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EFI current requirements

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johnbright

Joined: 14 Dec 2011
Posts: 165
Location: Newport News, VA

Posted: Mon Dec 23, 2019 4:13 pm Post subject: EFI current requirements

For those interested I'm sharing my calculations re dual SDS EM-5-F current requirements for my RV-6A O-360 not yet flying.



The file called "Load Analysis... " in folder 3 shows how I arrived at current requirements of 14.2/9.0/7.9 amps for low altitude/cruise/endurance cruise. These currents are for running the engine only... any other loads, for instance contactors and avionics, will add to the current draw.



The file called "Calculations Measurements... " in folder 3 includes how I arrived at injector current.



The image called "Pump current... " in folder 4 is where I got 5.25 A at 45 psi.



All files are at https://drive.google.com/drive/folders/1u6GeZo6pmBWsKykLNVQMvu4o1VEVyP4K

_________________
John Bright, RV-6A, at FWF, O-360
Z-101 single batt dual alt SDS EM-5-F.
john_s_bright@yahoo.com, Newport News, Va
N1921R links

Last edited by johnbright on Fri Mar 31, 2023 6:14 am; edited 3 times in total

markfw

Joined: 28 Feb 2019
Posts: 27
Location: Seattle, WA

Posted: Sat Dec 28, 2019 2:30 pm Post subject: Re: EFI current requirements

John,



This is a very impressive amount of due diligence on your part. 



Thank you so much for sharing all of this. It will help me up my game in my own planning.



The data on EM-5 current draw is very useful since I was using much higher numbers derived from Ross's very conservative numbers quoted in his manuals. 



Using your numbers I can see that a single large Lithium battery should give me all of the ALT-OUT endurance I would ever need over water or mountains here in the West.



Mark

johnbright

Joined: 14 Dec 2011
Posts: 165
Location: Newport News, VA

Posted: Sat Dec 28, 2019 3:05 pm Post subject: Re: EFI current requirements

 	  markfw wrote: 	
		  John,



This is a very impressive amount of due diligence on your part. 



Thank you so much for sharing all of this. It will help me up my game in my own planning.



The data on EM-5 current draw is very useful since I was using much higher numbers derived from Ross's very conservative numbers quoted in his manuals. 



Using your numbers I can see that a single large Lithium battery should give me all of the ALT-OUT endurance I would ever need over water or mountains here in the West.



Mark 	




Thanks Mark... you might learn something on VAF... thread started by Ross Farnham of SDS on 12/24/2019... "Backup Battery Testing LiFePO4 vs. AGM"... http://www.vansairforce.com/community/showthread.php?t=178037



If you join VAF you can subscribe to the thread.

_________________
John Bright, RV-6A, at FWF, O-360
Z-101 single batt dual alt SDS EM-5-F.
john_s_bright@yahoo.com, Newport News, Va
N1921R links

markfw

Joined: 28 Feb 2019
Posts: 27
Location: Seattle, WA

Posted: Sun Dec 29, 2019 10:37 am Post subject: Re: EFI current requirements

John,



Thanks for the link to the thread of Ross's evaluation of the Shorei battery. This is a good example of non-truth in advertising.



However, according to Ross the Shorei weighs 2.2 pounds and is good for approximately 6 ah. The EarthX ETX 900 battery is rated by them at 15.6 ah and weighs 4.9 pounds.



Since these Lithium battery manufacturers apparently all use the same (or similar) Chinese Lithium cells I would say that EarthX is rating their batteries properly for continuous use rather than just starting.



I will be using an EarthX 24 ah single battery in my day-VFR Carbon Cub. I will also have the EarthX 2 ah portable "starter" battery if I forget to turn off my master switch. It will be interesting to see if it will actually start my engine. It's counterintuitive that such a small battery could start an O-340, but it can supposedly do it. 



I am a Vans Air Force subscriber. I lurk there and learn a ton from the thousands of RV pilots and builders.



Thanks.



Mark

skywagon185(at)gmail.com
Guest

Posted: Wed Jan 01, 2020 1:31 pm Post subject: EFI current requirements

Mark,

Just a suggestion about your battery comments....

I would think that using the smaller battery to "boost charge" the larger battery might be better than trying to start an engine directly off the smaller.

The larger boosted battery has the internal hardware and cabling to handle huge loads like starting sequences.Â  The smaller battery could bring the larger back to life enough to get a good engine start.....



