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Suggestion: Self-Charging RoboMaster
2945 11 2019-10-17
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MediaElite
lvl.4
Flight distance : 408343 ft
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I watched and played with my friend's R oboMaster.  As a python user, I find it very interesting for some analysis.  There is one thing that hinders the workflow of my project....battery charging.  So I'd like to suggest something for the S2:  SELF-CHARGING.  I imagine it would be able to autonomously mount onto a charming base when idle or low on power (like RTH protocol).  Autonomous charging will expand it's use case exponentially, utilizing machine learning throughout the day without micro managing too much.   




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2019-10-17
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DJI Gamora
Administrator

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Hi, thank you for sharing this pool for us. Hope that you could get the best recommendation from our valued DJI members here in Forum that currently using the Robomaster S1. Thank you for your continued support!
2019-10-17
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rhoude57 - YUL
Second Officer
Canada
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Interesting proposal. One limitation which would be a killer for such a capability would be charging time.

Typical RoboMaster or robotics matches last only a few minutes. If it were to take ten of minutes or hours, the capability would rapidly become a mute point.
2019-10-17
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Duane Degn
First Officer
Flight distance : 598415 ft
United States
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"hinders the workflow of my project....battery charging."
I also find having to charge the battery a pain while programming. I made a Y-harness to allow the S1 to be powered from my bench top power supply. I had to make a small two wire jumper for the I2C lines which let the Motion Controller communicate with the Intelligent Battery.
After I power on the S1, I then connect the power in parallel with my bench top power supply. I start with the bench top supply voltage set to below the battery voltage and then I keep turning the voltage up until about 500mA of current is being pulled from the power supply. I then leave the voltage setting alone and as the Intelligent Battery drains, the current pulled from the power supply increases. Eventually the power supply provides all the power an the battery voltage doesn't decrease.
The robot complains if the bench supply voltage is above the battery voltage.
Using a bench supply in parallel with the Intelligent Battery allows me to program the S1 without worrying about the battery.
The S1 draws about 1 amp of current while idle.
Of course this requires the S1 to be plugged into the power supply. This also works best with an adjust able power supply with a current flow display.
A more mobile option is to use a second battery pack in parallel with the Intelligent Battery. This is a bit trickier since the other battery needs to be at almost the exact same voltage as the Intelligent Battery to prevent one from charging the other at too high of a current. I used a 3 cell LiPo in parallel but only once. It's too much of a pain.
I posted some photos of the inside of the Intelligent Battery in this thread. There's also information about the I2C exchange between the Intelligent Battery and the Motion Controller.
The charger uses only one of the two I2C lines. Post about charger on my Hackaday IO page.
2019-10-17
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gpvillamil
Second Officer
Flight distance : 210226 ft
United States
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A charging dock would be top of my wishlist!

What would be ideal as well would be some way to control the robot over the Internet, since in many ways it is an ideal surveillance robot. The inability to charge automatically is a major handicap for this application.
2019-10-18
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Koonwah
lvl.2
Flight distance : 149206 ft
United States
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Keep the topic. And please send the requirement to RoboMaster.app@dji.com
2019-10-25
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albertr
lvl.4

United States
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I don't think the charging docking station will be very practical for the reason already listed above. What would be good to have is a simple power adapter plug which goes instead of the battery for powering S1 on work bench.

-albertr
2019-11-6
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albertr
lvl.4

United States
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And then again, extended battery which protrudes inside the S1 under the turret would be great to have if it can double the capacity of the existing battery.

-albertr
2019-11-6
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Duane Degn
First Officer
Flight distance : 598415 ft
United States
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albertr Posted at 11-6 10:52
And then again, extended battery which protrudes inside the S1 under the turret would be great to have if it can double the capacity of the existing battery.

