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Old Jan 20, 2004, 08:48 PM
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Quote from DNA s post with link to a SINGLE CELL fire .not a unbalanced pack manufacturers always have excuses not everyone belives what they print.(Remember this is a SINGLE small lipo cell, not a pack of cells.)
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Old Jan 20, 2004, 09:06 PM
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Wingman33, not exactly sure of the point you're trying to make. DNA deliberately overcharged a single cell to destruction in order to simulate the failure of a cell in an unbalanced pack and videotape the failure mode. Many of the Li-poly failures reported by members of this forum have been the result of unbalanced packs. That's a known problem, not a phony manufacturer claim.

By the way, I replied to your PM yesterday, but you have apparently not yet read my PM back to you.
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Old Jan 20, 2004, 09:46 PM
MKH
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Ohio
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Here's the site for the Duraflite packs with safety charge devices, in case you care to read about them. Looks like another step forward, at least I hope so.
Marcus

http://www.duralitebatteries.com/
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Old Jan 21, 2004, 12:55 AM
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United States, NY, Mechanicville
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WJ Birmingham-
I will verify his ESC, but probably not til next weekend.. My friend is out of town for the week.

Someone else asked about cell life... The pack was about 3 months old, I would say less than 50 cycles, probably close to 20 cycles.


To All:

First and foremost - my intention was to draw a little more attention to the hazards of MISHANDLING LiPo packs. I believe there was a cause for the fire, and it was not the LiPo battery. The owner of the batteries feels the same way..

After talking with the seller of the pack, we are going to look a little more closely at the charger. I am not sure how much is left of it.. The leading theory is that the pack was not fully discharged, and the charger thought it was a four cell, not the three cell that it actually was. If the charger was using an older version of software, it may have been more likely to select the wrong cell count.

For what it is worth, in my recent studies on the Lipo's, I am not finding any info about imbalanced cells. For those who have been talking about inbalanced cells, could I ask you to post the info in another thread?

Could I also ask those that are obviously against LiPo usage to please post your opinions on another thread? I would like to keep this thread on topic, and make sure LiPo users, or potential users, are able to get through to ask any questions, or at least read the data about the fire.

Thanks in advance.

PS- I am still using LiPo's. There is nothing that can replace the weight to power ratio. That is why this post was put up, to make sure I understand what is going on, and others can understand as well.
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Old Jan 21, 2004, 01:09 AM
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San Diego, CA, USA
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Quote:
Originally posted by Dick
In reading comments by RCELECTFLY he says "as the cells fly around like a rocket when they ignite." I have been following threads on li pos for a long time and this is the very first time that I have heard of any mention of this taking place.

Gud Flying..........Dick
Dick,

The first time I heard about packs flying around like a rocket was an incident in europe where the charger and pack were on a work bench when the pack ignited it shot off of the bench and pulled the charger off of the bench they both landed on a hardwood floor and burned a large spot on the floor. the damage wasn't worse because the modeler was in the next room and was able to quickly put out the fire. In the case of my friend who was sleeping while charging in his bedroom his words were something like the pack was flying all over the place.

You can believe me or not but it does happen.

Chuck
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Old Jan 21, 2004, 01:38 AM
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Quote:
Originally posted by davensocal
WJ Could I also ask those that are obviously against LiPo usage to please post your opinions on another thread?
I am not against Lithium cell usage. I just want people to use them safely. I also wish that the industry would come up with better chargers and I believe they will shortly.

We all need to know the risks and use the cells with adequate precautions.

Lithium cells are here to stay and are a great advance for our hobby.

Use them safely. I do not want to see anyone injured by not following adequate safety precautions.

Chuck
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Old Jan 21, 2004, 02:12 AM
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Utah
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Quote:
Originally posted by RandyK1
This is why I WILL NOT USE LIPOS, EVER!! Sorry for your aircraft losses. I hope everything works out o.k. ...R... p.s. Glad to hear noone has hurt
Alot of cell phones, laptop computers, camcorders, digital cameras, and PDAs use lithium batteries, too. (Of course the safety charge/discharge circuits are in place.)
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Old Jan 21, 2004, 02:19 AM
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Quote:
Originally posted by WingMan33
Sorry for ALL your Losses guys , Just like the first Nimh packs they will get these batteries figured out in a year or so. Fire hazard is a real problem ,Burn down a farmers field or your house, Her is a Cheap, Safe ALT, 1100mah 15amp push to 25 amp,1 buck a piece wont burst in FLAMES>
I had a NIMH pack short out and "burst into flames". Well, a couple of cells blew and there was red hot metal scattered around.
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Old Jan 21, 2004, 09:25 AM
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Tallahassee, FL
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Pretty much every fire that hasn't been attributed to a crash or a mistake on selecting cell count on a charger has been attributed to cell imbalance.

