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Interesting Lead Acid Battery facts
I found this information in a e-book called "Batteries in a Portable
World" by Buchmann. In our ongoing watered golf cart vs. expensive maintenance-free gauze battery discussion, there are some very revealing facts the author points out that I'm sure the battery sales people wouldn't want you to look at too closely... Sorry for the wordwrapping nonsense I can't seem to stop.... It says: "The Lead Acid Battery Invented by the French physician Gaston Planté in 1859, lead acid was the first rechargeable battery for commercial use. Today, the flooded lead acid battery is used in automobiles, forklifts and large uninterruptible power supply (UPS) systems. During the mid 1970s, researchers developed a maintenance-free lead acid battery, which could operate in any position. The liquid electrolyte was transformed into moistened separators and the enclosure was sealed. Safety valves were added to allow venting of gas during charge and discharge. Driven by diverse applications, two designations of batteries emerged. They are the sealed lead acid (SLA), also known under the brand name of Gelcell, and the valve regulated lead acid (VRLA). Technically, both batteries are the same. No scientific definition exists as to when an SLA becomes a VRLA. (Engineers may argue that the word ‘sealed lead acid’ is a misnomer because no lead acid battery can be totally sealed. In essence, all are valve regulated.) The SLA has a typical capacity range of 0.2Ah to 30Ah and powers portable and wheeled applications. Typical uses are personal UPS units for PC backup, small emergency lighting units, ventilators for health care patients and wheelchairs. Because of low cost, dependable service and minimal maintenance requirements, the SLA battery is the preferred choice for biomedical and health care instruments in hospitals and retirement homes. The VRLA battery is generally used for stationary applications. Their capacities range from 30Ah to several thousand Ah and are found in larger UPS systems for power backup. Typical uses are mobile phone repeaters, cable distribution centers, Internet hubs and utilities, as well as power backup for banks, hospitals, airports and military installations. Unlike the flooded lead acid battery, both the SLA and VRLA are designed with a low over-voltage potential to prohibit the battery from reaching its gas-generating potential during charge. Excess charging would cause gassing and water depletion. Consequently, the SLA and VRLA can never be charged to their full potential. Among modern rechargeable batteries, the lead acid battery family has the lowest energy density. For the purpose of analysis, we use the term ‘sealed lead acid’ to describe the lead acid batteries for portable use and ‘valve regulated lead acid’ for stationary applications. Because of our focus on portable batteries, we focus mainly on the SLA. The SLA is not subject to memory. Leaving the battery on float charge for a prolonged time does not cause damage. The battery’s charge retention is best among rechargeable batteries. Whereas the NiCd self-discharges approximately 40 percent of its stored energy in three months, the SLA self-discharges the same amount in one year. The SLA is relatively inexpensive to purchase but the operational costs can be more expensive than the NiCd if full cycles are required on a repetitive basis. The SLA does not lend itself to fast charging — typical charge times are 8 to 16 hours. The SLA must always be stored in a charged state. Leaving the battery in a discharged condition causes sulfation, a condition that makes the battery difficult, if not impossible, to recharge. Unlike the NiCd, the SLA does not like deep cycling. A full discharge causes extra strain and each discharge/charge cycle robs the battery of a small amount of capacity. This loss is very small while the battery is in good operating condition, but becomes more acute once the performance drops below 80 percent of its nominal capacity. This wear-down characteristic also applies to other battery chemistries in varying degrees. To prevent the battery from being stressed through repetitive deep discharge, a larger SLA battery is recommended. Depending on the depth of discharge and operating temperature, the SLA provides 200 to 300 discharge/charge cycles. The primary reason for its relatively short cycle life is grid corrosion of the positive electrode, depletion of the active material and expansion of the positive plates. These changes are most prevalent at higher operating temperatures. Applying charge/discharge cycles does not prevent or reverse the trend. There are some methods that improve the performance and prolong the life of the SLA. The optimum operating temperature for a VRLA battery is 25°C (77°F). As a rule of thumb, every 8°C (15°F) rise in temperature will cut the battery life in half. VRLA that would last for 10 years at 25°C would only be good for 5 years if operated at 33°C (95°F). The same battery would endure a little more than one year at a temperature of 42°C (107°F). The SLA has a relatively low energy density compared with other rechargeable batteries, making it unsuitable for handheld devices that demand compact size. In addition, performance at low temperatures is greatly reduced. The SLA is rated at a 5-hour discharge or 0.2C. Some batteries are even rated at a slow 20 hour discharge. Longer discharge times produce higher capacity readings. The SLA performs well on high pulse currents. During these pulses, discharge rates well in excess of 1C can be drawn. In terms of disposal, the SLA is less harmful than the NiCd battery but the high lead content makes the SLA environmentally unfriendly. Ninety percent of lead acid-based batteries are being recycled." Most interesting.... No wonder they last longer up north where it's colder than here in the tropics....contrary to the idea of pulling them out of the boat and putting them in a warm place all winter... Looks like they're better off in the boat under the snow! |
