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#21
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a Li-Ion in a lead acid world.
On Nov 12, 9:29*pm, Mike the Strike wrote:
I remember fun days working in a lab where colleagues were developing the "revolutionary" sodium sulfur battery (colloquially referred to as the "fire and brimstone" battery). *The chief skill developers learned was how to run fast while wearing asbestos suits and full-face protective helmets. *If you've never had to deal with a bucket of burning molten sodium, you've never lived! *(Hint - water isn't terribly useful!) *You probably wouldn't want any quantity of burning (molten or otherwise) lithium near you or in your glider either. Lithium is WAY too close to the reactive end of the periodic table (right up there with sodium, magnesium and potassium). MIke Mike, I have no problem with considering Li-Ion's to be unsafe and to have no place in a glider, but I don't understand having that opinion and then flying with 1 to 3 of them. That was why I burned up an Ipaq battery, to see if they are too small to cause a problem. My conclusion is that anything from 800 mAH or larger, and probably smaller, will make a glider uninhabitable. But perhaps a better way of getting a handle on the risk is to look at the incident rate, said to be about 100 cell phones fires between 2002 to 2004, out of more than 200 million cell phones are in use. This is consistent with a fire risk of something like 1 in 4 million per year of use for 'good' batteries and 1 in 200,000 for defective ones. Laptop fires: There were two recalls, the first of 9.7 million laptops after 16 fires, the other of under 6 million after 50 fires. This was for defective units with metal particles that internally shorted out the battery. More info he http://www.consumeraffairs.com/news0...#ixzz157SfeqzG and he http://www.buchmann.ca/article28-page1.asp Really I am not trying to convince anyone that Li-Ions are safe, I thought it would be helpful to have a discussion about them. The most valuable fact for me was the existence of the 15AH lead acid unit. Brian |
#22
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a Li-Ion in a lead acid world.
On 11/13/2010 2:33 PM, brianDG303 wrote:
Mike, I have no problem with considering Li-Ion's to be unsafe and to have no place in a glider, but I don't understand having that opinion and then flying with 1 to 3 of them. That was why I burned up an Ipaq battery, to see if they are too small to cause a problem. My conclusion is that anything from 800 mAH or larger, and probably smaller, will make a glider uninhabitable. But perhaps a better way of getting a handle on the risk is to look at the incident rate, said to be about 100 cell phones fires between 2002 to 2004, out of more than 200 million cell phones are in use. This is consistent with a fire risk of something like 1 in 4 million per year of use for 'good' batteries and 1 in 200,000 for defective ones. Laptop fires: There were two recalls, the first of 9.7 million laptops after 16 fires, the other of under 6 million after 50 fires. This was for defective units with metal particles that internally shorted out the battery. More info he http://www.consumeraffairs.com/news0...#ixzz157SfeqzG and he http://www.buchmann.ca/article28-page1.asp Really I am not trying to convince anyone that Li-Ions are safe, I thought it would be helpful to have a discussion about them. The most valuable fact for me was the existence of the 15AH lead acid unit. I think there are some important differences between the Li-ion batteries used in consumer products and those we are contemplating using in our gliders: * the cell phone, laptop, power tool batteries are high volume production products. My guess is they are likely more consistent in quality than buying hand assembled, small batch (or only one-at-a-time) units. * they all have dedicated, proprietary chargers that plug in to only their intended battery * they store much more energy than a laptop battery, and far more than a cell phone battery, so even be a small problem is likely turn in to a bigger problem than the cell phone/laptop battery. * the high volumes make good engineering and testing of the designs for the battery, it's protection circuitry, and it's charger relatively cheap per unit * they aren't subjected to the low pressures of 18K and higher that many of us routinely achieve. The high price will keep most pilots from buying one, so I'm not too worried about imminent fireballs on the end of a tow rope. It does seem prudent to consider Li-ion only if you really, really, need to save a few pounds or increase the capacity a few amphours, then buy it from a reputable supplier (not the cheapest), and pay strict attention to the charging procedures. -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl - "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz |
#23
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a Li-Ion in a lead acid world.
