Learning About LiPo Batteries
Edited, updated, link checked - November 2016

Part 1 How Lithium Batteries Work Chemistry 101 Videos Batteries and How They Work Basic battery video demonstrating how ions move during discharge and charge - cute and understandable 4:51 Lithium-ion batteries: How do they work? Video describes the movement of Lithium ions during discharge and charging. This one requires a Little more thought but it is still good. 2:41 Web Sites Lithium polymer battery technology, An Introduction By Frank Siegert, Translated by John Julian This is an excellent document on how Lithium Polymer batteries work with a lot of information on why they will fail. The document is in Acrobat .pdf format and can/should be downloaded to your device for future reference. The HTML version is best for viewing online with any device with a Web browser. The Chemistry of LiPO The information is found on the RevoBlends Web site and includes:      What is LiPO and how does it work?      How are they made?      What is Blend 420?      What is Blend 427/435?      Any future Blends??      What is nanotechnology? and has the link to the Revo video on the manufacturing process noted below How Lithium ion, including Lithium Polymer Pouch (LiPo) Batteries, Are Made Videos LITHIUM BATTERIES HOW THEY MAKE THEM Good overall view of raw material to battery 7.21 Grepow factory tour Grepow cells are used in GensAce, Pulse, Tattu & Glacier brand packs. 4:17 Gens ace lipo battery production process-Powered by GensAce 2:46 Shorter version of Grepow factory tour, but does show filling of cells with electrolyte Tour of unknown factory that makes cells for Revolectrix 13.01 These LiPo batteries are known as RevoBlends. John Grazan explains how LiPo batteries are made. 6.50 He is also known as REVOJohn on RC Groups and he owns Revolectrix. He also covers what is different about HV, high voltage, cells. L&E Giant Power Dinogy LIPO Battery - start at 2:40 7:11 Dinogy Giant Power Team Orion LiPo Battery Production Insight 4:18 Turn down volume on your device before watching this video. This company is known for their hardcase car packs. Inside the Battery Pack Photo from Understanding RC LiPo Batteries at RC Helicopter Fun These videos show what is inside the battery pack by disassembling it. Disassembly of a 4S 1300mAh Hobby King Graphene LiPo Battery WARNING: The disassembly was done in a very unsafe manner. The person doing the video does not know what he's talking about. It does show the complete disassembly of one cell. While the cells are marked A123, it most likely has nothing to do with cells formerly produced by A123 Systems. 10:25 Disassembly Of A Lithium Polymer (Lipo) Battery with PCB. It is a Turnigy Zippy 6S 5800mAh pack. 4:48 LIPO Battery Balance lead repair by rcinformer.com Start the video at about 3:43 length is 9:40 LiPo Battery Circuit Connections - 11.1v 2200mAh Shows the wiring of the battery he's 'fixing'. Has G10 fiberglass 'circuit' board material used for connecting board. 1:18 G10 definition is found here. Web sites How Lithium Polymer Batteries are Made by Great Power Batteries Mostly a photo and text presentation but with videos of Battery Anode Preparation, Battery Terminal Welding, Battery Inner Cell Wrapping, Battery Massive Wrapping Machine Some packs have plates of aluminum or G10 on the top an bottom of the pack, why? Photo by rampman on RC Groups Fiberglass (G10) plate on Hobby King Graphene LiPo Battery RC Devotee, "Dinogy have an advantage the others do not, a G10 plate on the top and bottom of the pack to offer protection in a crash. This is a new feature for these packs, and something not found in other packs in this class (some use aluminum, but aluminum dents/bends and is not a good form of protection.) Nov. 2016 Update: Many of the so-called graphene cells now have G10 plates in them, including the Turnigy Graphene. MCSGUY, "I think we will see more of the hard side plates. A major brand has recently started using G10 because it provides the benefits of aluminum (protecting the cells and remaining solid) but will not bend from crash impact." Protection might not be the biggest asset of plates. REVOJohn, "Did you know squashing the packs between two tight plates (as they use carbon fibre) does help in cycle life?" Some of the Known Manufacturers of Cells and/or Packs Listing of China original equipment manufacturer (OEM) for LiPo batteries Grepow Grepow LiPo cell technical info Batteries made from Grepow cells Tattu, GensAce, Pulse and Glacier GensAce and Tattu Pulse Glacier A note about GensAce, Tattu, Pulse and Glacier batteries by RC Devotee on RC Groups "GensAce and Tattu are part of the same company (Grepow). GensAce is one of their brands and wholly owned subsidiaries. Tattu is their "factory brand". The brand they, Grepow, sell under. I've heard from a fairly reliable source that Pulse is owned by family of the Grepow owners. I imagine they buy them assembled and just rebrand them. Glacier are also the same cells, but the company is not related in any way (blood or legally) as far as I know. Some say Pulse gets the best cells, others Tattu, and others Glacier. My money is on they are the same exact lots rebranded with no consideration to who gets the pick of the lot. The testing seems to show they all perform the same. There are sure to be others that buy from Grepow and rebrand. These are just the most known brands selling those cells." SaiRi as manufacturer AKA Shenzhen SaiRi Battery Co., Ltd. Batteries made from SaiRi cells Genesis Power LiPol Battery Co., Ltd. Includes short, not very good video, but notes that they produce batteries for Apple. May or may not be a lie. Roaring Top LiPo may or may not be manufacturer's name Roaring Top Batteries Shenzhen VigorPower EnrichPower Link does not appear to be working, 10/26/16 Admiral LiPos Note the label similarity between the EnrichPower and Admiral on the EnrichPower Web site. More on this company in an RC Groups post. Revolectrix batteries are known as RevoBlends Cells produced in China, packs assembled in Singapore. A List of Brand Names and One Supplier Each for That Brand of LiPo Battery, February 2016 Many of the brands are available from other suppliers as well. The list does not contain hardcase LiPo batteries, which are mostly used in land based vehicles. A site search may be required to locate the batteries. Admiral at Motion RC AtasSphere BLITZ HV at Drone Matters Update 10/26/16: They no longer carry the Blitz. They sell Dinogy. Bonka at Multicopter Batteries Batteries are selected from the MULTICOPTER BATTERIES drop down menu. Cheetah at BP Hobbies DBY-Power at Heads Up Hobby They have to be searched by cell count under the batteries menu. Dinogy at Dinogy LiPo USA Dymond at Dymond Modelsport USA E-flite at Horizon Hobby E-flite, Kinexsis, Predator, Venom Fly and Yuneec at Force RC ElectriFly at Tower Hobbies EZ Flight Pro at Heads Up Hobby FlightPower at Tower Hobbies GensAce at Gensace & Tattu online shop Genesis Power at Banana Hobby GFORCE at Value Hobby Giant