I observed a pair of LiPo packs that were discharged too fast "plump up" due to heat buildup at the US AMA Precision Aerobatics contest this year. As an official I suggested the contestant remove them from the aircraft and place them a distance away from us frail humans as well. He concurred and carefully and quickly carried them away by the leads. The application runs at about 40 volts and 60+ amps... John Ferrell W8CCW "My Competition is not my enemy" http://DixieNC.US ----- Original Message ----- From: "Tim" To: "Microcontroller discussion list - Public." Sent: Tuesday, August 15, 2006 7:51 PM Subject: Re: [EE]: Lithium Ion Batteries.. I told Ya So >I believe that in most cases related to radio controlled aircraft the > rather spectacular failures that are reported occur when the LiPoly > cells are improperly charged. > > Tim > > > Tamas Rudnai wrote: >> Usually who uses LiPo or LiIon batteries for an airplane uses electric >> motors (with 2s, 3s or even 4s packs). For those you have to use a speed >> controller with a BEC that makes the 5V for the radio and I am not sure >> others but for example I have one that specially designed for LiIon/LiPo >> batteries so that it measures it I do not know how many times in a second >> and shuts the system (nearly) completly down if anything is wrong -- >> well, >> it does not measure the temperature of the battery which might be a good >> idea. I am also using a cell equalizer for charging and a quite expensive >> charger that also measures the battery several times a second but I know >> lots of others do not care about of that -- as far as I know the cell >> equalizer is nothing about the safety but the durability of the battery, >> however, using an improper charer has a risk of having an explosion. >> Well, >> mechanical protection... when I smashed my plane into the ground at >> around >> 60 Km/h the battery itself had not even scratched as it was housing in a >> styroplast strengthened by fibre glass -- I think it is much more >> protective >> than a mobile phone or a laptop battery, so i do not know, when you drop >> it >> onto to a hard floor I think you have a better chance to happen >> something. >> >> Tamas >> >> >> On 15/08/06, William Chops Westfield wrote: >>> >>> On Aug 15, 2006, at 11:14 AM, John Ferrell wrote: >>> >>>> Li-Ion are pretty tame compared to Li-Po technology. >>>> >>> I hear that, generally from the model plane community where they're >>> in the habit of using cells without any electrical protection, and >>> with very little in the form of mechanical protection. (in an >>> application where the mechanical protection might be important.) >>> But the technology is very similar to li-ion, and I'm not convinced >>> that they're fundamentally "less tame." >>> >>> (likewise, the last laptop battery pack I stripped for it's cells >>> happened to have LiPo cells rather than li-ion cells, so it's hard >>> to tell which is which...) >>> >>> BillW >>> -- >>> http://www.piclist.com PIC/SX FAQ & list archive >>> View/change your membership options at >>> http://mailman.mit.edu/mailman/listinfo/piclist > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist