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Battery mod project for Tello

Ricardo Penders

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UPDATE!! New battery cells with higher capacity, 1500mAh to be tested today!​

Hey everyone, I found new battery cells in a camera that fit into the original battery housing but these are 1500mAh and I'm charging them at the moment and I'm going to test the Tello later today to see how long it can fly with bigger capacity cells.

I've tested the 1000mAh battery cell which is new and got about 8 minutes of flight time, the new battery cells are 1500mAh so if I have to guess I might get about 20 minutes of flight time.

But I'll make a video of it, I have 2 of the 1500mAh battery cells and I've got the 1000mAh cell all charged up to be tested later.
I'll make a screen recording of the whole test and upload it to YouTube and I'll come back here and share the link so you can watch and see exactly how much flight time I now have with the new battery cells.
 

Ricardo Penders

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UPDATE!! The new cells didn't work...​

So I've tested the two new battery cells and they do work, I can connect to the Tello, I can activate the motors and I managed to take off just for a second or two and then the Tello cuts out because the new battery cells can't deliver the necessary power and I suspect because of that the voltage sags and that's what the Tello is measuring constantly.

It's all done in software which runs on the Tello, it's not that the battery itself has any smarts.

So I'm taking the new cells out again and use the one new battery cell from another drone that I got for free for testing and reviewing.

Those battery cells are only 1000mAh giving me about 8 minutes flight time which is better than no flight time at all and because the battery cells are already for a drone they can at least deliver the necessary power so I can at least fly the Tello again.

So the new plan is to try and get some single cell drone batteries on the cheap that have the right dimensions to fit in the original battery case and hope that I'll find some cells with a little bit higher capacity than the original Tello battery cells somewhere in between the 1200mAh and 1500mAh or even more if that's even possible and go with that.
I'll take the BMS off the new cells and solder the Tello BMS boards to the new cells as I've done with the drone cells I've already got and they work properly so I just keep doing that to keep my Tello flying for a couple more years.

I think that's the best way and cheapest way to go forward, I know that I'm not going to spend the crazy amount of money on new original Tello batteries those are way too expensive especially when you have to replace them every year or so.
 

Hacky

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Thanks for your report.
The problem is that cells with higher capacity usually can serve only lower C-rates. I guess that the cells which have been selected by Ryze are already the best compromise.
 
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Ricardo Penders

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Thanks for your report.
The problem is that cells with higher capacity usually can serve only lower C-rates. I guess that the cells which have been selected by Ryze are already the best compromise.
I know for sure that the original cells aren't just some cells that you can buy anywhere, in fact I've contacted a factory directly and they said they can make me cells that will work but they can't make cells that can take the high voltage when the cells are fully charged, which is 4.2 Volts by the way and most cells just don't go that high safely or they won't last very long if you push 3.7V or 3.8V cells to the 4.2V.

If it wasn't so expensive to get a batch of cells made by the factory and I didn't have to order way too many cells for me alone I would push those cells regardless, I've charged 3.8V cells so many time to 4.2V without any issues I don't believe that it's as harmful to the cells as they make us believe it is.

I don't know exactly how many I have to buy to get them manufactured for me but if it's only 50 or 100 cells per batch that's way too many cells for me alone and way too much money that I'm willing to spend on it, I guess the option is still open if I could do it together with other people and share the burden or I must have a couple people that I can sell some batteries so I don't have to use hundreds of cells myself.

If anyone has an idea or if there are enough of you who want to collaborate on this project please let me know, I'm open to any suggestion.
 

Hacky

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4.2 Volts would be a typical charge voltage for almost any Lithium cell. The difference of the Telle cells is that they are "HV" (high voltage) cell types already, which can be charged up to 4.35V.
 
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Ricardo Penders

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4.2 Volts would be a typical charge voltage for almost any Lithium cell. The difference of the Telle cells is that they are "HV" (high voltage) cell types already, which can be charged up to 4.35V.
Ah, okay that's what they mean with that.
Well I know for sure that the Tello batteries are not HV cells, they only get charged to 4.2 Volt maximum.
So normal cells would do fine I guess
 

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