This may be a stupid but I have been charging my Li-Polys up to 4.15 Volts per cell. My charger is running at 1.1 amps and the charging is via the balancing plug. The charger amps taper off as 4.15 V is approached. I have had a couple of batteries swell but I have attributed this to a bad batch of Chinese Li-Polys in one case and to running over the C rate in the other case.

Does this regime sound about right??

John

Crist,

I'm not sure what this has to do with my question but here is the information:

The charger is a Skyartec "Auto-Adjusted Closed Loop Current Feedback Charger." 1.10 Amp Max
Balancing, Auto detect: Battery type (Li-poly vs Ni-MIH), Cell number,  Voltage

I have several batteries:
    X-Cite 3S 20C 2200 mAh 10 months old
    ABF 3S 20C 2200 mAh 8 months old
    HexTronik 3S 20C 2200 mAh about 1 year old
    Hi Model 3S 20C 1700 mAh about 1 year old
    X-Cite 3S 22C 1800 mAh 4 months old

    The puffed batteries were a HexTronik 3S 20C 2200 that was replaced by the dealer (Hobby City) and a HI Model 3S 20C 1700 mAh that was  over driven when I put on a larger prop without checking the AMPs being pulled.

John

Mike,  Thanks for the information. I agree that HexTronik batteries are junk and Hi Models are right in there with HexTronik!! I was most interested in whether 4.15 Volts in an appropriate charging voltage and it appears to OK. I have had good luck, so far, with X-Cite and I like to keep the money in the US if the product price is competitive. Hobby City is now carrying Polyquest Li-Polys but I will stick to the X-Cite for now.

John 

The old caution about charging li-polys was recently brought to bear in the Phoenix area when a modeler lost his life in a fire in his shop.  The fire department could find no other cause for the fire other than a li-poly battery attached to a charger.   The individual was apparently trapped in his shop by the battery explosion, there was only one way out and the battery was between him and the door.

Hi Don,

THANK YOU .... ANY MORE INFO?

Thank you for the post on this tragic event. Do you have any more details on this? A link to a News paper or TV news report, a date, ? TIA

My guess is that there must be more to this story. I don't think the battery alone would be enough to trap a person in the shop. If the battery was anywhere near some flamables, paint, fuel, etc. these items burning could easily trap someone after being ignited by the burning battery.

SMOKE .... 40 SECOND BURN ... GOOD DEMOS, LIPOSACK

The other factor is the smoke! My 17' x 25' shop was completely filled with thick black/gray, foul smelling smoke. I have a very large door that I was able to open to the outside so there was never a safety issue.

Fortunately, our batteries do not explode like a bomb, they burn rapidly, very much like a large flare does. Our 4S batteries burn for approximately  40 seconds, roughly 10 seconds per cell. Fortunately for us they usually go off with the "bad" cell 1st, then it ignites the next cell, etc. I do not mean it is an organized burn, it is very sudden, and very messy with a LOT of smoke and ash.

Please go to this link to see several excellent demos of LipoPacks burning:     http://www.liposack.com/video.htm

I highly recommend using these Liposacks. I have used them for the past few years in ERC. I have posted this here before but it is worth repeating. These are excellent products. They are not made from simple Nomex material (Nomex would fail/melt at our temps.) they use a very expensive material used by NASA. Here is the link to buy them:     http://www3.towerhobbies.com/cgi-bin/wti0001p?&P=SM&I=LXSEA5

Another option is using small ceramic planter boxes from Home Depot (or equivalent home center). They are in the garden section. I have posted photos of mine here in the past. They are perfect for our ECL size batteries.

REAL LIVE DEMO YESTERDAY!

Strange that this post came up now because I just watched a 3S battery "go off" yesterday. I was flying both ERC and ECL at our electric field. A guy saw his battery PUFF UP during charge, then did the correct thing and removed the swelled up battery and put it in a safe place on the cement parking lot. (I would have liked to see him place it a little farther from his truck, than 5', but it worked out OK). I turned to see the battery "go off" about 10 min. after it was placed there. The flames were approx. 30" high and wide for a few seconds, then down to a smaller burn as each cell went off. Being outside in the wind, the smoke dissipated quickly. Several of the guys still charge their batteries on their cars, using the cars 12V battery. IMHO this is a NO NO, but it is hard to get modelers to change. :-(

THE "GOOD, THE BAD, AND THE UGLY"

BTW: He was using an inexpensive (red) battery. I agree 100% with Mike Palko, saving money on cheap batteries is "PENNEY WISE AND POUND FOOLISH!!!!" I use Thunder Power Batteries that are assembled here in the USA (LV NV :-). They are high quality batteries with excellent customer service. FlightPower also makes very high quality batteries. There is a large drop off in quality below these two top name brand batteries. ..... IMHO: If you can get the same V/Amps battery for 1/2 price, something is wrong with that battery for our use! The top two name brands above use very high quality cells combined with careful assembly. I trust Thunder Power batteries in my small 4S ECL planes and my larger 10S ERC planes.

