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01-11-2016 04:54 PM | ||
Ditchrunner |
Stanford boffins snuff out li-ion batt blaze risk • The Register If this comes to market it will resolve most of these issues. No help for now of course. The explosive side effects of overheated lithium-ion batteries have long been documented, and have caused everything from groin burns to the suspension of Boeing 787 flights. Now boffins at Stanford think they have the answer. If the electrolyte within a battery reaches 300 degrees Fahrenheit (150 degrees Celsius) then it can catch fire, and for years battery manufacturers have been trying to build in a safety system to stop this happening. While techniques have been developed to shut down a battery that overheats, it comes at a cost. "Unfortunately, these techniques are irreversible, so the battery is no longer functional after it overheats," said Stanford engineer Yi Cui, who invented just such a system. "Clearly, in spite of the many efforts made thus far, battery safety remains an important concern and requires a new approach." Cui and a team led by Zhenan Bao, a professor of chemical engineering at Stanford, have now built a solution – a polyethylene film studded with nickel that covers the battery's electrodes. The nickel spikes conduct electricity, but if the temperature rises the polyethylene expands and breaks the electrical connection, then shrinks to reestablish the electrical flow as it cools. "We can even tune the temperature higher or lower depending on how many particles we put in or what type of polymer materials we choose," said Bao. "For example, we might want the battery to shut down at 50 C or 100 C." The technique is not only reversible, but repeatable. The team applied a heat gun to the substance to activate the tiny circuit breakers, let it cool to reestablish power, and repeated the process many times. "Compared with previous approaches, our design provides a reliable, fast, reversible strategy that can achieve both high battery performance and improved safety," Cui said. "This strategy holds great promise for practical battery applications." ® |
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01-11-2016 03:42 PM | ||
CDA 455 |
Indeed. Having this important safety info in one thread will definitely help reduce the chances of one of us having an 'IED' moment ![]() |
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01-11-2016 03:36 PM | ||
makya |
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01-11-2016 03:27 PM | ||
bgaidan |
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I'm thinking I may have a metal toolbox that would fit the bill until I'm somewhere where I can find a good surplus store again. I don't like the idea of storing all of them in the same box either. If one goes, I lose $300 worth of lipos. |
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01-11-2016 03:24 PM | ||
makya |
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they also carry ammo cans at walmart: Blackhawk Ammo Can, 30 Caliber - Walmart.com |
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01-11-2016 02:31 PM | ||
87manche |
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That's a function of each cells internal resistance. That's also why cells can discharge at different rates and you need to balance charge the pack. It's all realted to internal resistance. The higher quality packs are all matched cells, so they discarge more evenly. Shitty packs are not, so one cell with higher resistance may not keep up with the other cells. |
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01-11-2016 02:15 PM | ||
bgaidan |
I really need to find some ammo cans...nobody seems to sell them locally. Especially now that I just got about a dozen 3 and 4s lipos from 3DR's clearance sale and I have several on the bench that are a little puffy. I had an 1800 3s drop to 6v on me this weekend. It's been puffed up for a while and I just kept it around to power stuff on the ground if needed. After seeing it go that low, I salvage the power lead off of it and then threw it on the driveway, repeatedly...trying to make it go critical. Even hit it with a hammer a couple times. ![]() I have a couple more 6000 3s in the mail, which will bring me up to about 20 total in the 3000 - 6000mAh range each. I have another 3000 3s that I was using to power my vid tx while I was trying to set it up on the bench. It wasn't charged very much when I started using it and I forgot how long I had it plugged in, but it's dropped pretty low too...about 2.8v per cell. Not puffy though. I may try to restore that one...in the middle of the driveway with an extension cord! ![]() |
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01-11-2016 02:03 PM | ||
XtremeJ |
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swell is slight, and the battery is firm to the touch. Part of me wants to put it on a charger and run current into it until it explodes and burns down the entire state. The other (cheap bastard) part of me wants to just get as many cycles as I can before it is toast |
