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In-Air Recharging

#1
So for a while I have pondered the idea of recharging a rc plane in-flight. So far I have a rough idea of how I would do it. So the plane that has the extra batteries and charging boom would probably be a vastly modified guinea pig or custom cargo airplane as they would have the capability to carry the extra batteries needed to charge airplanes. The conectors would have two main power supplies one for powering the airplane while it's batteries are charging and the other power supply would charge the flight battery. There would also be a small power supply that would operate a switch to stop power coming from the planes battery and instead from the Charging plane. The conectors would have small neodinium magnets to hold the connection tight. For the power conectors copper pads would transfer the power from the charger plane's conectors to the plane. The pads would have springs to insure good contact. I think this would be better for some of the larger autonomous planes like some members of the community have made. I plan on having a cad model at the end of the week. Any suggestions or recommendations would be appreciated. Thanks and Safe Flying everyone!
 

CarolineTyler

Well-known member
#3
Shame supercapacitors still don't have the energy density of lipos - the ability to transfer a huge charge in seconds would be really advantageous for air-to-air recharging.
 
#5
Shame supercapacitors still don't have the energy density of lipos - the ability to transfer a huge charge in seconds would be really advantageous for air-to-air recharging.
Definitely but I would worry about damageing the battery by charging so fast and especially since the planes that would be ideal for I.A.R.C. would have larger and as a result more expensive batteries.
 
#6
I'm confused. What's the benefit of this? Wouldn't it be better to just get a bigger mAh rated battery?
It would allow longer flights over longer distances that don't have good places to land and swap batteries ie water. The tanker would be able to fly to the plane and recharge it. I guess it might be better to have a bigger battery or a generator but that might be heavy and make the plane weigh more than the weight limit. That would be the main reason to do I.A.R.C.
 

DamoRC

Well-known member
Mentor
#7
Any suggestions or recommendations would be appreciated.
Good fire extinguisher would be useful ;).

Technically - this is a massively ambitious project. Forgetting the electronics portion, being able to fly two craft that would hook up in this fashion (tether / neo mags) is going to be incredibly difficult. So....


Go for it!

DamoRC
 

CarolineTyler

Well-known member
#8
Definitely but I would worry about damageing the battery by charging so fast and especially since the planes that would be ideal for I.A.R.C. would have larger and as a result more expensive batteries.
Have the supercapacitor in the plane receiving the charge and the carrier aircraft with the heavier, big capacity, in parallel batteries. The receiving plane would only need to dock for a short time to receive it's top up.
 
#9
Good fire extinguisher would be useful ;).

Technically - this is a massively ambitious project. Forgetting the electronics portion, being able to fly two craft that would hook up in this fashion (tether / neo mags) is going to be incredibly difficult. So....


Go for it!

DamoRC
I should also say that the budget for this project is around $0. I plan on giving the plans for the connectors and wireing here so other people can use it as I only have one plane and it is only partly made. I have experience in all the parts nessesary exept the automus planes that would be ideal. I just need to put all the experience together for this.
 
#10
Have the supercapacitor in the plane receiving the charge and the carrier aircraft with the heavier, big capacity, in parallel batteries. The receiving plane would only need to dock for a short time to receive it's top up.
That is a great idea but the capasitars would need a way to slow down the relese of power from the capasitars as not do damage the battery possibly a ultra striped down charger that could take the power from the capasitars and then charge the battery.
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#11
Air to Air refueling works best where the energy density of the fuel is high, and the energy flow is massively in excess of the energy expenditure rate.

As LiPo batteries require a maximum charge rate much less than the max discharge rate, should not be fast charged when hot, should never be charged in a enclosed space, should always be monitored, and finally should not be charged in close proximity to inflammable materials this could be an interesting spectacle if anything goes wrong.

DON'T forget to video it!

