation? As somebody else posted, the voltage should not be more that 14 or 14.2 tops. Fair Skies Doug King |
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Also Sprach Ernie :
Is it normal for the battery gauge to read 16 when the boat is in operation? The gauge only goes up to 18. The battery will be a year old next month. Should I be concerned? Regardless of the other replies, there are circumstances where charging a charging voltage of 16-17 volts is perfectly normal and expected. Specifically, many many older outboard engines, and even a few newer but down-market ones, have low current unregulated charging systems... in other words, they had a rectifier but no voltage regulator. Since they are low current, topping out at 6 or 8 amps, they typically won't fry your battery, so long as you make sure the water level is topped up. Now, if you have an inboard or stern drive, or a newer outboard with a regulated charging system, I'd do some troubleshooting, starting by measuring the voltage at the battery with a good digital voltmeter. Dan -- It's good to drink. It's good to laugh. But try to both at the same time and you'll pay through the nose. |
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"Ernie" wrote in message
. .. Is it normal for the battery gauge to read 16 when the boat is in operation? The gauge only goes up to 18. The battery will be a year old next month. Should I be concerned? Ernie - More accurately, this is a volt meter, not a battery gauge. This is nit-picky, yes, but an important distinction. When the motor's running, it measures the output of the charging system, not the state of the battery itself. Therefore, it's not the battery that is possibly "wrong" it's the charging system. I say "possibly wrong" because... As others have mentioned, the first guess is that your dashboard gauge is inaccurate. You can test the battery, charging system, and therefore the gauge, by getting a decent digital multimeter. The meter doesn't have to be expensive, but I recommend digital because they're easier to read. Set it to the volts DC scale, and test the charging system by putting the multimeter leads on the main battery cables while the motor is running. As mentioned, it should read "around" 14 volts (13.8-14.2). When the engine is stopped, the meter (and your dash gauge) would simply test the output of the battery itself. A fully charged 12 volt battery is 12.6 volts. This varies a little higher if it's freshly charged (it will "settle" at 12.6). But, if it's actually at 12 - it's almost dead. You can get a very cheap, little tester that will indicate (with various colored LED's generally) if the charging system and/or battery is good or bad. These LED's are, of course, set to indicate the ~14 threshold for the charging system and the ~12.6 volt threshold for the battery itself. But a multimeter is a handy tool to have and worth spending a few bucks on. I carry the little cheap tester in my small tool box though. Beyond that, I don't know how to trouble shoot or fix. I don't know from rectifiers, stators, regulators, etc. But if you find that the multimeter shows a good charging voltage of around 14 when the engine is running, you can be pretty sure your gauge is bad, and you need to buy a new gauge. You can find a lot of options on line from OEM to aftermarket and should be able to exactly, or closely match your existing gauges. I'd suggest you temporarily test the gauge before actually installing it. Gauge installation is a pretty easy DIY if you're so inclined. Cam |
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A fully charged 12 volt battery is
12.6 volts. 13.2 2.2 volts X 6 cells equals 13.2 |
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"Gould 0738" wrote in message ... A fully charged 12 volt battery is 12.6 volts. 13.2 2.2 volts X 6 cells equals 13.2 This is an often debated subject, because it depends on the type of battery, temperature, aging, etc. In general for lead acid batteries: Open circuit voltage Charge in % 12.6V and higher 100% 12.4 - 12.6V 75 - 100% 12.2 - 12.4V 50 - 75% 12.0 - 12.2V 25 - 50% 11.7 - 12.0V 0 - 25% 11.7V and less 0% Eisboch |
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"Gould 0738" wrote in message
... A fully charged 12 volt battery is 12.6 volts. 13.2 2.2 volts X 6 cells equals 13.2 Nonsense. You obviously have never actually used a voltmeter on a boat. The "open circuit voltage" varies a bit with the technology, but will generally be between 12.6 and 12.8. It may read a tad higher after charging, but settles in a few hours. http://www.trojanbattery.com/custome...erymaint4.html |
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Gould, it's 2.1 x 6, you get 12.6.
