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Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 26321
Location: Livermore CA USA
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 Posted: Sun May 03, 2009 10:40 am Post subject: System Off Current Requirements... |
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Greetings,
Since all of the panel and internal wiring is done, I thought I do a "System Off" current draw check today. There is a "keep alive" buss coming off the VP-200 system that I have connected the GRT HX displays to as well as the Kenwood DNX8120 and a couple of other things. I've currently got the standard Concord 25RG-XC battery that Van's sells. With the VP-200 system "off", I'm measuring about 6ma of constant current draw.
My question is, how long is the standard battery going to last with this amount of draw?
Also, is the Concord 25RG-XC the best choice for batteries? I've got an IO-390 and the battery is mounted in the back of the my RV-8. Is this battery going to have the staying power to support the electronics I've got as well as crank the engine?
Thanks in advance for the advice.
Matt Dralle
RV-8 #82880
Wiring Done, Gear Next...
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nuckolls.bob(at)aeroelect
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| Posted: Sun May 03, 2009 11:18 am Post subject: System Off Current Requirements... |
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At 01:34 PM 5/3/2009, you wrote:
| Quote: | Greetings,
Since all of the panel and internal wiring is done, I thought I do a
"System Off" current draw check today. There is a "keep alive" buss
coming off the VP-200 system that I have connected the GRT HX
displays to as well as the Kenwood DNX8120 and a couple of other
things. I've currently got the standard Concord 25RG-XC battery
that Van's sells. With the VP-200 system "off", I'm measuring about
6ma of constant current draw.
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| Quote: |
My question is, how long is the standard battery going to last with
this amount of draw?
Since this battery is rated for service in aircraft
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(i.e. not a 20 hr rated but a 1 hr rate) then your
battery charge available to support keep alive loads
is much better than 24000/6 or 4,000 hours. In other
words, if the airplane is flown with some degree of
regularity, those loads are insignificant.
If you were going to park the airplane for several
months, then it would be a good idea to either disconnect
the battery in a fully charged state . . . or leave
a battery tender type charger attached for the duration
of storage.
| Quote: | Also, is the Concord 25RG-XC the best choice for batteries? I've
got an IO-390 and the battery is mounted in the back of the my
RV-8. Is this battery going to have the staying power to support
the electronics I've got as well as crank the engine?
|
You don't mention what your e-bus loads are and whether
or not you have more than one engine driven power source.
You need to match your e-bus endurance requirements against
your design goals for battery only operations. There
are RV-8's with rear mounted 18 a.h. battery and Figure Z-13/8
that perform to the owner's design goals . . . but without
knowing more detail about your goals and your system
configuration, real reasoned advice is not possible.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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echristley(at)nc.rr.com
Guest
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| Posted: Sun May 03, 2009 12:08 pm Post subject: System Off Current Requirements... |
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Robert L. Nuckolls, III wrote:
| Quote: |
If you were going to park the airplane for several
months, then it would be a good idea to either disconnect
the battery in a fully charged state . . . or leave
a battery tender type charger attached for the duration
of storage.
Just an idea. The battery on a Dyke Delta is accessed through an
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external panel near the rear of the aircraft. I built my access panel
out of one of those solar trickle chargers.
Two birds. One stone.
Wait. Should I be talking about knocking down birds with rocks on this
list?
--
http://www.ernest.isa-geek.org
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ceengland(at)bellsouth.ne
Guest
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| Posted: Sun May 03, 2009 12:42 pm Post subject: System Off Current Requirements... |
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Matt Dralle wrote:
| Quote: | Greetings,
Since all of the panel and internal wiring is done, I thought I do a "System Off" current draw check today. There is a "keep alive" buss coming off the VP-200 system that I have connected the GRT HX displays to as well as the Kenwood DNX8120 and a couple of other things. I've currently got the standard Concord 25RG-XC battery that Van's sells. With the VP-200 system "off", I'm measuring about 6ma of constant current draw.
My question is, how long is the standard battery going to last with this amount of draw?
Also, is the Concord 25RG-XC the best choice for batteries? I've got an IO-390 and the battery is mounted in the back of the my RV-8. Is this battery going to have the staying power to support the electronics I've got as well as crank the engine?
Thanks in advance for the advice.
Matt Dralle
RV-8 #82880
Wiring Done, Gear Next...
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Absolutely stunning panel. Of course, I could support all my flying
habits just on the interest on the money it must have cost. 
You shouldn't have any problem with engine start, and once it's running,
the alternator is what powers all your electrical goodies. As long as
the alternator is sized to power everything electrical & still have some
snort to charge the battery, you're good to go.
If the keep-alive buss is drawing 6mA (6 one-thousandths of one amp),
and the battery is a 25 ampere/hour battery (25 thousand mA/hr), then it
should theoretically last a bit less than 25,000/6=4,166 hours. With a
generous fudge factor, call it better than 3000 hrs if the battery is in
perfect condition and fully charged. Somebody check my math.
Have you done the 'dead alternator' analysis to see how long the battery
will keep your essential electrical stuff alive if the alternator fails
in flight? For that, you need the manufacturer's info sheet on how long
it will last at *your* essential equipment's current draw. (It's not a
linear function.)