Power at Mojo Racing Glacier at Buddy RC Hobby People at hobbypeople.net Hyperion at All E RC Lectron Pro at Common Sense RC Leopard-Power - Looks like does OEM for others, has some sort of relationship to SkyRC and MAY be the producer for Sky LiPos for HobbyPartz.com. Lumenier were at Get FPV.com, but they have Tattu brand now. Hard to find sources, but some are at FliteTest.com and ProgressiveRC.com. Mad Dog at 2DogRC Magnum Energy at Motion Unlimited MaxAmps at MaxAmps.com Multistar Race Spec at HobbyKing.com NeuEnergy at NeuMotors PowerWing at HobbyExpress.com Pulse at Ultra Pulse RevoBlends at Revolectrix Singapore Store Rhino at HobbyKing.com Roaring Top at Roaring Top USA RRC at Radical RC SkyLipo at hobbypartz.com SMC at Superior Matching Concepts Spyder are no longer carried at Progressive RC. Dave has GensAce and Tattu. Tattu at Gensace & Tattu online shop Thunder Power at Thunder Power RC Turnigy Bolt (UHV) at HobbyKing.com Turnigy E-flite & Parkzone series at HobbyKing.com Turnigy Heavy Duty - HobbyKing.com - I can't find a direct link to the HD line but their search will find them Turnigy Graphene at HobbyKing.com Note: These are very new and just being released to the public on Feb. 3, 2016. Turnigy Graphene on RC Groups Turnigy Graphene Batteries on RC Groups Turnigy nano-tech A-SPEC G2 at HobbyKing.com Turnigy nano-tech at HobbyKing.com Turnigy LiPoly at HobbyKing.com VCANZ at Vcanz Power Venom at Venom Fly Xpower at Dualsky Zippy Compact at HobbyKing.com Zippy LiPoly at HobbyKing.com * * * * * Part 2 Incident Containment and Planning LiPo Sacks/Bags, Bunkers & Other Charging, Transportation and Storage Considerations What is/are your LiPo battery/batteries stored in right now? How many LiPo batteries do you have stored together in the same place? What size battery pack, or how many Watt-Hours (Wh), is your LiPo 'bag' designed or rated for? What is YOUR plan in case of a charging, transportation or storage incident? How does the way YOU handle a LiPo battery influence the chance of an incident? - - - - - A few brands of LiPo 'bags' note the pack size (cell count and capacity) or the Watt-hours (Wh), which is the energy capacity, that their brand of LiPo 'bag' is designed to contain in case of an 'incident'. Besides storing a LiPo battery, a 'bag' will most likely be used for containing a LiPo battery while charging, therefore, I use 4.2V per cell when calculating Watt-hours (Wh). It appears that suppliers use 3.7V for shipping purposes and as 'storage' voltage. Example: 4S 2200mAh (C-rate doesn't matter) I found a fancy equation using joules and coulombs to derive Watt-hours (Wh) but... This yields the same results: 4.2 (cell voltage) * 4 (number of cells) * 2.2 (capacity in amp hours) = 36.96Wh A Look At Some 'Bags' that give specifications Mark Woods' LipoSack (brandname) LipoSack small, size: 9" x 12" designed to contain a 3S 2200mAh incident, converted to maximum Wh - 27.72, Price: $24.95 Same bag available as a 2 pocket storage bag, has the same specifications and price. Same bag available as a 6 pocket micro battery storage bag, has the same specifications, price: 29.95. LipoSack large, size: 13" x 18" designed to contain a 6S 5000mAh incident, converted to maximum Wh - 126, $39.95 Same bag available as a 4 pocket storage bag, has the same specifications and price. LipoSack FREE REPLACEMENT GUARANTEE Avoid damage to the LipoSack. Replace if it becomes ripped, worn or is involved in a battery ignition. If your LipoSack is involved in an ignition resulting in a venting of the battery and fire send us an email at sales@liposack.com with a statement of the circumstances and receive a replacement LipoSack free of charge! LipoSack Survivors Stories and photos of folks saved by using a LipoSack brand LiPo 'bag'. Traxxas Charging Bag LiPo, size: 9" x 11.5" "Only for use with LiPo batteries rated up to 30 watt hours*", $21.83 Great Planes ElectriFly SafeCharge LiPo Charge Bag, size: 9" x 12.5" rated to 3S 3200mAh, converted to maximum Wh - 40.25, $21.99 "Perfect for 1-3 cell LiPo packs with capacities as high as 3200mAh" Somewhat ambiguous, so maybe not a 3S 3200mAh pack. And now the waters get murky!!! Hyperion LiPo Bag - small 7" x 11" photo shows less than (<) 100Wh on bag, price: $4.95 Hyperion LiPo Bag - large 9" x 13.75" photo shows less than (<) 100Wh, price: $6.95 Note: Hyperion appears to use the same photo for both sizes of bags. Prices shown for Hyperion bags are at allerc.com The problem: The international symbols on the bag, including less than (<) 100Wh, are provided for air travel with LiPo batteries. The symbols are required. The less than 100Wh is NOT a rating! Demonstrated later when a similar 'bag' is forced to have an 'incident' with a less than 40 Wh battery in it. The less than (<) 100Wh is noted in the August 2015 Model Aviation, p. 49; "Passengers may carry all consumer-sized lithium ion batteries (no more than 8 grams of equivalent content or 100 watt-hours [Wh] per battery). This covers AA, AAA, cellphone, PDA, camera, camcorder, handheld game, tablet, standard laptop computer batteries, and model batteries." Team Blacksheep, size: 9" x 11.8" less than (<) 100Wh, price: $7.95 Again, the less than (<) 100Wh shown on the bag is NOT a rating. Really, really bad video on the Team Blacksheep site showing too many and too large of batteries in one bag. And it gets even worse! Pulse Safety Bags Have VERY, VERY BAD info! Pulse Ultra Lipo Safety Bag, size 9.8" x 11.8", price: $11.99 "This LiPo bag can be used for up to four 5000mah 6S battery (not stick/long configurations)." 4 6S 5000mAh = 504Wh Pulse Ultra Lipo Safety Case for Stick Packs, size: 15"x3"x11.8", 4 Slots, price: $24.99 "It will carry the largest packs up to 14S with battery tray attached." Doesn't say what capacity. Pulse Ultra Lipo Safety Case, 9.45"x2.55"x7", 4 Slots, price: $24.99 "It will fit up to the largest 6 and 7 cell 5000 to 6000Mah lipos... 4x 6S-5000mah lipos easily fit." 4 6S 5000mAh = 504Wh Could it get worse? Common Sense Lipo Safe Charging/Storage Bag, 9" x 12", price: $14.99 "Our original Lipo Safe (9" x 12") is the right size to fit everything from small 3.7V Lipo batteries up to even large 29.6V (8S) Lipos." Capacity unknown - None of their other bags note Wh or number of cells and capacity Their video 'evidence' is only a 2S 1500mAh pack, 12.6Wh Videos - LiPo bag tests Cheap Safety bag Brand name is LIPO-SAFE, pack used is a 4S 2350mAh for 39.5Wh 2:39 The name LIPO-SAFE appears on many 'cheap' bags. They may or may not all come from the same place. This video demonstrates what happens when a LiPo battery ignites in a bag that is too small and of poor quality. Poor bag tested against a good one STANDARD LIPO GUARD vs. YUKI MODEL LIPO GUARD B1 1:52 This video also shows what happens when you "Overload" even a good bag. Yuki 'bag' appears to be similar material to the real LiPoSack of Mark Woods. A Blow Torch Test STANDARD LIPO GUARD vs. YUKI MODEL LIPO GUARD B1 1:00 The results are not surprising since they burned the 'plastic