I have reviewed several Chinese-made Li-Ion battery packs and although some are pretty good, the typical BMS that I see will not prevent from over-charging a cell, they typically only have a "bypass resistor when the cell is full" which is supposed to work well as long as most cells are well-balanced, but if cells are out of balance the charger will push much more current into the pack than the bypass can handle, so cell(s) do get over-charged in such a situation. Also I am not sure that there is a per-cell low voltage monitoring, I think the output simply turns off when the *pack* gets too low, which usually means that one or more cells are already "dead". On top of that, some packs are assembled from reject cells. I once had ordered several 10Ah 4-series packs and several of them were severely out of balance, one of the packs even had a cell at 0V. I have been able by careful and slow charging to resuscitate that cell and am still using the pack in a low current application (vehicle light) but I can see from the balancing that I have to do that this cell is permanently having a much higher self-discharge than the other cells in the same pack. Now, try to fast-charge such a pack with the simple BMS that does a low current bypass and you can see where that leads....
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Any unauthorized use, disclosure, distribution, or copying of any part of this message is prohibited. -----Original Message----- From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of brucedp5 via EV Sent: Friday, February 05, 2016 12:48 AM To: ev@lists.evdl.org Subject: [EVDL] Exploding hoverboard fires: Petaluma-CA house & Erie-PA SUV http://www.petaluma360.com/news/5167811-181/hoverboard-started-exploding -in-petaluma Hoverboard 'started exploding' in Petaluma house fire February 4, 2016 RIC GNECKOWARGUS [image http://www.petaluma360.com/csp/mediapool/sites/dt.common.streams.StreamS erver.cls?STREAMOID=hj9DY2BY0Fym2HLFhF65qs$daE2N3K4ZzOUsqbU5sYvNfnOaBrIe ZxqNvF2cLGKtWCsjLu883Ygn4B49Lvm9bPe2QeMKQdVeZmXF$9l$4uCZ8QDXhaHEp3rvzXRJ Fdy0KqPHLoMevcTLo3h8xh70Y6N_U_CryOsw6FTOdKL_jpQ-&CONTENTTYPE=image/jpeg (hoverboard fire damage) ] After witnessing an eruption of sparks and flaming-hot battery fragments ricochet across a corner of his Petaluma home and chasing down the ensuing fires burning at multiple points of impact with a fire extinguisher, Jim Beels became an unsuspecting character last week in one the most confounding consumer product dramas in recent memory - the periodic and seemingly random combustion of the hottest holiday toy, the hoverboard. The incident was one of more than 40 hoverboard-related fires documented in the United States and the second within a week in Sonoma County alone, the latest episode in the story of a gizmo whose balance-defying functionality has largely become a footnote to concerns of overheating and explosion. A Petaluma fire official said Beels was lucky to be home at the time, unlike the earlier hoverboard fire in Santa Rosa in which a resident came home to find his two dogs dead and up to a quarter-million dollars in damage. Beels himself agreed that he was lucky, recounting the episode from the scorched epicenter of ejecta in his home near Helen Putnam Regional Park. "It was a great toy, until it started exploding," he said. Marketed under a number of brands and a wide range of prices, hoverboards are something like a handle-less version of a Segway Personal Transporter. Beels said he researched the available options before choosing what firefighting officials would later identify as the Mini Smart Self-Balancing 2 wheel Electric Scooter with Led Light for his daughter, Lauren, as a birthday gift in September. Purchased from Amazon before the company's own voluntary recall, the product quickly became a hit with the family. "Believe me, I like to ride this thing probably more than my daughter," he said. The device had been charging for around 20 minutes in her room when Beels, who was down the hall arranging ski equipment while his 15-year-old son Josh played video games nearby, heard a hissing noise he described as the simultaneous opening of several soda cans. Shortly after walking down the hall to investigate, Beels said he witnessed the shower of sparks ejecting from his daughter's open door, including one large piece of flaming shrapnel that rebounded off the opposite wall to ignite a stack of clothes below. Sensing the cause was electrical, Beels called for his son Josh to flee the house as he ran through the barrage to turn off the