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Tello carbon fiber 135mm frame conversion

ph2t

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#1
Having to swap out a dead motor was a real pain in the arse and got me thinking about a frame conversion for the tello.
There is a 100mm frame (looks to be carbon fibre but I can’t be 100% sure till I get it) on eBay that takes my fancy.

6D636F49-F89A-4BB1-93B8-C0538FA3E26B.jpeg
4029B811-A357-4330-8FBA-F0BDF75E0F63.jpeg

Specifications are:

Item name: Micro FPV RC Quadcopter 100MM Brushed Frame Kit Support 8520 Coreless Motor
Wheelbase: 100mm
Bottom plate:1.5mm
Top plate:1.5mm
Weight: 8g
Motor: brushed 8520
Propeller: 50-60MM


I like the idea of accessibility and possibilities around a larger capacity batt.

If you can think of issues please share.

Cheers,
ph2t.




Dd
 

ph2t

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#2
OK, just busted a 2nd motor :mad:. The tello frame isn't fond of being modded, think I'm going to do this conversion once it arrives now. Gonna get rid of the battery pack crap and go a standard lipo as well, I think my 2C charging rates are killing the stock battery, haha...

ph2t.
 

ph2t

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#3
Got the CF frame today. It’s just too small. Can put some smaller props on it all ok but fitting the main tello pcb and battery doesn’t work well.

So a 100mm CF frame is too small. I have ordered a 135mm frame off eBay. It’s for brushes motors so the mounts are different but I’m sure I can hack something together. ;)

19C2861A-E066-43F9-84B5-FD8AA6875AD5.jpeg
Time will tell. :)
Cheers,
ph2t.
 

stewe12

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#4
I would try to drill the holes in the center of motor mounts to be bigger and use the rubber inserts from the smaller frame to hold motors in place.

And can I ask how are you going to convert it to standard LiPo? I thought there is third pin in our batteries and Tello needs it.
 
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ph2t

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Location
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#5
I would try to drill the holes in the center of motor mounts to be bigger and use the rubber inserts from the smaller frame to hold motors in place.
That’s a great idea, I’ll do that! Still waiting on frame number two.

As for the power? Yes I’m currently working on that. I’ve found that with an oem Lipo battery I can get it powered up, flight ready, app connect with vid feed but I haven’t achieved take off yet. The battery was low as I hadn’t charged it yet. That might be the issue. I could also be because I’m only using two of the four power pins.
 
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ph2t

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#6
Here some pics of my work on the power side of this CF frame conversion.

I soldered a JST battery cable to pins 1 and 3 on the tello power pins.

66E353D6-2EBA-427B-B1D6-EBE6E002313C.jpeg

This gets you going with any 3.7v lipo of your choice.

It’s important to remember that you can not use the tello to charge any lipo you may add. The stock tello battery is a high voltage lipo with a nominal 3.8V. Regular lipos are a nominal 3.7V.

I’m trying out these ones I found. It’s a 7.4V 2S pack that I ripped apart for the cells.
618F6D3E-3962-42AF-82AF-374C59E3961C.jpeg

70C discharge, tasty!

Here it is next to the stock tello batt.

576732FA-F50F-4197-8ADD-3E3A46414626.jpeg

Here’s some pics of the testing rig. As i said earlier, no flight yet but close!

7750658D-6B2D-4BE1-9438-B76B5488A779.jpeg
369BFD87-8959-4022-A50D-D67003D3DE3D.jpeg
There is a seperate piece of cardboard between the lipo and the heat sink. It’s not the best - this is a test to unlock the tello from its stock battery and not the final application. If all works out this is how I will power the tello in the CF frame.
Cheers,
ph2t.
 

stewe12

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#7
This guy managed to get it to work:

But I am afraid you need to salvage one original battery. There should be thermistor and chip with info about the battery on the other two pins if it is similar to phone batteries. Also these ZOP batteries you are using were performing like sh... not so good for me in my FPV freestyle quad. Maybe bad luck with that particular battery. Also Joshua Bardwell (knowledgeable man in FPV community) tested some LiHv and said something like it doesn't matter if it is regular or high voltage, you can overcharge every battery with so small impact on the life span.
 
Last edited:

ph2t

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#8
You are right as usual stewe12 :). I’ve found the circuit in the battery to be quite involved. I’m not 100% sure what is going on with pin 4 on the power strip. Measuring the battery pin 4 against GND and it sits at approx 10mV. I tried to solder four wires into the power strip and connect the tello battery at the same time to monitor what happens on pin 4 when it powers up but I couldn’t pull it off. Too tricky. I think, looking at the little pcb that there might be a diode offsetting the voltage on that pin to ground. Not sure.

In the meantime I pulled apart the battery and basically copied the YouTube video you posted. :)

To remove the battery you need to run a sharp hobby knife along the plastic seam of the case. It loosens the whole battery case up enough to remove the battery and power connector in one piece.

A18FEBCD-9C24-4D6A-9C14-E2C23655B3EE.jpeg

Here’s the little pcb on its own. There are few passive components R1,R2, C1, C3 etc but I’m not sure what the little 6 pin SOT packages are. ;(
2FBC3927-12F3-442C-B0C7-79E58DE53910.jpeg

I soldered the pcb in place on the tello power connector for stability. Connected a standard JST female plug.

97BBC98C-507A-44AB-B7FC-8046669084D8.jpeg

It is flying now! :)

Flys heavy, the setup is dodgy at best if you refer to pictures above showing how it was all taped together!