coating' off the cheap bag, but still interesting. I would like to have seen the LiPO GUARD open and them trying to burn it from the inside out. It is very apparent that any 'plastic' coating, or covering, on the outside of a bag actually exacerbates the situation. Real LipoSack Test By Lee of the Utah Flyers, includes 3S 2100 - 26.5Wh 3:09 There is no sound with this video. Other Ways to Store and Transport LiPo Batteries "Fire Safes" and ammo cans have been used. Safe Home Storage, LiPo Bunkers A simple, effective bunker from the UtahFlyers.org As with all 'containment' choices, smoke is still a problem. Also includes ammo can test with several 'other' batteries in the can. 5:59 FliteTest LiPo Bunker A lot of information and misinformation, but basically okay. 9:19 Another POSSIBLE, if it is not 'vaporware', 'Safe Charging' Option, the Bat-Safe - Battery Charging Box, February 15, 2016. It was fully funded on Kick Starter on March 07, 2016. Bat-Safe Video outside Shows the Bat-Safe used outside with a 4S 4000mAh (>67Wh) ignited in it 1:35 Bat-Safe Video Shows the Bat-Safe wrapped in tissue paper and placed in cardboard box with a 4S 3000mAh (>50.5Wh) ignited by over-voltage in the 'inventor's' garage 1:28 Deliveries were to start in July 2016. There have been no deliveries as of 10/26/16. Another Means of Creating a LiPo Battery Fire For 'Bag' and Bunker Testing There is a problem with the Battery 'bag' and bunker testing videos. It appears, that for all of the bag and bunker tests, the LiPo battery was intentionally overcharged to get it to ignite. The increasing voltage in each cell was the cause of the ignition. When the cell voltages rose, the watt hours (Wh) and energy went up as well. Wh = volts times capacity in amp hours The Buddy RC LiPo Bag Test gives an indication of how much the watt hours of energy were increased to before the incident took place. "A fully charged 2200mAh two cell LiPo pack was used in the test. The battery was over charged to almost 9.8V, and more than 1600mAh additional capacity was input to the pack." Fully charged 2S 2200mAh = 18.5Wh and 9.8V * (2.2Ah + 1.6Ah = 3.8Ah) = 37.2Wh The Wh of energy were doubled. Forcing an over-charge demonstrates what might happen if the charger is 'set' incorrectly, or if the charger malfunctions (i.e. during charging), but the Buddy RC example illustrates the major 'flaw' in testing LiPo 'bags' ONLY by forcing an over-charge. Forcing the over-charge increases the energy available to the incident. Dead shorting the battery does not. Dead shorting yields results based only on the stored energy (i.e. in storage). Many videos, demonstrating shorted LiPo batteries, show no visible flames. In some of the videos of 'dead shorts', sometimes the wires burned/melted, or tabs burned off first, or there was just no ignition. LiPo Battery Short FAIL goes up in Smoke but Burns wires off Somewhat typical for no incident 1:19 Lipo dead short test A real 'non-event' 1:32 old LiPo 3S 900mah short circuit no fire 1:06 Sometimes it takes some 'intervention' before a fire will start. Shorting Out a 3s Lipo Battery = Fire...eventually 3S 2200mAh - Shows problems getting it to ignite when shorted 6:02 Sometimes shorted LiPo batteries will just ignite. lipo short circuit and fiery explosion. 4S 3300mAh @ 4.0V per cell explosion with flames 1:42 LiPo short circuit 6 cell, 5000mAh good size fire 4:24 Demonstration of shorted LiPo in a Lipo Guard bag. LiPo Burn Test by Kansas City Northern Nights RC Airplane Club 7:26 It sounds like someone says 6S 22 volts, for the battery. They had a very hard time getting the LiPo battery to ignite. Start video viewing at 4:00. At 6:00 into the video, the bag can be seen burning. No flames are seen during the test, but burned spots can be seen on the ground and the bag is clearly damaged at the end of the video. Much of the bag's plastic outside has melted and burned off. Pack Handling The way the pack is handled can have a direct impact, pun intended, on the chances of an incident. LiPo pouch cell packs are not physically protected very well. Avoiding physical damage during storage, transport and use is important. A battery can be 'accidentally' set up to fail by pulling on the power lead or balance lead wires. Battery suppliers warn about this in the literature they provide with the battery, online or even on the battery leads themselves. John Julian (jj604 on RC Groups) reported the following: I had a never flown 6 month old Zippy Compact on the bench yesterday and noticed an ominous sizzle sound from within the pack when I loaded it up. Sure enough the positive tab had detached internally. John expected faulty assembly of the pack, since it had not been used. John Julian photos Rick (rampman on RC Groups) has disassembled and repaired over 1000 packs. Here are some highlights of what he has noted about pack construction. Talking about pack failures, "many of these were with a tab failure. NONE is safe from failure as I have seen it all." Regarding a pack he fixed, "I removed cell #1 from a 4S and made it a 3S. Reason? The "+" tab broke off at the cell. In this case it was NOT a short but being there was corrosion all over this area and this area only, it was most likely a leaking seal around that tab which weakened the metal tab via corrosion and it eventually snapped off under stress OR just in storage." "I have seen PCB failures (early large Turnigy packs), bad tab to tab soldering, failed spot welds, failed crimp connections (tab to tab on alum tabs (TP) where they somehow crimp the tabs together, I feel this is a very good process) cold solder connections, broken tabs for no seen reason..." GensAce Failure Neu Failure Zippy Compact 3700mAh Positive Wire Detached Frank Siegert, in "Lithium Polymer Battery Technology: An Introduction" demonstrates what another likely cause of 'tab failures' is, besides poor quality control and craftsmanship. It has to do with the where the heat development happens. If the pouch tabs get hot enough, anything soldered can melt. Handle all packs with great care. Other Cell and Pack Construction Considerations Added 10/26/2016 MSGUY on Dinogy and Thunder Power Pack Construction Damage inflicted at 40C with Dinogy on left, Revo 60 Diamonds in center and Revo 70C Silvers on the right MSGIUY: "I believe Dinogy does not show head damage because of a circuit board at the head used to collect and bond cells tabs and leads. I don't say this to be partisan, but to influence the industry. I have sent this photo to Revolectrix as a suggestion. A circuit board added to the battery head to collect and bond the cell tabs to the power leads appears to help the pack run cooler." (Subjective KM) Thunder Power and Dinogy pack construction compared There are five photos on this page that compare the TP 2S 65C 6000mAh and Dinogy 4S 5000mAh pack construction. MSGUY: "Both power heads bare, the TP utilizing spot welded tab to tab with soldered leads, Dinogy with intermediate festooning circuit board and significantly wider cell power tabs." The wider cell