|Jun 26, 2008, 09:44 AM|
LOL, I just love this thread.
Like the guy who didn't smoke, didn't drink, didn't gamble, always ate healthy food, did lots of sports...
... and got run over by a truck, age 30.
And I am sure he never even considered chargeing a Lipo in his long and fullfilled life!
|Jul 13, 2008, 12:00 PM|
Joined Apr 2008
Hey guys. I have this puffed pack I have used on numerous flights. It charges up fine and performs fine. the cells are still balanced. My question is, Can a swollen lipo explode only if it is being charged or discharged? Another way to ask is, is my swollen Lipo safer after I take it off the charger? Its always cool in temperature when it comes off the charger. Can these things just burst into flames at any time when they are puffed, like 30 minutes after its charged? In contrast, can the same battery explode AFTER I run it, while it is warm, and even if it is unplugged from my Heli?
Its not really getting fatter. The one thing i do notice however is it is really hard (when you squeeze it, its not so squishy) especially after flights. as it cools it softens up some.
I know 95% will say I'm a dumbass or that I am cheap. I have other batteries thats not the point. It works fine. I watch it when I charge it. It doesnt get hot on the charger. It doesnt get any fatter, or smoke, or anything.
Should I be worried at all because It seems fine. I cant imagine it just all of a sudden BANG. I seen the videos on youtube of LiPo explosions, but there is all sorts of warning signs, like they plump up ALOT or hiss before they blow. Mine just sits there granted I watch it like a hawk.
Would anyone that has a response please PM me, I don't visit this thread often.
|Jul 19, 2008, 08:42 AM|
If it is already puffed up, you won't get the full current out of it. Also you should see that it will not charge up to the full voltage.
I highly recommend that you do not use the pack any more. If it is already bloated, it my burst a seal and start a fire from that.
|Jul 25, 2008, 10:04 AM|
another roman candle
I will add my name to the list of people who have had batteries flame up and have now seen the light. I will be taking more precautions in the future. I've used lipos for 4 years without mishap until now. At the risk of being riddiculed for taking too many risks, I'm going to list all the things that I was knew that I shouldn't do, but I did anyway. If listing these things helps to convince others to be careful, it's worth it.
Error 1) I was field charging in the back of my SUV last Sunday off of a stand alone marine battery
Error 2) it was sunny outside, but instead of leaving all the windows down like I usually do, I rolled them most of the way up because there were a lot of strangers at the field
Error 3) the 4000 mah 5s pack was only on its 6th or so charge. I was putting 3 amps into it, so it was .75C. I usually balance every 3rd charge since I have 3 chargers but only 1 balancer. That probably led it to be more prone to get out of balance?
Error 4) I only have 1 temp sensor that hooks to the charger and forgot to bring it
Error 5) I had just maidened a new plane that is slightly larger. I didn't think about it then, but I bet the batteries were run down close to 3.1v or 3.2v per cell. Usually I only go down to around 3.4v per cell. I assume shoving 3 amps into a very low volt cell without a balancer could lead to more of a chance of the batt getting way out of balance.
Error 6) I was lucky because I had let the battery charge for the first 45 min unattended while I flew my other 3 batteries.
When I returned to the truck to check on the charge status, I saw that it was still around 20.5 volts (on it's way up to 21v). The truck was getting pretty warm inside so I left the tailgate open and decided to call my mom to say hi while I putzed around waiting for the battery to take a few more electrons. Just as I was hanging up and standing next to the truck with the tailgate open, I heard a "poof" and then a "pufffffffffffffffff" and saw a 3 foot flame shooting out of the battery!! I grabbed the charger and threw it with the battery still hooked up out of the truck onto the ground. I had a blanket in the truck that I quickly used to put out about 10 small fires in the carpet and roof in the back of the truck. As I was doing this, the battery continued to flame up about 20 feet away on the ground and I heard another "poof" and more "pufffffffffff" when another cell let go.
I got all the little fires out pretty easily (I assume the Expedition has fire resistant interior?). I was totally freaked out and just stood and watched as a third cell exploded after about 1 more minute. After everything cooled down, there was only 1 cell left unexploded.
I had used that charger at least 100 times in the past and trust it. I believe that the battery got way out of balance and one of the cells climbed above 4.2 volts and caused the problem. I won't name the brands of the charger or battery because I don't believe they had anything to do with it.
I believe that if any one or two of above errors had been avoided, I would probably have been fine. I'm going to buy a few more temp sensors and balancers. I will not charge lipos in my car any more.
|Jul 25, 2008, 02:02 PM|
well am i right or wrong, most chargers now days will not even let you charge your battery unless its at the right cell count, so even if you put it at the wrong option, it will not charge, at least thats how my Imax B5 works, or do i still need to be careful cause out of the blue while its charging there is a chance that it will blow up?????
|Jul 25, 2008, 02:27 PM|
Thanks for reporting your accident HUCK. Hopefully it will prevent someone else from having a fire. It was fortunate that you were there to eject the pack from the SUV.
littlephoenix, my suggestion is to assume that it will ignite and do whatever you think will make that ignition only a lipo loss with no other fires or other damage. After all, electronic devices do fail....... hopefully very infrequently.
