PLEASE HELP ME WIRE MY GIANT MOTOR AND ESC!!!

[Scoodles93]

Hello There! This is my FIRST POST EVER and I am usually a secrete post reader and I am on this forum everyday. I am a test pilot and electrical system coordinator for diesel and turbine motor drones. I also fly rc planes and AP quads and a lot of FT planes.

ANYWAY. I just came across a predator 37/6 motor and a schulze future xxl-40.300 ESC.. i have 10 PULSE 6S 5500mAh 22.2V 65C lipos and some more 4s 5000mah 20c lipos... My main question is how many lipos would i need, in series and how many in parallel in order to run the motor and ESC? here is the motors specs and INFO

http://www.plettenberg-motoren.net/...tenberg-brushless-motors/predator/predator-37

and the escs data http://www.matthias-schulze-elektronik.de/guide/gfut-l-xl-xxl-v6-book-ENG-black.pdf

This electric motor and esc is being used as a electric start for a 60lb 1400cc diesel drone motor for a DARPA drone. any help would be MUCH appreciated!!!

 

[RAM]

Average lipo cell voltage is 3.7 Volts

So, 6S (6 cell) lipo's run at an average of 3.7V X 6 cells or 22.2 Volts

The motor spec says it's voltage is 47 Volts:

To get near 47V with 22.2V batteries you need to put two of those batteries in Series (series adds voltage). So,,, Two 6S batteries connected in series will give you 44.4 Volts.

That is slightly lower than the 47V in the motor spec but you can't add another 6S in series or you will be too far above the motors 47V requirement (3 6S in series = ~ 66.6 Volts, too high).

So you wire two of the 6S batteries in series to create a 12S. You have 10 of the 6S so by combining them in pairs you end up with 5 12S batteries.

Your batteries are rated at 65C. Your motor specs pages shows it will draw 308 Amps with the 12" prop they listed.

So,,, A 5500mah (5.5 amps) battery rated for discharge at 65C can deliver ~357 Amps (5.5 Amps X 65 = 357.5)
That means each of your series paired up batteries should be enough for the motor giving you 5 sets of batteries (44.4V and 357 Amps)

If you want to lift all your batteries at the same time (doing this gives you more MilliAmpHours which would lead to more flight time) you need to take your freshly made 12S packs and wire them all in parallel. But,,,you will pay a price in flight time for all that extra weight, i.e. you won't get 5 times the flight time if you wire all 5 12S packs in parallel because you add extra weight.

NOTE: Don't run off and do this until someone else checks my math

 

[makattack]

It sounds like the op is using all this gear as an electric starter for an ic motor. I'm afraid I can't offer any help, but his interest wouldn't be for long flight time. I'm guessing he wants max torque in a short window.

I'm guessing this while setup will be a ground based starter. I'm just curious why go with a diy electric one? Don't they make commercial turbine starters?

 

[RAM]

It sounds like the op is using all this gear as an electric starter for an ic motor. I'm afraid I can't offer any help, but his interest wouldn't be for long flight time. I'm guessing he wants max torque in a short window.

Then all 5 of the 12S (2 6S in series) should be wired in parallel for max cranking amps.

 

[stay-fun]

The website of the motor says 12-14s lipo, so that's easy enough. About the esc, I don't know. Does it come with the motor? If so, it should be compatible. Check the voltage limit on the esc to be sure.

I wonder if it's suited for cranking though. It seems to be designed to run big props. That's quite a different application. (you're gonna need gears)

 

[Tritium]

The 12" prop is "Pitch"! Length is 28.5", 3 Blades

Thurmond

 

[Scoodles93]

Average lipo cell voltage is 3.7 Volts

So, 6S (6 cell) lipo's run at an average of 3.7V X 6 cells or 22.2 Volts

The motor spec says it's voltage is 47 Volts:

To get near 47V with 22.2V batteries you need to put two of those batteries in Series (series adds voltage). So,,, Two 6S batteries connected in series will give you 44.4 Volts.

