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Z102 w/AEC9005

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Eric Page

Joined: 15 Feb 2017
Posts: 242

Posted: Fri Oct 09, 2020 10:15 am Post subject: Z102 w/AEC9005

Hi Bob,



I'm building a Kitfox that will probably use an auto-based engine conversion.  I like the look of your Z102 architecture for its redundancy in engine electrical supply, as well as the auxiliary bus for pre-flight ground activities.  But, I have a couple of questions:



1. Am I correct in my understanding that:

a) the auxiliary battery is normally paralleled with the main battery during engine start *and* during normal operation (bus voltage >13V) so that it can be recharged by the alternator?

b) the auxiliary battery will be isolated to engine-related functions only, if the bus falls below 13V?



2. The Z102 schematic shows a START CMD signal from the push-to-start switch to an AEC90XX Aux Battery Management Module (ABMM).  The only thing like this that I can find is your AEC9005 series of Low Voltage Warning and ABMM devices.  However, the AEC9005 schematic in this document...



http://www.aeroelectric.com/DIY/LV_Warn_Fab_and_Install.pdf



...does not include an input for the START CMD signal.  Is there another ABMM design on the drawing board, or does Z102 contemplate an iteration of AEC9005 with the addition of the START CMD facility?  If the latter, then is it safe to assume that START CMD is simply a gate drive signal to the FET, diode isolated from the comparator output?



3. On the AEC9005 schematic linked above, what is the purpose of Zener diode Z118?  Is it to protect the FET against excessive V(d-s) in case the contactor's flyback diode fails to perform, or is missing?



Many thanks!



Eric

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Eric Page

Joined: 15 Feb 2017
Posts: 242

Posted: Mon Oct 19, 2020 7:30 am Post subject: Re: Z102 w/AEC9005

Trying again; I posted this ten days ago with no response...



 	  Quote: 	
		  I'm building a Kitfox that will probably use an auto-based engine conversion. I like the look of your Z102 architecture for its redundancy in engine electrical supply, as well as the auxiliary bus for pre-flight ground activities. But, I have a couple of questions:



1. Am I correct in my understanding that:

a) the auxiliary battery is normally paralleled with the main battery during engine start *and* during normal operation (bus voltage >13V) so that it can be recharged by the alternator?

b) the auxiliary battery will be isolated to engine-related functions only, if the bus falls below 13V?



2. The Z102 schematic shows a START CMD signal from the push-to-start switch to an AEC90XX Aux Battery Management Module (ABMM). The only thing like this that I can find is your AEC9005 series of Low Voltage Warning and ABMM devices. However, the AEC9005 schematic in this document...



http://www.aeroelectric.com/DIY/LV_Warn_Fab_and_Install.pdf



...does not include an input for the START CMD signal. Is there another ABMM design on the drawing board, or does Z102 contemplate an iteration of AEC9005 with the addition of the START CMD facility? If the latter, then is it safe to assume that START CMD is simply a gate drive signal to the FET, diode isolated from the comparator output?



3. On the AEC9005 schematic linked above, what is the purpose of Zener diode Z118? Is it to protect the FET against excessive V(d-s) in case the contactor's flyback diode fails to perform, or is missing?

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nuckolls.bob(at)aeroelect
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Posted: Mon Oct 19, 2020 7:11 pm Post subject: Z102 w/AEC9005

At 10:30 AM 10/19/2020, you wrote:

 --> AeroElectric-List message posted by: "Eric Page" <edpav8r(at)yahoo.com>



 Trying again; I posted this ten days ago with no response...

   

   Sorry 'bout that . . my bad.



   I've been pondering the 'step up' from Z101 to 

   Z102 . . . not sure I'm all that enthusiastic

   about it.



   Help us understand the motivation for an

   AUX battery added specifically to support

   the engine.



   Your total electrical needs for comfortable

   flight are predictable and/or measurable.

   The amount of energy contained in a battery

   is similarly known.



   If you split duties of the two batteries

   for alternator-out operations, then your

   endurance is set by whichever battery

   gives up first.



   Z101 offers dual feed bus structures with

   opportunity for load shedding to a predictable

   level. THAT number drives the battery

   selection and maintenance protocol.



   That's one of the reasons I discontinued the

   IBMM . . . $cost of ownership$ for a second

   battery is significant especially when it's

   not a quantum boost to system reliability.



