Battery Mod Hypothese

[Theo111103]

Hypothese: Battery Mod adding weight
will put stress on all 4 motors, motor drivers and internal thermal budget of the bird's main electronics....

Having a sense of the vertical accelleration capabilities versus battery current, i would say there must be an optimum somewhere between added weight, battery capacity and the current limit of the drivers...

Who has experience in batt modding and who has some scientific based experience/comments/ideas?

 

[surfbird]

I did some test for platinum, Master airscrews props. Air temp 22C

Added weight Power hovering
0 91W
210 124W
450 170W


I ended upp with adding one extra dji stripped battery (200g)
Gives me 42minutes hovering if I charge to 4.4V and run the batteries very low. Master airscrews props.

Feels like everything above 300gram increases the power drain so much it's not worth it.
Btw the dji batteries is 4400mAh if charged to 4.4V. Until I realized that the math didn't sum up,. Thats why you don't see that big improvement when adding heavier lipos.
It's hard to find anything better weight ratio than dji packs, maybe 18650 cells.

 

[Theo111103]

I did some test for platinum, Master airscrews props. Air temp 22C

Added weight Power hovering
0 91W
210 124W
450 170W


I ended upp with adding one extra dji stripped battery (200g)
Gives me 42minutes hovering if I charge to 4.4V and run the batteries very low. Master airscrews props.

Feels like everything above 300gram increases the power drain so much it's not worth it.
Btw the dji batteries is 4400mAh if charged to 4.4V. Until I realized that the math didn't sum up,. Thats why you don't see that big improvement when adding heavier lipos.
It's hard to find anything better weight ratio than dji packs, maybe 18650 cells.

@surfbird: Thank you, your test confirms my suspicion... maybe two of the mavic batt's internal cells would give the optimal result.... giving the fact that the consumption goes up by mach 2, due to W=P*T and P=I*I*R i suspect props with higher efficiency offering lower rpm
( hence lower current spikes due to less reversed current in the coils ) at same lift-performance could make a noticeable diff...
Would 3-bladed props offer more lift? Did order the MasterAirscrew props, did you see a difference in performance?

 

[surfbird]

Notice very little imrpvoement with airscrew compared to stock when it comes to power consumption.
I think the handling is much better though, with one extra battery it flies very well. Flew in gust up to 24knots and it handled it very well. Almost no decrease in top speed as well.

Havn't tried 3-bladed but everything I read about it says they are less effecient.

What I have found though, is that the power consumtion goes down when hovering in lower temp (5C), with 200g extra weight.

I think bigger props could be the answer. I done an app that meassures the power in real time. Makes it faster to test if a props are good or bad.

Anyway, I think the mavic can handle 200gram very well, both handling and power. If you add more all temps goes up with very little gain in flight time.

 

[Theo111103]

@surfbird: Thank you for your insights!
As soon as i receive my Airscrews and some other props i want to perform a test that creates some more datapoints per Prop...I want to use weight versus rpm versus hovering height ( as the anchor parameter), your findings gave me a good insight of what my guts already told me with regards to weight... That test should put prop-efficiency in relation to the types amongst themselves.

 

[surfbird]

Let me know if you want to use my app. It's just a modded version of dji demo sdk app. Calculates the mean value of the last 3 seconds. Very very basic :-/

I would like to try combine my batt mod with phantom4 props like in this video:

He has done som modifications on the props, it's a little bit unclear how he did it.

I also tried to have 2 big rprops in front, and airscrews at rear. Flew very well I thought that when running in cruise speed the front props are horizontally aligned and might give som extra lift. My thought was that the rear props make the forward propulsion, and the big at front mostly gives the lift. The COG could be moved forward a little if the battery is places a little bit forward. I know, crazy idea, but it flew so well, so I will do some more tests when I get time.

From one of my test flight with 200g extra weight.

 

[Turn11]

Who has experience in batt modding

A little background - MP/MPP
A little more background - M2

 

[Theo111103]

Let me know if you want to use my app. It's just a modded version of dji demo sdk app. Calculates the mean value of the last 3 seconds. Very very basic :-/

I would like to try combine my batt mod with phantom4 props like in this video:

He has done som modifications on the props, it's a little bit unclear how he did it.

I also tried to have 2 big rprops in front, and airscrews at rear. Flew very well I thought that when running in cruise speed the front props are horizontally aligned and might give som extra lift. My thought was that the rear props make the forward propulsion, and the big at front mostly gives the lift. The COG could be moved forward a little if the battery is places a little bit forward. I know, crazy idea, but it flew so well, so I will do some more tests when I get time.

From one of my test flight with 200g extra weight.

Thank you for your kind offer to use your modded App, i'd gladly accept that, it will indeed save time! In the meantime my MPP has been repaired by the DJI service group here in The Netherlands after an upgrade gone bad and i expect a wide range of Props dropping in next week... Hell of a week i had: no flying ;-)

 

[Theo111103]

Let me know if you want to use my app. It's just a modded version of dji demo sdk app. Calculates the mean value of the last 3 seconds. Very very basic :-/

I would like to try combine my batt mod with phantom4 props like in this video:

He has done som modifications on the props, it's a little bit unclear how he did it.

I also tried to have 2 big rprops in front, and airscrews at rear. Flew very well I thought that when running in cruise speed the front props are horizontally aligned and might give som extra lift. My thought was that the rear props make the forward propulsion, and the big at front mostly gives the lift. The COG could be moved forward a little if the battery is places a little bit forward. I know, crazy idea, but it flew so well, so I will do some more tests when I get time.

From one of my test flight with 200g extra weight.

Great Batt-Mod results @surfbird! I did read the Bare Cells weight is 210 grams, what would be the weight of the housing?
Maybe one cell on top ( above the front of the bird ) and one cell at each side would give the wanted result in shift of COG plus the added capacity?

 

[Theo111103]

Let me know if you want to use my app. It's just a modded version of dji demo sdk app. Calculates the mean value of the last 3 seconds. Very very basic :-/

I would like to try combine my batt mod with phantom4 props like in this video:

He has done som modifications on the props, it's a little bit unclear how he did it.

I also tried to have 2 big rprops in front, and airscrews at rear. Flew very well I thought that when running in cruise speed the front props are horizontally aligned and might give som extra lift. My thought was that the rear props make the forward propulsion, and the big at front mostly gives the lift. The COG could be moved forward a little if the battery is places a little bit forward. I know, crazy idea, but it flew so well, so I will do some more tests when I get time.

From one of my test flight with 200g extra weight.

The P4 Prop-mod is relatively simple: The base-plates on top of the motors can be taken off the P4 motor and installed on the MP motors after which the Props can be mounted as usual. It should take losening and tightening of only 2 or 3 small screws that hold the base-plates to the motors. The base-plats and Props are paired.

 

[Theo111103]

A little background - MP/MPP
A little more background - M2

Thank you @Turn11 ! Very helpful!!