Friday, January 18, 2013

787 batteries smaller than my car battery

Wall St Journal showed a picture of a well toasted 787 battery out of the 787 that had a fire sitting on the ramp at Logan.  Case was warped out of shape, top was gone, insides were all black.  Looked plenty capable of setting the entire plane on fire.  Not good. 
   Physically the battery looked to be less than one half the size of my car battery.  The Journal said it had an electrical rating of "63 amperes per hour".  Sounds like the Journal reporter knows nothing about batteries.  That should have been "63 ampere-hours" which means the battery can furnish 63 amperes for one hour or one ampere for 63 hours  or any thing in between.  That's not much.  My Mercury Gran Marquis battery is rated at 80 ampere-hours.  You would think a big jetliner would need more than a Detroit sedan.  The plane needs enough battery energy to keep the cockpit instruments and the radio alive  long enough for the crew to do an emergency landing in the event of total generator failure, or both engines failing.  I wonder if the 787 has an emergency ram air turbine generator like we had on Air Force fighters.   

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