Today's Message Index:
----------------------
1. 07:06 AM - Re: Starters (Robert L. Nuckolls, III)
2. 07:11 AM - Re: Re: Three Questions on Z-07 (Robert L. Nuckolls, III)
3. 08:22 AM - Re: Re: Three Questions on Z-07 (Ken Ryan)
4. 11:21 AM - Re: Three Questions on Z-07 (user9253)
Message 1
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At 02:15 PM 3/15/2019, you wrote:
>That is a very common battery, any battery store will test it for you.
>
>On Fri, Mar 15, 2019, 13:31 Steve Kelly
><<mailto:amsk22@gmail.com>amsk22@gmail.com> wrote:
>Bob,=C2 Thank you for the reply.=C2 I will try to
>get out to the hanger early next week and check
>the voltage readings.=C2 The battery is a PC680
>at three months old.=C2 =C2 Do you have a method
>you would suggest to do a load/capacity check on it.
That's a pretty fresh battery . . . this suggests
the problem is elsewhere. However, in answer to
your testing questions, I'll suggest that
every owner of an aircraft should also own
something like this
https://tinyurl.com/yag4529y
This LOAD tester allows you to load the battery
to an output of 9 volts while waiting for the
15 second timer light to go out. Note the current
at the end of 15 seconds . . . it should be in
excess of 200A for small engines, 300A for larger
engines. This test confirms the battery's avbility
to grunt the extra-ordinary demands for cranking
the engine.
A CAPACITY test seeks to quantify the battery's
ENERGY content . . . which is entirely separate
from the capability to grunt a cranking load.
There are some rather small batteries that have
demonstrated the ability to crank a turbine
engine
https://tinyurl.com/yye6znqp
But this product wouldn't run the aircraft's
critical systems for very long after the
alternator quits. There are dozens of 'tiny'
products that offer a similar utility
https://tinyurl.com/y2hzkq9l
The way to cap check your battery is to set
up your panel to operate your Plan-B (alternator
out) electrical loads and monitor battery voltage
with a voltmeter. The time it takes to reduce
battery voltage to 10V (the lower limit for
your avionics to operate).
For example, a NEW PC680 has the following
ENERGY delivery capability.
Emacs!
Assume a 4A endurance load. The curves say you're
good to 3 hours. Here you have to tailor the question
to match your own endurance requirements. If one hour
meets your own Plan-B design goals, then according
to the chart, the new battery is good for about 10A.
Actually, you would want to rate the battery for about
8A given that maintenance protocols suggest replacing
the battery at 75% of new capacity.
Then there's the real-life test . . . turn on the
goodies, start the clock, watch the voltage, measure
the time then recharge the battery. If that time
is equal to or greater than your design goals, then
you're good to fly.
How old is your starter? It MIGHT be that brushes
and/or commutator are worn to the point of producing
degraded performance.
Bob . . .
Message 2
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| Subject: | Re: Three Questions on Z-07 |
At 01:52 PM 3/15/2019, you wrote:
>
>I would leave that drawing available unless there is some unknown failure
>mode. There are different strokes for different folks. Someone will have a
>perceived need that Z-07 will fill.
"Perception" is the key term here . . . where
I have to ask, what are the failure modes being
addressed and what are the numbers that support
the selection of hardware.
A finely tuned Z07 might call for a 24 a.h.
engine battery and a 10 a.h. device for
avionics. But to what end? BOTH batteries
are expected and maintained to meet the same
design endurance. What then is the value for
having two batteries versus one battery
with the same energy content?
I don't recall the discussions now that
prompted the Z07 explorations . . . but
I don't see that it makes sense now.
Bob . . .
Message 3
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| Subject: | Re: Three Questions on Z-07 |
The best reason I can think of to have two batteries is to get the engine
started if the primary battery doesn't get the job done, and you happen to
be on some remote Alaskan gravel bar. Many modern aircraft cannot be hand
propped.
On Sat, Mar 16, 2019 at 6:15 AM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 01:52 PM 3/15/2019, you wrote:
>
>
> I would leave that drawing available unless there is some unknown failure
> mode. There are different strokes for different folks. Someone will have
> a
> perceived need that Z-07 will fill.
>
>
> "Perception" is the key term here . . . where
> I have to ask, what are the failure modes being
> addressed and what are the numbers that support
> the selection of hardware.
>
> A finely tuned Z07 might call for a 24 a.h.
> engine battery and a 10 a.h. device for
> avionics. But to what end? BOTH batteries
> are expected and maintained to meet the same
> design endurance. What then is the value for
> having two batteries versus one battery
> with the same energy content?
>
> I don't recall the discussions now that
> prompted the Z07 explorations . . . but
> I don't see that it makes sense now.
>
>
> Bob . . .
>
Message 4
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| Subject: | Re: Three Questions on Z-07 |
Sudden battery failure is rare, but it has happened . . . to me. My PC680
cranked the engine just fine. Then later, when I reduced throttle to land, the
EFIS rebooted. The EFIS did not have an internal backup battery at the time,
but now does. I sent the battery to Bob N. and he found a broken
internal weld. I still only have one battery not counting the backup batteries
inside of avionics.
Each builder will wire their airplane the way that they want to. All we can
do is educate them so that they can make informed decisions. A friend
installed an avionics switch in his panel. I told him that the need for that
switch is based on an old wives tale that has been handed down from
instructor to student. And I told him that switch makes his airplane less safe.
But I was only one person. Several others told my friend to install that
switch. So he did.
Some builders are willing to sacrifice money and performance for their
peace of mind. All we can do is look over their shoulder and point out
anything that is dangerous. If a builder wants to install two large
batteries, he will do it whether there is a Z figure for it or not.
Without guidance, his architecture could have a design flaw
--------
Joe Gores
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http://forums.matronics.com/viewtopic.php?p=488105#488105
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