DELL Notebook Battery Recall
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TexasStooge
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tomboudreau
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tomboudreau
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Rainband
I always let my computer turn itself off. I have a 600m and I love it. I do the same with my cell bettery. Thanks tomtomboudreau wrote:You should let the battery drain fully before charging it. Most likely cause is that the battery has developed a memory and will think it is fully charged when infact it isnt. This happens when the battery is not drained before charging. Cell phone batteries are also famous for doing this.
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MSRobi911
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Please everyone take this seriously!!!! My best friends daughter and her daughter is my daughter's best friend and Lindaloo's cousin had one of these at her apartment at college up at Delta State. She went to bed and left her lap top plugged in to charge, not on, but just charging. Her roommate woke up and the entire apartment was on fire with smoke billowing everywhere. They had to jump out of a second story window to get out. The apartment was a total loss, this was right after Katrina and she had lost everything she had at her home in Pascagoula and now she lost everything she had in her apartment at school. Dell denied any responsibility! Well Deb isn't letting it go, she has a special attorney and they are filing suit against Dell for not issuing a recall on the batteries. She went on line and found something that said they had already caused fires in different cases in other areas. And NOW they issue a recall??
Its such a shame, poor girl the only thing she had to her name was the t-shirt and shorts she had on when she jumped out the window, thank goodness for the people at Delta State who gave her some clothes to wear!!
She had never had any problems with her battery. The Fire Marshall said it was the direct cause for the fire, that it was where the fire started.
Mary
Its such a shame, poor girl the only thing she had to her name was the t-shirt and shorts she had on when she jumped out the window, thank goodness for the people at Delta State who gave her some clothes to wear!!
She had never had any problems with her battery. The Fire Marshall said it was the direct cause for the fire, that it was where the fire started.
Mary
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karenfromheaven
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The battery chemistry used in modern laptops and cell phones is known as lithium-ion (Li-ion). It is favored because it has the highest energy density of the commonly used chemistries. Nickel-metal-hydride (NiMH) is commonly used for those rechargeable cells (AA, AAA, C) that you can put into toys and cameras. It is an evolution from the older Nickel Cadmium (NiCad) chemistry.
The original NiCad cells suffered from an effect where if they were repeatedly discharged only partially and then recharged, they would seemingly "remember" this discharge point and would rapidly drop their discharge voltage beyond that point. This greatly reduced their capacity, and it would require the user to completely discharge and charge them several times in a row to get the cells to discharge past the memory point. So people were instructed to let the cells discharge all the way to keep the memory effect from occuring. I have heard that the newest NiCads have a modified chemistry that avoids this effect.
The NiMH battery chemistry results in a cell that has very similar capacities and discharge profile to that of the NiCad, with the advantage that is has no memory effect at all. Thus it can be repeatedly charged from a partial discharge state and maintain full discharge capacity. This partial discharge will also extend the lifetime of the cell, since complete charge and discharge cycles are harder on NiMH and NiCad chemistries than partial cycles. The biggest disadvantage of the NiMH is that it has a different charge profile and requires a more intelligent charger circuit than the NiCad.
The Li-ion battery chemstry results in a cell that is lighter and more powerful than either NiCad or NiMH. But lithium in its pure state is an unstable element in the presence of air, and early lithium batteries regularly burst into flames if the cell was damaged or overcharged. The Li-ion enhancement to the technology resulted in a much more stable chemistry, but one that still requires very careful charging. As a Li-ion cell approaches full charge, its ability to accept charge energy declines rapidly, and it will begin to quickly heat up unless the charge is stopped. This behavior is made worse by marketing and consumer demands for ever more rapid charging of their toys. Rapid charging makes the cell heat up, and unless its full state is carefully determined and the charge process stopped in time, the high charging currents can quickly overheat the cell and severely damage it.
In response to early Li-ion battery fires, the industry settled on a charging standard that requires all Li-ion battery packs to incorporate a microcomputer circuit into each battery pack. This circuit is responsible for continuously monitoring the charge and discharge characteristics of the battery and communicating this information over a serial link built into the battery connector. This makes the Li-ion battery an intelligent component of the complete system, and some sophisticated techniques are used within each battery to determine its state of charge during its charge and discharge states. When your laptop indicates the amount of charge left in the battery, it is mostly relying on the internal computer in the battery itself to report back that information. That same computer is also responsible for figuring out if the cells are fully charged, and to tell the laptop to stop the charge.
All this intelligence works well as long as the battery's computer keeps an accurate tab of all the energy withdrawn and replaced in the pack over time. Invariably, errors creep into this calculation, and eventually the computer will report a discharged battery, when in fact some capacity is still left in the cells. This makes a Li-ion battery look like it has a charge memory, even though the Li-ion chemistry itself does not have a memory effect. That's why some manufacturers, like IBM (for my ThinkPad), suggest that the battery be periodically discharged completely. A complete discharge will cause the battery's internal computer to recalulate the pack's charge-discharge profile and restore some "lost" capacity.
