dave.saylor.aircrafters(a
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 Posted: Sun Sep 04, 2011 1:32 pm Post subject: Initial experience with dual Odyssey PC680s powering RV-10 |
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Bill,
You might try moving one of the 680s closer to the firewall and tie
into the large no. 2 cable up there. Also, triple check all the
connections to make sure they're really solid.
Are you using a ground cable or strap back from the engine case to the airframe?
FWIW, I grounded my aft-mounted 925 to the vertical edge of the
baggage floor that supports the tailcone closeout. I used a braided
grounding strap. Works great.
Dave Saylor
AirCrafters
140 Aviation Way
Watsonville, CA 95076
831-722-9141 Shop
831-750-0284 Cell
On Sun, Sep 4, 2011 at 12:58 PM, Bill Watson <Mauledriver(at)nc.rr.com> wrote:
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I've just flown the first dozen hours with my new RV-10 and am a bit
disappointed with one design decision, that is, the use of dual PC680s.
When starting with a single new PC680, I don't seem to have the cranking
power I'd like to have.
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.
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.
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.
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....
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.
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
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