20Kw motor and 300A ESC (ultralight aircraft propulsion system)

[Mihai_F]

Hi there,
I managed this weekend to get one more flight (30min) out of my battery (21s left), it held 14 to 12kw for 4minutes, then 7kw for almost the rest of the flight. All monitored parameters ware in spec, and about toward the end of flight, all cells reached 3,3v to 3,4v about the same time. Then in about 30 seconds, i could feel the power was fading slowly, a cell (no15 witch was near to no14 that leaked and previously died this year) went almost to 2v, all warnings went on, i overwrite the "safety cutoff" (i knew that the cell is done, no recovery), restarted and then with reduced power turned for a landing (i was in a traffic pattern all the time to be safe and close to the runway), during the last 2 minutes, till on the ground, it wet to 0 volts and stayed 0V even the next day, so completely obliterated. I'l come back with pictures of the yet another dead cell, most probably got corroded like the last one. A note is that at 22s i could get 16Kw max last year, at 21s i got 14kw max this weekend, but from now at 20s, 12kw is not enough for initial climb out, at least not a safe one, at 14kw it felt marginal... I could split the reaming 20s in two 10s banks and use for my ground based projects and squeeze the remaining life out of it.

 

[SlowCo]

Will you build a new battery pack for this project? If so, what cells will you use?

 

[Mihai_F]

Will you build a new battery pack for this project? If so, what cells will you use?

the cells that would use are made by LG chem lithium NMC/ NCM712,- pouch rectangular, and will be ider individual or from vw id batt module, a pack with about 100 to 120Ah 50 to 64 kg 22 or 24s in order to have about 80-90 min flight time. I found some sources here in europe that have LG chem 51Ah cells, also found vw id modules NCM712 12S 6,85Kw/h , i would prefer the module since it has the structure that holds securely and tight the cells .
I'm not decided yet if to by new battery, everyone suggest to convert it to gas motor, because i'l have way more flight endurance, that sounds very tempting, but then there are some big technical challenges to overcome, plus it feels wrong to go backwards in technology, i mean electric is the way to go not smoky gas guzzling, mixed feelings here, i like the simplicity and smoothens of the electric but i like the range (and power) of gas, for the same amount of money invested...
Some cool things, is that at the airfield every time i fly or take out the plane, there are a many of people that come around to see it and they think is so cool, it has a reputation around there of being what it is, and every time i announce the flight with "Electric Ultralight" to the tower (we have class C airspace there, LRCL international airport near by) the controller pauses for a second to comprehend the "electric" term, so neat.
So, it is etching me bad to by new battery and continue....

 

[topspeed]

Hy guys, i will move here the discussion about my 20Kw motor and 300A esc. This is been a project for my past 6 years, it's been a huge learning curve. Before i started this project my experience with electronics was with power audio circuits, analog stuff, and nothing digital.
I will start first with the electronic speed controller because that took most of the time to learn and develop.
So i begun with a BLDC monolithic driver chip, the MC33035, and i made the circuit with wires, it took me a month to get it running and be able top spin a small BLDC sensored motor, it looked like this:
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It was capable of about 12w ,24v at 0.5A, then i learned what MOSFET stands for: Magically Obliterated, Smoke and Fire Emitting Transistor, i was amazed how much smoke can make a TO220 packge , inductance was my friend (bundle of wires), but at that time i was blissfully unaware of it. Then i learned a few things and moved the project to PCB, i was so impressed about my first toner transfer technique PCB, but from electrical stand point was crap, again i did not know that, this is how it looked,
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This was the first year and it was capable of about 48w ,24v at 2A, before it wood magically let the smoke out of the FET-s, at that level i learned about that thing called "ringing"... .Then i learned a lot more things, i added a few functionalities like safestart, rpm, voltage, current and tep readout, all made on 4 digit 7 segment display, it was a lot of work, and it looked like this, (the big motor was made at this point) ,
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This was the second year it was capable of about 120w , 36v at 3.3A, o about that time i realized i need to move up a bit and enter the AVR microcontroller world, i knew nothing about them, and all i knew about C programming language was that there was some things called "if" and "else"... , then another year of huge learning curve and another variant of the controller came witch was way easier to customize and change things, hence programmable microcontroller, it looked like this
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This was in the third year became V1.0 it is capable about 2.5kw 20S(84v) 30A (current sensor limited),IRFP4468 FET-s , it has BMS and a lot of functionalities including 128x64 GLCD with menu where a lot of parameters can be customized, then the learning curve was the most steep making the ESC to work up to 16kw, then i learned what inductance can really do, and what miller plateou, reverse transfer capacitance, stray inductance, and a lot of goodies that give a lot of headakes.... , then came next variantwitch looked like this
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This was in the fifth year, v1.2 witch worked up to 16Kw at 20S (84V), IRFP4468 FET-s (6/plase), PCB-s made by me. It was the first and last time i tested the motor by holding the table just myself... :lol: :lol: , it was exiting seeing my work succeed, but kinda scary because i could barely hold the table, the prop was pulling 78kgf

This was how later tests were made, the motor was strapped by the car, no more worries about flying with the table
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This was in the 6-th year the flight testing.
The motor was made by scaling up a smaller motor, (was still 20pp and 30 teeth but only 10kw), i did calculations for the winding, i drew it in 2D cad, went to a machine shop and told them what parts i need, the stator laminations were laser cut (unfortunatly 0,5mm thick), then a full day of winding. It was not even by far such complex to make as the ESC.
It's mass is 7.7kg, 216mm OD, 40mm stator hight, 40x10x5 N45 magnets, 6mohm and 10uH per phase, delta terminated, 3 halls and 1 temp sensors. It can do 16Kw continuous and 22Kw max (1 min) at 20 deg C ambient, being air cooled ambient temp affects max power.
And here are some photos of the system.
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And in the present the 7-th year V1.3 (IRF150P220 FET-s) gives headakes as mention in my other post (300A ESC help...). The change (FET-s) was made in order to go with 22s battery.
It looks like this, with PCB-s made by specialized company, power board has 1mm thick water jet cut busbars.
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This is just a short story, the hole experience has waaaaaay more detalis and waaaay more headakes.
There is a lots of room for improvement, this is very low tech, and to some may be even foolish, i know, up to this point it was the best i could do, but will see what future shows up.

Yes incredible.

 

[Mihai_F]

Hy there,
I bought 5000mAh hobby king cells to replace the 2 dead cells from the battery. I chose the same cells again, because I have 2 packs 3s and 4s that are 9yrs old (same batch as my ultralight plane batt) and i abused the heck out of them on my rc car and plane the past 3-4 yrs they still charge up to specks, a little puffy but they have the needed punch, so they're quality is quite good.... plus i only had the funds to fix the battery not to buy new battery and in the mean time i could do more flying. These cells i'll wrap and isolate them so that if other leak can not reach inside to them to corrode them...plus i'l check, isolate/replace any leaking cells, i'l apply all lessons learned so far... all in all was/is a good battery but i've made some mistakes with it... i did a test on it ant the rest 20cells work ok, so i'l fix it and continue forward!
Now, the FOC version is on work, the new PCB si nearly ready and the sensorless FOC SW works well for propeller load.