Have fun!
 

b-29er

Active member
#12
I could actually see this being useful on long-range fpv stuff. Rather than mid-air refueling though, have a pair of aircraft, one as a towplane and the other as a glider or low-power aircraft carrying an extra battery. Run both aircraft off the towplanes battery and drop it away when its time to switch to the onboard pack, fly the glider back once at cruise or land at an intermediate runway somewhere. Or do like that one guy on rcgroups did and have a dual power system, switch power sources in flight and drop the depleted batteries (onto the side of a mountain without a chute!)
 
#13
this would be great at each Flite Fest events, have the plane and have a hover mode, planes, choppers, gliders, come up to them and get charged without landing and back to flying.
 

DamoRC

Well-known member
Mentor
#14
That is a great idea but the capasitars would need a way to slow down the relese of power from the capasitars as not do damage the battery possibly a ultra striped down charger that could take the power from the capasitars and then charge the battery.
The more I think about this the more I think that the electronics side could be figured out (supercaps on the receiving plane to suck some charge onboard quickly (relatively) coupled to an onboard charger to charge the flight battery at the appropriate rate). There are a number of examples of these types of circuits on the interwebs. The nice thing about this part of the challenge is that it can be figured out on the bench. The"electrically connecting two planes in mid-air" piece to facilitate the transfer is gonna be hard, but probably not impossible. A noble goal - even if it ultimately is not practical.

DamoRC
 
#15
I think magnetically-bound connectors might not be the best choice as they could be difficult to disconnect at will. A mechanical latching system might work better, possibly incorporated into guides that bring the connectors together.
Perhaps the best way to experiment with the 'contact system' would be to initially leave out the recharging part and just try to link-up in flight for a tow. Unless, that is, you choose a system (like probe-and-drogue) in which the line is not normally under tension; but I think such a system would be much harder to link up with (particularly if you're not using FPV on the receiver 'plane) than one where the tanker can overtake the receiver trailing a kind of grapple that 'snags' a hook or loop on the receiver.
 
#16
I think if we can get a channel on our controller to talk to the refueling plane and use the toggle switch, flip the switch and our planes or even choppers, UAV vehicles, hook up that way and begin to charge, once done, have some sort of meter for our vehicles telling us when done, then flip the toggle switch and release. @DroneRocket Guy
 

DamoRC

Well-known member
Mentor
#19
I think magnetically-bound connectors might not be the best choice as they could be difficult to disconnect at will. A mechanical latching system might work better, possibly incorporated into guides that bring the connectors together.
Perhaps the best way to experiment with the 'contact system' would be to initially leave out the recharging part and just try to link-up in flight for a tow. Unless, that is, you choose a system (like probe-and-drogue) in which the line is not normally under tension; but I think such a system would be much harder to link up with (particularly if you're not using FPV on the receiver 'plane) than one where the tanker can overtake the receiver trailing a kind of grapple that 'snags' a hook or loop on the receiver.
Yep - I was thinking that the receiving plane would have to be FPV. Yes also on the idea of dividing and conquering - electronic stuff on the bench, flying and hooking - up stuff in the air. When both are 100% perfect (yeah, right) the two can be combined.

Seriously, sounds like crazy fun?

DamoRC
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#20
Ignoring the battery safety aspects of the problem there is a simple mechanism that could be used simply, reliably, and without the need for absolute precision.

First thing would to have 2 trailing cables from the "Tanker" plane. they should be far enough apart that the empty plane's propeller would not catch them. Also each cable would be a different polarity. i.e. One positive and one negative. At the end of each trailing cable there would be a metal cup shaped contact with a high strength magnet on the "Tanker" side of the cup. The rim or lip of the cup would be soldered to the trailing cable.

On the "Empty" plane there would be 2 probes fixed to the planes wings, (one each wing). Each probe would be for a single polarity and have a similar cup and magnet arrangement as fitted to the trailing cables from the "Tanker" plane. The magnets should be oriented such that the opposite terminal is repelled if held close. Ie north pole to North pole or south pole to south pole.

The probes could be as simple as a couple of BBQ skewers with the contact and magnet attached.

When the "Empty" plane approaches the "tanker" the probes would be magnetically attracted to the trailing wires and the metal ends would be the electrical contacts for the passing of the charge current.

Just a basic and simple approach!

Have fun!