tabs, noted by MSGUY, are possible because the cell is designed so that the anode material protrudes from one end of the cell and the cathode material from the other. Wider tabs 'should' be able to handle larger currents. A problem arises when making odd cell packs with this type of cell construction. A wire must run from one end of the pack to the other, as in the photo below. Four 5S Dinogy packs are shown in a racing boat. The photo was originally at http://losi5iveforum.com/mobiquo/minisite/site/MainTopic.php?cmd=getThread&tid=4271, but the link is no longer viable. In this case they chose the positive. End of added section 10/26/2016 WARNING The following is purely anecdotal information from Ken Myers! For many years I have carried an old 1/2 credit card, cut lengthwise, in my flight box. This tool has been used to slide between the hook-and-loop fastener between the battery tray and battery to loosen a LiPo battery for removal without pulling on any wires. I had read about this method years ago. It works well, IF the tool will fit in the battery compartment. I recently acquired a plane that, because of space limitations in the battery compartment, does not allow the 1/2 credit card method to be used. Keeping in mind that any pressure on the outside of pack is 'bad' for it, I used a method to get the packs out without pulling on the wires, but unfortunately, it still puts pressure on the pack. Actually just using Velcro to secure a pack in a plane puts pressure on it when it is secured and 'pull' on it when the pack is removed. Two pieces of strapping tape, the kind with the filament threads in it, are cut to length to allow for a bit of a wrap around on the top and bottom of the pack with an inch or so 'overhang' at the wire exit end. The 'overhang' is pinched together to form a pull 'tab'. The hook-and-loop battery fastener is added to the battery AFTER the tape 'tab' is completed. Whether, in the long run, this pull method is going to damage the pack is totally unknown. I am not recommending it anyone, but I'm just sharing what I am using right now, when I can't use the 1/2 credit card method. Update: 02/08/2016: Richard Utkan, EFO vice-president, visited today with some questionable batteries for me to look at and test. I noted that he uses the same type of pull tab on his packs. He had a problem, long ago, that involved pulling the wires out of a pack. This was his solution as well. The Importance of Having a Plan gocards, on RC Groups, did just about everything right when using and storing LiPo batteries. Unfortunately, he did not have a plan when the incident did happen while USING IT on his granite top bar in the kitchen. Narrative edited for pertinent information here, link has complete text. I've been working with lipo in RC for a few years now. I am generally careful. I don't leave them charging unattended. I store them in lipo safe bags. I charge them in lipo safe bags. When charge is over I remove the lipo and bag it, etc. Never occurred to me to have it in a bag on the counter when using the battery. I have a brand new Lipo, 2200 mah, 4s. Flown it in a 250 quad maybe 2, 3 times max...turn on Tx, plug in quad, plug into PC...looking through settings, then "SSSSHHHHHSSSSHHHSSSSHHHH" sound and SMOKE like a smoke bomb! Oh and it STINKS! I was sitting at the bar in my kitchen, lipo was on granite top, entire family is asleep... Its smoking like a train! Front door is close, its cold and wet outside, gotta get this thing outside ASAP before it catches something on FIRE! I reacted...grabbed it (stupidly) and chucked it out the front door into the wet lawn where it smokes and flames up and its TOAST. ...nothing was damaged (aside from the battery). Just trying to get a game plan in my head in case this happens again. I am thinking to keep small fire extinguisher out and close by...also thinking of keeping some hot mits, like Ov-Glove or something close by in case I need to grab the thing. Moral of the story...it can happen to you. Be ready in case it does! Boldface type was used to identify the relevant statements. A thread on RC Groups asked, "Best environment to charge batteries?" Mark Wood's answer was great, "Outside." Plan ahead to be PROACTIVE instead of REACTIVE. Questions How many LiPo batteries should YOU store together? What happens to the outside of a LiPo 'bag' that is covered with a "plastic-like" cover or coating when there is an incident? What battery capacity is YOUR LiPo bag rated for? What is your home, personal property, vehicle and life worth to YOU? What is YOUR plan, in case of an incident, in YOUR home; YOUR Vehicle; or at the field? Are you actually going to use this information or not? Reported LiPo Fires and their probable causes LiPo Fires: an every expanding list by hoppy on RC Groups LiPo Fires Are Real Video shows the loss of a stand alone workshop with 4 decades of modeling inside. A precautionary tale. 22:55 * * * * * Part 3 A Bit of LiPo History and Where Many of the Use and Care Recommendations Came From Actual FACTS regarding almost all aspects of Lithium Polymer Pouch Batteries (LiPo Batteries) are difficult to come by. Where did all of this information come from? What is its genesis? One of the earliest documents, and possibly THE High Discharge Rate (HDR) LiPo Battery Genesis Document, is: The Kokam USA Lithium Polymer Battery System by Fred Marks Nov. 2003 Historical Note: Thunder Power was started in 2003. They did not use HDR type cells. Their cells were rated at 3C and 4C with 5C bursts. p. 40, Kokam info. A synopsis of some of the 'History' of LiPo batteries, as presented in the document About 1980, Lithium Ion (Li Ion) cells began to be used for light duty, lightweight applications. Li Ion cells began to be modified for RC from retired cell phones and surplus sources only about two years ago. (That would be 2001 KM) Lithium Polymer (LiPo) cells began to see use in 2001 in a small way. The "small way" was primarily in the form of the Kokam Engineering Co., Ltd. 145 mAh cell. Mr. J. J. Hong, President of Kokam, provided the following brief history of the development of LiPo technology: Early in 1980, Motorola and Sony decided to apply lithium ion technology to the mobile phone... They developed a safety module, the so - called PCM (protection circuit module). Meanwhile, the Bellcore Lab in San Diego announced that they had developed the lithium polymer battery to increase energy density and safety by using a plastic pouch packaging/stacking method using an ion conductive separator named PVDF (polyvinyldifluoride) which has good binding characteristics at 1000 C. Sony, Toshiba, Panasonic, Samsung, Saft, Varta, Valence, Ultra-life, Polystar and perhaps 30 companies bought licenses to commercialize the Bellcore technology. No one was successful using that technology. Everybody gave up or went bankrupt. Kokam evaluated the Bellcore technology as an alternative, but realized that it is not a practical technology for commercialization due to the processing difficulty. Kokam decided to develop new