battery for twin settup

[doctormike]

I have a Grumman Widgeon twin that I want to use 2- 5060 motors, and 2- 85 A ESC's on. The required battery for a single motor settup is 6s 3300mAh 30c. What size battery should I use for the twin settup? This is actually the motor and ESC used in the largest FMS planes. Thanks, Doc

[Konrad]

RE: battery for twin settup

How much weight can the model handle and how long do you want to fly on a charge? Do you have any engineering data? Like wing area, weight props (Pitch and diameter) and measured amp draw.

Of the top of my head I'd think 5800 mAh to 6600 mAh would work. This is what I use in my Freewing twin EDF models.

All the best,
Konrad

[doctormike]

RE: battery for twin settup

How much weight can the model handle and how long do you want to fly on a charge? Do you have any engineering data? Like wing area, weight props (Pitch and diameter) and measured amp draw.

Of the top of my head I'd think 5800 mAh to 6600 mAh would work. This is what I use in my Freewing twin EDF models.

All the best,
Konrad

Thanks, Konrad!!! I figured that all out, going by weight and wing span. I concluded that 2 of these motors should be more than enough power. I want the FMS 3 blade props for the scale factor, also. The 6600 mAh should work great. By the way, I made graphics... Zee plane, Zee plane, to place on both sides of the nose. I really appreciate all your info. Doc

[fhhuber]

RE: battery for twin settup

Twins.. use the voltage for the single motors and capacity X2... but Y the ESCs to share the battery.

So if you already have 6S 3300 packs.. you y the ESCs red to red... and Y a pair of the batteries red to red.

You might think that is the same as putting one battery in for each motor, but its not. Both motors sharing the batteries results in more even power to both motors.

[OV10]

RE: battery for twin settup

Hello fhhuber,
I have to interject on your one comment about "Y"ing the ESC's red leads so as to save Doc and others a butt load of grief. If you were referring to the battery leads of the ESC then your comment is spot on and not an issue. If you were referring to the red lead on the signal line which is attached to the receiver then there is an issue unless he is using a separate BEC or a separate battery to power his Rx and other electronics which means that both ESC receiver cable red wires are "isolated".
If the onboard BEC of the ESC is being used, you DO NOT "Y" the Rx red leads of them because the majority of high powered ESC's use switching and the twin BEC's application will fight each other for voltage control. The protocol for twin ESC's with switching BEC's is to "Y" the signal(yellow or white) and ground(brown or black)leads to the receiver but isolate one of the red wires(remove from connector which is preferred choice or cut) from either ESC so that only one ESC will provide system power on the red to the Rx. The only reason I felt compelled to dive into the details is because there may be some other folks out there reading that may have inspirations of delving into twin operation but aren't aware of this mechanical/electrical requirement and if I was unsure of what you meant in your writing, am sure someone else could have been too.
Best regards,

[doctormike]

RE: battery for twin settup

SHEEEEEEZE! Now I'm really confused! Doc

[OV10]

RE: battery for twin settup

Doc,
Whats your confusion?

[fhhuber]

RE: battery for twin settup

Y together the battery-ESC leads..

ESC to RX... depends on the ESC as to how well they play together... Generally a good idea to disable the BECs of the ESCs and use a separate UBEC, RX battery or other mode of ensuring the ESCs BECs don't decide to burn each other out.

[doctormike]

RE: battery for twin settup

OK... I get it. thanks for all your help. Doc