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External Power to Use Avionics with Engine Off

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I?m a new RV-12 owner and am still learning the features of the plane?s Dynon Skyview HDX. I have a battery charger that I was able to use, with the engine off, when the plane was in a hangar that had 120 volt electricity. The plane is now tied down outdoors in a spot that does not have electricity. What do any of you use to power your avionics without an accessible 120 volt outlet?
 
Don't you start your engine up? Another option would be a 80w 12v solar panel with a 14.4v charge controller, put it in the cigarette lighter ?Power supply outlet. Good for about 4 amps

Otherwise, watch Skyview HDX videos on YouTube to learn how, without being in the plane. Or take someone else up with you while letting them fly, while you work with the Skyview. I'm not that far from you, in SFV, but it's been hotter than hades lately for flying. Come pick me up at VNY or WHP, traffic on the 405 is too brutal anymore to get to Santa Monica. I've got about 40 hrs now flying with a Skyview 1000 Touch, they are close enough to the HDX. Is your firmware up to date and current? 15.4.7 Aug 15 2019, I think?
 
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I just ordered a Garmin GNC 355 (back ordered), they have a great training app available. See if a similar type thing is out there for the Skyview, or as others suggest there are videos online.
 
I use an MJF 25 amp power supply with adjustable voltage. It is good for checking other things at lower voltage too. It is dead quiet for radio work too.

It is used for demo modes and hangar flying, also database and software installations.

Here is a 25 amp model, MJF has others.

https://www.mfjenterprises.com/Product.php?productid=MFJ-4035MV

Thanks for this recommendation. The online description says it needs to be plugged in to a 120 volt socket ? something I no longer have available near my plane. Have you figured out how to provide it with input power that doesn?t require a nearby electrical socket?
 
Battery and jumper cables, charge it when you get back to hanger.
Also safer for avionics than a cheap high ripple battery charger.
 
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You can always use a small generator and plug in whatever 12V power supply you have. I have a Honda 2000 that I use for things like that.
 
MGL comes with free simulator

Those of you building an Experimental (or building out of USA) could consider MGL for avionics: comes with free simulator. The sim is also usable without buying the stuff (http://www.mglavionics.com/), so perhaps you could learn from that perspective, as well?
 
Can you find a hangar or fbo that will let you plug in an extension cord? If not get a spare car battery and keep it charged so you can jumper it. You can use your car and jumpers, but not good news to drain it and be stuck. A small generator would be a good thing to have anyway. Good luck.
 
I bought one of these: https://www.dxengineering.com/parts/alo-dm-30tr

I used it before flying with battery disconnected (connected battery cable to the power supply) to test/set up avionics.

Used a similar power supply, however that doesn't get the OP over the hump of not having 115VAC available at the airplane.

The cheapest solution will be cheap jumper cables that you modify on the aircraft end to fit your specific aircraft electrical system (smaller alligator clamps, for instance, to fit better, clamped to the master contactor and ground). Then go find a 12V battery - borrow it from your friend's unused pickup truck, from the guy who has a boat that he's not using, whatever.

Charge the battery up fully before you get to the airport. Power the airplane via the jumper cables, then recharge the battery when you get home.

Stick a DVM on the battery and check that you don't take it down too low in voltage.

A Group 27 battery from my tractor will run my panel pretty much all day from a full charge.

Shed any unnecessary loads by pulling fuses/circuit breakers if those loads don't have their own switch. Things like fuel pumps, COMM radios, transponder... Their user interface is simple and should take you only a few minutes to learn. Once you've got them sorted out, power them down and save the juice for the EFIS and its adjuncts.
 
Thanks for all the suggestions. A friend gave me a 12-volt battery that's identical to the one in my plane. When I'm using the avionics with the engine off, I attach that battery to my plane's battery, positive terminal to positive terminal and negative terminal to negative terminal.

It seems to work. I haven't damaged or depleted my plane's battery. But I don't understand why it works or what's happening.

My plane's ammeter shows that my avionics are drawing 7 amps (-7). But I don't understand where those amps are coming from. Are the avionics drawing power from the plane's internal battery, with the external battery feeding power to the internal battery? Or are the avionics drawing power from both batteries simultaneously?

I began thinking about this because I wondered why the external battery was feeding the plane's battery, rather than the plane's battery feeding the external battery.

I have attempted to answer this question with online research, but haven't been successful. Most of what I've come up with are explanations of how to jump-start a car with an external battery.

I'm not expecting anyone to write an article about electricity (though I'd happily read one). But a link to an online explanation of what's happening when I connect an external battery to my plane's battery would be thankfully welcomed.
 
Assuming the two batteries are in a similar charge state, they will share the load, 50-50. What you should do: Remove the negative lead from the aircraft battery. Jumper the portable battery, positive to positive, and negative to a good ground (if convenient you can use the negative battery lead you disconnected). This way only the portable battery will supply the power for testing.
 
Connect the spare battery to the load side of the master contactor and leave the master switch off. That will eliminate 3/4 of an amp that the battery contactor draws.
 
Connect the spare battery to the load side of the master contactor and leave the master switch off. That will eliminate 3/4 of an amp that the battery contactor draws.

Is this 3/4 amp draw only when the master switch is turned on, that the master contactor is pulling current, or is there also a phantom load from the master switch when it's turned off?

Trying to help a friend trouble shoot his battery draw down problems.
 
The battery contactor uses about 3/4 amp more or less. If you touch a contactor after it has been on for a while, it will be very warm, maybe hot. No, there is no phantom load when the master switch is off. If a phantom load is suspected of running the battery down, here is a test: With master switch off, disconnect one of the battery leads (negative is safer), and put an ammeter in series between the battery post and disconnected lead. If there is no current with the meter set to amp range, set it to read milliamps. No current should be flowing with the master switch turned off unless something is connected directly to the battery.
 
Assuming the two batteries are in a similar charge state, they will share the load, 50-50. What you should do: Remove the negative lead from the aircraft battery. Jumper the portable battery, positive to positive, and negative to a good ground (if convenient you can use the negative battery lead you disconnected). This way only the portable battery will supply the power for testing.

The battery in my -12 is difficult to get to, so the builder added a quick connect plug that is easy to reach through the oil door. I connect the external battery using a cable that has a compatible quick connect plug, so doing what you suggest would be difficult if not impossible.

However, I have two identical external batteries -- identical to one another and to the battery in my plane. If, as you say, one external battery and the plane's internal battery share the load 50/50, would adding another external battery (attached to the first external, positive-to-positive, and negative-to-negative) mean that the three batteries would share the load 33/33/33? Or would adding a second external battery overload something?
 
Lon - you're likely over-thinking this and driving yourself into unfounded fears...

It doesn't matter how many batteries you have tied together outside the airplane, as long as they are all of nearly equal quality and state of charge. They need to be connected in parallel (+ of Batt1 to + of Batt 2, - of Batt 1 to - of Batt 2). You could have a hundred batteries connected like this and it would have no difference on the effect on your airplane.

Paralleling batteries just increases the total amount of stored energy available to be delivered to the load. The more energy available, the more slowly the voltage of the storage batteries will drop as their stored energy is consumed.

Think of it this way... Picture each battery to be a 5 gallon jerry can of gas. Connect a single jerry can to the airplane and the motor will run an hour. Connect two cans and the motor will run two hours. Now picture a long line of jerry can turned upside down with their spouts tied together in a big collector. If you've got 20 jerry cans, that's a hundred gallons of capacity. Each will flow at the same rate, so each will deplete at the same rate, 1/20th of the consumption rate of the engine. The engine will run for 20 hours. All jerry cans will empty out at very nearly the same time.

This analogy is a good way of visualizing parallel batteries.

If you're really concerned about doing this, just splash out the cash to purchase a 12V power supply (not a battery charger) and make a way to connect it to the aircraft bus without having to involve the master switch. (Remember to put a fuse in line with the supply so you have over-current protection.) A power supply will take 115Vac and convert it to nice clean 12V DC. OK what you're really looking for is something like 13.75V or so, but most power supplies put out something higher than exactly 12V.
 
Get a switching Power Supply. I run my very expensive Elecraft K3S ham radio off of one of these Mega Watt switching power supplies. You will need to get some 10 or 8 gauge wire to handle up to 30 amps.

If you want to use it as a power supply for your battery, set the voltage up for 13.6V and connect to your plane battery, with something like Anderson Power Pole connectors.

If you want it to recharge your battery, set it to 14.4V for recharging and remove from battery when your recharge take rate reaches 0.5% of battery capacity in milliamps 16 amp at 1/2 a percent is 80 milliamp charge rate. A RC Wattmeter in line in the recharging or power supply circuit, is a very helpful device in recharging expensive plane and LiPO RC type batteries.


Always measure the voltage with the power supply turned on and not connected to anything with a DMM.

These guys are local to you, the power supply is a very good, noise free model.

http://www.megawattpowersupplies.com/assets/Big_New_Stick_33_Amp.jpg
 
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Canadian Joy: You're right. I am overthinking this, for two reasons. This is the first plane I've ever owned. (I rented for years.) And I'm like a first-time parent -- afraid to do anything that might hurt the baby. The other reason is that years ago, when I was just a boy, I used to know stuff about electricity. (I built transistor radios when transistors were new gadgets and just beginning to replace vacuum tubes.) Now I'm having trouble remembering what I used to know back then, and that makes me nervous. I have taken off the shelf my copy of Rod Machado's Private Pilot Handbook, and am reviewing the chapter on Electrical Systems. Thank you, a lot, for your gas can analogy. It did help me, and has calmed me down.
 
See post #1, the guy's plane is located where there is no electric power available...

I camp, all the time, where there is no electrical power available. With a RV. We actually set ourselves up with Honda generators and solar panels, and they keep us fully charged. One just has to research their options so that they aren't powerless.

Improvise. Solar panel or generator comes to the hangar, so that it's not a problem.
 
Lon,

Van's RV-12 electrical system diagram shows that the 12 volt power outlet is powered directly from the battery (always hot). If it were to be rewired to the main bus, you could power your avionics through the power outlet with the master switch off, thus putting no load on the RV battery. A second power outlet powered by the main bus would work as well. Just fuse it appropriately. Connect your jumper cables to a cigarette lighter plug.

Cheers, David
RV-6A A&P
 
On my Cherokee the master relay has to energize to let the external input pass electricity. If the battery his dead the master won’t pick up. Tap in at the side of the really after the battery and there is no issue.
 
Another thought. If the battery is dead and you hand prop to start on a Cherokee (not a good idea) there is no power to flash the field on the alternator, so the engine runs but no electrical power. Fortunately ROTAX uses a permanent magnet exciter, so if it runs it produces electricity.
 
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