When I found that my cell phone and my iPAQ had Li-Ion batteries that
were 1 to 3 times the 800 mAH size that Brian feels could “make a glider uninhabitable”, I got motivated to look into what might cause a problem with Li-Ion. An EPA technical article said Li-Ion batteries were safe only if they operated in a small range of voltage and temperature (cell voltage between 2.0 to 4.2 volts, and cell temperature between 0 to 120 degrees C). Charging outside of this range causes most problems, but high temperatures can cause thermal runaway spontaneously. Underwriters Laboratories specifies Li-Ion battery tests that over- charge, short circuit, puncture, and over heat - they want to see no explosions or burning result. Shippers have to pack Li-Ion batteries so they are protected from damage and short circuit, and if they’re in a device it cannot accidentally turn on during shipment. As the Buchmann article Brian referenced pointed out, Li-Ion manufacturers try to achieve reliability by including safety mechanisms within the cell, and by adding protection circuits within the battery pack. But the protection circuits can be destroyed without the user knowing, via static electricity or a faulty charger. Further, internal defects can occur that might defeat the cell safety mechanisms. The massive Dell/Apple battery recall was for Li-Ion batteries made by Sony, whose batteries were contaminated internally during manufacture with microscopic metal particles. It was possible for the metal particles to trigger thermal runaway (also referred to as “venting with flame”) that cannot be stopped once it starts. For us glider pilots I conclude we’re probably OK as long as we don’t fly with dropped or damaged cell phones and/or iPAQs. It would also be a good idea to turn your cell phone turned of during flight. But one big problem for us glider pilots is that we’re charging our iPAQ’s Li-Ion cells while flying, and there’s a problem if repeated charging occurs below 0 degrees C. Metallic lithium will plate the inside of the cell, which causes the cell to be more vulnerable to thermal runaway if it is subjected to impact, crushing or high rate charging (like maybe if you run your iPAQ down and then connect it to the ship’s power). For those of you who fly in real cold weather or who fly at high alititudes, be aware. -John |
#24
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a Li-Ion in a lead acid world.
On Sun, 14 Nov 2010 08:04:47 -0800, jcarlyle wrote:
But one big problem for us glider pilots is that we’re charging our iPAQ’s Li-Ion cells while flying, and there’s a problem if repeated charging occurs below 0 degrees C. Metallic lithium will plate the inside of the cell, which causes the cell to be more vulnerable to thermal runaway if it is subjected to impact, crushing or high rate charging (like maybe if you run your iPAQ down and then connect it to the ship’s power). For those of you who fly in real cold weather or who fly at high alititudes, be aware. A very interesting description of what can cause a thermal runaway. Thanks. I use a Binatone PNA to run LK8000 and have a couple of questions: - when a PNA or PDA is running normally, how warm is the internal Li-ion battery, i.e. what are the limits on the battery staying warm enough to keep it above zero? - Is there any way of using these things that minimises the chances of damaging the battery? From what you say, running the PNA well down before plugging it to charge it isn't so clever at low temperatures. I keep mine fully charged when its out of the glider and its always connected to the charger when I'm flying with it. Is this the best way of keeping the battery warm and happy? -- martin@ | Martin Gregorie gregorie. | Essex, UK org | |
#25
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a Li-Ion in a lead acid world.
Martin, you're welcome.
I wish I could answer your first question, but I cannot. I suspect it depends heavily on how insulating the PNA case is, how much current the PNA draws, and how much heat the PNA's backlight and other circuitry generates. You'll need to experiment to find out, I'm afraid. And then you've still got some leeway, probably, because I suspect that the lithium plating doesn't start immediately at 0C and it will also depend on the charging current. As for your second question, what you propose is exactly what I think you should do. I keep my iPAQ on charge at home and also charge it in my car until just before I put it in the cockpit, when the ship's power takes over keeping the charge up. -John On Nov 14, 3:29 pm, Martin Gregorie wrote: A very interesting description of what can cause a thermal runaway. Thanks. I use a Binatone PNA to run LK8000 and have a couple of questions: - when a PNA or PDA is running normally, how warm is the internal Li-ion battery, i.e. what are the limits on the battery staying warm enough to keep it above zero? - Is there any way of using these things that minimises the chances of damaging the battery? From what you say, running the PNA well down before plugging it to charge it isn't so clever at low temperatures. I keep mine fully charged when its out of the glider and its always connected to the charger when I'm flying with it. Is this the best way of keeping the battery warm and happy? |
#26
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a Li-Ion in a lead acid world.
On Sun, 14 Nov 2010 13:33:59 -0800, jcarlyle wrote:
I wish I could answer your first question, but I cannot. I suspect it depends heavily on how insulating the PNA case is, how much current the PNA draws, and how much heat the PNA's backlight and other circuitry generates. You'll need to experiment to find out, I'm afraid. And then you've still got some leeway, probably, because I suspect that the lithium plating doesn't start immediately at 0C and it will also depend on the charging current. Now I think about it, I have a sort of partial, vague, sort-of datapoint. Recently The staff members of The Register, an online technical mag, dropped a paper aeroplane from 89,500 ft using a large weather balloon. It also carried payload in the shape of a box made from thick foam and containing a GPS tracker, a video camera, a still camera that took a photo every 10 secs and at least one chemical hand-warmer. The still camera quit on the way up at the cloud tops but the video ran for the whole flight, which lasted around 2.5 hours, so (surprise!) it looks as if you need a reasonable current drain to keep the battery warm. Unfortunately the mission wasn't instrumented enough to record temperature and the flight trace has no timestamps. Details are here if you're interested: http://www.theregister.co.uk/science/paris/ As for your second question, what you propose is exactly what I think you should do. I keep my iPAQ on charge at home and also charge it in my car until just before I put it in the cockpit, when the ship's power takes over keeping the charge up. That's good to know. Thanks. -- martin@ | Martin Gregorie gregorie. | Essex, UK org | |
#27
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a Li-Ion in a lead acid world.
