Panel power with engine off

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Kynadog

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Kynadog
I’m new to having a glass panel and know precious little about avionics and electrical systems, so this may be an obvious question, but how do you supply power to a glass panel (so that you can install database updates, configure screens, etc.) with the engine off? Can you just put a trickle charger on the battery and then turn on the battery half of the master rocker switch?


If this has been asked and answered, can someone direct me to the link? I couldn’t find it via a search.

Thanks in advance.
 
Kynadog said:
how do you supply power to a glass panel (so that you can install database updates, configure screens, etc.) with the engine off?
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Things like that should only take a few minutes. I just turn on the battery half of the master switch and do it. Perhaps pull breakers on stuff not needed beforehand just to be safe. Also, be sure the plane isn't sitting for too many days before the next flight. If you battery can't handle a few minutes of configuration and database updates then it's probably near the end of its life.
 
most glass panels have a backup battery that you can boot the system up on. on my dynon system i do all of that on backup power then go fly VFR to recharge the backup battery. the only thing that cannot be done on the backup is to install new system software, that must be on ships power, but I have never run the battery down that far loading software.
 
If you have access to an external power source, it takes some of the pressure off to move quickly when performing database updates, checking lights and flaps on preflight, etc.. Also good to have if you want to spend time one the ground learning your avionics.
 
Kynadog said:
how do you supply power to a glass panel (so that you can install database updates, configure screens, etc.) with the engine off?
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Your options are dependent on what model aircraft, if wired for external power to the avionics bus, and system voltage 12/14v or 24/28v.
Kynadog said:
Can you just put a trickle charger on the battery
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Usually not recommended. Battery trickle charger normally do not provide enough current to keep up with demands of various power consumers. This could lead to spikes in the charging output which can cause damage to the battery or possible further downstream. The normal recommendation is to get a dedicated ground power unit (store bought or DIY) and plug into the aircraft external power plug. If your aircraft doesn't have an external plug or it is not wired to the avionics bus like some Cessnas there can be several "custom" options depending on how far you want to get into it.

However, depending on the type of update like a database and your battery health is close to 100%, you should have no problem with using the battery for a short period of 5 minutes or so. Firmware updates on the other hand can last much longer and will drain/damage even a good battery. The other option for the larger updates is to remove the unit and have a shop bench load the update for a price.
 
Your airplane's battery is probably in the 17-24 amp-hour range. Your EIS or whatever should be pulling 5-10 amps. So you can easily run the panel for 10-15 minutes without seriously draining the battery.
 
Don’t overthink it. Plane battery will handle it just fine. When I update my Dynon and Avidyne, I just make sure al external lights are off and turn off my transponder and KX155 to reduce the load.
 
My G3X is powered through a TCW IBBS backup battery. I use it regularly for data uploads. Mine’s totally independent of the master. If I had to do it from my battery, and I have in the past, I connect a battery charger to the primary battery.
 
The G1000 pulls 9 amps (at 24 volts) when it's in emergency mode: only the PFD and essential COM stuff working. It's not a small draw for that battery. With it all running, the load is much bigger. If you do this, then shut everything off and go home, you leave the battery in a partially discharged state, ideal for permanently sulfating it somewhat and shortening its life. And if you just ground-run the engine to restore the charge, you pump moisture into it to start corrosion. Best to do the update, then fly for an hour.

Some of the other EFIS might have smaller current demands. I wouldn't know, only having worked on the G1000 stuff. The 24-volt external power supply is a good idea but it's not cheap.
 
Dan Thomas said:
The G1000 pulls 9 amps (at 24 volts) when it's in emergency mode: only the PFD and essential COM stuff working. It's not a small draw for that battery. .
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How long does an update require? That is part of the equation.
 
kyleb said:
How long does an update require? That is part of the equation.
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Not that long, but it also takes time to boot it up. I always had the young instructors do it; if I tried to muddle my way through it, the battery would be dead before I got it done.
 
A couple of comments on this:
1. As mentioned, a trickle charger will not supply enough power to run avionics. It will slowly charge up your battery and keep it topped off, but it is not suitable as an external power source.
2. Some things take longer than others. You may indeed need external power in some circumstances.

I recently updated the firmware in my Avidyne IFD-540. That took about an hour total, including time writing down all the configuration, the 45 minutes for the update, and then a few minutes verifying everything afterwards. If this process is interrupted it would brick the IFD-540, requiring it to be sent back to Avidyne to the tune of $1200. I just pulled my car next to the plane, and used jumper cables. I kept my car running during the whole process, and didn't need to worry.
 
I have a very well accessorized G3X Touch and in looking through the specs in the install manual I see it may draw 2a if all the peripheral boxes are on. It may spike about 4a additional if I’m transmitting on the radio but that’s not normal for hangar ops like data updates. I run my system all the time on my IBBS or the EarthX. No problems but it did reveal that after a winter in storage and occasionally using the IBBS I needed to but an IBBS-specific charger.
 
Could you just do the updates on battery power, then when you are finished, hook up the trickle charger to bring the battery back up to normal charge?
 
JOhnH said:
Could you just do the updates on battery power, then when you are finished, hook up the trickle charger to bring the battery back up to normal charge?
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You can do anything operationally as shown in the above posts. But if your priority is obtaining the longest possible service life of your battery then it depends. As I mentioned above, if your battery health is close to 100% per the OEM charts, you should have no problem with a typical update lasting 5 minutes or so provided there is not a large current draw during the update. In this case, the trickle charger shouldn't have to work at all once you are done. If your battery is less than 100% then other variables come into play which a trickle charger is not designed to offset.
 
External power is the best option. Updates can sometimes take longer than planned and if your battery dies while it updates, that's a whole other set of issues depending on the equipment.
 
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