On Sun, Dec 29, 2019 at 10:42 AM markfw <markwheelermd(at)icloud.com (markwheelermd(at)icloud.com)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: "markfw" <markwheelermd(at)icloud.com (markwheelermd(at)icloud.com)>

 

 John,

 

 Thanks for the link to the thread of Ross's evaluation of the Shorei battery. This is a good example of non-truth in advertising.

 

 However, according to Ross the Shorei weighs 2.2 pounds and is good for approximately 6 ah. The EarthX ETX 900 battery is rated by them at 15.6 ah and weighs 4.9 pounds.

 

 Since these Lithium battery manufacturers apparently all use the same (or similar) Chinese Lithium cells I would say that EarthX is rating their batteries properly for continuous use rather than just starting.

 

 I will be using an EarthX 24 ah single battery in my day-VFR Carbon Cub. I will also have the EarthX 2 ah portable "starter" battery if I forget to turn off my master switch. It will be interesting to see if it will actually start my engine. It's counterintuitive that such a small battery could start an O-340, but it can supposedly do it. 

 

 I am a Vans Air Force subscriber. I lurk there and learn a ton from the thousands of RV pilots and builders.

 

 Thanks.

 

 Mark

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=494093#494093

 

 

 

 

 

 

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ceengland7(at)gmail.com
Guest

Posted: Wed Jan 01, 2020 2:07 pm Post subject: EFI current requirements

While connecting them in parallel might       increase available current to start, it won't charge the other       battery, unless it's badly depleted.

       

       I missed the earlier posts in this thread; 'the google' sometimes       decides Aeroelectric emails are spam (likely due to 'unusual'       subject lines).

       

       The issue of AH ratings has been around as long as lithium battery       tech. Since the typical duty of a battery in a motor vehicle is       purely starting, the lithium guys have almost always used AH       'equivalent' ratings when it comes to the battery's ability to       *start* an engine. It's the difference between *power* (ex: 400 HP       Corvette) and *energy* (50 gallon gas tank). A Corvette with a       gallon of gas in its tank will get to the end of a quarter mile       first, and then it won't go any farther. A Chevette with a 10       gallon tank will win the 200 mile race every time over the       Corvette with a 1 gallon tank.

       

       Nothing really 'wrong' with the equivalent thing, as long as       everyone is on the same page and is using the battery purely as a       starting battery. But even in a car, the difference in capacity       might mean the difference between getting home after an alt       failure, or being stranded on the side of the road.

       

       Â IIRC, EarthX did the same 'equivalent' ratings thing early in       their venture into the a/c market, until a bunch of us pointed out       to them that if the plane is electrically dependent, those numbers       don't work.

       

       Those of you planning on using EX batteries do need to be aware       that the internal battery management system really is another       failure point, and has failed in at least one case. If it decides       that there are external problems, or the battery is near       end-of-charge (whether its assumption is correct or not), it will       disconnect the battery. Under the right conditions, with some,       older design alternators, the load dump could cause an alternator       failure. Not likely a risk with B&C alts, but many older       internally regulated alternators will die in a load dump       situation.

       

       In an 'alternator out' situation, the EX *will* disconnect at some       point, before the battery is fully depleted. Your call on use, but       do know the failure modes if you use them.

       

       Charlie 

       

       On 1/1/2020 3:29 PM, skywagon185guy . wrote:

     

      	  Quote: 	
		                         Mark,

         Just a suggestion about your battery comments....

         I would think that using the smaller battery to "boost           charge" the larger battery might be better than trying to           start an engine directly off the smaller.

         The larger boosted battery has the internal hardware and           cabling to handle huge loads like starting sequences.Â  The           smaller battery could bring the larger back to life enough to           get a good engine start.....

         

       

       

                On Sun, Dec 29, 2019 at 10:42           AM markfw <markwheelermd(at)icloud.com (markwheelermd(at)icloud.com)>           wrote:

         

          	  Quote: 	
		  -->           AeroElectric-List message posted by: "markfw" <markwheelermd(at)icloud.com (markwheelermd(at)icloud.com)>

           

           John,

           

           Thanks for the link to the thread of Ross's evaluation of the           Shorei battery. This is a good example of non-truth in           advertising.