circuit breaker in the garage. Re-entering the hallway armed with a fire extinguisher, Beels started putting out the various small fires that were burning all around the carpet, following the flames into his daughter's bedroom as bits of burning debris went whizzing past his head. It was there that he found the hoverboard, which he doused with foam on his way to the burning bits on the opposite side of the room. Thinking the flames were done, Beels turned around to see the device reignite, now putting the self-destructing toy between him and the door. With another round of spray to the hoverboard and another chase of the burning pieces it expelled, the fire was finally extinguished. "The whole house was filled up with gross smoke," he said. Petaluma firefighters arrived shortly after, and helped Beels to clear the smoke that had filled both floors of his home. Having developed so quickly, the fire could well have intensified to the point of the earlier incident in Santa Rosa, said Petaluma Fire Department Battalion Chief Mike Medeiros. "If this gentleman wasn't home, we would have had the same incident on our hands," he said. Beels said investigators, including those from the Consumer Product Safety Commission, have described the incident as a rare opportunity to observe the initial scope of damage from a hoverboard malfunction. "At CPSC, our investigators and engineers continue to work diligently to find the root cause of the hoverboard fires that have occurred throughout the country," CPSC Chairman Elliot Kaye wrote in a statement on the nationwide investigation. Absent specific guidance from regulators, Medeiros recommended that owners exercise extreme caution while charging the devices in particular. "The biggest thing with these things is that they're unknown. We don't know if it's the expensive ones, the cheap ones, a certain brand," he said. "We're recommending that, if you have one, when you're charging it, that you are present when it's being charged." Beels said his family was done with hoverboards until they've been thoroughly vetted, and hoped his experience would encourage other owners to do the same. "I don't want anybody near anything I own, or anybody I love, with a hoverboard," he said. [(c) petaluma360.com] http://www.erietvnews.com/story/31144511/mckean-man-warns-of-hoverboards -after-one-explodes-inside-suv Hoverboard Catches Fire, Explodes Inside SUV Feb 04, 2016 Mackenzie Stasko Ted Tecza has a warning for anyone who owns a hoverboard or who is considering buying one. "I was shocked, utterly shocked that this could happen with one of those units [hoverboards] sitting there, doing nothing," he said. Tecza bought a hoverboard online as a gift for grandson, but after hearing about how dangerous they can be, he tried returning it. After he was told it was too late, Tecza decided to keep it. On Tuesday, he placed the brand-new electric scooter in the back of his SUV. But when he went to leave Wednesday morning, the normally clear windows on his 2012 Ford Explorer were tinted black and the smell of fire in the air. "The gas tank is right underneath there," Tecza said, pointing to where he placed the hoverboard the night before. "My wife said, maybe it's that hoverboard you have in the back of the car, so I went back here and sure enough it was that." When the hoverboard exploded, the SUV was parked in the garage, and Tecza's wife Judy was sleeping in the loft upstairs. "We're very fortunate the car was locked tight and therefore it burned itself out because it didn't have any oxygen," he said, aware of how much worse the situation could have ended. It's no secret hoverboards can be dangerous; there have been countless cases of them exploding across the country. Some airlines, retailers and universities have even banned them. Experts say it's the lithium batteries used to power the hoverboard that cause them to explode. Tecza's warning for others, think twice before you buy one. "I just want people to be aware of what could happen with these units," he said. [(c) 2016 Frankly Media and WICU] [dated] http://electric-vehicle-discussion-list.413529.n4.nabble.com/Only-You-Ca n-Prevent-Hoverboard-fires-tp4679021.html Only You Can Prevent Hoverboard fires Dec 04, 2015 For EVLN EV-newswire posts use: http://evdl.org/evln/ {brucedp.150m.com} -- View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/Exploding-h overboard-fires-Petaluma-CA-house-Erie-PA-SUV-tp4680278.html Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com. _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
