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18650 cell experiment

pěšák

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Hello, I have decided to share my results from experiment with 18650 cells so if you had similiar idea you know what not to do. I wanted to use 18650 cells for their bigger capacity (and potentialy longer flight) and because they are cheap so you can have tens of them with you. Yes, I know they are hevier, but triple capacity of original battery coud compensate it if motors were able to handle it. Initial idea was to remove original battery and use 18650 cell instead. I have made improvised holder to try it firs before I 3D print a proper holder. After putting all together and turning Tello on, I got error 203 (not original battery) so I already knew this was not a way to do it. For fun I have tried to put original battery back in to work with 18650 cell in parallel. To a certain point it worked fine, tello was able to handle the weight, capacity seemed fine (although it showed only 76% at full charge - maybe because 18650 has 3,7V and original battery 3,8V?) but motors were running hot after just a minute of flight, it was just too heavy. So I have got into dead end and this is not a way to do it.

In the future maybe I will try to disassemble original battery and use some parts from it so Tello will think 18650 is original battery. I will probably not be able to charge 18650 from Tello directly because of higher charging voltage but that is not a problem. Maybe motors still won't be able to handle little more weight but it will be interesting to see the results.

I attach some photos from this experiment. I have used blade covers because I tested it indoors and was not sure that tello won't crash with more weight on one side.
96781055_245737643440987_3458946487289905152_n.jpg 97020578_1312595415606105_8387937435346010112_n.jpg 97137074_235563884364274_5363965204067516416_n.jpg 97194826_993810064366888_6088062231650500608_n.jpg

(Sorry for my English and maybe for syme typos too, I am not a native English speaker.)
 

Dan

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Hello, I have decided to share my results from experiment with 18650 cells so if you had similiar idea you know what not to do. I wanted to use 18650 cells for their bigger capacity (and potentialy longer flight) and because they are cheap so you can have tens of them with you. Yes, I know they are hevier, but triple capacity of original battery coud compensate it if motors were able to handle it. Initial idea was to remove original battery and use 18650 cell instead. I have made improvised holder to try it firs before I 3D print a proper holder. After putting all together and turning Tello on, I got error 203 (not original battery) so I already knew this was not a way to do it. For fun I have tried to put original battery back in to work with 18650 cell in parallel. To a certain point it worked fine, tello was able to handle the weight, capacity seemed fine (although it showed only 76% at full charge - maybe because 18650 has 3,7V and original battery 3,8V?) but motors were running hot after just a minute of flight, it was just too heavy. So I have got into dead end and this is not a way to do it.

In the future maybe I will try to disassemble original battery and use some parts from it so Tello will think 18650 is original battery. I will probably not be able to charge 18650 from Tello directly because of higher charging voltage but that is not a problem. Maybe motors still won't be able to handle little more weight but it will be interesting to see the results.

I attach some photos from this experiment. I have used blade covers because I tested it indoors and was not sure that tello won't crash with more weight on one side.
View attachment 6042 View attachment 6043 View attachment 6044 View attachment 6045

(Sorry for my English and maybe for syme typos too, I am not a native English speaker.)
Good experiment. There are dome on youtube modifying batteries also. We have tried one that uses a tiny LiPo batteries at 3.7V 300mah from Noiposi from amazon. We are using a Halocode on top of the Tello"s with this battery. One question, why did you not use the 18650 tunred in the direction of the Tello body? Seems the weight distribution and flight characteristics would be better. Please keep us up to date, as this is an important issue that needs to be solved.
 

pěšák

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Thank you. Battery could not be turned in the direction of the body because it interferes with blades on top or proximity sensor on the bottom. As said, this was only quick testing setup to see if it works and if it worked plan was to 3d print battery holder that would be on the top of tello above blades. Other idea was to put the cell vertically so part of the cell is in the place of original battery (if top cover is removed). But I am going to try that when I manage to get tello work with 18650 cells.
 

volate!lo

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Tello will trigger an early auto landing due to the lower battery voltage. You won't be able to use much of the 18650's capacity.
Combined with the higher weight you won't see any significant increase in flight time.

Fun experiment to kill some Covid time
 

Dan

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Than you for the quick reply. As a rule of thumb, we have found that many drones will lift at least 50% + of their weight, depending on facts such as location of payload. We are working with 3D printed legs found on Thingiverse, and modifying them as a holder for items such as the Halocode. have not done alot of electronic hacking yet, except for the tiny LiPo batteries. We are using the tello and halocode with the mblock IDE. We have tried tossing eggs with flips with a 3D printed tosser from Thingiverse on top of the tello.
 

AReResearch

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This is interesting. I have two dead/bloated Tello battery packs. The cells are toast, but the circuitry is probably fine. Ryze states 3,8V in the manual for the cells. These HV cells can be charged (as Volate!lo wrote) to 4.35V (rather than 4.2 for the usual cells). There are HV versions of 18650 cells like the LG ICR18650E1.
It might be possible to gut a dead pack and wire it to a 18650 HV cell strapped underneath the Tello.
The original capacity of 1100mAh goes up to to 3200mAh - at the cost of additional weight:
The original battery pack is 25g, while the LG ICR18650E1 is 49g plus the old battery housing, 18650 holder and some glue or straps. - This is significant extra weight for an otherwise 80g drone.

I have no idea how that will work out in the end, but it seems worth a try.

EDIT: Ordered one of the LG cells. - Will keep you posted.
 
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Dan

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Some ideas, we 3D print legs for the Tello, and now a cover for the Halocode that requires a similar light weight battery. We have found a tiny LiPo battery ( Noiposi, 3.7 volt battery on Amazon ) It powers the Halocode well . We are redesigning the Tello legs and Halocode/battery cases for this approach
 

AReResearch

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That solves that problem:
Tello18650HolderV2.jpg
With the extra weight of 58g, the the craft just barely manages to take off. The test was powered from the original battery, so it's weight will eventually go away. But the craft now is badly top-heavy.
Turning the battery 90 degrees and mounting it underneath the Tello, just clear of the bottom camera, is a possible alternative. (Meaning I arrived more or less at the point where pěšák started the discussion.)
 
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pěšák

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Good job! But I am still quite pesimistic about total weigth. I have done a little progress - I have gutted original battery pack and used electronics with 18650 cell and it worked. I didnť get to the test flight because when I changed the battery I accidentally put it backwards and fried battery circuit in half a second (luckily Tello itself is fine, although there was a lot of smoke). Next time I am going to solder a fuse to it so this wonť happen again. Diode might also do the work but I am afraid of voltage drop even if I used Schottky (about 0,3V). I will eventually get back to testing if I manage to fix my Tello which I have crashed quite badly.
 

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