My feeling is that the Dell laptop packs in question have some kind of bug or problem in their battery pack computer circuit, such that it incorrectly senses full charge in the cells. If the circuit thinks the cells are still capable of accepting charge when they are in fact full, it will allow the laptop to keep pumping in current, quickly overheating the now over-full cells and causing a fire. Since Dell is responsible for its own battery pack circuit, it would make sense that no other manufacturers would be having problems with their packs, even if they use the same Li-ion cells.
This ends today's lecture from your TechnoBabe, Karen (BSEE, MSEE, with too much time on her hands on Labor Day)
The original NiCad cells suffered from an effect where if they were repeatedly discharged only partially and then recharged, they would seemingly "remember" this discharge point and would rapidly drop their discharge voltage beyond that point. This greatly reduced their capacity, and it would require the user to completely discharge and charge them several times in a row to get the cells to discharge past the memory point. So people were instructed to let the cells discharge all the way to keep the memory effect from occuring. I have heard that the newest NiCads have a modified chemistry that avoids this effect.
The NiMH battery chemistry results in a cell that has very similar capacities and discharge profile to that of the NiCad, with the advantage that is has no memory effect at all. Thus it can be repeatedly charged from a partial discharge state and maintain full discharge capacity. This partial discharge will also extend the lifetime of the cell, since complete charge and discharge cycles are harder on NiMH and NiCad chemistries than partial cycles. The biggest disadvantage of the NiMH is that it has a different charge profile and requires a more intelligent charger circuit than the NiCad.
The Li-ion battery chemstry results in a cell that is lighter and more powerful than either NiCad or NiMH. But lithium in its pure state is an unstable element in the presence of air, and early lithium batteries regularly burst into flames if the cell was damaged or overcharged. The Li-ion enhancement to the technology resulted in a much more stable chemistry, but one that still requires very careful charging. As a Li-ion cell approaches full charge, its ability to accept charge energy declines rapidly, and it will begin to quickly heat up unless the charge is stopped. This behavior is made worse by marketing and consumer demands for ever more rapid charging of their toys. Rapid charging makes the cell heat up, and unless its full state is carefully determined and the charge process stopped in time, the high charging currents can quickly overheat the cell and severely damage it.
In response to early Li-ion battery fires, the industry settled on a charging standard that requires all Li-ion battery packs to incorporate a microcomputer circuit into each battery pack. This circuit is responsible for continuously monitoring the charge and discharge characteristics of the battery and communicating this information over a serial link built into the battery connector. This makes the Li-ion battery an intelligent component of the complete system, and some sophisticated techniques are used within each battery to determine its state of charge during its charge and discharge states. When your laptop indicates the amount of charge left in the battery, it is mostly relying on the internal computer in the battery itself to report back that information. That same computer is also responsible for figuring out if the cells are fully charged, and to tell the laptop to stop the charge.
All this intelligence works well as long as the battery's computer keeps an accurate tab of all the energy withdrawn and replaced in the pack over time. Invariably, errors creep into this calculation, and eventually the computer will report a discharged battery, when in fact some capacity is still left in the cells. This makes a Li-ion battery look like it has a charge memory, even though the Li-ion chemistry itself does not have a memory effect. That's why some manufacturers, like IBM (for my ThinkPad), suggest that the battery be periodically discharged completely. A complete discharge will cause the battery's internal computer to recalulate the pack's charge-discharge profile and restore some "lost" capacity.
My feeling is that the Dell laptop packs in question have some kind of bug or problem in their battery pack computer circuit, such that it incorrectly senses full charge in the cells. If the circuit thinks the cells are still capable of accepting charge when they are in fact full, it will allow the laptop to keep pumping in current, quickly overheating the now over-full cells and causing a fire. Since Dell is responsible for its own battery pack circuit, it would make sense that no other manufacturers would be having problems with their packs, even if they use the same Li-ion cells.
This ends today's lecture from your TechnoBabe, Karen (BSEE, MSEE, with too much time on her hands on Labor Day)
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It's not just batteries in Dells. The batteries for some of the Apple Powerbooks have been recalled.
According to this article,
According to this article,
Initially, Sony said the problem was limited to Dell machines; at the time of the first recall, a Sony spokeswoman said "this is an issue specifically down to Dell's battery-charging system". But the experience of some Apple owners and the subsequent recall squashed that theory.
The cause of the fires has been established. When the batteries were made, the metal case of the cell was crimped closed. In that process, microscopic shards of metal could have been released into the electrolyte of the battery and, in some cases, cause a short circuit - triggering overheating or a fire.
. . . Some experts say that while it is correct to identify individual faults, the underlying problem is with the technology inside lithium-ion batteries. Ming Chiang, materials science and engineering professor at MIT, maintains that current generation lithium-ion batteries can become unstable if they are overcharged.
This is because they use cobalt oxide, which can become dangerous if overheated - as has happened. Manufacturers are working on fresh approaches, replacing the cobalt oxide with more stable materials such as iron phosphate.
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