"Gould 0738" wrote in message ... A fully charged 12 volt battery is 12.6 volts. 13.2 2.2 volts X 6 cells equals 13.2 |
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Ernie, the best way to test a batter is with a load tester that uses a
carbon pile, but only shops would have that equipment. Autozone used to test your battery for free with one, maybe they still do. The voltmeter test is a good one to use on a battery, without the engine running. Another poster said that the "voltage will settle down" after a while....this is called a surface charge, what you get from a battery just after it has been fully charged. It'll throw the VM test off. To remove the surface charge, crank the motor for 15-30 seconds. Another good test for a regular lead-acid battery is the electrolyte test. It's a glass eye-dropper, you check each cell individually, and that way you can tell if you have any bad cells. I can't remember the pass/fail, something like if there are two cells that are bad, then the battery is trash, or if two adjacent cells are bad....I can't remember. But the electolyte test will tell you if your battery is bad. Drew "Ernie" wrote in message . .. Is it normal for the battery gauge to read 16 when the boat is in operation? The gauge only goes up to 18. The battery will be a year old next month. Should I be concerned? |
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On Wed, 19 May 2004 17:09:07 -0400, "Eisboch"
wrote: This is an often debated subject, because it depends on the type of battery, temperature, aging, etc. In general for lead acid batteries: Open circuit voltage Charge in % 12.6V and higher 100% 12.4 - 12.6V 75 - 100% 12.2 - 12.4V 50 - 75% 12.0 - 12.2V 25 - 50% 11.7 - 12.0V 0 - 25% 11.7V and less 0% ============================== Debated indeed, but that seems a wee bit harsh to me on the low end. I routinely run my deep cycles down to 11.5 under moderate load and they still have lots of juice left at that level, more than enough to start the engines for example. I've always regarded 11.5 volts as the 50% mark where you really should recharge but don't necessarily need to. A battery discharged to that level should be recharged ASAP of course. Regarging Chuck's 13.2 volts, that is about the right voltage for "floating" a fully charged battery, but the battery will soon drop back to 12.6 or 12.7 once the float charger/battery eliminator is turned off. |
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Gould, it's 2.1 x 6, you get 12.6.
If it were 2.1, you'd get 12.6. Corect. However, the potential capacity of a cell is 2.2 volts. Consider the "Ideal Charge Curve" described by Rick Proctor of Cruising Equipment Co: Bulk phase: Chare at a rate up to 20-40% of amp-hour capacity to a voltage of about 14.4 volts. (Gel: 14.1). For example, a 200 amp-hour battery would be charged at 40-80 amperes. This will bring the battery to about 75% of full charge. Aceptance phase: Maintain battery at 14.4 volts (Gel, 14.1) while the amperage is steadily reduced. This restores the next 25% of capacity at a declining rate. Your battery can be considered fully charged if it will accept current equal to 2% of cpacity at 14.4 volts. Example: A 200 amp hour battery accepts only 4 amps at 14.4 volts. Float phase: The voltage is reduced to 13.3 volts, (gel 13.7 volts) to maintain the battery without losing electrolyte from the cells. *THIS IS A MAINTENANCE PHASE, NOT A CHARGING PHASE* If you test a battery aboard a boat and it reads only 12.6, it is not fully charged. Fully charged to "float phase" is over 13 volts for flooded batteries and 13.7 for gel cells. |
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"Gould 0738" wrote in message ... If you test a battery aboard a boat and it reads only 12.6, it is not fully charged. Fully charged to "float phase" is over 13 volts for flooded batteries and 13.7 for gel cells. With the float charger attached, agreed. Remove the float charger for an hour or so and the voltage for a fully charged flooded battery will be 12.6 volts. Been that way for many, many years. Eisboch |
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Where do you get this nonsense? "Open Circuit Voltage" is not the same thing as
