Yes controls will quit when the batteries get to low. There is no practical way to have much warning with the cheap radios that use individual single cell alkaline batteries. Some may have lights or a simple meter but still that is not all that practical and not much warning.

I do avoid radios systems that do not use rechargeable packs with one exception I do keep a single Attack transmitter to buddy box fellows who have those systems. I tend to avoid problems simply by replacing the batteries often. It gets expensive.

Now on the positive side the batteries can last for weeks or days, it all depends on you. And you do not have to recharge every single trip to fly like you would with NIMH or NICD which are the most common rechargeable packs used in most Tx.

John