That is slightly lower than the 47V in the motor spec but you can't add another 6S in series or you will be too far above the motors 47V requirement (3 6S in series = ~ 66.6 Volts, too high).

So you wire two of the 6S batteries in series to create a 12S. You have 10 of the 6S so by combining them in pairs you end up with 5 12S batteries.

Your batteries are rated at 65C. Your motor specs pages shows it will draw 308 Amps with the 12" prop they listed.

So,,, A 5500mah (5.5 amps) battery rated for discharge at 65C can deliver ~357 Amps (5.5 Amps X 65 = 357.5)
That means each of your series paired up batteries should be enough for the motor giving you 5 sets of batteries (44.4V and 357 Amps)

If you want to lift all your batteries at the same time (doing this gives you more MilliAmpHours which would lead to more flight time) you need to take your freshly made 12S packs and wire them all in parallel. But,,,you will pay a price in flight time for all that extra weight, i.e. you won't get 5 times the flight time if you wire all 5 12S packs in parallel because you add extra weight.

NOTE: Don't run off and do this until someone else checks my math

I was going to only use 4 lipos .. 2 in series and 2 in parallel,..? this should give me 714 amps with 44.8v at 11000mah and 65c.. i think that would work? i dont see where i need 5 lipos.. anyways thanks for the help! heres a little drawing i made to show you how i plan on wiring them.

 

[Scoodles93]

It sounds like the op is using all this gear as an electric starter for an ic motor. I'm afraid I can't offer any help, but his interest wouldn't be for long flight time. I'm guessing he wants max torque in a short window.

I'm guessing this while setup will be a ground based starter. I'm just curious why go with a diy electric one? Don't they make commercial turbine starters?

I'm using this motor just to crank a IC motor over as an electric start. Then once it starts the power to the IC motor the brushless motor will turn off.. all US military/ nasa/ darpa/ socom drones are all started with a gokart motor starter .. not a single commercial turbine drone has a electric start.. I work with PREDATOR drones out of reno nevada and this will be the first electric start for any drone.. We have designed a IC motor for the new Predator and Nasa's explorer XVB specifically around this brushless motor.

 

[stay-fun]

Are you doing this for work?
I thought most cranking motors were brushed motors. I think that's what's in cars, right? The battery just connects to the starter motor when you turn the key. I think. But what do I know about combustion engines

 

[makattack]

Are you doing this for work?
I thought most cranking motors were brushed motors. I think that's what's in cars, right? The battery just connects to the starter motor when you turn the key. I think. But what do I know about combustion engines

Yeah, this post made me wonder kind of an obvious question "why are starter motors in cars still brushed?"

This article sort of explains why:

http://powerelectronics.com/content/inertia-stalls-application-brushless-motors-cars

Anyway, this seems like a cool project. Certainly with drones, it's easier to put in technology that is more experimental vs what you can install in manned aircraft.

All those lipos for example... oh wait: https://en.wikipedia.org/wiki/Boeing_787_Dreamliner_battery_problems

At any rate, I should think a brushless motor starter would work. I'm not a mechanical engineer, but I'd be guessing that you would still need gears, clutches, whatever doohickeys are needed to disengage the brushless starter motor from the IC motor once it's started.

Although... now that I think about it, if you don't have the gears and clutches, and the BL motor was powerful enough with a 1:1 ratio to start the IC motor, the BL motor could also act as they dyno/generator as long as the ESC can handle that back current. I'm sure there's a fundamental flaw in that idea somewhere, or else it'd have been done already!

Hah. I should have google'd it before the above paragraph:

http://www.skurka-aero.com/products/starter-generators/dc-brushless-starter-generators

Looks like someone else is making one of these!

And, here's a DIY version:

https://www.youtube.com/watch?v=HL1wzOx_JbU