Custom in-drone Battery Charging Development

StrictlySpeaking · Oct 28, 2018

Hi all - new to this thread so apologies in advance for any faux pas.

I'm trying to develop a way to charge my Phantom 4 as part of an autonomous basestation similar in concept to the product made by skysense. I'm wondering if anyone has any experience with this or knows anything about the related electronics? Obviously this would void the warranty, but I'm thinking if I modify the body of the drone or the battery slightly I can expose the pins then I can connect them to a charger mounted onboard. Connecting the onboard charger then to an external source is not trivial but at least a much more well understood problem. Obviously mounting the charger onboard is less than ideal because of the increased weight, but it seems like the only possible solution as I am only imaging I will be able to provide the drone with +V and GND - it would be hard to make all 10 or so connections the battery port requires. Anyway, I'm curious if people know/have any experience with:

A) Modifying phantom's/batteries to expose the connections

B) Charging the system while its connected to the drone. I need to do more research into this but I'm worried I could fry the drone's electrical system by exposing it the the signals/voltages the battery takes.

C) What all the different battery pins are for. Is there an electrical schematic for this somewhere?

Thanks!

With The Birds · Oct 28, 2018

What do you mean by “charger”?

The charge circuitry is all within the battery- the “charger” as it is often called is simply a regulated DC power supply.

The centre four pins are +VE, two either side -VE with the extreme outer pins being the com lines.

The com lines are not used while charging.

StrictlySpeaking · Oct 28, 2018

Oh that's great to hear! I don't have the charger in front of me so I didn't know how complex the logic was - so it seems like I could imitate the charger simply by having a DC power supply put +17.4V to the center 4 pins and GND to the 2 around that, leaving the 2 outermost unconnected. Do you know anything about if I tried to do that while the battery was plugged in would there be a chance that I fry the internal electronics of the phantom? I would guess not because the drone's +/-Vbat should be rated to handle a couple of amps during flight but don't know for sure...

With The Birds · Oct 28, 2018

There are 4 -VE connections, two either side of the centre 4.

25sec probing the energised battery with a DMM will demonstrate this- I suggest you do it anyway.

Your biggest issue will be finding a way to isolate the phantom electronics from the battery interface board while charging. You will have to do this. It may handle the oversupply voltage however it won’t last very long constantly powered while you are charging.

Just take the battery out and charge it- this seems like more trouble than it is worth.

StrictlySpeaking · Oct 28, 2018

Yes that would definitely be easier but the whole point of the system is that it could run autonomously for days/months at a time

With The Birds · Oct 28, 2018

Autonomously how? You also looking for a means to remotely/automatically power on the battery?

Keeping the battery at 100% SOC for extended periods is a great way to kill it prematurely.

StrictlySpeaking · Oct 28, 2018

The system is a base which allows the drone to make autonomous missions. For example 2 times a day fly around a property and take photos

With The Birds · Oct 28, 2018

Cool.... you have a bit more engineering to do given that scenario. You will almost certainly be looking at nodding the batteries. Battery will need three external contacts and very limited internal modification. As to the external interface an 8bit microcontroller and a handful of parts. The mechanical design (docking and launch) will be the biggest challenge.

Then you need to find a way to get litchi or another app to upload a mission and launch.

Your probably looking at $20K+ to get this to final prototype stage.