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Old Sep 13, 2003, 09:16 PM
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USA, NJ, Hackettstown
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Quote:
Originally posted by hoppy
They all recommend checking the balance before charging series packs but like you say, how?
hoppy
This can be critical. Today I discovered that a cell in one of my 2 cell packs was totally dead (Yes, 0 volts) for a very unlikely reason (cat bite). Please see here for a full description of what happened.

If I had not chosen to check the pack in question and had charged it as a two cell pack, we all know what would have happened. From now on, I will check my packs regularly. Remember, if a cell goes bad and it goes unnoticed, the pack will probably catch fire.

Louis
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Old Sep 14, 2003, 02:28 AM
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Spring Valley. MN
Joined Jun 2000
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Re: Another safety issue

Quote:
Originally posted by Jim13704

-Snip-

Are not the other providers of Li po packs doing a dis-service to users (and also creating a potential legal liability for themselves) by not providing a convenient means for users to guard against cell imbalance?
Yes I do believe they are doing a dis-service, But all of the venders that I know of also have a liability dissclaimer that states they are not responsible for any damages the use of these packs may cause!

Quote:
Maybe some of the other Li Po pack providers would like to comment on why they do not incorporate what would appear to be a very low cost safety feature in their packs. Or, alternatively, explain to me (and other readers of this thread) why it is really not needed.
Very good question!!
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Old Sep 14, 2003, 02:42 AM
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Re: Re: Another safety issue

Quote:
Originally posted by buzzsaw 46
Yes I do believe they are doing a dis-service, But all of the venders that I know of also have a liability dissclaimer that states they are not responsible for any damages the use of these packs may cause!

Very good question!!
I would speculate that if there was a serious acident with the potential of major damages, a good lawyer would have little difficulty getting past the liability disclaimer.

Here is a question:

If there is a major acident with a significant damage claim how long will the manufactures continue to sell Lithium batteries to the "tiny" RC market?

Another question:

If the insurance industry (including the AMA) excluded any liability and damage coverage from the use of Lithium batteries how would that effect your use of Lithiums?

Enough questions......

Brad
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Old Sep 14, 2003, 10:59 AM
Been There! Done That!
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Eugene, Oregon, United States
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I really wonder how well your homeowners coverage or for that matter auto coverage would pay if you destroyed the house or the car due to your use of an unsafe technology when you were aware of the dangers!! I would no more use lithiums than I would storing explosives including gasoline in the house! And yes I know the car contains gasoline and yes that ia an accepted risk covered by my homeowners and yes my garage does have a firewall between it and the house! But I disposed of all my Lithiums and will not use them again until proven at least as safe as my Nicads and NiMH packs! I didn't get this old taking those kind of chances! The great thing is I can still fly without feeling I am missing anything except a stiff neck and recharging after every flight session! I can buy enough additional cells for the differance in price to fly just as long as you using the lithiums and charging when I'm not flying is a no brainer! I'm usually in the shop building or whatever anyway!
boomer
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Old Sep 14, 2003, 12:31 PM
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what kind of pack was this? dealer built ? Name of cells at least. I think most problems are unfairly blamed on the technology and not the mistakes made by users. Lots of car fires have unknown sources. Daughter's car almost caught fire a week or so ago because the light switch was bad. Broad daylight and hadn't been driven since the day before. Lots of differences in the newer stuff compared to the old cells. The charger was in the car . was it in sevice at the time? Lots of variables here, too many to attack the cells as the only possibility. JMHO
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Old Sep 14, 2003, 03:00 PM
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Result from an explosion of 3x Etech 1200.
The cells are great (i still say....) but if it goes wrong it realy goes wrong !!

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Old Sep 14, 2003, 03:32 PM
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Well there's another LiPo bomb.... Word to the wise, if you still love LiPo after all the fires, explosions and such buy all you can while you still can buy them......

Unless somebody comes up with a solution fast theis IS going to be a serious injury or death and then IT WILL be in the hands of the lawers......