technology with assistance from the Korean government agency named KIST (Korea Institute of Science and Technology). J. J. Hong invented a new system which permitted Kokam to make the battery easier without losing any performance over Li Ion and provided better safety. Kokam acquired patents all over the world and started to design the full process and equipment suitable for mass producing Kokam cells. German and Chinese companies licensed Kokam technologies. Kokam technology created the first 20C discharge rate commercial LiPo battery. All electric solar car champions used Kokam batteries in 2002 and 2003 competitions. Fred Marks continues: June 2002, FMA, Inc. and Kokam Engineering Co., Ltd. signed an agreement for FMA to serve as the exclusive agent for Kokam in North and South America. In October 2002, FMA, Inc. began actively shipping Kokam Lithium Polymer (LiPo) cells. As of this writing (fall, 2003) some 100,000 cells are being used in RC models. LiPo technology advanced farther than NiCd technology advanced in nearly forty years. In 2002, the standard Kokam cell was capable of continuous operation at three to four times the multiple of capacity (3 to 4C) with 5C as the upper limit. In the past six months, Kokam introduced, and FMA markets, cells capable of sustaining up to 20C continuously with loss of but 12% capacity. (This is 2003. The 20C rating was NOT all of their HDR line, but only one cell. A bit misleading. KM) A general precaution p. 4 of document The use of LiPo cells in radio control applications is unique. All other applications require protective circuitry that prevents a) overvoltage during charging, b) discharge below 2.5V/cell and c) cell overloading. RC models can't tolerate complete loss of battery power (because the receiver and servos must be powered at all times during a flight), so protective circuitry is not an option. For this reason, the RC user bears special responsibility for the proper use of LiPo cells in radio control applications. This Application Note provides guidance for safe use of this new technology. IMPORTANT NOTE: While the precaution states that there is no use of a protection circuit module on RC LiPo cells, the document notes, p. 30, that Kokam developed a protective circuit, known as Safety Guard, for charging up to 4S packs and discharging up to 20 amps. FMA Introduced a Complete System to help modelers transition from high discharge NiCad and high discharge NiMH batteries. The document explains how each of the components of the system work together. Other significant mentions in the document "Kokam USA uses Deans Ultra connectors for larger packs." p. 18. "The preferred charge rate is 1C such that the cell can be charged to 90% capacity in one hour if the charger is designed to hold charge current at 1C without exceeding 4.235V/cell maximum charge voltage." p. 27. "Never exceed a maximum charge voltage of 4.235 VDC." p. 28. "Cell voltage at full charge is 4.235V." p. 29. Kokam HDR cells are compared to E TEC and Thunder Power non-HDR cells, p. 37 - 42. Why using a factor times the capacity is NOT a good way to 'rate' a LiPo battery, p. 38, "The rate can be presented as absolute rate in amps or as the rate as a multiple of the rated capacity. Note that the international standard for rating cells cautions against using XC to reflect discharge current since C = mAh, not mA. However, it is a convenient way to compare, even if not pure." No packs of the day had balance connectors, but the importance of balancing cells is mentioned and described on p. 43. Peak Burst Current Defined, p. 49, "*Peak burst current is a cycle consisting of less than 12 seconds of peak current followed by 50 seconds at 50-60% of peak current." A few of planes being flown with Kokam cells in 2003. Much other documentation, found elsewhere through the years, is based primarily on this pioneer work. Continuing from the document Safety p. 25 Potential cell damage causes include: Overvoltage during charge. Use of chargers not designed for LiPo chemistry. Sudden peak surge voltage from the charger when disconnecting. High current rapid charging by users who assumed LiPo can be charged at high current like some NiCd cells can. Incorrect selection of charge voltage. Excessive discharge rate. Use of aluminum soldering paste that deteriorates the tabs and causes a short circuit. Unreliable chargers. In some chargers with FET switching, the FET shorts when it fails and full supply voltage is applied to the cell. This can be avoided if appropriate crowbar protection1 or foldback2 is designed into the charger. Cell failure that creates an instant unbalance in the pack. Fundamental risk of lithium ignition when lithium is exposed to air entering through a damaged cell envelope. Faulty pack assembly. Physical damage and abuse. The author, (Fred Marks KM) for example, accidentally ran a T-pin through a fully charged cell, shorting all plates. That shortened the pin much faster than a pair of diagonal pliers! 1 An overvoltage protection circuit which rapidly places a low resistance shunt across the power supply output terminals if a predetermined voltage is exceeded. 2 A power supply output protection circuit whereby the output current decreases with increasing overload, reaching a minimum at short circuit. This minimizes internal power dissipation under overload conditions. Again Note, this is a, if not THE, genesis document. Some of the information has been borrowed and modified over time and some of the information has been 'dropped' altogether, by FMA Direct and others supplying LiPo batteries. WARNING Safety Precautions for Lithium Polymer and NiCad cells/packs stocked by FMA Direct p. 26 1. Never fast-charge any battery type unattended. 2. Never charge LiPo cells/packs at any rate unattended. 3. Only charge LiPo cells/packs with a charger designed specifically for lithium polymer chemistry.      Example chargers include the Kokam USA, LIPO402, LIPO102 and LIPO 202; Bishop Power Products Apache S1215 and S1500; Great Planes Triton; and Schulze chargers with lithium charging capability. 4. LiPo cells can ignite because of unmatched cell capacity or voltage, cell damage, charger failure, incorrect charger settings and other factors. 5. Always use the correct charging voltage. LiPo cells/packs may ignite if connected to a charger supplying more than 6 volts per cell. 6. Always assure the charger is working properly. 7. Always charge LiPo cells/packs where no harm can result, no matter what happens. 8. Never charge a cell/pack in a model. A hot pack may ignite wood,foam or plastic. 9. Never charge a cell/pack inside a motor vehicle, or in a vehicle's engine compartment. 10. Never charge a cell/pack on a wooden workbench, or on any flammable material. 11. If a cell/pack is involved in a crash:      a. Remove the cell/pack from the model.      b. Carefully inspect the cell/pack for shorts in the wiring or connections. If in doubt, cut all wires from the cell/pack.      c. Disassemble the pack.      d. Inspect cells for dents, cracks and splits. Dispose of damaged cells (see below). 