RARE EVENT!

Fortunately for us: THIS ACCIDENT IS A VERY RARE EVENT! Properly treated, our batteries are very safe. As I have said before on this list, I have over 1,000 E flights and friends with thousands of E flights, with only ONE burned battery. And that was caused by a faulty charger many years ago.

GREAT CHARGER .... TP 1010

I use the Excellent 1010 charger from Thunder Power because it has the "feedback" loop that stops the charge if there are any problems. I also always use a balancer during the charge.  I hope that more charges in the future combine this loop, and the balancer into one single unit. The trend seems to be in this direction. :-)

There are many things we can do to make our charging safer but here are a few that I think are important:

                          A FEW SAFETY TIPS

1. ALWAYS PLACE BATTERIES ON A CERAMIC TILE

Our batteries burn at 2,000 degrees F for a few seconds. This will "weld" the battery to the tile, which also melts around 2,000 degrees. This will prevent most fires and save your bench, table, home, etc. from going up in flames. Any tile from a Home center is OK, and very inexpensive. I have my charging table coated with all tan tile. My wife thinks it "looks" better too! ;-)

2. NEVER CHARGE IN YOUR CAR, OR IN YOUR ENGINE COMPARTMENT!

Please use a table next to your car if you have to use your auto 12V battery. It is better to use a separate 12V battery like Mike and I do. It is much safer!!!

3. HAVE A WINDOW/DOOR TO THE OUTSIDE "OPEN" WHILE CHARGING!

The smoke is terrible, it needs to get out ASAP

4. ALWAYS USE A "LIPOSACK" or SAFE CONTAINER

Please see above for LipoSack info. Or use ceramic container, ammo box, etc. with VENT holes to release the pressure.

5. ALWAYS USE A BALANCER

And a charger with a feedback loop if possible.

6. AVOID "CHEAP" BATTERIES ... FALSE ECONOMY!

Trust Mike Palko, he knows what he is talking about when it comes to ECL! :-)

Sorry for the long winded post, but I think E power is the future of modeling and it would be nice if we all used it safely.  There are a lot of modelers out there who are strongly against using E power in CLPA so we need to make sure we don't give them any ammunition to fire against us. ;-)

PS: Don, call me if you need help at your CL Speed/Combat contest. :-)

Regards,   

My brother did an experiment on a puffed Li-poly.  Outside on a concrete pad he punctured it with a long piece of music wire.  The pics of the flame and the volume of smoke were really frightening.  I can see where the smoke could overcome someone within a confined enclosure.

Then he shorted out the plates internally, if there was smoke and flame.  I've carefully punctured the plastic envelope on puffed LiPos a couple of times - there was no noise, heat, smoke or vapor even.  I was trying to see if just relieving the pressure and resealing the small hole  with tape would allow the cell to charge/discharge a few more cycles or any better than it did before I punctured it.  Those tests were not terribly enlightening, but the cell did "re-puff" up and didn't take any better charge than before it was done.

We did have an incident at the field where a battery mount made from wire - like you might use to mount a fuel tank on a profile plane - apparently wore a hole in the plastic on one cell - then shorted out the plates.  When the plane landed after an otherwise normal flight, smoke began to appear from the battery.  I pulled it off the model (a profile) and tossed it aside - apparently removing the short circuit.  It smoked for about 10 more seconds, then stopped.  That cell is dead and you can see copper plates through the hole burned in the plastic - the other two are fine.  The plates are interleaved with a black substance and the copper is mechanically deformed - again suggesting that the wire mounting strap was physically abusing the internal structure of this cell.  All this was just a week or so ago.

One other "it happened to me" story - flying a different profile model I had a minor "lawn dart" type "landing" - the battery, a 3-cell 1300 mah, kept going forward, breaking the rubber bands and ended up about a foot away from the model/motor and unplugged itself in the process.  It apparently hit something sharp and/or metallic in its travels and after about 5-10 seconds - I was still walking to the model from the center of the circle - it began to smoke.  Again, I picked it up by the battery leads and tossed it about 10 feet away - it made like a roman candle for about 15 seconds with a lot of smoke being blasted out but I don't remember any violent flames. (Actually "blasted" is too strong a word - forced out under some pressure is more accurate) Then when the smoke died down and it cooled off, we removed some of the melted tape and looked it over - left it sit away from people and planes for the rest of the session - took it home and discarded the melted cell.  I'm still flying the other two cells as a 2s1p in a small plane and they continue to take and deliver a charge equal to the other two batteries that I regularly use in that plane.  In fact I've been flying it fairly heavily the last couple of weeks and I really can't tell any difference between that battery and the other two.

My conclusions are that just puncturing the plastic is not a hazard in itself, which makes the most sense if you think about it.  But get metallic intrusion that reaches the plates and you will create short circuits which will cause very quick and very high heat concentrations internally.  Results may well be spectacular, in that case ..

My 2-cents --

Mike A