HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Aug 06, 2003, 09:27 PM
DNA
registered user
DNA's Avatar
NE Ohio
Joined Jun 2001
3,311 Posts
I think I should be out in my garage watching my can of gasoline.
DNA is offline Find More Posts by DNA
Reply With Quote
Sign up now
to remove ads between posts
Old Aug 06, 2003, 10:49 PM
Registered User
Arkansas
Joined May 2003
410 Posts
"All energy-storing mediums have the potential to self-destruct and cause damage. Only the failure modes differ."

Excellent comment. As I mentioned in another post, I was around Li battery R&D for several years. I did occasionally help the guys in the Li-ion dept, but did not work with them extensively. They did ruin several enviromental chambers in the lab we shared. There were many "unexplained" problems with the cells. Many of their cells vented. This was about 15 years ago and Li battery technology has advanced tremendously since then.

Re: "exploding" cells. I have never seen one "explode". I have seen many overpressurize the case to the point you think they exploded. Loud bang and all. I seriously doubt the burn rate was high enough to fit the pyrotechnician's definition of "explode". I'm also surprised "explode" made it to a MSDS. Maybe they used the word in layman's terms.

Re: gasoline being dangerous. Sure is flammable. However, gasoline usually doesn't catch on fire because the can it is in gets dented.

My viewpoint is definitely skewed. Since I worked in state-of-the-art battery R&D, there were many failures on the path to success. Maybe I'm just traumatized. I have never had a problem with NiCd's or NiMh's in 15 years (knock on wood twice!!!), so I'll just stick to them.

Mike in Arkansas
Mike4122KSA is offline Find More Posts by Mike4122KSA
Reply With Quote
Old Aug 06, 2003, 11:24 PM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
21,107 Posts
Dave,
Your comment: "A recent discussion of an "exploding Li-poly" cell turned out in actuality to be a Li-ion cell. In fact, that's the one that scorched the wood floor in a gymnasium."

It actually was a Kokam cell on a hardwood floor in a house.
http://www.rcgroups.com/forums/showt...kam+fire+floor

Your comment: " I'd like to know the technicalities of how an explosion can take place when the lithium polymer core is contained in a soft, thin plastic "bag."

The small Webster defines 'explosion' as "burst noisily".

Like this one: http://www.hornet-heli.com/ubb/Forum3/HTML/003428.html

The main thrust of all my comments is to be "on guard". To lose respect for these cells can be a problem. I'm going to continue to use them with precautions. If the Lipo cell is not flying it's in a pyrex dish. If it's in the house, it's in the dish inside of a metal cabinet. If it's charging, I'm there with it. I sure wish I knew if they would fly out of that dish if they ignited. Any reports of flying batteries?


hoppy
hoppy is offline Find More Posts by hoppy
Last edited by hoppy; Aug 07, 2003 at 12:48 AM.
Reply With Quote
Old Aug 07, 2003, 12:51 AM
LSF 004 - AMA 5055
bobandris's Avatar
United States, CA, Saratoga
Joined Dec 2000
592 Posts
Increase Fire Safety, Inexpensively

I went down to Home Depot and got a half dozen ceramic floor/wall tiles. You can get 8"x10" ceramic tiles approx 1/2" thick, with a deep waffle pattern in their back face for about a buck a piece. I keep a couple in the car and four in the shop. Put your batteries on the waffle side for air circulation. If they get hot, I feel a lot safer.

FWIW,
Bob
bobandris is offline Find More Posts by bobandris
Reply With Quote
Old Aug 07, 2003, 02:39 AM
Registered User
Gordon's Avatar
Joined Aug 2000
3,920 Posts
Quote:
Originally posted by Dave Hederich
[BStatistically, only a small percentage of e-flyers ever experience a battery-induced fire. [/B]
Until the advent of Lipos.

Additionally, where is your database of statistics that lets you make such a statement with the utmost confidence?

Gordon
Gordon is offline Find More Posts by Gordon
Reply With Quote
Old Aug 07, 2003, 03:00 AM
Registered User
gbruce's Avatar
Canada, AB, Airdrie
Joined Oct 2001
2,324 Posts
Mike

Don't leave us Hangin' like that ...what battery chemistry ARE you using?



Bruce
gbruce is offline Find More Posts by gbruce
Reply With Quote
Old Aug 07, 2003, 07:49 AM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
21,107 Posts
Quote:
Originally posted by Dave Hederich
I thought it would be appropriate to collect all of the NiCd and NiMH fire stories together in one thread so that a link to that thread could be inserted in every Li-poly fire thread just to provide a little perspective.
[/B]
In my opinion, that would only dilute the message. Based on the reported incidents involving the different chemistries, the accidents involving the other chemistries are not in the same league as LiPo accidents. This technology needs a higher level of respect than the other chemistries..........
I'm joining boomer.........

