Avoiding problems as batteries die

I'm revisiting my Arduino R/C car from the ground up project after a year-long hiatus. It uses an L298N motor driver module (like this one) to drive four motors (like this one). Wireless communication is facilitated by a couple of NRF24L01+ modules.

The project continues to be a lot of fun and keeps too many cobwebs from forming in my head.

What I'm running into now, is that the motors draw down the voltage from the batteries to the point that the NRF24L01+ modules become unreliable. With fresh batteries (2 x lithium ion AA) all is well, but it doesn't take long before communication begins to break down.

I will be moving to batteries which can deliver more current. That will delay the problem. A better motor driver is also on the way. However, it seems like one could limit the current delivered to the motors if the battery voltage drops. I can imagine doing this with the help of a voltage divider to monitor the available battery voltage and ratcheting down the current to the motors (by reducing the PWM duty cycle to the ENA pins on the driver). To me, that seems like a decent solution.

Does that sound completely insane? It also seems like something that could be implemented in motor drivers and would have a succinct name.

It was worse than I thought. The wireless connection drops fairly regularly, even with charged batteries. The range is abysmal, a couple of metres at best. So I replaced the AA Li-ion batteries (Trustfire) with 18650s (also Trustfire). That didn't help.

On the car, I noticed that I was filtering the power coming out of the AMS1117 LDO regulator, but had missed a cap on the LDO's input. I noticed that the NRF24L01+ module on the controller end did not have a 10 uF cap installed (between the GND and VIN pins). With the caps in place, the reliable range of the car has increased from about two metres to at least eight (the long dimension of the room I'm testing in).

I'm not sure what will happen when the batteries begin to die. The controls are only forward and reverse at the moment and it gets boring really quick.

Use separate batteries for the motors and the radios, so as the motor batteries die , it wont affect the radios or the range.