Interesting Lead Acid Battery facts
Larry,
How would you count a charge / discharge cycle according to this article? When I use my two paralleled AGM's to start my little 15 hp diesel, is that a cycle? I don't see how it could be since I sail nearly every day during the summer and my batteries ought to be nearly dead now. If the battery is good for 200 cycles and my draw down is only 10% (In reality, it's probably less than that since my engine lights of almost as quickly as a good car engine) can I expect to get closer to 2000 charging cycles? I feel even better about leaving my batteries in the boat now. Thanks for the article. -- Roger Long |
Interesting Lead Acid Battery facts
Roger Long wrote:
Larry, How would you count a charge / discharge cycle according to this article? When I use my two paralleled AGM's to start my little 15 hp diesel, is that a cycle? I don't see how it could be since I sail nearly every day during the summer and my batteries ought to be nearly dead now. If the battery is good for 200 cycles and my draw down is only 10% (In reality, it's probably less than that since my engine lights of almost as quickly as a good car engine) can I expect to get closer to 2000 charging cycles? I feel even better about leaving my batteries in the boat now. Thanks for the article. Roger, starting a 15 hp diesel probably takes less than 80 amps for 20 seconds. This is less than half an amp-hour, probably less than one percent of the battery's capacity. Mere noise in charge/discharge cycle space. Chuck ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Interesting Lead Acid Battery facts
"Roger Long" wrote in
: How would you count a charge / discharge cycle according to this article? When I use my two paralleled AGM's to start my little 15 hp diesel, is that a cycle? I don't see how it could be since I sail nearly every day during the summer and my batteries ought to be nearly dead now. If the battery is good for 200 cycles and my draw down is only 10% (In reality, it's probably less than that since my engine lights of almost as quickly as a good car engine) can I expect to get closer to 2000 charging cycles? I believe he was referring to drawing down the battery in a deep discharge cycle, not just a burst of starter current. Hell, we'd have to put 4 batteries a year in my car if that were so...(c; A good diesel fires on the 2nd TDC it rolls over. When Dan had the old Hatteras 56, I told him I'd be afraid to jack over the 8v92TAs by hand as they would probably start as soon as something moved. Both those engines you just touched the starter and they popped up running...2-strokes, gotta love 'em. I think the 300 real cycles, using the batteries for lights and loads, then recharging them properly to full charge SLOWLY is quite realistic for lead acid AGMs or Gelcells. I just spent $70 putting 2 new 12AH AGMs in my dock scooter. It's like driving a hot rod! Even at full throttle, the status light stays green as soon as it comes up to speed. The acid soaked gauze gets used up in about 200 cycles in the scooter....less than a year the way I use it all summer. There were very important graphs to study in this report that boaters need to see, especially about charging.... I found the book for free on his website: http://www.buchmann.ca/toc.asp In figure 4-3 on pdf page 61, notice how the 3-stage charging is measured in HOURS, not running the diesel for 30 minutes like boaters dream of. Notice how the current drops very rapidly near the start of the charge, not when the charge is near complete. My assertion of why it's stupid to put a 140 amp alternator on a little sailboat diesel is obvious. The accompanying text: "A multi-stage charger applies constant-current charge, topping charge and float charge (see Figure 4-3). During the constant current charge, the battery charges to 70 percent in about five hours; the remaining 30 percent is completed by the slow topping charge. The topping charge lasts another five hours and is essential for the well-being of the battery. This can be compared to a little rest after a good meal before resuming work. If the battery is not completely saturated, the SLA will eventually lose its ability to accept a full charge and the performance of the battery is reduced. The third stage is the float charge, which compensates for the self-discharge after the battery has been fully charged." See the time in HOURS, not MINUTES? He's especially talking about AGM and Gelcell batteries boaters think are superbatteries because of the awful prices. So, you're looking at charging them for several hours, not just when the charging voltage pops up as is so often the case in a boat trying to get that diesel shut down ASAP...shortening battery life in the process by first overcharging, then not giving the chemistry TIME to charge the cells. To quote the text, again: "The charge algorithm for lead acid batteries differs from nickel-based chemistry in that voltage limiting rather than current limiting is used. Charge time of a sealed lead acid (SLA) is 12 to 16 hours. With higher charge currents and multi-stage charge methods, charge time can be reduced to 10 hours or less. SLAs cannot be fully charged as quickly as nickel-based systems." 