Someday we are going to look back and say "I don't believe that we used LiPo packs without adequate protection"

Brad
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Old Sep 14, 2003, 04:25 PM
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Montrose, CO
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Quote:
Originally posted by boomerace
I really wonder how well your homeowners coverage or for that matter auto coverage would pay. . . .
boomer
Good point, Boomerace. Also, does AMA insurance cover this? Ken, did AMA insurance cover your car and personal things in it?

What if?

What if another club member's car parked next to Ken's had burned? Would AMA insurance cover it?

What if a vistor's car parked next to Ken' had burned? Would AMA insurance cover that?

Anyone have any knowledge on these AMA insurance issues concerning Li Pos?
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Old Sep 14, 2003, 04:38 PM
Random Flier
Oxford (UK) and Mtn View CA (USA)
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Quote:
buy all ... while you still can buy them
Hmmm... It would be interesting to see any data on actual accidents involving:
a) using Li- batteries in r.c hobbies
and
b) flying 1-10lb aircraft at various speeds without strict licensing or controls.

I know of at least 2 deaths due to r/c aircraft (in the UK). Not heard of any due to r/c batteries yet. Both require responsible usage. So we should keep the Li battery "dangers" in perspective.

It's also interesting to note that the latest 18650 Li-Ions (complete with hard shell and PIC protection) that are 2200mAh+ each with 4+C discharge rates are not available to hobbyists due to safety concerns in the supply chain... yet Li-Poly cells are becoming increasingly available over-the-counter in LHSs! (Along with afore mentioned 1-10lb aircraft of course)...

Wishing everyone safe flying...
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Old Sep 14, 2003, 04:44 PM
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Eugene, Oregon, United States
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I don't fly 10 lb aircraft any more either!!! And I don't fly around people and I don't.......................... I know ... you don't live longer it just seems longer!!
boomer
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Old Sep 14, 2003, 04:53 PM
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Montrose, CO
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Quote:
Originally posted by isvana
Hmmm...

It would be interesting to see any data on actual accidents involving:
a) using Li- batteries in r.c hobbies
and
b) flying 1-10lb aircraft at various speeds without strict licensing or controls.

I know of at least 2 deaths due to r/c aircraft (in the UK). Not heard of any due to r/c batteries yet. Both require responsible usage. So we should keep the Li battery "dangers" in perspective.

. . . .


I agree, the problems with Li Pos should be keep in perspective. However, it should be noted there there seem to be quite a few fires wilth LiPos being reported --- given the very short time period they have been in use by RCers.

Here is another LiPo fire reported recently on another thread in this Forum:

Lipo's at the NEAT Fair
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Old Sep 14, 2003, 05:14 PM
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The Netherlands, DR, Emmen
Joined Aug 2002
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Yep,

Nice pic Marcel, you're allways good for some good Burning Action

It could have been worse you know, if we hadn't pulled the Extra 3D outside, it would have burned up the transmitter-container with 5 or 6 (about 3500,= to 4000,=) of transmitters in it

Then you would really have had a bad day at the field


The motto is, BE REALLY CAREFULL WITH THESE CELLS !!

Fly & charge save,

Appie
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Last edited by Appie; Sep 14, 2003 at 05:19 PM.
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Old Sep 15, 2003, 07:57 AM
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Joined Aug 2003
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We are our own biggest danger. These cells certainly offer a significant "danger" challange. We will eventually overcome the challanges and lipo's will be safer. However, yesterday at the Neat Fair I stood spotter for one vendors "hired gun" demo flyer. He was great! But he was asked to keep his flight under 15-20 minutes so others could use the freq. His comment after the flight was that he usually flies his lipos until they "puff up like a pillow." Maybe it was his just his poor attitude. Maybe he was just kidding. Whatever, we need "leaders" who demonstrate how to do our hobby safely.
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Old Sep 15, 2003, 09:44 AM
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I really appreciate this thread as I am planning a Li-po ship now.

Can I throw out my take on the situation for criticism and suggestions?

*****************************

Li-polys do appear the be more dangerous than the Nicad and NiMH cells we have all used for some time.

