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Old 01-26-2021, 05:46 PM
newt's Avatar
newt newt is offline
Join Date: Jan 2011
Location: Sydney, Australia
Posts: 384
Default G3X Touch Power

Working through some final details here:

The GEA24 and the GDU displays have "Aircraft Power #2" inputs.

Section in the G3X Touch Installation Manual mentions the use of third party backup power systems, or integration of a backup battery into the aircraft electrical system.

I want to make sure that the system is adequately powered through transient voltage sags at engine start to ensure reliable oil pressure indication.

My current thinking is to use a small backup battery (alarm system gel cell or similar) on Aircraft Power #2 on the GEA and GDU, wired to the aircraft's main bus through a diode so that it can accept charge but can't power anything else.

Is that reasonable? Short of a full dual-bus architecture, how else have folks been working through this?

- mark
[ Paid up on 3 Feb 2020 ]
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Old 01-26-2021, 07:36 PM
PilotjohnS PilotjohnS is offline
Join Date: Jan 2016
Location: Southwest
Posts: 1,283
Default Keep alive

My second power input is from my keep alive power per the G3x installation manual; it comes from the GAD27. You have one of those, dont you?

I dont have a dual bus nor a dual battery, except a small battery integrated into the G5.
John S

WARNING! Information presented in this post is my opinion. All users of info have sole responsibility for determining accuracy or suitability for their use.

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Old 01-26-2021, 09:09 PM
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newt newt is offline
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Location: Sydney, Australia
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No, the aircraft has manual flaps and trim, there's no GAD27 in this installation.

- mark
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Old 01-26-2021, 09:26 PM
kyhunting kyhunting is offline
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Old 01-26-2021, 10:50 PM
Touchdownzone Touchdownzone is offline
Join Date: Jan 2011
Location: Switzerland
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a backup battery charged by the main bus via a diode is exactly what I did on my G3X touch installation.

Add a CB before the diode and a (backup-) power switch on the output side and you will be able to isolate the backup battery from the rest of the electrical system in case you need to do it.

Using a set of blade type fuses I was able to build a simple dual bus system that powers the essential stuff on my panel.

I used a 5Ah lithium battery as a backup, works really well.

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Last edited by Touchdownzone : 01-26-2021 at 10:57 PM.
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Old 01-26-2021, 11:49 PM
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newt newt is offline
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Perfect, that's pretty much exactly where my mind has been heading. Very pleased to hear it's gone well for you!

- mark
[ Paid up on 3 Feb 2020 ]
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Old 01-27-2021, 08:57 AM
lr172 lr172 is offline
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Location: Schaumburg, IL
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My avionics are off during start up, though I do have a dual bus on the 10. I don't really see a need for the instruments during the 15 seconds after start up while the EFIS boots. The chances of oil pressure being fine at last shut down, yet not working on the next start up are so low That I am not sure they can be measured. Failures related to start/stop, while relevant to many things is not IMHO relevant to the oil delivery system. I would not add 2-3 lbs of dead weight for this purpose. Better to install a cheap oil pressure switch and tie it to an LED. I have this on the 6, mostly to insure that I don't leave the master on a shut down.

I suppose if you think that you are the type to forget to put oil back into the engine after an oil change, this is probably a necessary function.

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Last edited by lr172 : 01-27-2021 at 09:02 AM.
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Old 01-27-2021, 09:14 AM
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Brantel Brantel is offline
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I also used a sealed lead acid "alarm" battery as by backup power source for the G3X system. It has its own switch and is charged off the main bus thru a Schottky diode and a current limiting resistor.

Works great. I have replaced it once as a preventative measure.

My G5 also has its own battery for when stuff really goes bad.
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