Today's Message Index:
----------------------
1. 05:51 AM - Re: Battery charging (Steve Kelly)
2. 09:06 AM - Re: Re: Battery charging (Robert L. Nuckolls, III)
3. 11:52 AM - Re: Battery charging (Steve Kelly)
4. 02:28 PM - Re: Re: Battery charging (Robert L. Nuckolls, III)
5. 03:24 PM - Re: Battery charging (user9253)
6. 06:09 PM - EFIS power switch - part 2 (Scot)
7. 06:45 PM - Re: Battery charging (Steve Kelly)
8. 07:39 PM - Re: Re: Battery charging (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Battery charging |
Just a followup on this thread.
The question was how to charge an "accessory" battery off the main buss.
I ran about 16' of #20 wire, with the schottky diode and a 7.5 amp fuse in line
from the main buss to batt #2.
Since the airplane is not running yet , I used the charging system on my car
to test.
With the #2 battery discharged down to 10.7 volts the draw was 5.7 amps. The
initial surge was 6.8. At 12 volts the draw was 4.2 amps. So it looks like
this will work.
Increasing the wire size allowed a bigger fuse, but also drew more amps, which
I don't particularly want.
A simple way to make this work.
Thanks for all the help on this, Steve
--------
Steve
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=459832#459832
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| Subject: | Re: Battery charging |
At 07:45 AM 8/24/2016, you wrote:
>
>Just a followup on this thread.
> The question was how to charge an "accessory" battery off the main buss.
> I ran about 16' of #20 wire, with the schottky diode and a 7.5
> amp fuse in line from the main buss to batt #2.
> Since the airplane is not running yet , I used the charging
> system on my car to test.
> With the #2 battery discharged down to 10.7 volts the draw was
> 5.7 amps. The initial surge was 6.8. At 12 volts the draw was 4.2
> amps. So it looks like this will work.
> Increasing the wire size allowed a bigger fuse, but also drew
> more amps, which I don't particularly want.
> A simple way to make this work.
Let's back up a bit. What accessories
are on your "aux bus"? How big is the
second battery?
Bob . . .
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| Subject: | Re: Battery charging |
Bob,
The second battery is a small 9 ah sealed lead acid batt. The kind with 2 fast-on
tabs to connect to. It's purpose is to operate a few things on the ground,
like comm, efis, cabin lites, cigarette liter outlet for charging phone, i-pad.
These and some other items are powered by the aux bus. The other items would only
be used in flight.
The aux bus is powered either by the main bus in flight or by the small battery
while on the ground. An on-off-on switch selects the source. If needed, battery
#2 could also power these items in flight.
I have been charging it with a charger and wanted a way to do it when the engine
is running.
Another question I have here is if I changed to a larger battery, say a 15ah,
would it draw more amps than the current one.
Steve
--------
Steve
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=459845#459845
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| Subject: | Re: Battery charging |
At 01:38 PM 8/24/2016, you wrote:
>
>Bob,
> The second battery is a small 9 ah sealed lead acid batt. The
> kind with 2 fast-on tabs to connect to. It's purpose is to operate
> a few things on the ground, like comm, efis, cabin lites, cigarette
> liter outlet for charging phone, i-pad.
>These and some other items are powered by the aux bus. The other
>items would only be used in flight.
>The aux bus is powered either by the main bus in flight or by the
>small battery while on the ground.
What is the power demands for all this stuff . . . and
how long would you expect to operate all of it
without running the engine.
In other words, what is the predicted battery life
for running the aux bus with the battery you have?
> An on-off-on switch selects the source. If needed, battery #2
> could also power these items in flight.
>I have been charging it with a charger and wanted a way to do it
>when the engine is running.
Okay, what size is your main battery . . .
and what kind of engine?
> Another question I have here is if I changed to a larger battery,
> say a 15ah, would it draw more amps than the current one.
Yes . . . but that cart is WAAaayyy in front of
the horse. I'm exercising the old "Short Circuit" ploy,
"Input, I need input."
Bob . . .
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| Subject: | Re: Battery charging |
Steve K,
Below is a link to an electrical drawing that I drew some time ago. Two separate
master switches could be used instead of one double pole switch as shown.
The circuit features a small brownout battery and E-Bus which are isolated during
engine start.
