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Old 03-03-2021, 01:20 PM   #1
cessna180
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2 batteries or 1 for 2 edf’s


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I am building a F22 using 2 edf’s. Should I power both edf’s with 1 battery or should each edf have its own battery? What are the advantages and or disadvantages of using either system.
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Old 03-03-2021, 01:56 PM   #2
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Re: 2 batteries or 1 for 2 edf’s

How big are the batteries?

If its a small jet and you can install one big battery, why not?

But if its a large jet, say running of 6S packs, I doubt you could go with a single-battery set-up to feed two motors and still have sufficient flight time.

I don't have any twin jets, but many twin aircraft. For my twins I prefer to have the packs in parallel so that both motors are running off the same combined power. If you ran them off separate packs, you could have one motor lose power before the other and on a twin prop model, this could be disastrous. Its not such a big deal on an EDF, but just the same, I would want both motors running at the same speed.

In the attached diagram, I prefer the lower set-up

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Last edited by Max; 03-03-2021 at 02:02 PM.
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Old 03-03-2021, 03:02 PM   #3
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Re: 2 batteries or 1 for 2 edf’s

I also have smaller twin prop aircraft and I power them with one battery. Max. amp draw is 60 amps. The 2 edf’ will run on 6s 5000 ma and will draw 110 amps at WOT. I am thinking it would be easier on 2 batteries (6s 2500 ma, both same C rating) powering each edf separately. Each battery would draw 55 amps vs. 110 amps from 1 battery. I realize that after the splitter each esc and edf will draw 55 amp each. Other comments appreciated.
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Old 03-03-2021, 05:22 PM   #4
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Re: 2 batteries or 1 for 2 edf’s

If I were doing it I would be choosing Max's option B. But not an expert just the fact that parallel will tend to keep it all balanced for thrust and draw.
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Old 03-03-2021, 05:27 PM   #5
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Re: 2 batteries or 1 for 2 edf’s

I'll second... third? that.... option B makes the most sense.
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Old 03-03-2021, 05:58 PM   #6
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Re: 2 batteries or 1 for 2 edf’s

Been running two different twin propped aircraft for over 10 years as separate battery inputs to the ESC’s and never an issue. I feel that if an issue developers with one input source then that can drag down the other battery source with some not so good results.
The little difference you have with a slight imbalance in voltage to each motor is not worth the effort of the extra complexity of wiring. Just check before plugging in , that both batteries are fully charged and you will have no issues. If I have the packs charged to 99% and the other to 98% ; Input the higher one plugged into the ESC that is using the BEC for receiver/ servo power.
For those worried about matched brushless rpm ; if they were To check each motor on the same pack you will likely find that no two motors run at exactly the same rpm. The kv rating is only approximate and can vary a slight amount . Had that happen once with one being 2% high and the other 2% low with an imbalance differential of 4% which was noticeable at about 300-40O rpm difference .
Used two receiver throttle inputs and set the higher rpm motor on a lower throttle curve and got a match to within about 20 rpm at that last 1/3 top end. Got lucky first time with the percentage I used.

With Edf , you will never notice that there is a difference. Also for Edf , I would look at the weight of one large pack vs the weight of two single packs that total the same capacity and then there is the fitting space available, also.

Last edited by stegl; 03-03-2021 at 06:06 PM.
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Old 03-03-2021, 06:15 PM   #7
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Re: 2 batteries or 1 for 2 edf’s

It is easy to wire things in parallel and provide a fuse in case one side has some bad fault.
Advantages,
Synchronized motors,
Strong battery helps the weaker one.

If the motors are 70mm one decent pack should work fine. Today we flew our twin 70mm Gloster Meteor for over five minutes. Only consumed less than 3400mah from our 6S 5500mah pack. Same deal for our ME262, SU 47, and a friends 737.
Our latest 737 is larger but still a twin 70 so we will use one large 8000mah 6S pack.

On our larger twin 80mm jets, we use two 6S packs but in parallel.
Works great.
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Old 03-03-2021, 06:15 PM   #8
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Re: 2 batteries or 1 for 2 edf’s

Thank you for several opinions. If I was not clear with my question it was whether to use 1 battery to power 2 edf’s or power each edf with their own battery. In the diagram by Max, the second one the batteries are hooked up in parallel. He has just made 1 battery out of 2. But it does not answer my question.
You can make a battery pack using 2 batteries which would act as a single battery.
When 2 batteries are hooked up is series the voltage is doubled but the amps remain the same. Eg, 2/2s /2200 ma batteries hooked up in series make 1, 4s/ 2200 ma battery.
Now when those 2 batteries are hooked up in parallel you have a battery that is still 2s but now you have 4400 ma of capacity. Again my question was, one battery to power both edf motors or each edf to be powered by their own battery. On twin motor aircraft where the motors are a distance apart I use 1 battery to ensure both motors run in sync. It would not matter on the plane I am building as both edf’s will be close together and if there is a slight difference in thrust due to voltage differences it should not matter.
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Old 03-03-2021, 06:18 PM   #9
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Re: 2 batteries or 1 for 2 edf’s

Tell us what EDF’s you plan to use. How heavy is this model?
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Old 03-03-2021, 06:20 PM   #10
cessna180
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Re: 2 batteries or 1 for 2 edf’s

My reply was after Len and Flyboy. Thanks guys for the useful info.
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