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Initial experience with dual Odyssey PC680s powering RV-1

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nuckolls.bob(at)aeroelect
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Posted: Tue Sep 06, 2011 4:58 pm Post subject: Initial experience with dual Odyssey PC680s powering RV-1

At 07:55 AM 9/6/2011, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Kelly McMullen <kellym(at)aviating.com>



 Actually, a "standard" 35 series battery, as used in many certified planes with battery in the tail cone is only 29 amp hours(CB35A or RG35A) or less. The battery that I recall Vans recommending is either 22 or 24 amp hours (RG25  or RG25XC).

 	


    Ampere hour ratings of batteries can be exceedingly

    short on useful information. A battery's internal

    resistance can have a profound effect on DELIVERED

    energy. Here is an exemplar energy delivery plot on

    a 33 a.h. RG battery:



 [img]cid:7.1.0.9.0.20110906194510.01dcdb28(at)aeroelectric.com.0[/img] 



    Note that it will deliver 33 a.h. at a 20 hour discharge cycle

    loaded at only 1.65 amps. When loaded with say, 6.6A of endurance

    loads, you get just over 4 hours or 26 a.h.  Load it heavier to like

    53 amps an the critter tosses in the towel in 20 minutes or 1/3 hour

    for a 'rating' of about 17 a.h.



    A flooded battery would not do as well as this AGM example.



    So there are TWO characteristics you're interested in for

    assessing a battery's flight worthiness:



    Delivery at heavy loads for cranking and delivery at moderate

    loads for alternator-out endurance. But any notions that

    paralleling a couple of batteries will combine for a 'name

    plate rated' level of performance is kind of wishful thinking.



 

   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Sep 06, 2011 5:07 pm Post subject: Initial experience with dual Odyssey PC680s powering RV-1

At 08:54 AM 9/6/2011, you wrote:

  	  Quote: 	
		  (my original post seems to have been  blank - pardon if this is a re-post with some additional info)

 

 Some data:

 Using the HF Battery Load Tester with a 200amps load applied at the disconnected starter lead,  I got  7.5 volts on one battery, 8 volts with both batteries.  That is short of the 9 volts you suggested I should get,

 I used a 6" 8awg lead for the ground attached to one of the starter's mounting bolts.  

 I saw a similar results when I went to a ground block directly on the firewall (I think this block has a 8awg line running back to the batteries in addition to it's airframe connection). 	


  Okay, those batteries are crippled by virtue

  of discharge, worn out or both.



 

  	  Quote: 	
		  My plan is to repeat this test tomorrow after re-charging the batteries.  I'll also test the battery directly.  Assuming I get the same result, and the battery is good,  it appears that I have some deficiency in either the  ground or power circut for the starter.



 I'll try to use the tester to work my way from the starter back thru the power circuit and the ground connections. 	


   Might be a waste of time. If you can't get 400-700

   amps from a freshly charged battery, then you're

   starting the race with holes in the soles of your

   sneakers. 



  	  Quote: 	
		   



 Some more data:

 After charging overnight and working my way back towards the battery, I hooked up the tester to the battery side of the starter solenoid and the ground stud on the firewall.  I got 8.5 volts going to 8.0 volts after 15 seconds with a 200 amp load.



 Then I took the tester directly to the battery - 8.5 volts with a 200amp load (??!!).  Bad Battery?  I think not, so... 	


   I think so. 



 

  	  Quote: 	
		  Yesterday, I went out an bought Schumacher charger at Walmart.  I had been using another 'maintainer' type charger (I'll get the brand and specs later).  With all this electrical work, I felt like I needed something with more options like fast/slow charge.  I charged up some older batteries including my old 680s.  One battery was clearly bad per the tester and wouldn't take a charge.  The other one seemed good.  And after a full charge, it tested 10 volts (at) 200amps for 15 seconds.  That's more than I was getting with my 'fully charged' new battery. 	


   Those batteries are toast.



 

  	  Quote: 	
		  I think I have some charging issues.  I suspect at this point that the 'maintainer' type charger is not fully charging my 2 batteries for some reason.  That combined with the fact that almost every flight is followed by much battery draining panel work followed by charging. 	


    What kind of "maintainer type charger" are you

    using? The Schumacher will do the job . . . assuming

    the battery is willing and able to take on the energy

    offered.



  	  Quote: 	
		  So, right now I'm using the new charger on the batteries in the aircraft.  I suspect when finished, I'll be getting 10 volts (at)200 amps at the terminals, and close to that at the starter. 	


    Those batteries are essentially shot. Your experience

    goes to my oft repeated recommendations for periodic

    load and cap chencking of the ship's batteries. Given

    that you have Z-14, perhaps cap-checks are not so important.

    You're not going to depend on batteries for endurance

    issues. But LOAD checking after an over-night on the

    charger will tell the tale without ever turning your

    master switch on.



 

   Bob . . .    [quote][b]

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