It does seem that most failures and disasters are likely traced back to a specific and avoidable situation.

But is sure looks like more 'procedures' are definitely called for with Li-po.

Glow fuel, gasoline, and such are also dangerous, but need some external help (like a spark or extreme heat) to make a major disaster. And most other battery types need some external fuel to ignite into a fire if the cells manage to generate enough heat to do so.

The "Li-Poly" packs, on the other hand, have a full set of materials self-contained to make for big trouble.

A complete "disaster package", I guess.

Li-poly's have lots of energy and combustable fuel, and the means to light it all up via simple mechanical failure of the external circuit (the wires and connectors in the pack), OR mechanical failure of the internal structure.

Also, apparent susceptability to damage, and fire, from both overcharging and excessive current draw via chargers and airplanes respectively.

It seems to me (like anybody asked) that you need to take care of ALL of these factors to be using Li-po's reasonably safely.

I looked at the Sentry Box at Home Despot. It has only been heat and explosion tested by placing it in a very hot environment and seeing it not explode or burn the contents. This is not the same as lighting up a Li-poly inside the box. But in looking it all over, it seems to me that a long and unlikely chain of events would have to happen to actually blow a Sentry box apart:

1. Li-poly fire
2. Melt and seal the box interior before losing gasses.
3. Manage to have enough fuel left to need no outside air.
4. Blow the box apart.

But yes indeed, putting the plastic-coated concrete (of some sort) box inside a containment cage would be better, but that sounds like going too far to me.

Venting the box is probably a good idea, but even this could have its downsides. The box is already vented via a loose seam. It is designed to melt the seam closed in an external fire.

(I suppose it is really designed to be cheap to make and then they found out that the seam melted in tests.)

I think I will buy a Sentry box, small fire extinguisher, and cables long to field charge outside the car.

I plan to use the Hobbico charger and E-tech 3s1p 1200.

The Hobbico charger has a few issues.

It peaks at 4.13 V and not the 4.2 recommended for "li-poly". This is a minor issue and I am willing to give up the 40 seconds - or whatever - of flight.

It handles a maximum of 3-cells but has no manual cell-count setting. This is OK as I am only going to use 3-cell packs. I think I would not trust it on 2-cell packs.

At 49.00 it is a very handy NiMH and Nicad charger too.

I will probably also build the Li-po charger shown here at some point, but the Hobbico will do for now.

The E-tech packs have no taps to test individual cells for balance. It is my understanding that this is possibly important.

All 3 unused packs I have read exactly the same voltage to 2 decimal places (I forget exactly, but it was 11.38 or something with no load).

I suspect that it is a good bet that if the voltage of each of the three packs remains within 0.01 of the average, then it is extremely unlikely that I have any imbalance within the pack.

Plus with the 4.13V (vs 4.2V) peak and by always checking for heat, I think I will not add taps for cell testing until I find reason to suspect a problem.

This may change if I get the heebie-jeebies at some point.

I consider the above to be alot to think about in order to run Li-poly with reasonable safety.

Just a thought:

The next best thing to E-tech 3s1p 1200 for my application (Stevens Park CAP) would be 8 or 9X KAN 650 NiMH. That is 1/2 the fuel (650 vs. 1200) and ~ 1.6X the weight.

In favor of the KANs - they are very cheap as I think you can get 8 cell packs now for 10.00 USD. (Maybe not "KAN'"s but they will do the job based on the specs.)

So maybe 20 dollars to fly for 12 to 15 minutes (with a battery change midway), vs. 40 to 50 dollars to fly on E-tech 1200 with no battery change.

And far lower potential for trouble.

Makes you think I suppose.

Anyway, I would really welcome any suggestions. Please feel free to find the holes in my thinking as it will certainly help.

Chris Parent
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Old Sep 15, 2003, 02:12 PM
DNA
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NE Ohio
Joined Jun 2001
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Another reported fire in case you missed it. Very small plane using
small lipo cells, yet still was able to cause another car fire.

I guess the question is ...... why?

http://www.rcgroups.com/forums/showt...01#post1296201
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