|Jul 25, 2008, 02:33 PM|
Huck, you are probably right about the deeper discharge on that pack being a contributing factor. The farther down they are discharged, the more imbalance shows up. That greatly increases the chances of a cell going over 4.2. For Lipo's, balancing chargers are really the way to go. Can't ever get the cell count wrong and no cell gets over 4.2.
|Jul 25, 2008, 05:53 PM|
I believe that if any one or two of above errors had been avoided, I would probably have been fine. I'm going to buy a few more temp sensors and balancers. I will not charge lipos in my car any more.[/QUOTE]
There is another safety item that you could use, I use it on ALL my lipos,
it is an in-flight INDIVIDUAL CELL lipo monitor, ie. if any cell drops below
a preset voltage, then it slows-down your motor or shuts-down, depending on
the setup. I am very surprised that there so very few mentions of
Currently I only know of 3 manufacturers being;
Dimension Engineering is good for up to 6 lipos and needs to be used with BEC, but to its credit , it has adjustable cut-off point, sensitive temperature sensing (with fly-lead) and you can plugged-in to the battery in any position.
has individual LED per cell and one for temperature.
The Liton is the cheapest, only good for up to 4 lipos. pin connection is strict , has a temperature sensor also, but it is in a case and has a high latency.You cannot adjust the cut-off point. Has individual LED per cell.
Requires BEC type controller.
Schulze makes different versions for lipos and A123s for a large range
of cells. It has limited cut-off point selections and requires strict pin
connection to the battery. Does not have individual LEDs.
has two opto-couplers and therefore can be used with or without BEC.
Units can be cascaded (daisy chained) to suite a big cell count.
My advise; use balancers for charging and these devices in flight to
prevent INDIVIDUAL CELLS over-discharge or pack over-temperature and your problems should be virtually over.
I firmly believe that unexplained lipo fires during charging are due to a previous event during the discharge process, either under-discharged or over temperature.
another solution is to get a tiny car that prevents charging a model IN the car
|Jul 26, 2008, 05:06 AM|
However, I'd still be carefull if you do not fully understand what exactely your charger does (most manufacturers don't advertise theyr software...)
Error 1 = no error at all. Where else would you charge? in the (wet) grass?
Error 2 = well, unless it was well over 120°F in there, that should be OK
Error 3 = that may have been the most crucial problem. You should realy consider to charge only with a balancer, or a balance-charger
Error 4 = I am not sure if the temp sensor would have helped. As you stated, the cells let go one after another. So you would have to pick that cell which was the first to blow up to attach the heat probe. Kinda like "Lipo-roulette"...
Error 5 = correct, and that fits error 3, as well
Error 6 = Again, I don't think the main problem was the abient temperature. But this shows that lipos ignite only when being charged (or physically damaged in some cases)
If you field charge often (alternative: buy more packs and only bring the charged ones, go home for charging), Get some kind of "loading-box", like a sheet metal ammo box. Put a shelve in there for the charger, and run the PS cable outside. Line the lid with something insulating, like a foam matt, and charge the battery in there, outside the car. This way any fire will char the lid of the container, worst case.
|Jul 26, 2008, 08:58 AM|
My advice for the field charging is to get a lipo sack or largish clay flower pot to charge in. I highly recommend the cellpro 4s with the 3foot extension leads. You can put the pot or lipo sack on the ground while the cellpro is still in the car or setting on the motor by the car battery. It allows you to keep the battery a bit farther away from flammable items. Although, just using the cellpro cuts the fire risk down immensely. Barring that I would consider longer leads for your charger, although I don't know the implications of lengthening the main charging leads or the leads to your car battery. So check that before you do any mods.
|Jul 26, 2008, 01:21 PM|
thanks for the report... glad to hear that damage isn't excessive.
But when I read this
>>cause out of the blue while its charging there is a chance that it will blow up
I just want to laugh out loud. Yes there is, sorry for the bad news. Of course there is, just read through this thread. That is the whole point.
You can reduce the risk that a LiPo bursts in flames, but you cannot prevent it completely. It's simply not fully under your control (think manufacturing defects).
All you can do is prevent that a burning LiPo starts a fire. In other words, charge in a fire safe place, and keep under supervision (i.e. where you can see them and react). You can put out almost any fire within the first couple of seconds, before it grows. That's why "keep under supervision".
At least that is what the industry agrees on (i.e. the warnings printed on the pack).
It's also my own conclusion, after doing some research - I usually have three or four gallons of nitro fuel in the trunk, you bet I'm not too keen on a LiPo going fireworks in the vicinity.
Of course, there are always some people who are "smarter" than others or just like to argue for the fun of it. Keep in mind, you make simplifying assumptions, and in theory (under just a few simplifying assumption) the Titanic was impossible to sink. Textbook equations let you prove that bumblebees are incapable of flight. 'nuff said.
PS: gas stations sell wires to jump-start cars. With those, you can put some distance between chargers and car, and it does not affect performance. They can handle much much higher currents.
|Jul 28, 2008, 12:18 PM|
the TURNIGY Sentry escs form hc have individual cell monitoring (my understanding is all turnigy escs are rebranded hobbywing which really make good escs )
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