           

           However, according to Ross the Shorei weighs 2.2 pounds and is           good for approximately 6 ah. The EarthX ETX 900 battery is           rated by them at 15.6 ah and weighs 4.9 pounds.

           

           Since these Lithium battery manufacturers apparently all use           the same (or similar) Chinese Lithium cells I would say that           EarthX is rating their batteries properly for continuous use           rather than just starting.

           

           I will be using an EarthX 24 ah single battery in my day-VFR           Carbon Cub. I will also have the EarthX 2 ah portable           "starter" battery if I forget to turn off my master switch. It           will be interesting to see if it will actually start my           engine. It's counterintuitive that such a small battery could           start an O-340, but it can supposedly do it. 

           

           I am a Vans Air Force subscriber. I lurk there and learn a ton           from the thousands of RV pilots and builders.

           

           Thanks.

           

           Mark

markfw

Joined: 28 Feb 2019
Posts: 27
Location: Seattle, WA

Posted: Thu Jan 02, 2020 5:14 pm Post subject: Re: EFI current requirements

 	  skywagon185(at)gmail.com wrote: 	
		  Mark,

Just a suggestion about your battery comments....

I would think that using the smaller battery to "boost charge" the larger battery might be better than trying to start an engine directly off the smaller.

The larger boosted battery has the internal hardware and cabling to handle huge loads like starting sequences.Â  The smaller battery could bring the larger back to life enough to get a good engine start.....



EARTHX SELLS A CONNECTOR TO THE BATTERY TERMINALS WHICH IS USED BY THEIR RECOMMENDED CHARGING UNITS AND BY THEIR "JUMP START" BATTERY. IT IS RATED AT 400 AMPS. I ASSUME THAT THE BMS FIGURES OUT HOW TO ROUTE THE JUMP START CURRENT TO THE STARER.



On Sun, Dec 29, 2019 at 10:42 AM markfw <markwheelermd> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: "markfw" <markwheelermd>

 

 John,

 

 Thanks for the link to the thread of Ross's evaluation of the Shorei battery. This is a good example of non-truth in advertising.

 

 However, according to Ross the Shorei weighs 2.2 pounds and is good for approximately 6 ah. The EarthX ETX 900 battery is rated by them at 15.6 ah and weighs 4.9 pounds.

 

 Since these Lithium battery manufacturers apparently all use the same (or similar) Chinese Lithium cells I would say that EarthX is rating their batteries properly for continuous use rather than just starting.

 

 I will be using an EarthX 24 ah single battery in my day-VFR Carbon Cub. I will also have the EarthX 2 ah portable "starter" battery if I forget to turn off my master switch. It will be interesting to see if it will actually start my engine. It's counterintuitive that such a small battery could start an O-340, but it can supposedly do it. 

 

 I am a Vans Air Force subscriber. I lurk there and learn a ton from the thousands of RV pilots and builders.

 

 Thanks.

 

 Mark

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=494093#494093

 

 

 

 

 

 

 ===========

 br> fts!)

 r> > target="_blank" rel="noreferrer">http://www.matronics.com/contribution

 Â  Â  Â  Â  Â  -Matt Dralle, List Admin.

 ===========

  -

 Electric-List" target="_blank" rel="noreferrer">http://www.matronics.com/Navigator?AeroElectric-List

 ===========

  FORUMS -

 _blank" rel="noreferrer">http://forums.matronics.com

 ===========

 WIKI -

 lank" rel="noreferrer">http://wiki.matronics.com

 ===========

 b Site -

 Â  Â  Â  Â  Â  -Matt Dralle, List Admin.

 target="_blank" rel="noreferrer">http://www.matronics.com/contribution

 ===========

markfw

Joined: 28 Feb 2019
Posts: 27
Location: Seattle, WA

Posted: Thu Jan 02, 2020 5:19 pm Post subject: Re: EFI current requirements

 	  ceengland7(at)gmail.com wrote: 	
		  While connecting them in parallel might       increase available current to start, it won't charge the other       battery, unless it's badly depleted.

       

       I missed the earlier posts in this thread; 'the google' sometimes       decides Aeroelectric emails are spam (likely due to 'unusual'       subject lines).

