The controller is like a watertap that's
switched on and off very fast (8,16, 32kHz
PWM voltage chopping) to get the desired current. Turning off the current, in combination with the battery wire
inductance, causes voltage spikes because the current wants to continue on its course (ref. inertia of the moving watercolumn). These voltage spikes are
higher!!! than the battery voltage. The input capacitors (cylindrical aluminium 'barrels') take care of these spikes (they reduce the wire inductance). The longer the wires, the higher the voltage spikes induced in the wires, the harder on the input capacitors. They will get warmer, heat up and explode and the rest of the controller will feel the full brunt of the voltage spikes. This is caused by the wire
inductance, not by wire
resistance.