"Float Voltage." Did you even look at the link I provided, or are you claiming to know more about batteries than Trojan? http://www.trojanbattery.com/custome...erymaint4.html "Gould 0738" wrote in message ... Gould, it's 2.1 x 6, you get 12.6. If it were 2.1, you'd get 12.6. Corect. However, the potential capacity of a cell is 2.2 volts. Consider the "Ideal Charge Curve" described by Rick Proctor of Cruising Equipment Co: Bulk phase: Chare at a rate up to 20-40% of amp-hour capacity to a voltage of about 14.4 volts. (Gel: 14.1). For example, a 200 amp-hour battery would be charged at 40-80 amperes. This will bring the battery to about 75% of full charge. Aceptance phase: Maintain battery at 14.4 volts (Gel, 14.1) while the amperage is steadily reduced. This restores the next 25% of capacity at a declining rate. Your battery can be considered fully charged if it will accept current equal to 2% of cpacity at 14.4 volts. Example: A 200 amp hour battery accepts only 4 amps at 14.4 volts. Float phase: The voltage is reduced to 13.3 volts, (gel 13.7 volts) to maintain the battery without losing electrolyte from the cells. *THIS IS A MAINTENANCE PHASE, NOT A CHARGING PHASE* If you test a battery aboard a boat and it reads only 12.6, it is not fully charged. Fully charged to "float phase" is over 13 volts for flooded batteries and 13.7 for gel cells. |
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On Wed, 19 May 2004 23:23:28 -0400, "Eisboch"
wrote: With the float charger attached, agreed. Remove the float charger for an hour or so and the voltage for a fully charged flooded battery will be 12.6 volts. Been that way for many, many years. ============ Yes. |
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Where do you get this nonsense? "Open Circuit Voltage" is not the same thing
as "Float Voltage." Did you even look at the link I provided, or are you claiming to know more about batteries than Trojan? No I don't know more about batteries than Trojan. However, if you test the batteries on your boat and you think that 12.6 means the batteries are fully charged, that means I know more about batteries than you. I won't dispute that if a battery is removed from a charging system and allowed to sit around in your garage, or languish on a retailer's shelf, the voltage will drop. The initial drop may well be rapid, and 12.6 could be considered OK for a partially discharged, idle battery. Put that battery back in a working environment where it has access to charge from an alternator or a 110 charger, and it will be "fully charged" when it achieves 2.2 volts per cell, or 13.2 volts total. Rather obviously, the battery would not accept additional voltage if it was "fully charged" at 12.6. Since a "smart" charger will maintain a 13.2 voltage on a flooded, 12-volt batery in good condition, that is the standard for full charge. If that same charger cannot bring the voltage above 12.6, that's a likely sign that the battery is beginning to fail. |
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"Gould 0738" wrote in message ... Since a "smart" charger will maintain a 13.2 voltage on a flooded, 12-volt batery in good condition, that is the standard for full charge. If that same charger cannot bring the voltage above 12.6, that's a likely sign that the battery is beginning to fail. So what was the full charge standard before the advent of smart chargers? Answer: 12.6v Not to kick a dead horse, because if you're happy with 13.2v and I am happy with 12.6v, then we're both happy -- but: A charger has to develop a higher voltage than the battery voltage, otherwise it won't charge. (Basic electrical rule of difference of potential required for current flow). Smart chargers in the bulk charge mode usually try to run in a constant current mode with the voltage set at 14.4 volts for flooded batteries. The absorption mode drops the voltage to 13.5 typically. Flood maintains the charge at 13.5 volts (depending on charger manufacturer - I happen to be looking at a Prosine unit manual at the moment) at very low current to minimize electrolyte evaporation, but it is still charging. Remove the charger and a flooded battery will return to it's normal state of 12.6v within a hour or so. Try it. I just tested three known good batteries. I charged each one with a smart charger that finished with a float charge potential of 13.3 volts on each. When I removed the charger, each battery read as follows within a couple of hours: Group 24 Marine Deep Cycle/Start Combination battery (flooded) --- 12.6v AGM Deep Cycle Battery --- 12.8v Two, U2400 six volt batteries in series (flooded, RV house batteries) --- 12.6v According to your position on full charge, I must have three batteries that are going bad which is not the case. Eisboch |
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"Gould 0738" wrote in message ... Rather obviously, the battery would not accept additional voltage if it was "fully charged" at 12.6. I think this sentence is the core of your confusion. You can apply any voltage you want on the battery. "Equalization" or "Reconditioning" modes of chargers often apply 17 volts, and the battery will rise to that potential. It will also boil and melt if you leave it there too long. Eisboch |