10 HOURS, not 30 minutes. Most sailboat captains would have a heart attack....(c; Of course, if you're headed back to the dock to plug in the little 10A chargers...or a mooring with big solar panels or wind charger...that's exactly what happens...HOURS. I still prefer liquid electrolyte to gells and wicks. I can charge them to a full charge and replace any electrolyte that vents. I can also adjust their specific gravity to balance the cells over time to maximize life. "Maintenance Free" just means you can't help them, once they start down. Larry -- Why is it, in any city, all traffic lights act as if they have rotary timers in them, like they did in 1955, and are all set to create maximum inconvenience and block traffic movement, entirely? |
Interesting Lead Acid Battery facts
The battery power required to start the engine raises a question for me. I
have a Universal 18 in my boat. I have not tried to manually crank it by attaching a handle to the crank shaft, but I have been told that it can be done by hammering a wrench socket onto the shaft, and cranking it with a ratchet. It seems like this would be a good way to conserve battery power if there were a non-destructive way to manually crank the engine. Is there some sort of racheted, removable socket that would fit on the shaft to enable a manual crank, sort of like automobile crank handles at the turn of the century? A little elbow grease might save a tree in the long run. "Larry" wrote in message ... "Roger Long" wrote in : How would you count a charge / discharge cycle according to this article? When I use my two paralleled AGM's to start my little 15 hp diesel, is that a cycle? I don't see how it could be since I sail nearly every day during the summer and my batteries ought to be nearly dead now. If the battery is good for 200 cycles and my draw down is only 10% (In reality, it's probably less than that since my engine lights of almost as quickly as a good car engine) can I expect to get closer to 2000 charging cycles? I believe he was referring to drawing down the battery in a deep discharge cycle, not just a burst of starter current. Hell, we'd have to put 4 batteries a year in my car if that were so...(c; A good diesel fires on the 2nd TDC it rolls over. When Dan had the old Hatteras 56, I told him I'd be afraid to jack over the 8v92TAs by hand as they would probably start as soon as something moved. Both those engines you just touched the starter and they popped up running...2-strokes, gotta love 'em. I think the 300 real cycles, using the batteries for lights and loads, then recharging them properly to full charge SLOWLY is quite realistic for lead acid AGMs or Gelcells. I just spent $70 putting 2 new 12AH AGMs in my dock scooter. It's like driving a hot rod! Even at full throttle, the status light stays green as soon as it comes up to speed. The acid soaked gauze gets used up in about 200 cycles in the scooter....less than a year the way I use it all summer. There were very important graphs to study in this report that boaters need to see, especially about charging.... I found the book for free on his website: http://www.buchmann.ca/toc.asp In figure 4-3 on pdf page 61, notice how the 3-stage charging is measured in HOURS, not running the diesel for 30 minutes like boaters dream of. Notice how the current drops very rapidly near the start of the charge, not when the charge is near complete. My assertion of why it's stupid to put a 140 amp alternator on a little sailboat diesel is obvious. The accompanying text: "A multi-stage charger applies constant-current charge, topping charge and float charge (see Figure 4-3). During the constant current charge, the battery charges to 70 percent in about five hours; the remaining 30 percent is completed by the slow topping charge. The topping charge lasts another five hours and is essential for the well-being of the battery. This can be compared to a little rest after a good meal before resuming work. If the battery is not completely saturated, the SLA will eventually lose its ability to accept a full charge and the performance of the battery is reduced. The third stage is the float charge, which compensates for the self-discharge after the battery has been fully charged." See the time in HOURS, not MINUTES? He's especially talking about AGM and Gelcell batteries boaters think are superbatteries because of the awful prices. So, you're looking at charging them for several hours, not just when the charging voltage pops up as is so often the case in a boat trying to get that diesel shut down ASAP...shortening battery life in the process by first overcharging, then not giving the chemistry TIME to charge the cells. To quote the text, again: "The charge algorithm for lead acid batteries differs from nickel-based chemistry in that voltage limiting rather than current limiting is used. Charge time of a sealed lead acid (SLA) is 12 to 16 hours. With higher charge currents and multi-stage charge methods, charge time can be reduced to 10 hours or less. SLAs cannot be fully charged as quickly as nickel-based systems." 