       

       The issue of AH ratings has been around as long as lithium battery       tech. Since the typical duty of a battery in a motor vehicle is       purely starting, the lithium guys have almost always used AH       'equivalent' ratings when it comes to the battery's ability to       *start* an engine. It's the difference between *power* (ex: 400 HP       Corvette) and *energy* (50 gallon gas tank). A Corvette with a       gallon of gas in its tank will get to the end of a quarter mile       first, and then it won't go any farther. A Chevette with a 10       gallon tank will win the 200 mile race every time over the       Corvette with a 1 gallon tank.

       

       Nothing really 'wrong' with the equivalent thing, as long as       everyone is on the same page and is using the battery purely as a       starting battery. But even in a car, the difference in capacity       might mean the difference between getting home after an alt       failure, or being stranded on the side of the road.

       

       Â IIRC, EarthX did the same 'equivalent' ratings thing early in       their venture into the a/c market, until a bunch of us pointed out       to them that if the plane is electrically dependent, those numbers       don't work.

       

       Those of you planning on using EX batteries do need to be aware       that the internal battery management system really is another       failure point, and has failed in at least one case. If it decides       that there are external problems, or the battery is near       end-of-charge (whether its assumption is correct or not), it will       disconnect the battery. Under the right conditions, with some,       older design alternators, the load dump could cause an alternator       failure. Not likely a risk with B&C alts, but many older       internally regulated alternators will die in a load dump       situation.

       

       In an 'alternator out' situation, the EX *will* disconnect at some       point, before the battery is fully depleted. Your call on use, but       do know the failure modes if you use them.

       

       Charlie 



CHARLIE, YES THE EARTHX BMS SHUTS DOWN THE BATTERY GRACEFULLY AT 11.5V. THEY SAY THAT THIS IS WHEN ONLY 5% OF THE BATTERY ENERGY IS LEFT. I THINK THE INTENT IS TO AVOID A LOAD DUMP ONTO THE ALTERNATOR. I AM USING A B & C ALTERNATOR.

       

       On 1/1/2020 3:29 PM, skywagon185guy . wrote:

     

      	  Quote: 	
		                         Mark,

         Just a suggestion about your battery comments....

         I would think that using the smaller battery to "boost           charge" the larger battery might be better than trying to           start an engine directly off the smaller.

         The larger boosted battery has the internal hardware and           cabling to handle huge loads like starting sequences.Â  The           smaller battery could bring the larger back to life enough to           get a good engine start.....

         

       

       

                On Sun, Dec 29, 2019 at 10:42           AM markfw <markwheelermd>           wrote:

         

          	  Quote: 	
		  -->           AeroElectric-List message posted by: "markfw" <markwheelermd>

           

           John,

           

           Thanks for the link to the thread of Ross's evaluation of the           Shorei battery. This is a good example of non-truth in           advertising.

           

           However, according to Ross the Shorei weighs 2.2 pounds and is           good for approximately 6 ah. The EarthX ETX 900 battery is           rated by them at 15.6 ah and weighs 4.9 pounds.

           

           Since these Lithium battery manufacturers apparently all use           the same (or similar) Chinese Lithium cells I would say that           EarthX is rating their batteries properly for continuous use           rather than just starting.

           

           I will be using an EarthX 24 ah single battery in my day-VFR           Carbon Cub. I will also have the EarthX 2 ah portable           "starter" battery if I forget to turn off my master switch. It           will be interesting to see if it will actually start my           engine. It's counterintuitive that such a small battery could           start an O-340, but it can supposedly do it. 

           

           I am a Vans Air Force subscriber. I lurk there and learn a ton           from the thousands of RV pilots and builders.

           

           Thanks.

           

           Mark

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jan 03, 2020 2:09 pm Post subject: EFI current requirements

 	  Quote: 	
		  The issue of AH ratings has been around as long as lithium battery tech. Since the typical duty of a battery in a motor vehicle is purely starting, the lithium guys have almost always used AH 'equivalent' ratings when it comes to the battery's ability to *start* an engine. 	


   I don't think there was any misunderstanding about

   the ratings. The 'equivalency' thing was about cranking

   current . . . period. In the early days, they deliberately

   omitted comparisons of battery capacity . . . which made

   their marketing numbers for weight and size versus 

   performance look better. My earliest conversations with

   EarthX confirmed this.