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"Gould 0738" wrote in message ... Where do you get this nonsense? "Open Circuit Voltage" is not the same thing as "Float Voltage." Did you even look at the link I provided, or are you claiming to know more about batteries than Trojan? No I don't know more about batteries than Trojan. However, if you test the batteries on your boat and you think that 12.6 means the batteries are fully charged, that means I know more about batteries than you. That would appear very doubtful. If you only test your batteries while a battery charger is runnning, then you know very little about batteries. I won't dispute that if a battery is removed from a charging system and allowed to sit around in your garage, or languish on a retailer's shelf, the voltage will drop. Not "lanquish," it only takes an hour or two, and can be hastened by applying a small load. Actually, it will go below 13 Volts within minutes. The initial drop may well be rapid, and 12.6 could be considered OK for a partially discharged, idle battery. Put that battery back in a working environment where it has access to charge from an alternator or a 110 charger, and it will be "fully charged" when it achieves 2.2 volts per cell, or 13.2 volts total. No. You're just saying that a smart charger will be at a 13.2 Volt float level when it desides its fully charged. Take the charger off and the battery quickly drops to 12.6. Why do you call a "working environment" one with a charger running? Are you one of those bozos that runs a genset all night long? Rather obviously, the battery would not accept additional voltage if it was "fully charged" at 12.6. What do you mean by "accept additional voltage"? What do you think would happen if I took a fully charged battery and put 17 Volts on it? Would it read only 13.2? Since a "smart" charger will maintain a 13.2 voltage on a flooded, 12-volt batery in good condition, that is the standard for full charge. No. That's the standard for a float charge. Or are you claiming that without the float charge the battery can't really be at 100% because it will self-discharge some tiny amount as soon as the charger is removed? You may be right in a pedantic way, but 99.99% is close enough to 100% for me. If that same charger cannot bring the voltage above 12.6, that's a likely sign that the battery is beginning to fail. Well, I haven't killed too many batteries, but I usually find that the Voltage will come up on the charger, but falls too quickly when a load is applied. I'd guess this is why people use "load testers" to test the quality of a battery. |
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Thanks to all of you who contributed to resolving this issue.
"Wayne.B" wrote in message ... On Wed, 19 May 2004 23:23:28 -0400, "Eisboch" wrote: With the float charger attached, agreed. Remove the float charger for an hour or so and the voltage for a fully charged flooded battery will be 12.6 volts. Been that way for many, many years. ============ Yes. |
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"Ernie" wrote in message ... Thanks to all of you who contributed to resolving this issue. Resolved? 8-) |
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According to your position on full charge, I must have three batteries that
are going bad which is not the case. You do not have batteries going bad because they can be charged to 13.2. The fact that they then partially discharge to 12.6 doesn't make them bad batteries. If your batteries could not be charged above 12.6, they would be starting to fail. As you noted, they can be charged to 13.2. |
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I think this sentence is the core of your confusion. You can apply any
voltage you want on the battery. "Equalization" or "Reconditioning" modes of chargers often apply 17 volts, and the battery will rise to that potential. It will also boil and melt if you leave it there too long. 17 volts is overcharged. "Equalization" involves the short term overcharge of a battery to blow the crud off the plates, but it is not a charge that a battery can sustain for a long period- as you correctly note. 13.2 is the proper reading for a fully charged battery. That is the level which any decent charger will maintain, and there is no "overcharged" condition. There is a serious difference between a fully charged reading of 13.2 and an equalization charge. |
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If you only test your batteries while a battery charger is runnning, then you
know very little about batteries. You must have a very clean hog, with all that wash on hand. Real life scenario for you: When I go aboard my boat and prepare to get underway, I check the battery voltmeter on the distribution panel. It always reads just over 13 volts. Before I start the engine, I shut off the shorepower to the vessel. When the shorepower is shut off, the battery charger is not "running". Does the voltmeter take a nosedive to 12.6? No, it does not. It remains at over 13. Yes, if I wait long enough the voltage will begin to drop. But my fully charged batteries show 13.2 volts *without* the charger running. Are you one of those bozos that runs a genset all night long? I don't run a genset at all. Propane galley boat with a diesel furnace. Two Rolls 8D batteries. Not even equipped with a genset. Are you one of those bozos who prefers to believe that the state of charge represented by the .6 volts between 13.2 and 12.6 never existed, simply because the first .6 volt bleeds off? |