Charlie
Charlie
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user9253
Joined: 28 Mar 2008
Posts: 1928
Location: Riley TWP Michigan
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Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 26321
Location: Livermore CA USA
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| Posted: Sun May 03, 2009 3:41 pm Post subject: System Off Current Requirements... |
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At 04:36 PM 5/3/2009 Sunday, you wrote:
| Quote: |
I see some space left on the panel that is not being used. What a waste!
I can imagine his radio transmissions:
Center: descend and maintain 7 thousand. Turn right heading 320 degrees. Contact approach control on 126.65.
Matt: Center, can you wait until the commercial? I do not want to miss this
good part on TV. [Laughing]
Joe
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Now, that's funny, right there...!
Matt
PS - And, btw, I'm saving that little space on the right hand side of the panel for an analog HOBBS meter. NOT. 
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Mon May 04, 2009 3:33 am Post subject: System Off Current Requirements... |
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At 03:03 PM 5/3/2009, you wrote:
| Quote: |
<echristley(at)nc.rr.com>
Robert L. Nuckolls, III wrote:
>
> If you were going to park the airplane for several
> months, then it would be a good idea to either disconnect
> the battery in a fully charged state . . . or leave
> a battery tender type charger attached for the duration
> of storage.
Just an idea. The battery on a Dyke Delta is accessed through an
external panel near the rear of the aircraft. I built my access
panel out of one of those solar trickle chargers.
Two birds. One stone.
Wait. Should I be talking about knocking down birds with rocks on this list?
|
Solar chargers should be applied with understanding
and some caution. These are rudimentary "trickle"
chargers without regulation. Some readers of this
forum many moons ago fitted solar chargers to their
hangar roofs and left them attached to the battery
for the duration of winter storage. They came back
to find the battery trashed.
AGM/SVLA batteries have exceedingly low self-discharge
rates. If stored fully charged, they should start your
engine a year later. But this thread started with
a query about keep-alive currents that are perhaps
2 to 5 times the battery's self discharge rates. These
are worthy of some external support if the airplane
is not going to be flown for several weeks to months.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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ixb(at)videotron.ca
Guest
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| Posted: Mon May 04, 2009 5:40 am Post subject: System Off Current Requirements... |
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So is there any way to use solar to maintain the charge on my RV9A? How
about connecting the panel to a 110V inverter and then back using a
good quality maintenance charger? Would the losses in the conversion to
110V and back be too great for the tiny currents generated by a
relatively small solar panel?
Ian Brown, Bromont, Quebec
,On Mon, 2009-05-04 at 06:32 -0500, Robert L. Nuckolls, III wrote:
| Quote: |
At 03:03 PM 5/3/2009, you wrote:
>
><echristley(at)nc.rr.com>
>
>Robert L. Nuckolls, III wrote:
>>
>> If you were going to park the airplane for several
>> months, then it would be a good idea to either disconnect
>> the battery in a fully charged state . . . or leave
>> a battery tender type charger attached for the duration
>> of storage.
>Just an idea. The battery on a Dyke Delta is accessed through an
>external panel near the rear of the aircraft. I built my access
>panel out of one of those solar trickle chargers.
>
>Two birds. One stone.
>
>Wait. Should I be talking about knocking down birds with rocks on this list?
Solar chargers should be applied with understanding
and some caution. These are rudimentary "trickle"
chargers without regulation. Some readers of this
forum many moons ago fitted solar chargers to their
hangar roofs and left them attached to the battery
for the duration of winter storage. They came back
to find the battery trashed.
AGM/SVLA batteries have exceedingly low self-discharge
rates. If stored fully charged, they should start your
engine a year later. But this thread started with
a query about keep-alive currents that are perhaps
2 to 5 times the battery's self discharge rates. These
are worthy of some external support if the airplane
is not going to be flown for several weeks to months.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
|
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kuffel(at)cyberport.net
Guest
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| Posted: Mon May 04, 2009 6:49 am Post subject: System Off Current Requirements... |
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Matt,
<< I built my access panel out of one of those solar trickle chargers.>>
<< Solar chargers should be applied with understanding
and some caution. These are rudimentary "trickle"
chargers without regulation. Some readers of this
forum many moons ago fitted solar chargers to their
hangar roofs and left them attached to the battery
for the duration of winter storage. They came back
to find the battery trashed. >>
You might wish to consult the article by Jim Weir in January 2007 Kitplanes
about building a smart solar charger.
Tom Kuffel
Whitefish, MT
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skywagon
Joined: 11 Feb 2006
Posts: 184
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| Posted: Mon May 04, 2009 9:23 am Post subject: System Off Current Requirements... |
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Tom is completely correct.... most so called 12 v. solar panels can go up as
high as 18 v. Even though the current is small from a small wattage panel
it can still gas out a 12 v. battery after time. Low power panels can be
easily regulated with a simple zener diode or other similar solid state
device. Just don't exceed the current that it can shunt. A panel with 0.25
amp of current should be capable of maintaining healthy batteries, but, it
must be regulated to not go over about 13.2 v while charging.
Dave
---
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