Hoppy
hoppy is offline Find More Posts by hoppy
Reply With Quote
Old Aug 07, 2003, 09:52 AM
Registered User
Gordon's Avatar
Joined Aug 2000
3,920 Posts
Besides, fire isn't the only dangerous failure mode. A squirt of electrolyte from any ruptured cell into your face, or indeed onto any body part would be traumatic enough for many.

One thing about nicad/nimh is that if you overheat them without rupturing, a self-sustaining chemical reaction doesn't begin which keeps the cell getting hotter and hotter.

From what I've read on here or somewhere, possibly a manufacturer's website, get a lipo hot enough, and you won't need to keep heating it up - it'll continue to do that all by itself.

One thing about these reports of lipo hot failures will do is concentrate peoples' minds on safety requirements. It's early days for lipos, so al user info is valuable

If you bother to read the manufacturers' max limitations which they publish on their websites, you'll see not one of them recommending a discharge current greater than 2C for a single cell. Do mobile phones, laptops etc exceed that recommendation? We R/C-ers are being told that we can go to 5C and 10C.

As with nicads and nimh, R/C aircraft lipo users exceed the mfrs' specs handsomely, so must be ready for trouble.

I hope to go lipo when I have saved enough money to buy enough cells for a days' flying - no point in just one pack when I want to draw 40-50A from 30V. Plus I'll need the special charging gear, which will comprise a Schulze isl8-936 software upgrade, and either a 40A 13.8V stabilized mains psu to power the Schulze or a laboratory-style mains psu capable of charging to 35V-ish.

Then of course, for EDF flying I'll need to review my motors and escs to see if I need to replace them with more efficient ones which will withstand the longer motor runs at high powers. I already run Hacker B50-Ls and a Pletti 220-30 using Schulze 30-cell 55A escs, which are fine on RC2400s and GP3000s. But these could fail if subjected to long flights with 8Ah lipos. So Hacker B50-XLs or Lehner equivalents will most likely be needed.

So you can be sure that with the financial strain involved in getting there, I'm very grateful for all the warnings and website references quoted on the Ezone. When I get going on lipo, I intend to be as well prepared beforehand as I can.

Gordon
Gordon is offline Find More Posts by Gordon
Reply With Quote
Old Aug 07, 2003, 12:29 PM
Electric Coolhunter
Thomas B's Avatar
United States, TX, Fort Worth
Joined Jun 2000
14,622 Posts
Hoppy, there is ANOTHER thread about a prismatic Li-ion pack that burst and burned a gym floor in the UK. A search under "burnt floor" will turn it up here:

http://www.rcgroups.com/forums/showt...ht=burnt+floor

Gordon, we hear you about the data posted in the manufacturers web site. I think the reality is that progess in the new breeds of Li-poly cells is occuring MUCH faster than some of the info on the various manufacturers web sites can be updated. I think the info provided in this forum by the new Li-poly manufacturers superceeds the web site info, especially the info found on sites like Panasonic and such that still refer to old Li-ion design.

We are on the bleeding (burning) edge of technology here and care is incredibly important.

I have 7 2 cell Li-po packs that I am using in various park flyer models. Luckily, the force involved in a parkflyer impact is a LOT less than a larger sport model. But, I have to admit that I have been getting a little cavalier about charging the cells in models, unattended overnight in the house and once unattended overnight in my van (small gulp).

I think a complete reevaluation of my practices are in order, with a fireproof storage/transport/charging box of some kind high on the list.

Ken, thanks for sharing such a sobering experience with us.
Thomas B is offline Find More Posts by Thomas B
RCG Plus Member
Last edited by Thomas B; Aug 07, 2003 at 01:31 PM.
Reply With Quote
Old Aug 07, 2003, 12:59 PM
AMA 148796
Where it Rains
Joined Jul 2002
1,058 Posts
Thomas, you're welcome.

Good news - I have a car on the way (bought this one through a broker).

Great ideas in this thread on how to manage the risks associated with the new technology.

Glad I could help generate discussion.

Ken
ken_keeler is offline Find More Posts by ken_keeler
Reply With Quote
Old Aug 07, 2003, 01:10 PM
Registered User
Houston, Tx.
Joined Jan 2003
3,736 Posts
Guess we better not use gasoline to power our planes either....... or for that matter our cars
http://www.click2houston.com/news/2388210/detail.html

A little common sense and caution may save us all from an unwarranted disaster.
Bill Bergman is offline Find More Posts by Bill Bergman
Reply With Quote
Old Aug 07, 2003, 02:29 PM
Registered User
Walled Lake, MI, USA
Joined Feb 2000
11,182 Posts
>> Until the advent of Lipos. Additionally, where is your database of statistics that lets you make such a statement with the utmost confidence?

Where's your database of statistics that let's you make the opposite statement with the utmost confidence? Those kinds of questions don't accomplish a lot, do they?