  	  Quote: 	
		  Those of you planning on using EX batteries do need to be aware that the internal battery management system really is another failure point, and has failed in at least one case. If it decides that there are external problems, or the battery is near end-of-charge (whether its assumption is correct or not), it will disconnect the battery. Under the right conditions, with some, older design alternators, the load dump could cause an alternator failure. Not likely a risk with B&C alts, but many older internally regulated alternators will die in a load dump situation. 	


   "Load dump" is nearly an non-existent phenomenon

   and it would not happen due to the actions of

   the BMS. Recall that the BMS breaks the output

   as the battery is being discharged . . . if you

   have a working alternator on line, then the battery

   will be charging and the BMS will be happy. It would

   never disconnect while a functioning alternator

   was doing its job.



 

  	  Quote: 	
		  In an 'alternator out' situation, the EX *will* disconnect at some point, before the battery is fully depleted. Your call on use, but do know the failure modes if you use them.

 	


 ---------------------



  	  Quote: 	
		    	  Quote: 	
		  Just a suggestion about your battery comments....

 I would think that using the smaller battery to "boost charge" the larger battery might be better than trying to start an engine directly off the smaller.

 	
	


     BATTERIES CANNOT CHARGE BATTERIES. 



  	  Quote: 	
		    	  Quote: 	
		  The larger boosted battery has the internal hardware and cabling to handle huge loads like starting sequences.Â  The smaller battery could bring the larger back to life enough to get a good engine start..... 	
	


    SORRY, DOESN'T WORK THAT WAY. If the smaller

    battery stores enough watt-seconds of snort

    to crank the engine, then use it to do just

    that. But 'charging' a dead battery from

    a 'full' battery doesn't work. 



 

  	  Quote: 	
		    	  Quote: 	
		  On Sun, Dec 29, 2019 at 10:42 AM markfw <markwheelermd(at)icloud.com (markwheelermd(at)icloud.com) > wrote:

   --> AeroElectric-List message posted by: "markfw" <markwheelermd(at)icloud.com (markwheelermd(at)icloud.com) >



  John,



  Thanks for the link to the thread of Ross's evaluation of the Shorei battery. This is a good example of non-truth in advertising.



  However, according to Ross the Shorei weighs 2.2 pounds and is good for approximately 6 ah. The EarthX ETX 900 battery is rated by them at 15.6 ah and weighs 4.9 pounds.



  Since these Lithium battery manufacturers apparently all use the same (or similar) Chinese Lithium cells I would say that EarthX is rating their batteries properly for continuous use rather than just starting. 	
	
 

    I got on EarthX a few years back about the 'equivalent' 

    rating and they started adding contained energy (CAPACITY)

    values to their advertising literature.



  	  Quote: 	
		    	  Quote: 	
		    I will be using an EarthX 24 ah single battery in my day-VFR Carbon Cub. I will also have the EarthX 2 ah portable "starter" battery if I forget to turn off my master switch. 	
	
 

    You don't have active and insistent LOW VOLTS

    warning?



  	  Quote: 	
		    	  Quote: 	
		     It will be interesting to see if it will actually start my engine. It's counterintuitive that such a small battery could start an O-340, but it can supposedly do it. 

 	
	
 

    If you're carrying an 'extra' battery around as

    a hedge against failure to use a checklist, perhaps

    it would be more elegant to upsize the main battery,

    ditch the 'ohmygosh' battery and include some means

    for making sure the master doesn't get left on.



    A little buzzer on a low oil pressure switch works

    good . . . little irritating flashing lights work

    too . . .



    But adding more batteries for any reason only increases

    your battery maintenance time and costs by the same

    factor. The elegant solution has ONE battery and

    a failure mode analysis that confirms exceedingly

    low risk. If you've got an unused vacuum pump pad,

    TWO alternators and one battery (perhaps smaller than

    a 900) is about as reliable as you can get.



 

   Bob . . .

markfw

Joined: 28 Feb 2019
Posts: 27
Location: Seattle, WA

Posted: Fri Jan 03, 2020 2:33 pm Post subject: Re: EFI current requirements

 	  nuckolls.bob(at)aeroelect wrote: 	
		   	  Quote: 	
		  The issue of AH ratings has been around as long as lithium battery tech. Since the typical duty of a battery in a motor vehicle is purely starting, the lithium guys have almost always used AH 'equivalent' ratings when it comes to the battery's ability to *start* an engine. 	