10 HOURS, not 30 minutes. Most sailboat captains would have a heart attack....(c; Of course, if you're headed back to the dock to plug in the little 10A chargers...or a mooring with big solar panels or wind charger...that's exactly what happens...HOURS. I still prefer liquid electrolyte to gells and wicks. I can charge them to a full charge and replace any electrolyte that vents. I can also adjust their specific gravity to balance the cells over time to maximize life. "Maintenance Free" just means you can't help them, once they start down. Larry -- Why is it, in any city, all traffic lights act as if they have rotary timers in them, like they did in 1955, and are all set to create maximum inconvenience and block traffic movement, entirely? |
Interesting Lead Acid Battery facts
Larry wrote:
Snip In figure 4-3 on pdf page 61, notice how the 3-stage charging is measured in HOURS, not running the diesel for 30 minutes like boaters dream of. Notice how the current drops very rapidly near the start of the charge, not when the charge is near complete. My assertion of why it's stupid to put a 140 amp alternator on a little sailboat diesel is obvious. Snip In fairness, typical automotive chargers are not rated for use with the aggressive, constant-current charging cycles used in popular marine "smart chargers". Replacing the stock alternator with a higher-rated one when switching to a smart charger is not a bad idea, providing engine, pulleys, and belts are also willing. I agree that 30 minutes is not going to restore 50% of capacity on 200 Ah deep-cycle lead acid batteries. With a 140 amp alternator, gasses, venting, etc., permitting, it would take more than an hour. Hard to generalize, but with an adequate alternator, belt, engine speed and charger, it is heat and gassing that ultimately limit the rate at which you can jam amp-hours into a storage battery, and the better smart chargers monitor terminal temperature and fold back current to try to keep things intact. Haven't heard many horror stories of smart chargers destroying batteries. Remember too, even though you recover most of the lost charge quickly through constant-current charging, that last 10-15% is what will take hours to accomplish under typical voltage-limited charging, even with smart chargers. So the author quoted is perhaps overconcise in his statements. Don't sell the smart chargers too short, Larry! ;-) Chuck ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Interesting Lead Acid Battery facts
|
Interesting Lead Acid Battery facts
Larry wrote:
In our ongoing watered golf cart vs. expensive maintenance-free gauze battery discussion, there are some very revealing facts the author points out that I'm sure the battery sales people wouldn't want you to look at too closely... [snip] Good stuff. My own experience with lead-acid batteries leads me to believe that no matter how well you take care of them they don't last more than a 2 or 3 years. For example I had a pair of deep cycle marine batteries in the truck to run ham radio equipment, I installed those in about November of 2004. They aren't deeply discharged, and the truck is driven every day for at least 20 miles and usually much more than that, rarely is it left a whole day without moving at all (when left at an airport only). The radio equipment is on all the time so there is a constant load and it did happen on rare occasions (airport) that the batteries would get drained completely, but I consider that typical of what a cruiser does to batteries, sometimes it just happens. The batteries have been well maintained, I check the water in them often and replace it as necessary, and the batteries are sitting on a wooden battery "tray" that I made for them behind the passenger seat. I wouldn't say they are pampered, but they certainly are not abused. Recently these batteries have degraded to the point that they won't run the radio equipment over an entire night (10 hours let's say) before they go completely dead. Now of course those "completely dead" dicharge cycles are rapidly eating the batteries and sucking out what life they had left in them, because it's a bad thing to completely discharge lead acid batteries. But they degrade naturally to that point, that is to say that I didn't suddenly change my habits, they are being subjected to the same conditions as when they were first installed in the truck. This is very similar to experience I have had with lead acid batteries over my lifetime, but I always thought that they "died" because I wasn't taken good enough care of them. I'm convinced now, however, that it really doesn't matter much, that no matter what you do with deep cycle lead acid batteries they are not going to last more than about 2 or 3 years, maybe a few years more if you have a really huge bank that is under a very light load, and