In article ,
Eric Greenwell wrote: * the cell phone, laptop, power tool batteries are high volume production products. My guess is they are likely more consistent in quality than buying hand assembled, small batch (or only one-at-a-time) units. * they all have dedicated, proprietary chargers that plug in to only their intended battery Are you referring to internal charging circuitry with this last item? Because many (most?) cell phones will charge off any standard USB port, as long as you have the appropriate cable (and many can use a standard USB cable for it). I believe the batteries themselves have enough circuitry that the external charger doesn't need to be all that good to keep things safe. I agree with your point overall. While I carry my cell phone with me in flight without a second thought, I'd be hesitant to have an order of magnitude more battery capacity on board in Li-ion form. -- Mike Ash Radio Free Earth Broadcasting from our climate-controlled studios deep inside the Moon |
#28
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a Li-Ion in a lead acid world.
On Nov 14, 5:32*pm, Mike Ash wrote:
In article , *Eric Greenwell wrote: * * * the cell phone, laptop, power tool batteries are high volume * * * production products. My guess is they are likely more consistent * * * in quality than buying hand assembled, small batch (or only * * * one-at-a-time) units. * * * they all have dedicated, proprietary chargers that plug in to only * * * their intended battery Are you referring to internal charging circuitry with this last item? Because many (most?) cell phones will charge off any standard USB port, as long as you have the appropriate cable (and many can use a standard USB cable for it). I believe the batteries themselves have enough circuitry that the external charger doesn't need to be all that good to keep things safe. I agree with your point overall. While I carry my cell phone with me in flight without a second thought, I'd be hesitant to have an order of magnitude more battery capacity on board in Li-ion form. -- Mike Ash Radio Free Earth Broadcasting from our climate-controlled studios deep inside the Moon Lithium batteries come in many chemistries - some with problematic safety, others as safe as any battery can be. To group them all under the heading "lithium-ion" is at best uninformed. Many of us will soon be driving around with several hundred pounds of "lithium-ion" in our cars. One of the safest and best is "Lithium Iron Phosphate" (LiFePo4) chemistry. This safety comes at the cost of lower energy density than is typical of cell-phone or laptop batteries but they are still far more energy dense than any lead battery. They also have a discharge voltage curve which allows full use of their capacity. |
#29
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a Li-Ion in a lead acid world.
On 11/14/2010 4:32 PM, Mike Ash wrote:
In , Eric wrote: * the cell phone, laptop, power tool batteries are high volume production products. My guess is they are likely more consistent in quality than buying hand assembled, small batch (or only one-at-a-time) units. * they all have dedicated, proprietary chargers that plug in to only their intended battery Are you referring to internal charging circuitry with this last item? Because many (most?) cell phones will charge off any standard USB port, as long as you have the appropriate cable (and many can use a standard USB cable for it). I believe the batteries themselves have enough circuitry that the external charger doesn't need to be all that good to keep things safe. I agree with your point overall. While I carry my cell phone with me in flight without a second thought, I'd be hesitant to have an order of magnitude more battery capacity on board in Li-ion form. I'm pretty sure the charge control circuitry is in the cell phone, the Ipaq, or the laptop itself, not in it's battery, and the "charger" that plugs into the wall is really only a power supply without a charge regulator. It's not obvious from my writing, but that's what I meant by the "proprietary chargers that plug in to only their intended battery". The cell phone and Ipaq batteries I've seen are single cell units; laptop batteries are multiple cell in series (and some are multiple series units in parallel). The K2 battery in the Soaring article looks interesting, and is closest I've seen to a drop-in replacement, but the datasheet was sparse. It didn't go into what protection circuitry was installed in the box, or what the charger was like. It seems very "one-off" to me, and I'd like more data and more field history before committing to one. -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl - "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz |
#30
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a Li-Ion in a lead acid world.
The battery in an Ipaq is a flat foil covered package, I wish now that
I had opened up the one I burned. The 12 volt batteries that I was working with, that I gave a link to, are composed of 3 similar flat foil packages, each when opened have a long narrow circuit board along the top. These apparently 'turn off' the battery when you dead short or put to much load on them and probably have other protective properties as well. Under some conditions these will fail and at that point I could never get the battery to work again. Brian |
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