Iterative process to simulate Propeller Battery model

Hello Guys,

I´m currently trying to simulate a DC motor which is connected to a propeller. Therefore I created a Model for the propeller, battery and the DC motor ( according to a equivalent circuit) .

Propeller :

INPUTS : pitchInches, diameterInches, rpm, rho, Pprop, Thrust

OUTPUTS : Ct and Cp

Battery:

This model is based on the model presented here https://www.mathworks.com/help/physmod/sps/powersys/ref/battery.html#bry4req-2

The only necessary physical Input is the IBattery. The necessary constants were obtained through experiments.

DC motor:

The governing equations for the Model I chose are : w_em = (V-I*Ra)*Kv | T_em = (I-I0)/KV

I assume that w_em is equal to w_prop

My problem is the equation w_em = (V-I*Ra)*Kv ! I try to numerically recreate a experimental setup. In this test the throttle setting of the EM was swept from 10% up to 100% and the rpm, torque, current and voltage were recorded. The power is supplied by batteries.

Now my problem is :

-> when I increase the throttle over time the voltage of the battery drops while the current is increased ( results of the experiment )

-> but according to this formula when the voltage decreases and the current increases the rpm should decrease which is wrong !!

I must interpretate some variables in the formula wrong. Can anybody help me ?