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EFI- two batteries vs. two alternators

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shoskins(at)MCHSI.COM
Guest

Posted: Tue Mar 04, 2008 5:25 am Post subject: EFI- two batteries vs. two alternators

All,

 

 I have a 1,600 hr. Q-200 that I am retrofitting to be an all electric airplane.  Chucked all the steam gauges for a Dynon Flightdeck D-180 and I am going with a RWS all electronic fuel injection and ignition system.  I have a Continental O-200 with B&C 30a alternator installed on the rear of the engine.  With the EFI & fuel pump, my normal operation current needs will be about 8 amps.  

 

 I am in in the decision process for two batteries, vs. two alternators.  I may have room for the B&C standby alternator on the vacuum pad, but I'm not 100% sure.  



 Since the G.W of this plane is only 1,100 lbs, I really need to keep the weight down (favors the alternator).  On the other hand, the alternator costs three or four times that of a second battery.  On the other hand, It may be difficult to find room for a second battery.

 

 What say you all?

 



Sam Hoskins

 Quickie Blog

 Quickie Website

  [quote][b]

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jon(at)finleyweb.net
Guest

Posted: Tue Mar 04, 2008 6:08 am Post subject: EFI- two batteries vs. two alternators

Hi Sam!

  

 It is very kewl to see all the work you are doing (Q-Talk)!

  

 I think it is important to define/select the mission that you want your airplane to accomplish.  If it is to finish the planned x-c flight (as Bob has discussed) then a standby alternator is likely to be your best option.  If it is to catch the "problem" and terminate the flight uneventfully but soon, then you may arrive at a different decision.  Knowing your history (coast to coast in a single day, multi-hour races, many long x-c), I would suggest that your best bet is a small backup battery (8-ish amps) and the backup alternator.

  

 Jon

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nuckolls.bob(at)cox.net
Guest

Posted: Tue Mar 04, 2008 6:20 am Post subject: EFI- two batteries vs. two alternators

At 07:21 AM 3/4/2008 -0600, you wrote:



 	  Quote: 	
		  All,



I have a 1,600 hr. Q-200 that I am retrofitting to be an all electric 

airplane.  Chucked all the steam gauges for a Dynon Flightdeck D-180 and I 

am going with a <http://www.rotaryaviation.com/eficont.html>RWS all 

electronic fuel injection and ignition system.  I have a Continental O-200 

with B&C 30a alternator installed on the rear of the engine.  With the EFI 

& fuel pump, my normal operation current needs will be about 8 amps.



I am in in the decision process for two batteries, vs. two alternators.  I 

may have room for the B&C standby alternator on the vacuum pad, but I'm 

not 100% sure.



Since the G.W of this plane is only 1,100 lbs, I really need to keep the 

weight down (favors the alternator).  On the other hand, the alternator 

costs three or four times that of a second battery.  On the other hand, It 

may be difficult to find room for a second battery.



What say you all?


	


   What are you design goals for endurance? If

   8A is your running loads and you have a well

   maintained 17 a.h. battery, then assuming you

   cannot do any judicious load shedding for

   and endurance mode, then according to



http://www.aeroelectric.com/Pictures/Curves/17AH_12V_Capacity_vs_Load.gif



   your 8A load will run you about 90 minutes.

   3X the "faa blessed" battery-only ops minimums.

   If you carry hand-helds and a flashlight

   like I do, then perhaps your endurance load

   shedding can extend this time out further.



   Throwing a question like this out to the

   List will get you a host of responses that

   tend to describe the worst fears of those who

   choose to respond . . . NONE of which will

   be based on a considered analysis for

   the size and kind of hardware you need to

   meet your mission profile and performance

   goals.



   You are the very best individual to make this

   assessment based on the support of simple-

   ideas that go into the crafting of your

   final invention.



   We've got a bucket full of ideas, tell us how

   they might serve you?



   Bob . . .

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n8zg(at)MCHSI.COM
Guest

Posted: Tue Mar 04, 2008 6:21 am Post subject: EFI- two batteries vs. two alternators

Sam - 

  

 The SD-8 is smaller, lighter, has zero maintenance  cost, will deliver it's promised 8 amps indefinitely, and you should only need  to buy one.

  

 How often will you replace the $125 second battery, and how  long will it take you to spend more on batteries than the "expensive"  SD-8?

  

 I'd  mount the SD-8.  You'll get a few extra pounds of usable payload, lower  true cost of ownership, and if the main alternator ever quits making electrons,  you'll never have to wonder if the battery will last long enough to get you to  your intended destination comfortably.

  

 Neal

 RV-7 N8ZG  (baffles)

 Z-13/8



 

 

 

All,



I have a 1,600 hr. Q-200 that I am retrofitting to be an  all electric airplane.  Chucked all the steam gauges for a Dynon Flightdeck  D-180 and I am going with a RWS all electronic fuel  injection and ignition system.  I have a Continental O-200 with B&C 30a  alternator installed on the rear of the engine.  With the EFI & fuel  pump, my normal operation current needs will be about 8 amps.  



I am  in in the decision process for two batteries, vs. two alternators.  I may  have room for the B&C standby alternator on the vacuum pad, but I'm not 100%  sure.  



Since the G.W of this plane is only 1,100 lbs, I really need  to keep the weight down (favors the alternator).  On the other hand, the  alternator costs three or four times that of a second battery.  On the  other hand, It may be difficult to find room for a second battery.



What  say you all?

Sam Hoskins

Quickie  Blog

Quickie Website

[quote] [b]

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Ed Anderson

Joined: 10 Jan 2006
Posts: 475

Posted: Tue Mar 04, 2008 7:04 am Post subject: EFI- two batteries vs. two alternators

Hi Sam

  

 Flying an "all electric" aircraft myself for the past 10  years, I'd like to provide you my viewpoint (and that is all it is).    I first started out with 1 alternator and two 22 lb 25 AH Concord RCG batteries  for a total of 44 lbs of battery power.  After carrying that weigh around  for a couple years, I replaced them with two 14 lb 17 AH Odyssey batteries  shedding quite a bit of weight.  After flying a couple more years with the  two Odyssey and never in all those years having need for the standby battery (I  did use it to aid starting on cold mornings), I removed one and now fly with the  single 17 AH 14 lb Odyssey which I swap out every 2nd year.

  

 With battery technology improving, I may in the future add  a small 7 AH battery as an emergency back up, but given the lesser load  capability of your platform, you may want to give more study and thought to your  basic electrical power concept.  As someone else has already mentioned, it  needs to fit your typical flight profile.

  

 FWIW

  

 Ed

  

  

 [quote]   ---

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_________________
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com

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