Here:

http://www.rcgroups.com/forums/showt...15#post1626015

and here:

http://www.rcgroups.com/forums/showt...56#post1628256


In fact, it's widely accepted that cell imbalance is a huge problem; thus the reason why TANIC packs include taps to check the voltage of all 3 cells of a 3s pack for example, and also why more and more retailers are now offering packs set up in PARALELL configurations instead of series. A paralell pack cannot become unbalanced.

another few posts talking about how imbalance is a serious issue. Keep in mind, if you had clicked on any of the links above posted by hoppy (second post in the thread) you'd have read all of this anyway

Here:


http://www.rcgroups.com/forums/showt...61#post1631661

http://www.rcgroups.com/forums/showt...92#post1632592

then, even try searching for "lipo imbalance"...


http://www.rcgroups.com/forums/showt...cell+imbalance

Here's a guy actually asking specifically "lipo cell imbalance causes what kind of problem?:

http://www.rcgroups.com/forums/showt...38#post1667838

This is relevant to the situation at hand because it is quite possible the charger didn't do anything wrong, but the pack was heavily unbalanced thus causing one or 2 cells to be overcharged to explosion.
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Old Jan 21, 2004, 12:08 PM
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I have several reliable sources in LiPo manufacturing that have recently informed me that if you take a LiPo below 2.7V per cell, it will outgas.

Once it outgasses, air is allowed into the pack. When it's next placed on the charger, the pack WILL catch fire. Outgassing will also occur if you push the cell beyond it's rated limits, also destroying the vacuum seal.

That's why I'm asking about the LVC of the speed controller.

WJ
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Old Jan 21, 2004, 12:14 PM
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Houston, Tx.
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I reset all my programables and the non-programables.....I'm "Fly in the Danger Zone"
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Old Jan 21, 2004, 12:21 PM
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Space Coast
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Videos of Lipo's burning - Is your charging setup safe?

Lipo Fire Video’s

Videos
http://mywebpages.comcast.net/tedcoo...losiion2_d.avi
http://www.rcstuff.us/battery/lipo/lipo_DNA.html

Threads
http://www.rcgroups.com/forums/showt...ipo+fire+video
http://www.rcgroups.com/forums/showt...5&pagenumber=1


hoppy
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Last edited by hoppy; Jan 21, 2004 at 12:23 PM.
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Old Jan 21, 2004, 12:23 PM
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Can individual cells (in a Li Po pack say 3S2P Tanic) be monitored while charging is taking place?

Mike
------------------------------------------------------------------------------------
Is there a diagram anywhere to show how to wire in chargeable taps?

Bill Bergman
------------------------------------------------------------------------------------

You can monitor individual cells in a multi-cell LiPo pack while the pack is charging. The principles to keep in mind are:

1) monitor the voltage across a cell while it’s charging in series, and
2) monitor the current flowing through a cell while it’s charging in parallel.

That’s because the current flowing through series-connected cells will be the same for all the cells and the voltage across parallel-connected cells will be the same for all the cells.

On the diagram, a tap wire (sometimes called a “center tap”) will come from each of points A and B to the outside of the pack. Voltage will be measured between charger minus and A for the first parallel pair of cells (i.e., 1 and 2), between A and B for the second pair and between B and charger plus for the third pair. Current can be measured by by means of a clamp-on ammeter around any one of the individual cell connectiors, e.g., “O”.

Charging each of the pairs individually is done by connecting the charger minus to pack minus in the diagram and connecting the charger plus to A. Second set: charger minus to A, charger plus to B. Third set: Charger minus to B, charger plus to pack plus.

- RD
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Old Jan 21, 2004, 12:26 PM
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Thanks RD!
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Old Jan 21, 2004, 12:28 PM
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What about 3 cells in series?
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