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Old Jan 01, 2005, 05:15 PM
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Walled Lake, MI, USA
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360mAh 9V Li-ion Polymer Rechargeable Battery

What next?

http://www.hecell.com/en/product.asp
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Old Jan 01, 2005, 06:14 PM
Southern Pride
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I could make a remark about this being a very popular size for Smoke Detectors and how convient it would be to have the source so close to the detector but I shall not.

Charles
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Old Jan 01, 2005, 09:20 PM
Molded Hotliner Destroyer
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A consumer product like that would have protection circuitry built in for sure. Lipos are as safe as any other battery technology when charged and discharged within their specs.
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Old Jan 01, 2005, 10:29 PM
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Quote:
Originally Posted by Magnum9
A consumer product like that would have protection circuitry built in for sure. Lipos are as safe as any other battery technology when charged and discharged within their specs.
Any consumer cell can fail from factory defects or other odd problems even when charged and discharged within their specs. LiPos are not as robust as other types of cells, and are more prone to damage. LiPos also contain more energy for their size than other types of cells. Now we get into the failure modes of various cells. LiPos go into a thermal runaway condition and vent with flame when they fail catastrophically. They have a greater tendency to set fire to combustible materials nearby and create collateral fire damage. So LiPos are not as safe as any other battery technology even when charged and discharged within their specs. The only question is, how much less safe.
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Old Jan 02, 2005, 02:31 AM
PGR
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Quote:
Originally Posted by Dave Hederich
Any consumer cell can fail from factory defects or other odd problems even when charged and discharged within their specs.
Dave, be prepared to bear that cross for the long haul; that or put it down. Rechargable LiPo technology is rapidly becoming a part of our everyday lives and that isn't going to change until something better comes along. And there's no guarantee that the new will be any safer than what we already have. By their very nature, high energy densities involve dangers which are directly proportional to the energy density.

Them's the rules, my friend, and you or I can't change the rules. We can only recognize and abide by them.

Or not.

Pete
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Old Jan 02, 2005, 10:15 AM
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Pete, I've tried to be clear and consistent in my position on LiPo and Li-ion cells. Perhaps you haven't read enough of my messages yet to be clear on my position. I have been encouraging the use of Li cells for about 5 years now. My first message on this forum in February 2000 was in response to someone who said that Li cells would never be big in e-flight. My response was, "Oh yeah?"

I started about 5 years ago with Li metal cells, then surplus Li-ions, then surplus LiPos. I've been involved in most of the discussions on this forum whenever a new failure mode was discovered, and people lost model aircraft, personal vehicles and parts of their houses to fire damage.

All devices and materials that retain energy can be dangerous if not handled properly. Some are more volatile than others. Those whose hazards are not acknowledged are the most dangerous of all, because people will not prepare for the worst case scenario if they believe that there is no significant danger.

My purpose, along with many others on this forum, has always been to promote the safe use of Li cells. This cannot be accomplished if people treat them just like other types of cells. Li cells require special care and attention. Some people already understand this and some don't. Those who don't need to be educated. Those who refuse to learn should be discouraged from using Li cells.
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Old Jan 02, 2005, 10:48 AM
PGR
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Perhaps it would help me understand your position a little better if you would explain your reasoning behind the "What next?" in post #1 of this thread. Maybe I'm misreading it but to me, it smacks of disdain.

I haven't dug back through the archives to read your history but I detect the same level of disdain in many of your recent postings on this subject.

Maybe I have you figured wrong but all I have to go by is what you write.

Pete
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Old Jan 02, 2005, 11:33 AM
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Pete, all we have to go on about anyone we see in an internet forum is what they write. We just have to be careful not to make the wrong assumptions about people. For instance, I could allow myself to assume that I detect disdain in your messages for people who are focused on safety issues. But I can speak from experience about how assumptions often lead to incorrect conclusions.

My "what next" comment was simply based on the fact that Li cells are rapidly expanding into many different areas, but I did not expect to see a rechargeable Li 9V battery. It was a surprise to me. The two simple words "what next" do not automatically carry a disdainful tone unless you have prejudged the person making the statement.

Thinking about it a little more, this battery does have standard 9V connectors. This means that it will fit into any standard NiCd or NiMH 9V battery charger. Previous rechargeable Li cells have been made in non-standard sizes so that they would not fit into standard consumer NiCd and NiMH chargers. So unless there is an internal safety circuit built into this rechargeable 9V battery, it could represent a problem for the typical WalMart shopper who doesn't even know that you shouldn't try to charge NiMH cells with a NiCd charger.
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Old Jan 02, 2005, 11:48 AM
Southern Pride
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Pete my point of view on this is that advancements in batteries is great. I enjoy having 2300 mAh NimH AAs to replace the lower capacity(1200 mAh?) Nicads which in themself were a major improvement over the 500 mAh ones which we were stuck with for years however there are problems which come with new battery technology, especially in the consumer market. I can invision these new 9V Li Po packs being charged(?) on/with many of the charges which are intended only for the current (rechargeable)Nicad / NiMh batteries which look the same to many. Why buy a new charger when they already have a good one at home? Many consumers may fee like,they just want to sell me something more which I relly do not need right? To many consumers just refuse to read and follow instructions. Some E flyers are still trying to get by without purchasing a LiPo charger and one would hope that E fliers would be more inclined to do a little research than someone just wanting a rechargeable battery for use around the house.
That's my Redneck point of view.

