Hi Aircruiser!!

Any News about the Project?

Did you try to hack the drone's firmware? 

https://i.imgur.com/mQOWKIv.png

I can do it another way. Let me ask, do I need to change the value in the right frame?
https://imgur.com/a/iw0ZM0l

Hey, nice work, maybe you can help, I have battery communication error after minor crash on the battery. It looks like battery locks out itself, is there any way to unlock the battery?

Hi. When you said that you got 7 mins fly with 18650 batts how did you detect the end if fly? Was it return to home/autoland feature from the DJIbsoftware? If it was the case, there is a way to disable it so you can controll yourself how much you want your battery to be discharged.

I think at this point the problem was that I was charging the 18650 batteries with the smart control board to make it work. But either way, the Samsung 18650 E35s aren't ideal for the job. The max. discharge current is too low. But I can recommend Molicel INR18650 P28A :)

what if we provided fake voltages ( generated by a boost converter, source is a 3v coin battery for example ) to the board of the smart battery, and balancing voltages, those fake voltages can be controlled over the time to decrease. yet the power supply to the drone is a 6s battery, basically using the smart battery board just to communicate with the drone as it should, would that work ? im thinking about trying this once i find a cheap defective battery. cheers

As far as i know, defective DJI Smart battery will write and "ERROR" code and it wont work anymore. But there is a way how to overcome this, only it is not easy. You need to reprogram BMS with new capacity and other things to work correctly but it is possible to do, only it is not about replacing the cells. 

I think this would not work for several reasons. The battery board "remembers" how much current was used to charge the battery and measures the current when the battery is in use. If you disconnect the battery from the board, the calibration will be reset and the board will send an error message to the drone. Because of this, the drone refuses to start the engines. And even if you could keep the memory intact (I tested it with a LARGE capacitor), the drone wouldn't see any current when you fight the drone. Maybe that's enough to get an error. If not, you still have the problem that no power is detected and therefore the battery percentage in the goggle OSD does not change. It doesn't matter if you change the voltages with a boost converter. The board "counts the current". So you don't know how much capacity is left. If that's not a problem, you don't have to do any of this. You can change one firmware parameter and use any battery. But then there is no percentage display and you have to guess how long you can fly and when your drone will fall from the sky ;)

Very interesting project. my couple of thoughts about possibility hacking DJI FPV Battery. 

As I see it have another two ways for hacking ,one of them it is modify original BMS with chip bq9006 firmware for any elements like 18650 etc. another one is to root DJI FPV Drone system and modify original battery system file for switch off security identification/check original battery. As I know chip bq9003 already hacked, but bq9006 is on develop status. About root DJI FPV Drone as I know it's already done. 

Do you know how https://airdata.com/ works? I mean they somehow know how to download and interpret DJI logs. And it works well with my dji fpv, just plug android to goggles and synchronize.

May be you can combine their logs interpretaion and your communication logs together and find out someth useful.

(unfortunately cannot apply an image https://drive.google.com/file/d/1b8GU5Y_tUYvz46i7CaubmCIgj7JQjqLx/view?usp=sharing)

There is no public chat in your project :)

>> But every time you disconnect them, the control board resets and the battery needs a few percent (up to 100 %) of charging to "calibrate" the battery to the new LiPo.

May be it's not enoght. Lipo in contrast to Lion has a vary flat discharge characteristic, so it's almost impossible to say how much power does it left in your battary if you know only its voltage. It's ok, when you fly just till you battary reaches 3,5V per cell (no matter how long it takes, but you have to see th voltage), but not ok if you whant to know how much time have you left during the flight (eq to see battary percantage). It seems that smart battary counts the capacity during the whole charging, and then, calculates left capacity during discharging, plus controls the voltage for emergancy landing. That's why the battary is 'smart'. So, when you change lipo, you need minimum one full charge-discharcge-charge cycle to calibrate battary brains for it. Better 2-4 cycles. Without it, the percantage indicator is not accuracy and shows 'the weather'.

I did something similar for a different drone (which I cannot remember the name of) but all I did was to dismantle a knackered lipo which had its own make connector I just soldered a XT60 connector to the back of the original battery connector then took the end cover of the knackered battery which had a built in clip to hold the battery in place so now I could fit original battery's or any 3s 2500 mA or more battery's  in.

I also did a very similar project to some cordless tools where I took apart one of the original batteries and removed all of the parts I attached an electrical project box which had hinges and clips to close it, I ran some wires from the old battery connectors down through to the inside of the project box and fitted two XT60 connectors wired in parallel so if I wanted I could fit either one or two 3s lipo battery's inside of the box depending on which tool I was using on a couple of tools it was a bit to large and clumsy but on most of them it worked better than any of the supplied battery's that came with the tools whilst not being the most aesthetically looking modification this was a great where it mattered ie at powering the tool.

Thanks for sharing your work. I was afraid DJI wouldn't make it easy to swap batteries. It seems like you have a semi-workable solution for now. I'll likely try something similar in the future.