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"Gould 0738" wrote in message
... If you only test your batteries while a battery charger is runnning, then you know very little about batteries. You must have a very clean hog, with all that wash on hand. Real life scenario for you: When I go aboard my boat and prepare to get underway, I check the battery voltmeter on the distribution panel. It always reads just over 13 volts. Before I start the engine, I shut off the shorepower to the vessel. When the shorepower is shut off, the battery charger is not "running". Does the voltmeter take a nosedive to 12.6? No, it does not. It remains at over 13. Why do you care? If it was on the charger overnight it should be fully charged. Even if the battery is near death it probabaly won't show at that point. Yes, if I wait long enough the voltage will begin to drop. But my fully charged batteries show 13.2 volts *without* the charger running. Are you one of those bozos that runs a genset all night long? I don't run a genset at all. Propane galley boat with a diesel furnace. Two Rolls 8D batteries. Not even equipped with a genset. Are you one of those bozos who prefers to believe that the state of charge represented by the .6 volts between 13.2 and 12.6 never existed, simply because the first .6 volt bleeds off? So if you stop and anchor, shut off the engine, relax for an hour or so, then check the battery and it reads 12.6, do you assume the battery is discharged? Everyone else would say it virtually fully charged. The bottom line is that the extra 0.6 Volts is an artifact of a recent charge, not a sign of depletion. |
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"Gould 0738" wrote in message ... I think this sentence is the core of your confusion. You can apply any voltage you want on the battery. "Equalization" or "Reconditioning" modes of chargers often apply 17 volts, and the battery will rise to that potential. It will also boil and melt if you leave it there too long. 17 volts is overcharged. "Equalization" involves the short term overcharge of a battery to blow the crud off the plates, but it is not a charge that a battery can sustain for a long period- as you correctly note. 13.2 is the proper reading for a fully charged battery. That is the level which any decent charger will maintain, and there is no "overcharged" condition. There is a serious difference between a fully charged reading of 13.2 and an equalization charge. I understand Gould. My point was that just as the battery will take a charge of 13.2 volts when on a float mode charger, it will also temporarily take the 17 volt equalization charge. Neither has anything to do with the battery's natural full charge of --- 12.6 volts. Two final questions for you, then I will give up and let the electrons fall as they may ... Following your logic, if 75% of the battery charge takes place during the bulk charge mode at 14.4 volts - why aren't you claiming that a fully charged 12 volt battery should read 14.4 volts? Secondly, if the bulk charge takes place at 14.4 volts, then drops to 13.5v or whatever for the absorbsion and float modes, what happened to the .9 volts? The charger never turned off. Hmmmm .... where did those electrons go? The answer is that your "fully charged" value of 13.2 volts is really just the output voltage of the charger, not the value of the battery potential by itself. Eisboch |
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Equation 8 is certainly not the whole story. I haven’t done the experiment
myself, but according to “common knowledge� lead sulfate is formed on the “+� plate, more in agreement with equation 3 than equation 8. It is a tangentially interesting question whether any of the hypothetical reactions listed above play any role -- even as intermediates -- in the real reaction. That is only tangentially interesting, because whether or not those reactions occur, we are still left with a major mystery: how and why does anything containing the SO4 group attack the “+� electrode? Neutral H2SO4 could reach the plate by simple diffusion, but it is present in fantastically low concentration. The bisulfate ion is present in high concentration, but would have to swim uphill against the electric field. The sulfate ion is present in low concentration and would have to swim doubly hard uphill. That means that when the cell is under heavy load, i.e. when