   I don't think there was any misunderstanding about

   the ratings. The 'equivalency' thing was about cranking

   current . . . period. In the early days, they deliberately

   omitted comparisons of battery capacity . . . which made

   their marketing numbers for weight and size versus 

   performance look better. My earliest conversations with

   EarthX confirmed this.



  	  Quote: 	
		  Those of you planning on using EX batteries do need to be aware that the internal battery management system really is another failure point, and has failed in at least one case. If it decides that there are external problems, or the battery is near end-of-charge (whether its assumption is correct or not), it will disconnect the battery. Under the right conditions, with some, older design alternators, the load dump could cause an alternator failure. Not likely a risk with B&C alts, but many older internally regulated alternators will die in a load dump situation. 	


   "Load dump" is nearly an non-existent phenomenon

   and it would not happen due to the actions of

   the BMS. Recall that the BMS breaks the output

   as the battery is being discharged . . . if you

   have a working alternator on line, then the battery

   will be charging and the BMS will be happy. It would

   never disconnect while a functioning alternator

   was doing its job.



 

  	  Quote: 	
		  In an 'alternator out' situation, the EX *will* disconnect at some point, before the battery is fully depleted. Your call on use, but do know the failure modes if you use them.

 	


 ---------------------



  	  Quote: 	
		    	  Quote: 	
		  Just a suggestion about your battery comments....

 I would think that using the smaller battery to "boost charge" the larger battery might be better than trying to start an engine directly off the smaller.

 	
	


     BATTERIES CANNOT CHARGE BATTERIES. 



  	  Quote: 	
		    	  Quote: 	
		  The larger boosted battery has the internal hardware and cabling to handle huge loads like starting sequences.ï¿½  The smaller battery could bring the larger back to life enough to get a good engine start..... 	
	


    SORRY, DOESN'T WORK THAT WAY. If the smaller

    battery stores enough watt-seconds of snort

    to crank the engine, then use it to do just

    that. But 'charging' a dead battery from

    a 'full' battery doesn't work. 



 

  	  Quote: 	
		    	  Quote: 	
		  On Sun, Dec 29, 2019 at 10:42 AM markfw <markwheelermd> wrote:

   --> AeroElectric-List message posted by: "markfw" <markwheelermd>



  John,



  Thanks for the link to the thread of Ross's evaluation of the Shorei battery. This is a good example of non-truth in advertising.



  However, according to Ross the Shorei weighs 2.2 pounds and is good for approximately 6 ah. The EarthX ETX 900 battery is rated by them at 15.6 ah and weighs 4.9 pounds.



  Since these Lithium battery manufacturers apparently all use the same (or similar) Chinese Lithium cells I would say that EarthX is rating their batteries properly for continuous use rather than just starting. 	
	
 

    I got on EarthX a few years back about the 'equivalent' 

    rating and they started adding contained energy (CAPACITY)

    values to their advertising literature.



  	  Quote: 	
		    	  Quote: 	
		    I will be using an EarthX 24 ah single battery in my day-VFR Carbon Cub. I will also have the EarthX 2 ah portable "starter" battery if I forget to turn off my master switch. 	
	
 

    You don't have active and insistent LOW VOLTS

    warning?



  	  Quote: 	
		    	  Quote: 	
		     It will be interesting to see if it will actually start my engine. It's counterintuitive that such a small battery could start an O-340, but it can supposedly do it. 

 	
	
 

    If you're carrying an 'extra' battery around as

    a hedge against failure to use a checklist, perhaps

    it would be more elegant to upsize the main battery,

    ditch the 'ohmygosh' battery and include some means

    for making sure the master doesn't get left on.



    A little buzzer on a low oil pressure switch works

    good . . . little irritating flashing lights work

    too . . .



    But adding more batteries for any reason only increases

    your battery maintenance time and costs by the same

    factor. The elegant solution has ONE battery and

    a failure mode analysis that confirms exceedingly

    low risk. If you've got an unused vacuum pump pad,

    TWO alternators and one battery (perhaps smaller than

    a 900) is about as reliable as you can get.



 

   Bob . . . 	




Bob,



I DO have both audio and visual (thanks to you) warnings of low voltage. 



But for the "forgot the master switch" problem I think you are right. It would be simpler (and save weight) to have an audio warning, like in a car. Since my EFIS will still be on after I turn off the engine I will investigate having it make some kind of cabin-audible noise based on low oil pressure, since I would have my headset off when I was leaving the airplane.



