Li-Po Sack
 

For those of you who charge their Li-Po batteries in their planes, take a look. This happened with me sitting 6 feet away. A battery exploded while charging inside the Li-Po Sack.
THANK goodness it was in the sack and not in my plane.
I was one of those guys who thought it would never happen to me.. WRONG!!!

John S.

RE: Li-Po Sack
 

I almost burned my house down with a cheap 1300mah lipo that I had put on the back porch in a document fire safe! It puffed while charging, I put it 3' away from my house on a on concrete in a document safe and still charred the side of my house... TP packs are all I use now.

RE: Li-Po Sack
 

WOW , money well spent on the Lipo Sack!!

Any idea what made the battery cook off?<br type="_moz" />

RE: Li-Po Sack
 

What is a "tp pack"?

RE: Li-Po Sack
 

http://thunderpowerrc.com/html/products.html

RE: Li-Po Sack
 

I agree the li-po sack is better then charging in your plane... but it's still not a safe place! Li-po packs holds an enormous amount of juice, I use a 3S 2200mAh to jumpstart my Volvo diesel in the winter, doing the work my 120Ah lead battery can not do. I would never recommend anyone to trust a li-po sack with anything larger then a 500mAh pack.

When a pack caches fire there have been something wrong, mostly user error when setting up the charger. Would be intresting to know if you did find the answer to why this pack cought fire.

A concrete box with 2" walls would be a fire proof place to charge your packs, but the smoke would ruin alot of the stuff in the surroundings any way.

RE: Li-Po Sack
 

I've been in the hobby long enough to know two people who did lose their garages or part of their homes...I think dantley had a similar problem as well? I always make sure the proper number of cells is showing on the charger, and NEVER leave the batteries. I have a smoke detector sitting above them and fire extinguisher right next to it. My error was using a cheap ass off brand pack that were probably QC'd by a ten year old while he was watching cartoons. I still use lipos for my jets, but I have them taped together and easy to remove out of the plane to charge. Newer projects are A123.

RE: Li-Po Sack
 

I designed the Venom Stronghold metal battery charging box when I worked there. In the process I blew up many LiPo battery packs including 2S 5000mah, at least 12 packs in one day in the same container at one point.
My point is I know how difficult it can actually be to blow up a LiPo on purpose. I would say that the pack failures and subsequent fires and damage could have been directly related to charger set up error AND lack of supervision. The charger when set to NiMh charge mode can pop a pack but it takes a long time.
In general if your pack has not recharged in about 1 hour at the standard 1C rate then there is an issue of some kind. Being present to check the charging parameters will prevent a catastrophic failure. Most chargers will fault and stop a charge cycle if there is a problem provided it is set to the right mode of charge.
I have not seen, in the millions of packs we sold, a single pack explode during charge due to a defect. Ive always seen packs fail due to misuse and incorrect charger set up.

Also the one great benefit to a LiPo pack is its early warning by ballooning BEFORE bursting open.
In most cases Ive seen or purposely caused failure in metal round cells there is very little warning before a catastrophic event. When a NiMh cell explodes its literally a grenade sending shrapnel flying at high velocity outward followed by material on fire.
Ive seen cases of misuse and mishandling resulting in the loss of an eye and/or property damage.

I prefer LiFe or LiPo for my models and Ive been testing this for over 4 years straight in nitro, edf and jet models.

MAKE SURE YOUR CHARGER SETTINGS MATCH YOUR PACK BEFORE YOU PRESS START!
DO NOT STORE YOUR LITHIUM PACKS FULLY CHARGED FOR A PERIOD LONGER THAN A WEEK
DO NOT CHARGE ANY BATTERY PACK IN YOUR MODEL

RE: Li-Po Sack
 

I normally don't post on RCU anymore, amongst all the good stuff there too many keyboard warriors posting complete rubbish (not on this thread though ) and getting stroppy if you challenge them !

However, if you really want to understand lithium technology, in its various forms, you can do no better than read the PPrune thread on the problems of the 787 electrical system (causing its grounding since January, slowly being returned to service this month) with particular relevance to their Lithium Ion batteries, and the two fires experienced , used on this aircraft. Many of the contributors are highly qualified to comment and contains some extremely valuable information to us as lithium users, particularly on the care and management of this chemistry. The information on failure modes is interesting to say the least. The various charts and tables are of particular value as is the direction to "Battery University". There is also coverage of the difficulty experienced by the firefighters at BOS when trying to kill the lithium fire on the ANA 787.

In my own research into model lithium batteries I have found that the PowerBox packs really ARE ahead of the game as these packs contain, in their integrated charging electronics, temperature monitoring to detect and protect against, the possibilty of thermal runaway, and also monitor temperatures to ensure that the charging process is conducted only within permitted temperature boundaries which should go a long way to prevent the possibility of fires and/or explosions and extend battery life.


The location is:

http://www.pprune.org/tech-log/50569...-part-1-a.html

David Gladwin.

RE: Li-Po Sack
 

Thanks for sharing David. Extremely interesting. I had a look at this thread on Pprune thread initially but dropped it and missed most of the useful information...