12. Dispose of cells/packs as follows:      a. Discharge: with the cell/pack in a safe area, connect a moderate resistance across the terminals until the cell/pack is discharged. CAUTION: cell/pack may be hot!      b. Discard: NiMH: place in regular trash. NiCd: recycle (cadmium is toxic). LiPo: puncture plastic envelope, immerse in saltwater for several hours, place in regular trash. 13. Handle all cells/packs with care, as they can deliver high currents if shorted. Shorting by a ring, for example, will remove a finger. 14. Always store cells/packs in a secure location where they cannot be shorted or handled by children. 15. When constructing a pack, use only cells of the same capacity (mAh). LiPo disposal mentioned in this document, p.29 "...If a cell is found to be swelling during charge, remove the charge current immediately. Then allow the cell to cool before taking any other action. You can imagine that rupture of the cell could allow hot gasses and electrolyte to spew out. Once the cell has cooled handle it as a fully charged cell with full energy available. This means you do not "poke a hole in it" in preparation for disposal. First, discharge the cell at a reasonable rate. This can be done by using clip leads to attach it to an electric motor, a resistor or some other electrical load. Do not hurry this-a slow, complete discharge to zero volts while still under load is a safe way to do the job. Once the cell is depleted, poke a small hole in the envelope, then immerse the cell in salt water for a few hours. After that, the cell may be disposed of in the trash." LiPo Battery Disposal LiPo Battery disposal instructions/directions illustrate the problem of obtaining factual information. The genesis information can be seen in many of the following examples. Questions Have YOU disposed of any LiPo batteries? If so, what procedure did you use? Were any disposal instructions provided with your LiPo battery? Did you follow them? Have YOU ever read the disposal directions supplied with your LiPo batteries, if there were any instructions? Does YOUR LiPo supplier have disposal instructions on their Web site? Have YOU ever looked up LiPo disposal on the Internet? What did YOU find? Have YOU ever seen conflicting LiPo disposal directions? HobbyKing instruction sheet/manual Dispose of Batteries in the manner required by your city, county, state or country. GensAce/Tattu - pack insert instruction sheet/manual This product must not be disposed of with other waste. It is the user's responsibility to dispose of their waste equipment by handing it over to a designated collection point for the recycling of waste electrical and electronic equipment. Great Planes - pack insert instruction sheet/manual Lithium-polymer batteries are environmentally friendly. For safety reason LiPo cells should be fully discharged before disposal (however, if physically damaged it is not recommended to discharge LiPo cells before disposal - see below for details). The batteries must also be cool before proceeding with disposal instructions. To dispose of LiPo cells and packs: 1. Place the LiPo battery in a fireproof container or bucket of sand. 2. If any LiPo cell in the pack has been physically damaged, resulting in a swollen cell or a split or tear in the cell's foil covering do NOT discharge the battery. Jump to step 5. 3. Connect the battery to a LiPo discharger. Set the discharge cutoff voltage to the lowest possible value, and the current as low as 20mA if possible. It's also possible to discharge the battery by connecting it to an ESC/motor system and allowing the motor to run indefinitely until no power remains to further cause the system to function. 4. Discharge the battery until its voltage reaches 1.0V per cell or lower. 5. Disconnect the battery and submerse it into a bucket or tub of salt water. This container should have a lid, but it does not need to be air-tight. Prepare a bucket or tub containing 3 to 5 gallons of cold water and mix in 1/2 cup of salt per gallon of water. Drop the battery into the salt water. Allow the battery to remain in the tub of salt water for at least 2 weeks. 6. Remove the LiPo battery from the salt water and place in the normal trash. Model Aviation magazine 2015 Greg Gimlick, "LiPo Battery Basics: Understanding the technology and its safe use", August 2015, p. 32 "Disposal When your batteries get to the point that they need to be disposed of, one of the simplest options is using a no-cost used rechargeable battery and cell phone collection program offered within a network of more than 34,000 collection sites throughout the United States. Call2Recycle accepts NiMH, Lithium Ion (Li-Ion), LiPo, and NiCad batteries weighing up to 11 pounds. Simply visit the program's website, www.call2recycle.org, and enter a ZIP code to find a collection center near you. If you don't have Internet access, call (877) 273-2925. Drop-off centers are located at corporate offices, healthcare facilities, manufacturers, military bases, and at major retailers such as The Home Depot, Lowe's, Staples and Best Buy." Jay Smith and Rachelle Haughn, "LiPo Battery Basics: Storing and disposing of your batteries", October 2015, p. 61 - p. 62 This article notes exactly the same information as provided by Greg. Neither article noted discharging before recycling. Roaring Top LiPos The waste batteries are better to be handled by professional recycling factories. If not, please dispose them into salty water, so that the cells can be oxidized slowly. Common Sense RC Lithium Polymer disposal instructions. 1)Discharge the battery to 0 volts. 2)Puncture each cell and immerse in saltwater for 24 hours. 3)Wrap the battery in a bag and place in an appropriate disposal canister. 4)The pack can now be thrown in the garbage - there are no special disposal requirements for Lipo batteries. Thunder Power Batteries that lose 20% of their capacity must be removed from service and disposed of properly. Discharge the battery to 3V/Cell. Ensure wire leads are insulated, and soak battery in a mixture of 60 parts water to 1 part salt, by weight, for 2-3 days. Then wrap battery in a bag for disposal. Horizon Hobby Battery Life Batteries that lose 20% of their capacity must be removed from service and disposed of properly. Discharge the battery to 3V/Cell, making sure output wires are insulated, then wrap battery in a bag for disposal. Revolectrix As you can see, lithium cells/packs can be very dangerous. Just throwing them in the rubbish is not safe enough. 