 

   Bob . . .

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Eric Page

Joined: 15 Feb 2017
Posts: 242

Posted: Tue Oct 20, 2020 8:48 pm Post subject: Re: Z102 w/AEC9005

 	  nuckolls.bob(at)aeroelect wrote: 	
		  Sorry 'bout that . . my bad. 	


Thanks, Bob, no worries.  There's been a lot of signal here lately, so it was easy to fall below the noise floor!



 	  Quote: 	
		  I've been pondering the 'step up' from Z101 to Z102 . . . not sure I'm all that enthusiastic about it.



Help us understand the motivation for an AUX battery added specifically to support the engine. 	


The presence of Z102, and its labeling for "automotive conversions" led me to believe that it was the current state-of-the-art for aircraft so equipped.  I'm in the early planning stages at this point, so I'm happy to entertain other ideas.



The plane will be a day/night VFR-only aircraft.  I plan to use it for back-country flying, so keeping the starter spinning at off-airport locations and the engine running over expanses of hostile terrain are primary concerns.  The plane will have LED lights, a transponder, an ADS-B receiver, a single comm radio, one EFIS screen, and perhaps a lightweight, low power multi-function backup instrument.  I would view minimum equipment as engine, lights, comm and backup instrument.



The engine I'm considering (AeroMomentum AM15, based on a Suzuki 1.5L inline 4-cyl) ships with a single 65A (probably Denso) alternator.  I don't yet know whether it's supplied as an internally or externally regulated unit, but I suspect that it will need modification.  I also don't know if the engine has a spot for a second alternator, but given the absence of a power steering pump or AC compressor, it's probably feasible to mount one.



 	  Quote: 	
		  Your total electrical needs for comfortable flight are predictable and/or measurable.  The amount of energy contained in a battery is similarly known.



If you split duties of the two batteries for alternator-out operations, then your endurance is set by whichever battery gives up first. 	


Indeed.  My working assumption was that Z102 had identical batteries supporting separate, smaller loads so that the time-to-darkness-and-quiet would be pushed farther into the future than with a single battery of similar capacity.  Since the engine-only electrical load -- especially at a constant cruise power setting -- would be very predictable, I suspect that you would be able to make an eerily accurate estimate of remaining fan-assisted flight time.



That said, a second alternator extends endurance to the bottom of the fuel tank, doesn't leave you dead in the water once you land, and given my simple VFR equipment, would likely impose no requirement to load-shed.



 	  Quote: 	
		  Z101 offers dual feed bus structures with opportunity for load shedding to a predictable level. THAT number drives the battery selection and maintenance protocol.



That's one of the reasons I discontinued the IBMM . . . $cost of ownership$ for a second battery is significant especially when it's not a quantum boost to system reliability. 	


I see.  So, given the reliability of batteries in general, and the simplicity of Z101 vs Z102, it sounds like you're leaning toward a recommendation for Z101 with a battery sized and maintained to achieve worst case engine-off pre-flight activities followed by spirited engine starts.  The single battery would not be expected to support alternator-out flight loads for any longer than it takes the pilot to identify the problem and flip the AUX ALT switch.  Operation in this condition would be assured by pre-flight testing of the standby alternator/regulator.



Is that more-or-less accurate?



Thanks again,



Eric

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nuckolls.bob(at)aeroelect
Guest

Posted: Fri Oct 23, 2020 10:49 am Post subject: Z102 w/AEC9005

 	  Quote: 	
		  

 I see.  So, given the reliability of batteries in general, and the simplicity of Z101 vs Z102, it sounds like you're leaning toward a recommendation for Z101 with a battery sized and maintained to achieve worst case engine-off pre-flight activities followed by spirited engine starts.  The single battery would not be expected to support alternator-out flight loads for any longer than it takes the pilot to identify the problem and flip the AUX ALT switch.  Operation in this condition would be assured by pre-flight testing of the standby alternator/regulator.



 Is that more-or-less accurate? 	


   Yeah . . . a well crafted system doesn't suffer emergencies.

   Low volts should not be an emergency. It's not even

   an especially urgent event.



   If mitigating action for a low volts warning doesn't

   happen until, say, one minute later . . . outcome

   of the flight for electrical insufficiency will

   not change. Hence, if you have active notification

   of low voltage, then an aux battery manager doesn't

   do much to reduce risk.



