Hi all. I have a 777-200er awaiting take off - the only thing is, I am slightly worried about the electric system I am gona use.

System setup As follows:

2 x 90mm EDF’s with max. 63amp draw
2 x 70A ESC with 5V/5A internal BEC(BEC Wire will be removed - I am using a separate receiver pack (6V) to power rest of aircraft components.
2 x 3300mah 35C 22.2V 6S battery - one for each esc+edf pair

Reciever battery pack connected to BATT port on receiver
One battery connected to one ESC which is connected to one EDF
Both red wires(BEC) of ESC are removed
Y harness the ESC’s together into the THRO port of the receiver

After doing some calculations, each battery can provide ~115.5A to the edf but only 63A needed. Max flight time at 3.14 minutes:
Discharge time = battery capacity(ah) / max. required edf current * 60
=3.3/63*60
= 3.14......

My question is, using this setup will my ESC’s or EDF (or any components for that matter) burn out because of the battery amperage provided(is it too high)?

I have a diagram of the setup. If needed, just ask.

Thanks

It is the motor that draws the amps so as long as its load (the fan) does exceed its capabilities or that of the ESC the capacity of the battery is not significant provided it is able to deliver the required amps.
On paper you should have no problem but it would be much safer to actually measure the Amps the EDF draws at full power using a Watt meter.

You should never fully discharge a LiP0, you will likely at best damage it at worst cause a fire so your duration of 3.14 minutes will only apply if you spend quite some time flying at less than full power.

You are using a battery for each EDF . What happens if one set runs down faster than the other? The fans on a 777 are quire widely spaced.
It may be better to link the batteries (with suitable sized wires) so in effect you will be running a single 6600 mAh battery.

So how would that be wired, would I remove both red ESC wires and y harness Them to the 2 linked batteries seeing as I have a separate receiver pack?

Connect your batteries in parallel. Connect your ESCs in parallel to the batteries in parallel. Now both ESCs will draw from both batteries at the same time.

3300mAh 35C batteries might lead you to think they can deliver 3.3*35=115.5A but that is a mistake. The C discharge rate is an absolute maximum rating. The battery won't explode if you draw that much current from it, but neither will it last very long or perform very well, and it'll get really hot. In practice you want to draw 50% of the battery's C rating which would be 57A in this case. Assuming the 63A draw rating of your fan is accurate this is close enough you should be OK. But higher C batteries have lower internal resistance, which can matter a lot to performance under high current loads. So for an applications like a EDF it generally pays to get the highest C you can.

Originally Posted by rocketsled666

Connect your batteries in parallel. Connect your ESCs in parallel to the batteries in parallel. Now both ESCs will draw from both batteries at the same time.

3300mAh 35C batteries might lead you to think they can deliver 3.3*35=115.5A but that is a mistake. The C discharge rate is an absolute maximum rating. The battery won't explode if you draw that much current from it, but neither will it last very long or perform very well, and it'll get really hot. In practice you want to draw 50% of the battery's C rating which would be 57A in this case. Assuming the 63A draw rating of your fan is accurate this is close enough you should be OK. But higher C batteries have lower internal resistance, which can matter a lot to performance under high current loads. So for an applications like a EDF it generally pays to get the highest C you can.

I see. I will order 2 60C batteries. Do I still take out both BEC red wires? Because I have a separate pack powering the receiver

Yes, if you power the RX with a separate pack.

Brilliant. Thank you very much for the help. Kinda new to the twin edf thing so. Hopefully I'll grasp it soon enough. Planning to make an A380 next

Note that it's something of a philosophical argument, but IMO there is no need for a separate radio battery in an electric airplane. And lighter is better. Or if you don't need it to be lighter, you can use those mAhs in your flight pack for a little increase in flight time. And if you use the flight pack as a power source for the RX, you never have to worry about whether you've got enough of a charge on the radio battery. If the problem is that the servo loads are greater than the ESC's BEC capacity, then use a separate stand-alone BEC that can deliver the current you need.

I would snip one ESC's red lead, leave the other in place, and scrap the radio battery entirely.

I do tend to agree with rocketsled666. It is a bit bizarre when you have a huge electrical capacity in the main flight batteries to then add some more much smaller ones to provide power for the rest of the electrics.
Note the ESC BECs may be voltage and current limited - the BEC max amps may reduce as the LIPo count is increased. It will depend entirely on the spec of the BECs.
The better alternative is to use a separate UBEC (they are quite small and light) which can be specified to suit the volts of the flight batteries and the current required to drive the servos.
Yes, there are possible circumstances where an separate rx battery can be a saviour but in the real world total loss of plane control due to the rx battery failing in some way is just as likely if not more so.
Even if you accidentally run the flight batteries down to the ESC low voltage cut off (maybe due to one or more of the cells failing!) however as long as the remaining battery voltage is above 8V the UBEC will still be able to provide the electrical energy to run the planes systems for many minutes, but don't worry with no EDF power you will be on the ground well before that happens!

Even for a 1S powered airplane, the plane will stop flying long before the radio stops working.

If I may add my 2 cents worth. If your drawing 63 Amps, I would go with a larger capacity ESC, 80 Amp at least. No heavier and the extra cushion is insurance against overdriving the electronics.