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01-11-2016 01:58 PM | ||
87manche |
that's the problem though. You don't know what you don't know. and no one reads the page of text about battery safety. |
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01-11-2016 01:50 PM | ||
Alpine4x4 |
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![]() I run the el cheapo turnigys, never an issue. Charge balanced on 2c. Dicharge/charge to storage voltage when not in use. Store in ammo can. Charge in lipo bag. Be smart about it and educate yourself and it's not an issue. |
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01-11-2016 01:35 PM | ||
87manche |
some swell is normal over the life of a pack. It should still be firm to the touch. When it feels like it's a balloon, then it's puffed to the point of being dangerous. just make sure that you don't latch the ammo box, or at least drill some good sized holes in the top to let it vent if one goes wrong. |
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01-11-2016 01:27 PM | ||
XtremeJ |
Thanks to the folks who have posted good info in this thread. I have a small quad which uses Battery LiPo, 1200mAh 2-Cell/2S 7.4V 25C, JST Connector batteries. I only use the factory charger w/ balancer. After reading the Lance RV thread, and noticing one of the batteries showing a slight (very slight) bulge I figure I might as well be safe than sorry. Charging in an ammo box now which has a cord on the handle so I can remove it outdoors when / if it catches fire. Just how bad must a battery swell before it is fatally bad? I took pics but the bulging is so slight I cannot tell which is a good battery and which is the bad one in the pics. |
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01-11-2016 12:54 PM | ||
87manche |
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and I told him to make sure that shit was at least 20 feet from his RV and to do it only until the pack voltage came up for the charger to see it, and that it was probably going to burst into flames. You can do stupid shit, just be aware that you are literally playing with fire. I liked the "it's just like a cup of gasoline" analogy. |
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01-11-2016 12:41 PM | ||
87manche |
Turnigy Lipo Bunker - Lipoly Safety Charge Box $22. It's a pre-vented stainless ammo can. |
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01-05-2016 08:28 PM | ||
CDA 455 |
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01-05-2016 07:32 PM | ||
DWT |
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01-05-2016 07:00 PM | ||
y2kmxz |
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01-05-2016 06:23 PM | ||
bgaidan | Ammo cans are more than enough to contain the potential fire. No need to go crazy with a fireproof "safe". These fires burn hot and fast. If they don't have any other fuel to keep them going, they're done in a minute or two. An ammo can has no problem containing that. | |
01-05-2016 04:54 PM | ||
CDA 455 |
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Not excessive at all. |
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01-05-2016 04:38 PM | ||
y2kmxz | I just got back into RC's about 2 years ago with my son. I've been charging the Lipo's in the garage on the work bench. On the way home tonight I stopped at the local hobby shop and purchased a lipo charging bag. Going to set up an area for Lipo storage and charging, and will be getting a fire proof document box or equivalent for transporting. It might be excessive, but what happened to the Clifford family and the info provided in these posts has convinced me to take the extra steps. | |
01-05-2016 02:43 PM | ||
reklund5 | Sorry...i was thinking about what I leave plugged in and charging and rambled a bit. Has nothing to do with LiPo batteries. Carry on! | |
01-05-2016 01:31 PM | ||
DirtyComanche |
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01-05-2016 01:27 PM | ||
Pat |
Charge with the proper current for the size of battery Charge outside Use a decent charger or one specific for the battery, make sure it is set correctly for LIPO's If damaged watch out |
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01-05-2016 01:16 PM | ||
spot4me |
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All it takes is one person to not prepare it for the landfill by discharging it completely or tossing one in that damaged but still has juice and it could still cause a fire. Why not treat it like other batteries and take it to Lowes or Best Buy or a similar place that will take it? |
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01-05-2016 12:50 PM | ||
CDA 455 |
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As long as you post your knowledge and/or experience, post as much as you want ![]() Fug everyone else ![]() |
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