Mark

ceengland7(at)gmail.com
Guest

Posted: Fri Jan 03, 2020 3:23 pm Post subject: EFI current requirements

On Fri, Jan 3, 2020 at 4:15 PM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:



 	  Quote: 	
		     	  Quote: 	
		  The issue of AH ratings has been around as long as lithium battery tech. Since the typical duty of a battery in a motor vehicle is purely starting, the lithium guys have almost always used AH 'equivalent' ratings when it comes to the battery's ability to *start* an engine. 	


 Â  I don't think there was any misunderstanding about

 Â  the ratings. The 'equivalency' thing was about cranking

 Â  current . . . period. In the early days, they deliberately

 Â  omitted comparisons of battery capacity . . . which made

 Â  their marketing numbers for weight and size versus 

 Â  performance look better. My earliest conversations with

 Â  EarthX confirmed this.



  	  Quote: 	
		  Those of you planning on using EX batteries do need to be aware that the internal battery management system really is another failure point, and has failed in at least one case. If it decides that there are external problems, or the battery is near end-of-charge (whether its assumption is correct or not), it will disconnect the battery. Under the right conditions, with some, older design alternators, the load dump could cause an alternator failure. Not likely a risk with B&C alts, but many older internally regulated alternators will die in a load dump situation. 	


 Â  "Load dump" is nearly an non-existent phenomenon

 Â  and it would not happen due to the actions of

 Â  the BMS. Recall that the BMS breaks the output

 Â  as the battery is being discharged . . . if you

 Â  have a working alternator on line, then the battery

 Â  will be charging and the BMS will be happy. It would

 Â  never disconnect while a functioning alternator

 Â  was doing its job.



 

  	  Quote: 	
		  In an 'alternator out' situation, the EX *will* disconnect at some point, before the battery is fully depleted. Your call on use, but do know the failure modes if you use them.

 	
[large snip]



 

 Â  Bob . . .

	




There may be no misunderstanding among the engineers at the lithium battery companies, but respectfully, there has *always* been a misunderstanding among a great many *aviators* about actual capacity of commercially offered lithium tech vs SLA and/or wet cell lead acid. You seem to reinforce my point with,Â 

"In the early days, they deliberately

 Â  omitted comparisons of battery capacity . . . which made

 Â  their marketing numbers for weight and size versus 

 Â  performance look better. My earliest conversations with

 Â  EarthX confirmed this."

Â The recently referenced thread on the Vans Air Force forum proves that it's still the case. The original poster of that thread has been building electronic ignition and electronic injection systems for aircraft for at least a couple of decades, and he stumbled upon the knowledge while doing periodic load testing (that he obviously didn't do before putting the lithium tech battery of choice into service). This was not an EarthX aviation battery; it was one of the offerings from a motorsports company.

Â  To their credit, EarthX seems to have modified their aviation offerings and increased the cell size (count?) so that total energy does compare with the various SLAs they are marketing against. It did take some rather pointed, public comments on aviation forums for that to happen.Â  Â Â 



On the 'load dump' issue: The BMS in the EarthX (according to EX's own literature, and their rep who posts frequently on VAF) will disconnect the battery under what it considers an overvoltage charge condition, and IIRC, also when it thinks the battery is in danger of being excessively depleted, or too high a current demand is being placed on it. The very fact that the BMS *can* disconnect the battery (for whatever reason), should, it seems to me, require us to include that fact in failure mode analysis. If the BMS itself fails in a fashion that disconnects the battery, that's a new and different failure mode (which may come as a complete shock if one hasn't done his homework). If the BMS gets confused and thinks the alternator is in an OV condition, it may disconnect from the electrical system> load dump>potential alternator failure>dark airplane.

  People like me that have some electronics skill can set up an IR alt with OV protection for less than 1/2 the cost of just a B&C regulator.  A lot of us are still running internally regulated alternators, many of which likely still have 'prehistoric' regulators that are not immune to load dump issues because they are sourced from cars built back in the 1970s/1980s.  While load dumps might not be an every day occurrence, they do happen. Many years ago, I killed an alternator with an ill-advised switch flip, so I know it can happen. An EarthX battery mixed with one of those old school IR alternators does up the odds of a dark airplane, if failure modes aren't accounted for.

Charlie



Â Â

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