Hi Michal and Peterlee,
just by coincidence I did some tests with 9V battery-setup and 11.1V rechargable LiPo accumulator aad steering through the Android App yesterday, Having seen this thread now, I’d like to contribute my results.
Setup:
- Ultimate Robot Kit BT, purchased Dec 2014 through the Norwegian distributor.
- Energy supply through original 9V battery setup, and through 11.1V (peak-current 12.6V) LiPo rechargable accupack.
- Android App latest version on Samsung Galaxy Note 3 (and experience with older version from my memories).
Results:
1. 9V battery setup and old version of BT app (from my memories): I found the originally supplied power too weak (as also reported here in the forum before) when using the Cross-Control example delivered with the app (old version). Thus I bought this LiPo accu and installed it, in order to improve.
2. 9V battery setup and latest BT app: The cross controller did not work any longer. So I set up my own layout with two motor controllers (M1 and M2) and a joystick controller. To my surprise, the 9V setup was good enough now, although the batteries were already worn-out a bit. Turning on carpets (which did not work well before) was no issue any longer. Hence the comparison is from my mories only it may be somewhat subjective, though.
Controlling the tank with two separate motor controls was fine with me (in fact, this is how real tanks have been driven in the past, with two separate and independent controls). Using the joystick control worked well, the robot was well controllable, although I confirm Michals experience with it being fiddly.
3. 11.1 (12.6) V LiPo accu and latest BT app:
First, I really got a shock when my robot capsized because it accelerated two fast with the motor controls set to “150” 
. Then I turned the value down to 75 and the robot worked extremely well, powerfull, yet controllable.
However, when using the joystick now, it turned out that the belts tended to turn way too fast, even on small deviations from the center of the control. The robot was not controllable (or only after a looot of training) with the joystick on this setup.
Conclusions and Recomendations
- Personally, I do not really miss the cross-controller. Two independent controls work fine with me. But as it already exists, it should also be available from the design parts panel, like all other controllers. It is missing there.
- Interesting that the two versions of the app deliver so different driving experience in terms of motor power. Has there been done some tweaking on base values behind the scenes?
- I am missing a function to rotate controls on the display. The Motor controllers move the belts forward and backward, but the controls look like they control “left” and “right”. Not very intuitive (turning the tablet does not help, as then the other modules work wrongly oriented. Just allow rotation of individual controls in 90 deg steps and this is solved.
- For the joystick, some kind of potentiometer function is needed to control the power delivered to the motors. Not only for those who want to run the robot with there own accu supply, but also when the 9V battery setup starts to weaken.
- I’d also appreciate the BT app to be open-sourced. There is a lot of potential in this app and it would be good to bring in the expertise of the community here in order to improve it. Although the biggest issues seem to have been solved in February, it is still clearly a weekpoint in the system (see also the latest comments at the Google Play Store regarding this app!).
Note When using rechargable power supplies do not only look for the nominal voltage, but also to the peak voltage when fully loaded. My accupack delivers 11.1V nominally, but 12.6 V when fully loaded. This is beyond specs for the Arduino and may damage it. It works for me, but is not guaranteed. I’ll post some information on my setup and an image later in the relevant thread.
So much for now,
Stefan
. Then I turned the value down to 75 and the robot worked extremely well, powerfull, yet controllable.