RE: Li-Po Sack
 

Hi,

I have 3 of these Robbe LiPo-Tresor boxes now so it feelslittle more safe to store all LiPo batteries I have in them.
Weight of the box (empty): 8 kg / 17.6 lbs
Inner dimension where the LiPo is placed: 320 x 220 x 75 millimeter / 12.6 x 8.7 x 3 inch.
Link to Robbe homepage about this "LiPo-Tresor":
http://www.robbe.de/lipo-tresor.html..._from_store=de

Video that show a 6 cell 5000 mAh LiPo on fire inside this box:
http://www.youtube.com/watch?feature...;v=hK4ECoV66Kg

It is little unclear how much LiPo packs You should safely place in one box and the box would still be able to handle aLiPo-fire in the box.
But Robbe said this when I asked them:

Hi,
You can put many batteries there if you have enough place for this. The case is to eliminate open fire - not for smoke or something else....

with best regards

robbe&reg; Modellsport GmbH &amp; Co. KG
i.A.
Carsten Druleib
Robbe-Service-Center
Metzloser Strasse 38
36355 Grebenhain


Not crystal clear answer.

I do not think there are any Robbe dealers in US but maybe the CentrySafe Small Capacity Fire-Safes that is available in US can work OK also
for storing LiPo packs:
http://www.sentrysafe.com/Series/89/...ity_Fire-Safes (View all)

/Bo

RE: Li-Po Sack
 

I would be interested in how this fire safe is different than the one I had. A 1300 mah pack completely destroyed it. That one looks identical to the one I had. The pack burned through the fire safe, then the side of my house.

RE: Li-Po Sack
 

Hi,

That is the big question: how much total LiPo packs can be in such box. How large packs (how many cells and mAh) can be safely in the box.

I have 3 old 6 cell 5200 mAh LiPo packs that could be the "fuel" in a test but it would be an expensive test for me to find out what happen if
in a test all that should go on fire in a Robbe safety box. Little to expensive experiment for me.

At least the box is better then the standard grey LiPo sacks I had before. But the LiPo safety boxes like the one from Robbe may lead You to think You are safe but in reality it is no guarantees Your house will not go up in smoke if a LiPo pack in the box goes on fire.

Only proof is the video, that it can handle one 6 cell 5000 mAh LiPo that catch fire inside the box.

I know Graupner also has a LiPo safety box but it is much more expensive (close to 5 times more then the Robbe safety box).

http://www.graupner.de/en/products/c...1/product.aspx

/Bo

RE: Li-Po Sack
 

John S.

How big was that battery pack?

I use a lipo sack, inside of a metal Ammo can sitting ontop of 1" dry cast concrete stepping pavers.

RE: Li-Po Sack
 

Do these also pose a risk if not under charge/ sitting idle ?

RE: Li-Po Sack
 

That's a great question Hans. I have 1 dozen or so bigger packs that I use in my electrics...not my jets but, wonder if they pose a risk just being in the house with a storage capacity charge on them?

Mike

RE: Li-Po Sack
 

Exactly Mike, thats whats scaring me , because mine are also stored in the house.....(basement)

RE: Li-Po Sack
 

This has been discussed in RCGroups EDF forum. The general consensus is that properly cared for, "stored" state, Lipos are safe. They can be stored for several years this way.

There is a bit of justification, because this is the way they are shipped from the manufacturer and obviously they have a warehouse full of Lipos in this state.

Caveat: exception would be an FEJ Lipo if they make em. : o

RE: Li-Po Sack
 

At what C rating were you charging and hopefully the charger was set up properly with correct chemistry and number of cells

RE: Li-Po Sack
 

The two Venom LiPo containment boxes I designed were ment for up to 60 Watt Hours.
That means any pack configuration up to this specification is ok when the pack fails inside the box. The box is meant to allow the pack to out gas and smolder but not explode or project fire. The box has ventilation but the pressure exiting the box will prevent the atmosphere from entering immediately and feeding the fire with fresh oxygen. That is what keeps the event contained inside the box. The lithium material will feed off of oxygen in the air and from water so it has to be snuffed out. I blew up over 12 packs of various sizes in one container featuring a polycarbonate window with no failures to the box. The box was discolored and window was blackened but the situation was contained with no collateral damage. The smoke is horrible and will stain the area with scent and soot.

In terms of storage your container, like an ammo box, is not the best idea but it will do for 2 or 3 packs maximum as long as they are 2 or 3 cells a peice. For larger packs 3 cells and up these should be isolated to one container per pack ideally.

Do Not Store all of your LiPo packs in one container. Spread them out over a couple containers to prevent a runaway fire situation and potential explosion.
LiPo packs EXPAND to 4-5X's their size when they fail. If several of them are in one container they will probably burst the container and effect anything surrounding the immediate area.

Also what keeps a LiPo pack hot after the fire is over is the many sheets of copper that make up the individual cells. These will be very hot and will contribute to the fire situation.

Storing of LiPo packs should be done at the nominal voltage of 3.7VPC. If not the packs chemistry will cause more internal resistance, poor performance and loss of capacity. LiPo is not the best "storage" chemistry. LiPo is designed for cycles not storage. For storage applications use LiFe.

LiPo packs fail in a couple of ways; cold and hot. A cold failure is a condition like a steady trickle discharge until the pack is dead. A hot failure is typically when the pack is under load and pushed below 2.8VPC. In both cases it is likely that the pack will balloon, an indication that the chemistry has out gassed. At this point if its a slight puffing up and the voltages across all cells are normal it is likely the pack can be used again but it should be watched closely. Typically a dead pack will not recover.

The Boeing pack failure is an intesting case. They used Yuasa from Japan who to my knowledge has little experience in Lithium Polymer battery tech. Their expertise has been for decades in lead acid and gell cells typical of cars and motorcycles. They should have used BYD from China but I'll bet their relationship with ANA Airlines had something to do with their sourcing decision.