I would wire the aux battery with 14 AWG and a 15 amp fuse and not be concerned
with charging current.
Good going with your test using 16' of #20 wire. That convinced me that a resistor
is not needed to limit charging current.
https://drive.google.com/file/d/0B7ZTG2VpCuDRSVNVa3JwUmFuMzQ/view?usp=sharing
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=459851#459851
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| Subject: | EFIS power switch - part 2 |
Rather than hijack the previous thread I thought it prudent to start a new discussion.
My RV-7 has Dynon background devices (ADAHRS, autopilot panel, etc) connected to
an Advanced Flight System EFIS. The backup power supply for the AFS EFIS is
a TCW battery that will also power the Dynon devices connected to the Dynon network.
My intent was to install an 8 Amp secondary alternator to my vacuum pad for emergency
backup power. With the TCW battery I had hope to have the option of driving
the EFIS and Dynon network powered devices to the backup battery via a switch.
That would allow the secondary alternator to support radios and any lighting
I chose to leave on in that situation.
However the TCW battery system has an internal device that allows power to be delivered
when the system voltage drops below 11.5 volts. Herein lies my problem.
If I activate the secondary alternator via a field switch the voltage will
not drop below 11.5 volts therefore the battery would not deliver power to the
EFIS.
I suppose I could switch "off" the battery, that is to say disconnect it from the
buss, and then disconnect the EFIS via a second switch. Not a complex solution
but not an elegant one either.
I do not know of another solution, maybe the brain trust here could devise an elegant
solution that is not prohibitively expensive. I know I could just install
a larger secondary alternator but I would like to explore this option fully
before abandoning it completely.
Thank you for your assistance.
Scott
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=459856#459856
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| Subject: | Re: Battery charging |
Okay, some more info.
I have a glastar with an O-320 and a B&C 40 amp alternator and LR3C.
The main battery is an Odyssey 680 mounted on the firewall.
Battery #2 is the 9 ah located in the back behind the baggage compartment. A #14
wire runs from batt #2 forward to the on-off-on switch, then to the aux bus.
The charging wire is a separate #20 with the diode that runs from the main bus
to Batt #2.
The main current draws are the com- .6A recieve and 3A transmit, and the GRT
Sport. Don't know the draw on this offhand, it has a 3A fuse. Cockpit lite is
a small led. Other equipment in the panel is a GTX327 and a GRT EIS4000.
I have been doing test and setup on the com and flight display but haven't paid
attention to the time to discharge. If I got an hour that would be plenty.
Not planning to fly IFR. At least not intentionally.
Steve
--------
Steve
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=459857#459857
Message 8
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| Subject: | Re: Battery charging |
At 08:42 PM 8/24/2016, you wrote:
>
>Okay, some more info.
>I have a glastar with an O-320 and a B&C 40 amp alternator and LR3C.
>The main battery is an Odyssey 680 mounted on the firewall.
>Battery #2 is the 9 ah located in the back behind the baggage
>compartment. A #14 wire runs from batt #2 forward to the on-off-on
>switch, then to the aux bus. The charging wire is a separate #20
>with the diode that runs from the main bus to Batt #2.
> The main current draws are the com- .6A recieve and 3A transmit,
> and the GRT Sport. Don't know the draw on this offhand, it has a
> 3A fuse. Cockpit lite is a small led. Other equipment in the
> panel is a GTX327 and a GRT EIS4000.
> I have been doing test and setup on the com and flight display
> but haven't paid attention to the time to discharge. If I got an
> hour that would be plenty.
How about putting an ammeter in the line,
turn all the goodies on and measure it?
But assuming 5a, you can certainly expect
a hour of support from this battery.
But why a 9 a.h. battery at about 8 pounds
when you can have UNLIMITED support of
those same loads and have 3A left over . . .
for about 1/2 the weight?
An SD-8 on your vacuum pump pad will
give you 8A+ at cruise. If you had Z13/8
installed, simply closing the alternate
feed switch would give you an hour of
ground ops and still start the engine.
Better yet, the design problems you're
wrestling with go away along with the
preventative maintenance and periodic
replacement costs of a second battery.
If it were my airplane with a un-used
vacuum pump pad, Z13/8 would be my first
choice. It's a two-layer system with
exceedingly low risk.
Bob . . .
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