1. ask your local battery retailer if they will take your old batteries and recycle them 2. lower the voltage of the pack by loading it all the way down below 1.5V, then soak the packs in salt water for 2 - 3 days 3. Many metal recycling firms will be willing to take them too MaxAmps.com Although environmentally friendly, lithium polymer cells must be FULLY discharged before disposal. Use a resistor setup (light bulbs, for example) to accomplish this, to avoid the possibility of a short-induced fire after disposal. Immediately discharge damaged batteries at 1/2 C rate and dispose. Note: That is all it says about disposal FMA LiPo Handbook Section 3 Do not "poke a hole in it" in preparation for disposal. First, discharge the cell at a reasonable rate. This can be done by using clip leads to attach it to an electric motor, a resistor or some other electrical load. Do not hurry this - a slow, complete discharge to zero volts while still under load is a safe way to do the job. Once the cell is depleted, carefully slice a small slit in the envelope, then immerse the cell in salt water for a few hours. After that, the cell may be disposed of in the trash. FliteTest Web site Disposing of LiPo's safely When your LiPo reaches the end of its life (and they don't live forever), it is important to give it a proper send-off. The best way is to drop them into a bucket of salty water for a couple of days. This totally kills the chemistry in the cells rendering them safe for disposal. In fact, a totally dead LiPo is safe to go in the general household waste (but please do check with local laws before you do this). If you want to take it one step further then this is a great guide on how to render a LiPo totally inert. Thanks to Kona R/C flyers for putting the effort into producing this. See more at: http://flitetest.com/articles/lipo-safety#sthash.K9iZiqCl.dpuf Konarc Flyers Web site: The Definitive Guide to Proper Disposal of Lithium-Polymer (LiPo) Batteries has been taken off the Internet. It described the 'saltwater bath technique'. Discharging LiPo Packs for Disposal How to Discharge and Dispose of LiPo Batteries T JinTech How-To: Safe lipo preparation for disposal and This link is full of pretty good ideas and warnings. It also links to how he builds dischargers. Inexpensive Lipo Discharger That Works! 3-in-1 Battery Balancer, Voltage Indicator and Discharger Really best used for lowering battery with up to 6S to storage voltage. For more informational reading: The Genesis Document Information Update of 2005 The follow-up to the FMA Direct 'genesis' document In July 2005, 19 months later, FMA, Inc. published The Handbook of FMA, Inc. Lithium Polymer Battery Systems Section 1 - FMA LiPo Systems, The Handbook of FMA, Inc. Lithium Polymer Battery Systems Section 2 - Evaluating and Selecting Cells, and The Handbook of FMA, Inc. Lithium Polymer Battery Systems Section 3 - Safety, Charging, & Discharging. The author is noted as FMA Staff. The various Sections are in Adobe Acrobat .pdf format. FMA LiPo Handbook Section 1 Introduction      A brief history FMA Li Po Systems Building Li Po packs      The basic cell Wiring an individual cell      How cells are connected        Series connected cells        Parallel connected cells        Series/parallel connected packs How modular packs are manufactured The Li Po modular pack connection system Building a modular Kokam Li Po "Super Pack" Unitized packs Stick Packs The FMA SKYVOLT System SKYVOLT Application Examples Balance Pro and Scorpion for the Two Cell Packs BalancePro Application Examples Cell Pro Balancing System (Coming mid-2005) What Li Po packs can do What goes in to design of FMA cells and packs Significant mentions Skyvolt System: a dead end system that used only balance leads on the battery and was charged and discharged through a PCM type device. Balance Pro cells introduced with both power leads and balance leads. The CellPro 4S balance charger was introduced. FMA LiPo Handbook Section 2 Evaluating and Selecting Cells      What defines cell performance      How to determine the propulsion your airplane needs      A look at performance parameters in greater depth      It all begins with the discharge curve      The first real indicator: voltage depression      Lower temp and HDR capability = long service life      Capacity depression mirrors voltage depression      A design example illustrates the effectiveness of the method      Energy density (specific energy) normalizes the weight of cells      Understanding the Ragone Chart      The payoff for High Discharge Rate (HDR) capability Related components      Speed controls        FMA SUPER Speed Controllers      Radio flight packs        FMA SPORT VRLI Significant mentions Kokam cells are compared to Thunder Power, Tanic, E TEC, and PolyQuest. A means of assigning a Figure of Merit (FOM) is described for evaluating different cells. FMA LiPo Handbook Section 3 Safety Charging      Chargers      Charging through a protective circuit        Safety Guard specifications      FMA Cell balance charging very simply measures the voltage of each individual cell in the pack as it charges and applies a sophisticated charge control algorithm that:      Charging in series or in parallel Discharging      Li PoCalc How to use Li Po batteries effectively      Gas Gauging using the discharge curve data      "So, what do I need for my bird, since it isn't a Tu-4?"        Li Po power suggestions for various electric aircraft types and sizes Significant mentions Lithium metal oxide is the base material (cathode) and Carbon is the anode in Kokam cells p. 5 Both are deposited on high quality copper. and "Yes, your Li Po cell has good value when dead because there is a nice strip of copper in each plate!" - p. 5 At first the statement of both the anode and cathode being made of copper seemed strange, until I found the following in a post by REVOJohn (John Grzan), "We just started playing with a new purely Cu (copper) collector (rather that Al) that does not need a 2nd tab welded to it in order to join into packs." It should be noted that John Grzan worked for/with J.J. Hong at Kokam. Use of aluminum soldering paste that deteriorates the tabs and causes a short circuit. p. 3 Charging in series and parallel are described. p. 12 Photo of ammo can in text p. 13 "By international standard, all cells are rated for capacity at 0.2C, where C = nominal capacity of the cell when discharged at a rate equal to 0.2 times the predicted capacity for the cell. The rated cell capacity is actually statistically established since the actual is not known until tested." p. 18 "That is about 80% of capacity and time to stop flying if you wish to maximize cycle life...", p. 19. * * * * * Part 4 LiPo Battery Facts or Fancy? Understanding whether LiPo Battery facts are truly facts, recommendations or opinions is extremely difficult. The previous sections laid the foundation for understanding LiPo batteries and presented many facts, and demonstrated how opinions varied on LiPo battery disposal. The source, and YOUR trust in the source's information, as well as YOUR trust in the source's author determine for YOU whether some statements regarding LiPo batteries are true facts or just opinions, and there are a lot of opinions out there! FAQs and Facts About LiPo Batteries An Example: LiPo Operational Temperature Ranges It is important to remember that the following temperatures are the operational temperatures of the cells/packs and NOT the ambient temperature. In 2003 The Kokam USA Lithium Polymer