Still it’s a proof of concept to know i can use regular lipos know and charge them at stupid arse high C rates on my hobby lipo charger, haha!

Cheers,
ph2t.
 

stewe12

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#9
I am glad you made it to air. Sadly I am not that knowledgable in electronics, so I am not able to help you more. I just tried searching for info on 4 pin phone batteries and that was what I found...
 
Last edited:

ph2t

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#10
@stewe12, well it helped me understand the battery so thank you :)

I have got the battery sorted now.
I feel that I have the motor mounts sorted too, got a set of DIY FPV 8250 motor mounts off ebay and they arrived today. Initial tests are promising. The motor mounts (surprisingly!!) align up well with the brushless motor mounts on the CF frame I got. I'm just working on the best way to place the motors in the mounts as it requires some cutting to ensure the motors don't push their power leads onto the CF frame and short out.

The frame is just a little larger than the tell, here is a pic with the tello sitting on top of the CF frame. You will see one red prop on the CF frame, mounted in place. The red prop sits a little further out than the tello yello prop.
IMG_4670.JPG

Here's a nasty work in progress picture, lol. The motor mount is on the right of the CF frame.

IMG_4671.JPG

So much to do, I have to remove the pcb from my tello…...again....haha

cheers,
ph2t.
 
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ph2t

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#12
@briest, haha :cool:.

I've done a bit more work. Have test mounted the motors and all OK there. I had to cut out a bit of the CF frame for the VPS system, it's a messy job and I'll clean it up once I've confirmed VPS is running OK.

Here are some pics, hope to have it running tonight.

IMG_4676.JPG

IMG_4677.JPG

I have tilted the camera UP the other way for a better FPV experience, I usually FPV in fast mode so I prefer this angle for myself.

IMG_4684.JPG

Cheers,
ph2t.
 

ph2t

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#14
Great job !
Can you post your bill of material ?
I'd like to follow your steps.
Thanks Dino :)

I have used these items so far


JMT 3 inch Carbon Fiber Rack 135mm Wheelbase FPV Racing Drone Quadcopter Frame Kit fit for 1106 1306 1407 1506 Motor

4x Motor Mount Motor Seat for DIY Micro FPV Quadcopter 8520 1020 Coreless Motor

Racerstar 8520 8.5x20mm 53500RPM Coreless Motor Upgrade for Eachine QX80 DIY Micro FPV

1pc IPEX 8dBi Antenna for ESP-07 / ESP32-Wrover

Cheers,
ph2t.
 

ph2t

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#15
I got it flying tonight. Very happy! :)

B07F4B59-EDE9-4FB2-9FFA-1CE6A092C2C3.jpeg

I soldered on the motors and also connected a set of antennas. They’re cool little 8dbi ones I got off eBay. They’re flat pcb and I mounted them underneath the arms. I’m not sure on the polarisation or radiating pattern but I will enjoy testing them out.

C26157D5-C44D-4754-9EEB-449D453DDDB6.jpeg

Here are the antennas. I’m hoping better high altitude signal strength comes with these.

7C5EFD02-1D4C-4EFA-9D24-E19E9A9E0D81.jpeg

Here you can see the tello battery circuit board permanently soldered in place so I can connect oem lipoly batts.

AA4A6382-8BE9-41B8-80B4-53299A2CD60C.jpeg

Here’s an example with a 1000mah oem battery installed.

E6A680D2-0D84-41A4-A539-F412910DCE5E.jpeg

My tests have been quick as it was late once I finished nodding but so far I’m happy!! VPS is working well and battery is very close to the centre of gravity so handing is tight as stock at least.

FPV is where I’m focusing for this mod. The camera has been tilt up and it makes a mad arse difference. FPV in fast mode is cool and works well.

More updates soon.

Cheers,
ph2t.
 

ph2t

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#17
I’m testing out a few different battery configurations.

From left to right: 1S 1000mah 70C (supposedly) lipo, 1S tello 1100mah lihv, 1S2P 800mah lipo.

085E396E-344B-41EE-A601-9905AFE1EA03.jpeg

I’m getting a few issues with error -13, the power down and land procedure happens a bit too.

I feel that the tello battery monitor is suited to the lihv battery’s that have a higher operating voltage(4.35v). Putting a lipo in with the lesser operating voltage(4.2v) might be causing unknown responses within the tello.

I dunno, gotta test more....getting cranky, it’s late...

cheers,
ph2t.
 
Likes: Santiago
Joined
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#18
I’m testing out a few different battery configurations.

From left to right: 1S 1000mah 70C (supposedly) lipo, 1S tello 1100mah lihv, 1S2P 800mah lipo.

View attachment 3067

I’m getting a few issues with error -13, the power down and land procedure happens a bit too.

I feel that the tello battery monitor is suited to the lihv battery’s that have a higher operating voltage(4.35v). Putting a lipo in with the lesser operating voltage(4.2v) might be causing unknown responses within the tello.

I dunno, gotta test more....getting cranky, it’s late...

cheers,
ph2t.
Why not use a 1s LiHV battery.... Should be the same voltage as the Tello battery...

Sent from my SM-N950F using Tapatalk
 

ph2t

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Location
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#19
@Jesusfreak - I have bought some lihv batts, used in those tiny whoop drones. Yet to test them out.

Unfortunately I think I’ve killed something with all my modding. Will get another tello battery (stock) to test if the issue is in my hacked battery pcb to regular lipo pack setup.

Did a silly thing and ordered to tello edus. Haha!

Cheers,
ph2t.
 

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