[othello]

I think it is a good idea to keep mechanical brake with the MGM ESC. My buddy uses the brakes of his MGM ESC, but experiences braking problems in his MBX5T.

>use the controller to brake pull lots of curent of the batterie, and cut on the runtime

Actually, braking with the ESC regenerates energy back to your battery pack, thus runtime will be longer. During braking with the ESC current flows back to the battery and therefore you see some amp spikes resulting in a rising voltage (can be compared to charging your battery pack). This puts additional stress to your ESC and it will run hotter.

I would not recommend running your Neu 1515/1Y (2200kv) with 6s. RPMs could exceed 50000rpm. 5s is more then enough and would give you around 40000rpm. This seems way more reasonable and as i already posted does work in a MBX5T and gives you very good acceleration and top speed (with a good battery).

With a good battery 5s could definitively give you better acceleration (if you have enough grip). Let's assume your actual 4s flightpower pack is able to pump out 150A@3,5V x4s = 2100 Watt. The same 5s battery pack would be able to generate 150@3,5V x5s = 2625 Watt. More Power means you could gear it for higher speed and you won't accelerate any slower as you have more power at your fingertip. On the other hand if you use more power, runtime will come down and your components will run hotter.

If you want to benefit from higher voltage (and thus using less amps) you have to gear accordingly. Meaning: If you switch from 4s to 5s, you have 25% more voltage (theoretically 25% more motor rpm), therefore you have to change gearing by almost 25% (for example from 1:14 with 4s to 1:17,5 with 5s). The car will have about the same speed. Amps will drop, as will temperature of your components. Thus leaving more room to gear it for more top speed (if you want to).