Charles.
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Old Jan 02, 2005, 11:50 AM
PGR
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Quote:
Originally Posted by Dave Hederich
So unless there is an internal safety circuit built into this rechargeable 9V battery, it could represent a problem for the typical WalMart shopper who doesn't even know that you shouldn't try to charge NiMH cells with a NiCd charger.
Unless these batteries contain a revolutionary new cell chemistry, then there has to be some regulation circuitry involved. LiPo chemestry produces 3.7v/cell regardless of the size of the cell. So if these 9v batteries contain 2 (unregulated) cells they will have a 7.4v output which is too low for most 9v consumer devices. If they contain 3 (unregulated) cells they will have an output of 11.1v which is too high.

So there is obviously some kind of regulation circuitry involved and in this age of lawsuit-happy attorneys, I'm sure that the circuitry contains bulletproof protection to prevent over charge/discharge situations.

Pete
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Old Jan 02, 2005, 11:58 AM
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Quote:
Originally Posted by PGR
LiPo chemestry produces 3.7v/cell regardless of the size of the cell. So if these 9v batteries contain 2 cells they will have a 7.4v output which is too low for most 9v consumer devices. If they contain 3 cells they will have an output of 11.1v which is too high.

So there is obviously some kind of regulation circuitry involved and in this age of lawsuit-happy attorneys, I'm sure that the circuitry contains bulletproof protection to prevent over charge/discharge situations.
Actually, most of the NiCd and NiMH 9V batteries have 6 cells, which results in 6 x 1.2V = 7.2V actual voltage. So I suspect that there are 2 Li cells in this one. There's a lot of expertise on this forum regarding 9V batteries, because many of us dissected them to find the rare ones that had 7 cells for 8.4V. We used the 7-cell, 8.4V 9V batteries to power the GWS IPS motors in Tiger Moths. Some ran the batteries whole and some stripped off the shells to save a few grams.

I suspect you are correct about some type of protection circuit in the rechargeable Li 9V. There aren't too many general consumers who are prepared for common 9V batteries that vent with flame when used in the wrong 9V charger. Big stores with deep pockets such as Wal-Mart are pretty sensitive about this.
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Old Jan 02, 2005, 01:15 PM
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Wow

those are cool!

Quote:
Originally Posted by Dave Hederich
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Old Jan 02, 2005, 06:29 PM
Random Flier
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Quote:
Originally Posted by Dave Hederich
...I suspect you are correct about some type of protection circuit in the rechargeable Li 9V. There aren't too many general consumers who are prepared for common 9V batteries that vent with flame when used in the wrong 9V charger. Big stores with deep pockets such as Wal-Mart are pretty sensitive about this.
Hmmm... I wouldn't be too sure (about there being any safety circuitry inside). Maybe a chemical-based PTC. Compare the dimensions of this vs a regular Ko 340 2S pack. I doubt there is room inside for circuitry (remember the size of the circuits in the cell phone packs). Also recall this is a product announcement - not necessarily for the retail / Walmart channel. I don't recall seeing too many Hecells in Walmart (still stocked in R/C stores though, albeit one suspects as older stock...).
Still, would be interesting to try these out for R/C use.

[Safety note: the design of this type of battery is disconcerting as it is easy to short. Bit like having a male connector on your R/C pack. NOT a good idea. So I *hope* it has a PTC in there to limit current overload...]
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Old Jan 02, 2005, 06:59 PM
Molded Hotliner Destroyer
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Quote:
Originally Posted by Dave Hederich
I started about 5 years ago with Li metal cells, then surplus Li-ions, then surplus LiPos. I've been involved in most of the discussions on this forum whenever a new failure mode was discovered, and people lost model aircraft, personal vehicles and parts of their houses to fire damage.
From the limited reading I have done on failures, I was under the impression there had been no failures under normal charging (<1C) or discharging within the manufacturers parameters, unless a cell imbalance occurred, which a protection circuit would prevent. Also, are you aware of any cell phones or laptops venting with flames? I think I have more lithium battery products in my house than I do lipo packs for my planes, and until this post wouldn't have given them a second thought.
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Old Jan 02, 2005, 07:49 PM
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You are correct that most of the reported Li cell failures have been from human error during discharge or charge. However, there have also been a number of really odd circumstances that I've picked up from reading 5 years of reports on this forum and throughout the internet.

Recently there have been a couple of instances reported on this forum of Li cells venting with flame while sitting in the sun in a parked car on a hot, sunny day. In the past, a couple of instances of LiPos being chewed on by household pets resulted in big problems. At least one charger was reset during the charging process by a brief power failure in a neighborhood electrical grid, and resumed charging at an incorrect rate, resulting in a failed Li pack.

Bottom line is, LiPo cells can fail for a variety of reasons, not all related to direct human error. That's why it pays to always keep them stored in a container where venting flames can't set fire to nearby combustible materials, resulting in a much bigger fire than just a few cells burning.

If you want a quick education on Li cell failures in the consumer electronics world, try a Google search for the terms: lithium battery recall

You will get ~57,600 hits, some of which document flaming Li cell incidents related to a variety of causes. As PGR said in another thread, he respects Li cells rather than fearing them. I agree. You must respect the potential of catostrophic failure for a variety of different reasons. But it also should be kept in perspective. The number of people who actually experience such failures is very small. The most important lesson is that if you are prepared for such an unlikely event, you will come out much better in terms of potential property loss or personal injury.

http://www.google.com/search?num=100...ll&btnG=Search
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