maybe a few years more beyond that if you are using something more substantial than a marine deep cycle, something made as a UPS backup for example or for unattended telephone stations. I have started to think that it's best to just plan on replacing the bank after 3 or 4 years (conservatively) and buy accordingly. In any mega-store store you can get 100aH 12vdc batteries for 50$us/each. So for 2000aH at 12vdc that's about 1000$us, amortized over 3 years let's say, that's about 333$us/year. Compare that with West Marine AGM 8D batteries in a bank, 180aH per 12vdc battery for 410$us/battery, that comes out by my math to be 2000aH for 4551$us/bank, or about 4 times as expensive as the cheap lead acid batteries. Are the expensive ones going to last 4 times as long ? Say that again ... are the expensive AGM marine deep cycle batteries from West Marine going to last 12 years ? Anyone have experience that says yes ? They'd have to last that long to give the same cost/benefit. Do they last that long ? I have my doubts. In fact, I'm starting to think that the best way to go is to just find a supplier of the cheapest thick plate lead acid battery you can find and buy your banks there with the intention of replacing them all after 3 or 4 years. |
Interesting Lead Acid Battery facts
"roger lothoz" wrote in
: Because all of us would not have enough time in our life to experiment all brands of batteries available on the market place. I would suggest to express individual experiences. Would it be a good idea? AS there is really no difference in the CHEMISTRY of the lead-acid battery, does it really make any difference who makes the same ol' technology we've always used? I think not. Sales hype and outrageous pricing doesn't change chemistry, much....not that much. |
Interesting Lead Acid Battery facts
"purple_stars" wrote in
oups.com: Recently these batteries have degraded to the point that they won't run the radio equipment over an entire night (10 hours let's say) before they go completely dead. Now of course those "completely dead" dicharge cycles are rapidly eating the batteries and sucking out what life they had left in them, because it's a bad thing to completely discharge lead acid batteries. I used to run a rather powerful HF station mobile: Yaesu FT-900 remote mounted in trunk Highly modified TenTec Hercules II, 120 amps from golf cart beasts with 650 watts output to a 15' tall, trailer-hitch-mounted, homebrew using Henry Allen's Texas Bugcatcher's biggest coil and 8-spoke, 36" capacitor hat. On 20M, my favorite band, the coil was shorted out, completely, and the whip on top was tuned so only the capacitor hat was used, pulling the current lobe way up the mast for more H field. Maybe some day I'll put it back in the car when the sun cooperates better.... I, too, drove the car every day and didn't really tax it much with much transmitting power, except on long trips with ham friends. The big batteries got weaker over time and it took me a while to figure out what was going on..... Like you, my daily drive was around 25 miles of city driving, which is part of the problem. I used a continuous duty solenoid to connect the ham batteries in parallel with the diesel starting battery in the finest ham radio car (zero electrical noise) ever invented, the 1973 Mercedes 220Diesel with no electronics, at all. I still drive it. I restored it. The car has a 80A alternator, plenty of juice, and a huge starting battery for the diesel. I started tracking the specific gravity and plotting it after a long overcharge (2 days) from 1.280 sg. Each day, upon arriving home from the driving, I got out my hydrometer and recorded/plotted the gravity, the only REAL means of measuring cell condition in lead acid batteries. The chart started falling from that first day. Well, maybe it'll level off at some point, as we did start with a really full charge. Nope, it never did. The 25-45 mile drive each day in stop and go traffic never produced enough charging TIME to recover the gravity all the way up to full, or even close. It looked good on the voltmeter, 14.5 volts charging, until I stopped or keyed the beast around 140A (with the radio) on packet or rtty. There simply wasn't enough charge TIME to cause the chemistry to reverse. I gave up the test around 1.180, defeated..... The solution was quite simple. Leave a drop cord by the car and mount a 10A automatic shutoff battery charger in the trunk by the batteries....and simply plug in the car all night. Specific gravity recovered the first day from the SLOW, SLOW recharging at 3-4A and each morning the charger would by slowly cycling on with long off periods as the battery's high gravity voltage held it off very nicely. I remoted the charger's AC plug to under the trailer hitch to make connecting it as easy an painless as possible. The batteries went from lasting a year and a half to five and a half years, same batteries, same manufacturer....lots less unrecoverable sulphation. Boats that have a little charger plugged into the dock and water their batteries with DISTILLED ONLY get that gravity back up after the abuse of dreaming you're going to charge them at 50A for 30 minutes on the engine at sea. Same effect....charging happens very SLOWLY OVER TIME. |
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