Want to make 20 minutes with truggy..

[BrianG]

Just using a low kv doesn't necessarily mean an efficient setup if you gear high to compensate for low rpm. Also, efficiency does play a role in runtime amounts, but won't get you an extra 8 minutes to reach your 20 minute goal.

In your current setup, you say you get 12 minutes on 4s 5Ah. That equates to 25A average draw and 370w average power. Of course bursts will be higher, but that's average.

To get 20 minutes without changing your gearing/speed, you would need to run 6s on a 1300kv motor using 5700mAh cells. Adding in a little extra capacity to make up for the greater battery weight, I would go with 5800mAh. That seems a bit much for just 20 minutes in a truggy. Without looking at the vehicle speed, I would suggest gearing down if you can afford a little loss in top speed. Also, change ESC settings to tame those runtime-robbing huge current bursts: high punch control, low timing, etc.