Heading South:
Based on my experience I wouldn't be too quick to dismiss the relevance of lithium batteries as used in model aircraft . True, most batteries used for this application are lithium polymer and there have been a lot of flame events caused primarily by using the wrong or mis-set charger, the non use of a balancer (essential) as well as physical damage. I use these batteries for their high energy density, high discharge currents and quick charging ability and always remove the batts. from the airframe for charging due to the fire risk. For me so far so good, firewise, although failure rates (voltage collapse, and cell swelling) ) have been high !
However, I have also been using lithium Ion batteries for some years both for airframe electronics (numerous powerful digital servos) and engine power (ECU, Starter and ignition on gas turbine powered models). Although the packs I use have an internal balancer and dedicated, slowish, charger (about .2c) I have noticed a very high failure rate for LiIons compared with NiCd and NiMh chemistry even though the discharge currents on my applications are not excessive. The failures have been non "flaming" but many packs have lost voltage and the ability to accept a charge at way below the cycles one might reasonably expect (some have failed after less than 50 cycles).
With the fire/explosion risk of LiPos, the poor reliabiltity of LiIons a lot of us are moving over to LiFe batteries which appear safer chemistry even though they can't quite deliver the performance of other lithium chemistry but do show an ability to recharge VERY quickly and can deliver quite high currents without much voltage drop off. Never heard of a fire or explosion with LiFe cells, perhaps this may be the way to go.
Still putting my money on a single cell failure and the charger trying to bring the pack upto full voltage, but isn't that what a balancer circuit is supposed to do ?
So, don't totally dismiss our lithium experience !!
(and no, not an aeromodelling troll, ex 75/76 captain who once flew an earlier, nearly, all-electric aeroplane, the Valiant ! Not a lot of people know the Valiant was almost fully electric, inc engine duct anti-icing, except for hydraulic wheelbrakes and N/S, lipos in this days, never been heard of !!)
Anyway I wish Boeing every success in getting to the bottom of this, and rapidly too, the 787 should soon be helping pay my pension !
Last edited by RetiredBA/BY; 12th Feb 2013 at 19:40.
Reason: sp/punct.