there is a large field across the electrolyte, the SO4-related reaction would come to a halt. Let’s put in some numbers: The cell has an open-circuit voltage of 2.2 volts are so. Suppose that we put it under heavy load, so that there is ? v = 0.4 volts “IR� drop across the electrolyte. As always, room temperature corresponds to 25 meV (.025 electron-volts). Putting it all together: the Boltzmann factor that tells you what fraction of the bisulfate ions manage to climb the potential is exp(q ? v / kT) = exp(.4 / .025) = 9,000,000. So we would expect the reaction to proceed millions of times slower when we need it to proceed faster. In the foregoing calculation, we ignored the effect of dielectric screening. This may or may not have been the right thing. Argument pro: energy is conserved. At the end of the day, to move a bisulfate ion up a hill 0.4 volts high, you have to do 0.4 eV of work. Argument con: most of the height of the hill is associated with the dipole layer at the edge of the water, at the place where the electrolyte meets the plate; within the bulk of the electrolyte the field is smaller. The ions can with relatively resonable probability get close to the “+� plate, just outside the dipole layer. Unanswered question: if they get that close, is that close enough? ********************** Note the basis of calculation, opening sentence, paragraph four: 2.2 volts per cell. From http://www.av8n.com/physics/lead-acid.htm |
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"Gould 0738" quoted in message ... a bunch of theoretical mumbo jumbo from: http://www.av8n.com/physics/lead-acid.htm Ok, Chuck. Next time you need a new battery for your boat, run down to West Marine and ask for a 13 volt battery. More volts to you! Eisboch (happy to have 12.6 when I can get it) |
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An informed reference citing that voltage in a lead acid battery should not be
allowed to "fall below" 2.1 volts per cell. http://www.batteryuniversity.com/partone-6.htm (Rather a long way from jam-packed to capacity at the same value). |
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A source with yet a third opinion:
Describes a fully charged cell as 2.17 volts, float voltage at 12.9. http://www.keelynet.com/energy/sylcell.htm |
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Yet another opinion:
"2.15 volts per cell." Includes a chart showing a 12-volt battery is about 25% discharged at 12.6 volts http://continuouswave.com/whaler/ref...geBattery.html |
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An SLA must always be stored in a charged state. A topping charge should be
applied every six months (or other time intervals as recommended by the manufacturer) to avoid the voltage from dropping below 2.10 volts per cell. An approximate charge-level indication can be obtained by measuring the open terminal voltage of the cell while in storage. A voltage of 2.11V reveals that the cell has a charge of 50% and higher. If the voltage is at or above this threshold, the battery is in good condition and only needs a full charge cycle prior to use. If the voltage drops below 2.10V, several discharge/charge cycles may be required to bring the battery to full performance. (from) http://www.allegromicro.com/techpub2.../index3311.htm ******************* 2.11 volts per cell indicates as little as a 50% charge, according to this source |
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"Gould 0738" wrote in message ... Yet another opinion: "2.15 volts per cell." Includes a chart showing a 12-volt battery is about 25% discharged at 12.6 volts http://continuouswave.com/whaler/ref...geBattery.html I see where you are coming from Chuck. I think our differences are real world vs theoretical. Once discharged, even modestly, a brand new battery cannot be charged back to and hold (without benefit of a float charger) it's theoretical capacity. Initially the difference is small, but over time and with subsequent discharges, the difference gets larger until it's time for a new battery. During it's lifetime, the battery is considered "good" even though it is slowly degrading. Equalization or reconditioning extends the useful life of the battery, but it can never achieve and hold the theoretical per cell charge. To make matters worse, I doubt you could find a mass produced battery that has each cell producing exactly the same voltage, and more so as the battery ages. A couple of years ago I had to replace three 8D batteries in my big boat. Since I didn't want double hernias from this process, I checked the voltage on the new batteries before lugging them down into the engine room. 12.6 volts on each. I guess we exhausted this subject. Eisboch |
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Of lot of interesting links. Of course, none are relevant to the discussion.
For example, much of it refers to SLA batteries, what here in the States are usually called Gel batteries. Admittedly, their "open circuit voltage" is higher: 13.0 Volts is considered 100% charged, and 12.6 would be roughly half discharged. Further, the settling time is considerably longer. However, for a normal flooded battery an open circuit Voltage of over 12.6 to 12.8 (depending on the model) implies 100% charged. As Nigel Calder says "If Voltage readings are to be a meaningful reflection of the state of charge, the battery must be allowed to sit for at least 10 minutes; and hour or two would be better, overnight would be best (gel-cell batteries may to 48 hours to stabilize)." He then refers to a chart that indicates 100% charged for 12.6 Volts or greater (typical wet-cell);13.0 (Gel-Cell). A fuller description at: http://www.optimabattery.freeserve.c...AQ/carfaq4.htm where it explains that "Surface charge is the uneven mixture of sulfuric acid and water along the surface of the plates as a result of charging or discharging. It will make a weak battery appear good or a good battery appear bad." In other words, of you read the Voltage immediately after removing the charger, you will be misled as to the state of charge. You mentioned you have Rolls Batteries. Here's their service bulletin, where they say "Determining state of charge by voltage is more difficult as there must be no load or surface voltage present", but they indicate 100% charged is at 12.6 Volts: http://www.rollsbattery.com/Bulletins/600.htm "Gould 0738" wrote in message ... An SLA must always be stored in a charged state. A topping charge should be applied every six months (or other time intervals as recommended by the manufacturer) to avoid the voltage from dropping below 2.10 volts per cell. An approximate charge-level indication can be obtained by measuring the open terminal voltage of the cell while in storage. A voltage of 2.11V reveals that the cell has a charge of 50% and higher. If the voltage is at or above this threshold, the battery is in good condition and only needs a full charge cycle prior to use. If the voltage drops below 2.10V, several discharge/charge cycles may be required to bring the battery to full performance. (from) http://www.allegromicro.com/techpub2.../index3311.htm ******************* 2.11 volts per cell indicates as little as a 50% charge, according to this source |
Battery Meter
Of lot of interesting links. Of course, none are relevant to the discussion.
The discussion question revolves around the voltage of a fully charged battery. When evaluating battery charge to determine whether the charger has done its job, the voltage you want to achieve is 2.2 volts per cell, or 13.2. If you are disconnecting a charger when you get to 12.6, you have not fully charged your battery. If your charger cannot raise the voltage above 12.6, you have a bad charger or a failing battery. Several hours later the state of charge may deteriorate from 13.2 to 12.6. Your quote from Nigel Calder says that it might take as long as "overnight" for the battery to self-discharge to 12.6. The final .6 volts are there in the beginning, when the battery is *fully* charged, and before it drops off to the lower number. Therefore, a fully charged battery is 13.2 unless the final .6 volts can be shown to be a mass hallucination. There is no logic at all in a position that says the battery is not "fully charged" until the reading declines .6 volt. |
Battery Meter
On Fri, 21 May 2004 10:32:00 -0400, "Jeff Morris"
wrote: You mentioned you have Rolls Batteries. Here's their service bulletin, where they say "Determining state of charge by voltage is more difficult as there must be no load or surface voltage present", but they indicate 100% charged is at 12.6 Volts: http://www.rollsbattery.com/Bulletins/600.htm =========================================== The Rolls web site information is right on the money in my experience. If memory is correct, Rolls was founded by John Surette who has long been regarded as a leading battery engineer. |
Battery Meter
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