Battery System document had only one note about temperature. "Both cells (KOK 1500 and 2Ah) have continuous capability without excessive heating (about 500C) up to 8C." 500C is 1220F But by 2005 the FMA LiPo Handbook Section 3 - Safety Charging 00C to 450C (320F to 1130F) Discharging 200C to 600C (680F to 1400F) "running cells so hard that the combination of discharge and ambient temp puts them over 85 degrees C will ruin them for sure." 850C = 1850F RevoBlends "1. in cold weather lithiumION migration within the cells is more difficult 2. at higher temperatures (30 - 40degC) (860F to 1040F) lithium cells have the best energy and power performance" Roaring Top Charging: 00C to 450C (320F to 1130F) Discharge - recommended: 200C to 400C (680F to 1040F). but also Discharging: 200C to 600C (680F to 1400F) "For maximum performance of our high-power series batteries, discharge temperature between 200C (680F) and 400C (1040F) is recommended." They have several conflicting statements on this FAQ page and a typo showing minus (-) 200C for discharging. LiPol Battery .COM Charge: 32 to 113 degrees F (00C to 450C) Discharge: 32 to 140 degrees F (00C to 600C) ThunderPower Charge: 50 to 100 degrees F (100C to 37.80C) Discharge: 50 to 130 degrees F (100C to 54.40C) Hobby King manual/instruction sheet packed with packing slip in box Never expose Batteries to extreme temperature, or direct sunlight. The temperature range must be between 40-1200F (40C to 490C). Never charge batteries that are hot to the touch (above 1000F or 380C) All of the statements regarding the operating temperature range of LiPo batteries are stated as facts by the various sources. Close inspection shows the 'recommendations' fall within the the same temperature range. Sometimes, as in the case of LiPo battery disposal, this is NOT the case. The procedure I use to determine the validity of a fact or 'recommendation'? How does fact or 'recommendation' compare to information in Frank Siegert's previously recommended "Lithium Polymer Battery Technology: An Introduction". __________ Temperature Related Failures If the temperature is too high, greater than 600C (1500F) (greater than 550C (1310F) with newer type cells) the Cathode releases oxygen and the Anode has a SEI layer breakdown. If the cell temperature is too low, less than 15-200C (59-680F) at a high C-rate, the Cathode is stressed from too high of a lithium-ion flow and breakage and cracks occur during discharge. If the temperature is too low, Lithium-Plating occurs during the charge on the Anode. __________ Frank does not note an actual minimum charge temperature. Next: Is there reference to the factor or 'recommendation' in the genesis document? In this case there is not. Is there a reference in the 2005 FMA LiPo Handbook Section 3 document? Yes, noted previously. Is there a reference to the fact or 'recommendation' on the RevoBlends site? Why I trust RevoBlends information. RevoBlends is owned by John Grzan. John Grzan worked with J.J. Hong in Korea on Kokam High Rate Discharge LiPos in 1996, and was part of the FMA staff that put together the 2005 FMA Handbook. More on John Grzan can be found on the RevoBlends Web site. The Roaring Top and LiPol Battery info 'coordinates' with the FMA info and may, or may not, be taken from the same source. The question is: Is it the same info given three times, or separate instances? The Thunder Power and Hobby King recommendations are reasonably close to the same temperature range. MY conclusion is that the temperature ranges given by all the references are valid. What Makes a Valid Source? A Guide to Understanding Battery Specifications Source: MIT Electric Vehicle Team, December 2008 A listing of definitions often associated with batteries. Does this seem to be a 'trusted' source? Roaring Top A trusted source? Most 'About Us' or similar Web pages on a Web site should have the information about who is providing the information. If there are many typos or misspellings, the source may not be as reliable as other sources, or it might be. Steps in checking out a site for validity The site used in this example is Understanding RC LiPo Batteries Who maintains and presents the information on the Web site? A name? Background? Who the Heli is this guy? A trusted source? "My number one LiPo battery pick right now are Buddy RC's Glacier LiPo's . I have been so impressed with these LiPo's over the past several years since Dale started carrying them. The other nice thing is they all come with the AB clip connectors on the JST-XH balance plugs adding yet more value. I personally feel the Glaciers are just as good as Gens Ace & Pulse Ultra (my 3rd picks) at pretty much the same low cost as NanoTechs'. " What does that say about this source? A Homework Assignment The February 2016 Skywriter, newsletter of the Skymasters RADIO CONTROL CLUB OF MICHIGAN, has an article based on a club presentation. It is "Lipo Care and Feeding With Paul Goelz and Joe Rubinstein", p. 6 & p. 7. Based on what YOU have learned so far, evaluate the following. In the section "Lithium... You MUST know this" 4. A lithium cell is fully CHARGED at 4.2V... 10. Any cell reading less than 3V or more than 4.2V at any time under any circumstances is permanently degraded and potentially dangerous. In the section "Lithium... You should know this" (last statement in left column - it doesn't have a number) Degradation is minimized at lower storage temperatures EXCEPT for fully charged cells. Since the full charge voltage is 4.1V below 50 degrees F, a cell charged to 4.2V at room temperature is considered overcharged. The questions YOU should know the answer to, or be able to find, now. Is 4.2V fully charged for a LiPo battery? When is a cell under 3V potentially dangerous? Where is information regarding, and supporting, "Since the full charge voltage is 4.1V below 50 degrees F, a cell charged to 4.2V at room temperature is considered overcharged" found? Sources that I have found to be trustworthy Only YOU can determine the trustworthiness of your source(s). The following is a list that I have found to provide accurate information. My Trusted Sources John Julian, Melbourne, Australia RC Groups: jj604 A simple LiPo performance tool Mark Forsyth, So. California, RC Groups: mrforsyth The Lipoly Objective Performance Database Wayne Giles, Rugby, UK, RC Groups: Wayne Giles ESR / IR Meter for Lipos and ESR Meter - New updated version - Wayne Giles, Rugby, UK, Wayne Giles Joe Giamona, State of Washington RC Groups: MCSGUY Battery Load Test Comparisons All about lipos for RC models from Bruce Simpson at RC Model Reviews His YouTube Video Race Miata (RC Groups) of Vancouver, CA His thread on RC Groups Rick Gilbert, AZ RC Groups: rampman A thread of his on RC Groups At the other end of the Spectrum! The following represents what I believe to be very bad information, and I would not view this person as a trusted source. Really Bad Recommendations by Danal Estes This is NOT a trusted source. (Used as an example.) Degassing a Puffy LiPo on RC Groups * * * * *