nuckolls.bob(at)aeroelect
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 Posted: Thu Sep 08, 2011 11:25 am Post subject: Initial experience with dual Odyssey PC680s powering RV-10 |
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At 06:18 AM 9/8/2011, you wrote:
So going back through the archives, it seems like my charging setup
would serve as a good ground power unit if the charger were upgraded
from a 2 amp "maintainer" type to a 10 amp "smart" charger like the
X10 Schumacher I recently picked up from Walmart.
Maybe. If the charger is no noisier than an alternator,
this might be useful.
It would power all or most of my panel setup and practice work,
prevent the batteries from getting deep discharged, and bring them up
to full charge pretty quickly once the load was removed.
Assuming that's right, the problem I'm having right now is that the
Schumacher doesn't seem to like to be connected to both batteries
simultaneously. It goes into some kind of blinking fault mode. Any thought?
(I'm going to check the model number again but recall "X10")
How are you connecting 2 batteries in parallel?
If it's Z-14 with all three contactors closed,
keep in mind that three contactors will waste about
2.5 amps of your charger/power-supply output.
If the charger is barfing . . . check the open-circuit
voltage of each battery while not connected to anything.
Most modern chargers will have an automatic rejection
feature for connecting to a badly discharged battery.
If either or both of the batteries is below 11 volts,
then they contain less than 5% of capable capacity.
A short term connection with a BEEFY charging source
might pump them up enough to allow a finish charge with
the automatic charger.
I've often used jumper cables to put a really dead battery
across a vehicle battery with the engine running. A couple
minutes is enough . . . then move it to the bench for
automatic charging.
Understand that TIME any battery spends in the lower regions
of rated capacity eats away at the battery's vital chemistry.
Batteries in normal service will last many years. But they
are similar to house plants. They will recover from a pretty
severe case of droopy leaves if you address the shortage of
water soon and in adequate quantity. Delay beyond a point
where living cells die off, and total recovery is impossible.
Continued performance is degraded if not terminated.
Visualize your battery as 6-cells rated at about 2.2
volts each . . . wired in series to form a "12-volt"
battery. Each cell is comprised of millions of micro-cells.
All are in parallel, each has a very high source impedance
(perhaps 1000 ohms), each contributes a tiny portion of
total capacity to store energy. Allow the battery to set
in a depleted or semi-depleted state and there is risk
for loosing a percentage of micro-cells. If you loose 1/2
of them, capacity drops by half and source impedance doubles.
This makes for a VERY soggy battery. For most purposes
in aviation, such a battery is no longer serviceable . . .
even if you manage to crank an engine with it.
There are many products that claim to 'recover' worn
out or abused batteries. Do a Google on "battery desulfator"
and you'll get thousands of hits. Check out the Concorde Battery
website for this document.
http://www.concordebattery.com/otherpdf/5-0171.pdf
On page 106 you will find a "conditioning charge"
procedure. This is a real sledge hammer approach that
has a limited value in recovering some batteries that
do not test strong enough for return to service.
I've seen similar procedures called out in countless
maintenance manuals. It's not a sure bet but it's
the most promising in this world of TV Infomercials
that offer, "the world's greatest battery charger and
recovery system."
The production lines at Beech are fitted with "trash
batteries" on little carts that are connected into
the airplane and then supported by a ground power cart.
The ship's flight battery doesn't get connected until
the airplane is out the door.
Bob . . .
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