If you would like to do a Search, you'll find that I've been active in the lithium threads in this forum for more than 3 years now. I was among the first to attempt to charge primary CR2 lithium cells for e-flight, which I quickly learned was not wise. I was also among the first to use Tadiran rechargeable lithium metal cells for e-flight. And I was among the first to use surplus Li-ion cells for e-flight.

The E-Zone, before it became part of RC Groups, is where many of the early implementers of the various lithium chemistries in e-flight shared their results. I've learned a lot from people here with more experience than I have. Naturally, it's the early implementers of any new technology who are first to learn what can go wrong. Without going back and documenting every lithium-related incident, I'd guess that there may have been 2-3 dozen reported here where any damage was done beyond cells swelling up and being rendered unusable.

In all of those lithium threads in which I've participated, I think you'll find that I've been consistently on the side of safety. In particular, when someone makes a comment treating lithiums lightly, as if they presented no special danger, you will find that I was pretty consistent in warning that this is not a healthy attitude. At the same time, when a few alarmists talked about huge explosions and 20-foot walls of flame, I said that it was not productive to exaggerate the danger to scare people, as this just destroys the credibility of a rational safety warning.

I do think I have a pretty good handle on lithium cell safety in general. By participating in so many lithium threads over the years, I've communicated with hundreds and hundreds of people who've successfully used various lithium cells with no problems at all. I'm also aware of those 2-3 dozen who've had serious incidents. So, yes, as a matter of fact, I do have a lot of confidence that the number of people using lithium cells who've had a serious problem is relatively small. In every case, the serious problems would have been minor problems had reasonable safety precautions been in place. In most cases, those who've had a big problem have been courageous enough to share the details here and admit that they made mistakes.

The important thing about these lithium safety threads is to have a proper perspective. Li-poly cells should neither generate paralyzing fear nor cavalier fearlessness. We should all strive to understand them better, and always respect what they are capable of doing under the worst circumstances. When we allow these threads to degenerate into petty bickering, we become part of the problem rather than part of the solution.
Dave Hederich is offline Find More Posts by Dave Hederich
Reply With Quote
Old Aug 07, 2003, 02:52 PM
Been There! Done That!
boomerace's Avatar
Eugene, Oregon, United States
Joined Sep 2001
19,187 Posts
Very UN-Dave like...... I just checked this thread and Dave I never get my feelings hurt! I was out O here because I tire of the stonewall stances and petty bickering! Me thinks you protest too much people disagreeing with your views! No problem with that, I'm just not interested in continuing the debate! Peace!
boomer
boomerace is offline Find More Posts by boomerace
Reply With Quote
Old Aug 07, 2003, 03:29 PM
Suspended Account
USA, FL, Apopka
Joined Dec 2000
4,072 Posts
Liabilities?

Question for the lawers, insurance agents/adjusters or others knowledgeable in insurance law.

1.) If I use a product in a fashon contridictory to a Manufactures Data Sheet and through that use cause injury or damage will my insurance (Homeowners/Auto/Other) cover me?

2.) Same question but substitute AMA Insurance?

3.) If the Manufacturer and/or Distributor is promoting the non standard use even if it contradicts with the Manufactures Data Sheet does that change anything, as a user, as a Manufacturer/Distributor?

4.) By participating in this forum/thread, have I become "knowledgeable" user who should fully understand and mitigate the risks in the use of LiPo's?

Paranoid? Perhaps, but if there is a large claim or injury I would think the lawers, insurance agents/adjusters will be asking these questions.

Brad
bradpaul is offline Find More Posts by bradpaul
Reply With Quote  (Disabled)
Old Aug 07, 2003, 04:09 PM
MKH
Registered User
Ohio
Joined Mar 2000
2,597 Posts
One thing I've found very helpful in understanding and utilizing the technologies of this hobby, is to listen more closely to those who have hands-on experience with the items under discussion. The post that begat this thread is a first-hand account, and I appreciate it very much. What can quickly muddy the waters, are posts about any given topic, from people without such first-hand experience. I don't know if everyone in this thread has actually used lipo batteries or not, but I've often seen posts in other threads about lipos, brushless motors, chargers, materials, etc., from people who are only repeating what they've read elsewhere. I take all posts with a tiny grain of salt, focus on actual real-life accounts from those involved, and go from there. I don't care how Webster defines an explosion, or what the internal chemistry means to a chemist. I just need to know what the manufacturer says about the product, and whether users of said product find those directions to be practical and applicable. I applaud anyone who's posts attempt to educate me, and keep me safe, but in the end, its still my responsibility. I cannot afford to have an emotional attachment to any particular point of view. I also try to remember that this is the internet, and I don't really know any of you people. Health and happiness to all of us.
Marcus
MKH is offline Find More Posts by MKH
Reply With Quote
Reply


Thread Tools