   If the ship is fitted with an auxiliary alternator

   of lesser size, then design goals and plan-B

   calculations will determine what actions are

   needed after the warning . . . and time-to-

   lights-out are KNOWN.



   If an aux alternator can carry 100% of endurance

   loads, then the flight can be continued to

   airport of original destination. If it carries

   less than 100% of endurance loads, then energy

   stored in the battery can be drawn down with

   an alternator assist. Endurance in this instance

   is predictable.



   If no aux alternator, then energy bucket is not

   so big. But it can still be diligently allocated

   for predictable endurance.



   Splitting energy storage between two 

   batteries only doubles maintenance labor and

   complicates endurance management when

   loads assigned to each battery are not

   identical.



   Spitting that goal into two separate, probably

   unequal tasks seems inelegant. It 

   seems that one battery, sized and maintained

   to meet design goals for battery-only

   endurance is more reliable and certainly

   easier to meet design goals. The idea behind

   'aux batteries' sort of evaporates. Indeed

   all forms of 'standby' battery for the various

   electro-whizzies should be evaluated. If the

   engine is happy, then everybody is happy.



   The steps to meeting design goals are validated

   by doing the load analysis homework.  Been

   through this exercise many times . . . it's a

   regulatory GIVEN on TC aircraft . . . for

   both selection of battery capacity and protocols

   for verifying conditions for continued airworthiness.



   Contrary to the dreams of some program managers,

   a quest for elegant design is not a straight line.

   I've seen many a PERT chart forecasting time-

   to-market . . . few were very accurate especially

   for programs with new technology or promising

   but untried philosophies.



   I would describe the design process more like a spiral

   path that circles the design goal several if

   not many times with each circuit gathering in

   useful ideas while pitching out the not so useful;

   a process exceedingly difficult to plot on

   a PERT chart!



   When the first half dozen z-figures were published

   30+ years ago, I couldn't begin to imagine

   what Z101 would have looked like. Nor could

   I imagine countless conversations and experiments

   here on the List that drove the architecture. The

   most interesting feature is a kind of plug-n-play

   selection of busses and power sources easily tailored

   to a wide range of projects. One drawing 

   may indeed replace most if to all those that

   preceded it all managed by not more than 3 switches.



   Z101 could have existed 30 years ago.

   Nothing radically new in terms of technology.

   If we'd only known then what we know

   now! What's that timeless adage? Too

   soon we get old and too late we get

   smart?



   And who is to say Z101 is the ultimate

   solution? Not me. Let's continue to refine

   the recipe for success while staying

   mindful of the laws of physics, the

   quest for reduction of weight, complexity,

   cost and RISK while addressing the practical

   matters of owning and operating airplanes.



 

   Bob . . .

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Eric Page

Joined: 15 Feb 2017
Posts: 242

Posted: Sun Oct 25, 2020 8:04 am Post subject: Re: Z102 w/AEC9005

 	  nuckolls.bob(at)aeroelect wrote: 	
		  [SNIP]

If the ship is fitted with an auxiliary alternator

of lesser size, then design goals and plan-B

calculations will determine what actions are

needed after the warning . . . and time-to-

lights-out are KNOWN.



If an aux alternator can carry 100% of endurance

loads, then the flight can be continued to airport

of original destination. If it carries less than 100%

of endurance loads, then energy stored in the

battery can be drawn down with an alternator

assist. Endurance in this instance is predictable.



If no aux alternator, then energy bucket is not so

big. But it can still be diligently allocated for

predictable endurance.



Splitting energy storage between two batteries

only doubles maintenance labor and complicates

endurance management when loads assigned to

each battery are not identical. 	


I'm sold.  A system with a second alternator capable of supporting endurance loads does seem a more useful and less maintenance-intensive solution than carrying around a second battery.



Given the minimal equipment in my aircraft, supporting even normal flight loads with an auxiliary alternator should be trivial.  In addition to that configuration getting me to my original destination, it gets me there with a charged battery, so I'm not stuck there, AOG.



I suspect that the factory-supplied 65A alternator could be replaced with a smaller, lighter unit with half the capacity, still have headroom to spare, and buy back some of the weight penalty of the second alternator.



Thanks, Bob.  I'll probably be back for more when I get to the load analysis.

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