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Super-whizzy energy management systems

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nuckolls.bob(at)aeroelect
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Posted: Thu Apr 30, 2020 3:59 pm Post subject: Super-whizzy energy management systems

 	  Quote: 	
		  BTW, maybe I'm missing the obvious, but what is the point of having two batteries if they always connect and disconnect together, albeit through some diode array (part-count counts) ? 	


    Do ya think?  It seems that having two

    batteries is an admission to lack of confidence

    in the maintenance of your battery(ies)



    The top dogs in SVLA batteries produce

    very consistent products on highly

    automated production lines. Consistency

    of performance and mechanical robustness

    is excellent. The weakest link in a battery's

    ability to perform is chemistry. They will

    only 'cycle' so many times. Further, the

    chemistry can be abused in ways that does

    not immediately manifest in an observable

    drop in performance.



    I would have much more confidence in one,

    well maintained SVLA battery than in any

    pair of batteries that don't get replaced

    until the engine doesn't start. 



    This is the reason for periodic checks

    for suitability for flight. This means

    that a battery gets pulled BEFORE it

    quits cranking the engine but after

    it fails minimum capacity for battery-only

    operations.



    Another problem with the diode bridge -ored-

    batteries, how do you know if all the diodes

    are performing as intended? There's no way

    to preflight all the functions of that

    box.



    Integrity of any power steering diode in the

    Z-figures is pre-flight testable.



 

   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue May 05, 2020 7:55 am Post subject: Super-whizzy energy management systems

At 08:06 AM 5/5/2020, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "bcone1381" <bcone1964(at)gmail.com>



 	
My 1st question is whether that alternator ground wire was the only connection between the engine and the airframe, as seems likely.



 

 CharlieÂ [/quote]



 Throttle, mixture and prop cables will ground an engine.  Its a mystery what other grounds existed.[/quote]

   Yes . . . sort of . . . all those conductors

   are steel, long and terminate on various

   and widely separated mountings designed

   for mechanical integrity, not electrical

   conductivity.



   It is not uncommon for those 'ground paths'

   to suffer serious overheat events during

   engine cranking when a mechanic inadvertently

   fails to replace the crankcase-to-firewall

   bond strap during maintenance. This very

   event occurred on one of my rental airplanes

   back about 1990 but it was double grounded

   p-lead shields that smoked. This is why

   the z-figures show p-lead termination that

   is contrary to some legacy practice.



   A ground lead to an alternator case is

   not common practice. The crankcase-to-

   firewall ground strap is generally 2AWG

   equivalent or better and seeks good

   electrical conductivity at locations

   suited to that service.



   We don't know where the other end of

   the illustrated ground lead was terminated,

   nor do we know if it was in addition to

   another ground path. The overheating

   observed in the picture does suggest

   that the ground system on that engine

   was inadequate by design or compromised

   by error.



   I'm hoping to get back to our hip-pocket

   accident analysis but as participants

   will note, there are more questions

   than answers. Lacking a good schematic

   for how the airplane was wired, we'll

   never know how an engine became electrically

   starved (assuming that's true) while

   a data acquisition system RECORDED

   the presence of voltage in the system.



   This wasn't an electrical 'black out' . . .



   The alternator output went to zero

   but again, we're not privy to all the

   hardware between the alternator and

   the bus . . . the breaker was not open

   so something caused the alternator

   output to zero with what appears to

   be simultaneous engine failure.



 

   Bob . . .

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