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Initial experience with dual Odyssey PC680s powering RV-10

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nuckolls.bob(at)aeroelect
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Posted: Mon Sep 05, 2011 1:27 am Post subject: Initial experience with dual Odyssey PC680s powering RV-10

Unless the battery is fully charged, it just barely turns over the 

first compression stroke on a cold engine (IO-540).  If it does turn 

over, it cranks fine but sometimes it takes several tries to get over 

the first compression stroke.



    Do a load test on the battery to make sure it's

    good. Use legacy automotive load tester to drag

    battery down to 9 volts for 15 seconds. Read

    current needed to do this at the end of 15 seconds.

    Should be 400 amps or better . . . most new 18 a.h.

    batteries are good for more.



At the same time, my EAA Tech Counselor has been working on a rear 

battery for a Citabria.  He used the certified version of the 680 but 

found the same situation.  Now he is in the process of changing it 

out for the same reason.



    Did he check this battery independently of

    airplane issues?



If I crossfeed the 2 batteries, I get better cranking performance but 

again, unless both batteries are fully charged, I'm likely to cause a 

re-boot of the 3 GRT HX screens powered by the 2nd battery.



At this point, I'm thinking I need to change my battery configuration 

to include 1 PC925 for cranking.  But doing so will lose the periodic 

interchange capability I was after.



    When B&C started handling the svla/rg/starved electrolyte

    batteries many moons ago, it was discovered that they

    would out-perform their flooded counterparts that had

    twice the capacity.



I'd be interested in comments or suggestions.  If you are planning 

something similar, I'd say "beware" at this point.   Here's some more 

background....



    There's been some mention of the extra cranking

    current demands of starters supplied on Lycoming

    engines. It would be VERY interesting to do a swap

    out for a B&C starter as an experiment. I can probably

    arrange to have one shipped to you at no cost

    if you're willing to do the work.

My RV-10 has the batteries installed behind the cargo area with (1) 

2AWG cable feeding the starter from 1 or both batteries.  A 2nd 8AWG 

cable carries the rest of the power forward.  The batteries are both 

grounded close to where they are located and no separate ground cable 

is used.  I followed Bob's grounding advice  pretty closely.



What I was after with the Z-14 was the ability to run most of the 

panel on one battery without the engine running. And then to have a 

second battery capable of most engine starts.  Linking the batteries 

together providing an option for tough starts or partially discharged 

batteries.



Why run the panel?  I've been in a couple of situations where I've 

had to compromise between running the avionics for extended periods 

or conserving power for a  start.



   A starting operation should not demand more than

   a few percent of a battery's total capacity. If you

   have sluggish starter performance, the problem

   is probably not related to battery size.



What I also envisioned was a panel with as few switches as possible 

(Z-14 req'd switches not withstanding) and as few breakers as possible.



So it is a fuse-centric design, with 4 breakers and no avionics 

master or separate on/off switches for any of the panel stuff.  I 

really like the result.  However, I've already found myself having to 

crossfeed the batteries for a start which caused me to lose my engine 

instrumentation on the GRT HX display while it re-booted.



So, I really like the design except for not having enough cranking 

juice on a single battery.  I'm thinking  the next size Odyssey on 

the starter will  fix it but cost me 10.5 lbs (in a good W&B spot), 

interchangeability, and the need to design a new battery mount.



Bill "really loving the new '10" Watson



    I'd really like to see the outcome of a

    swap-out experiment.

    Bob . . .





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Mauledriver(at)nc.rr.com
Guest

Posted: Wed Sep 07, 2011 5:56 pm Post subject: Initial experience with dual Odyssey PC680s powering RV-10

That's exactly what I was trying to say.  From what I'm beginning to     understand, it's bad for the batteries.  I'm not using any kind of     power supply other than the 2 batteries hooked to a 'trickle'     charger.  Bad stuff.

     

     I'm still into a lot of panel configuration work and I'm still     depending on the flight batteries for that work.  Now that I'm     flying, it's probably not so damaging.

     

     I thought that hooking up the 10 amp Schumacher charger to my 2     batteries during this work might be a viable solution.  But it     appears that the Schumacher has enough 'smarts' to see that there     are 2 batteries involved and it goes into error mode for some     reason.

     

     Bill "now that the weather has cleared, we're going back to flying"     Watson

     

     On 9/7/2011 8:35 PM, Timothy Farrell wrote:

     [quote]Bill,

       

       This particular comment got my attention:

       

        	  Quote: 	
		  [b]"That combined with the fact that almost every flight is 

      followed by much battery draining panel work followed by charging."

[/b]I recall recently reading that draining the power of the Odyssey batteries by doing service items such as long database upgrades and gear swings is particularly bad for them.  I don't know how much panel work you got into, but it is possible that there was some damage caused this way by not using an APU.

-Tim



	
     [b]

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