-albertr

There's plenty of room for an additional three 18650 cells in the S1. Adding four wires to the original cells would allow one to connect additional cells in parallel.
I have a few concerns about doing this.
Would the charger complain about the extra capacity?
Would the Intelligent Battery's control chip complain about the extra capacity?
The four wires which would allow the parallel cells would also allow one to charge the larger pack with a different charger than the one which came with the S1. I wonder how the Intelligent Battery's control chip would cope with external charging.
The S1's charger doesn't balance charge the batteries directly. The Intelligent Battery takes care of balancing the cells directly. The individual cell's + and - ends can't be accessed from the battery's connector.
Since I've already voided my battery's warranty, I might try adding additional cells in parallel with the Intelligent Battery's cells.  As I mentioned elsewhere, I've previously added a three cell LiPo in parallel with Intelligent Battery but this was a pain since I had to make sure the voltage level of the two packs matched. Having the individual cells in parallel while the battery is charged would eliminate the concerns of trying to match voltages.
2019-11-8
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MarkusXL
Second Officer
United States
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Our S1 batteries are all Lithium Ion, or Li-Ion, not Lithium Polymer, or LiPo batteries.  LIon batteries are safer and more stable.  LiPo batteries are wildly dangerous but pack the best punch.

A friend of mine had his house burn down due to LiPo fire - when those thing go, they go.  We're talking yard long streams of blazing hot plasma, and potentially grenade-like plasma explosions.

Wildly dangerous.  

Good for RC planes and flying drones though, as they have a very high energy density and for not much weight you get plenty of amp-hours.

Even with the much safer LIon batteries, putting either of those batteries in parallel is problematic - because if they are not perfectly matched for impedance and capacity, the slightly stronger cell will always try to charge the weaker one.
2019-11-19
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Duane Degn
First Officer
Flight distance : 598415 ft
United States
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MarkusXL Posted at 11-19 10:11
Our S1 batteries are all Lithium Ion, or Li-Ion, not Lithium Polymer, or LiPo batteries.  LIon batteries are safer and more stable.  LiPo batteries are wildly dangerous but pack the best punch.

A friend of mine had his house burn down due to LiPo fire - when those thing go, they go.  We're talking yard long streams of blazing hot plasma, and potentially grenade-like plasma explosions.

"putting either of those batteries in parallel is problematic"
Not really.
When the cells are first placed in parallel they need to be at the same voltage but as the cells drain and charge they balance automatically.
It's very very common to parallel both Li-Ion and LiPo cells.
LiPo cells are often used in RC vehicles because they can provide higher currents than Li-Ion cells. Li-Ion cells generally have better power densities.
Hot rod quadcopters use LiPo packs. Airplane builders who want the longest flight times often switch to Li-Ion packs.
Again, both types are often used in parallel.
Here's a video talking about the two types of cells:

A video with info about Li-Ion packs in RC airplanes:

Here's a video about charging cells in parallel even if they have different capacity:


Cells should use the same chemistry when charging in parallel.

Many smartphones use multiple LiPo cells of differing capacities in parallel.

As I mentioned earlier, you want cells to have the same voltage when placed in parallel. Once cells are wired in parallel, the voltages of parallel cells will automatically remain equal.

Battery protection circuits added to many Li-Ion cells could make using the cells in parallel problematic. It's probably a good idea to use use cells intended for pack building when placing Li-Ion cells in parallel.

FWIW, I was slow to believe lithium cells could be safely used in parallel. Watching videos like those I linked above finally convinced me.
2019-11-19
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MarkusXL
Second Officer
United States
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I know some of this - but it still remains problematic, especially for hobbyists.  The cells will eventually drift apart, and the weaker ones that drift faster will slowly demand more and more from its neighbors.

This effect is accelerated by heavy loads and high temperatures.  And gets worse as the cells age.

So many fires...

Yes it's often done but especially when doing DIY stuff, use extreme caution.
About power densities, I didn't think LiOn would win.  Maybe they are made super light these days?  That would kick up the ratio of Ampere-Hours / Mass in Kg.

LiPo are very lightweight / low mass.  Hard to beat.  But the punch comes at a risk.  LiOn are much safer, especially with the Smart Chip like we have in the Intelligent Battery.  (I just recently confirmed it bleeds off some juice when put in storage - to keep it at a more stable "storage voltage".  Very smart, I like that feature.)

The worst case seems to be the EDF jet aircraft.  In those forums, the hobbyists talk about to get the most mAh and C for the least weight, and so you need the highest power density possible.
2019-11-20
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