Originally Posted by onegreenev
Is there such a controller for the RC vehicle with the ability to cut back power once a low voltage is reached?
I would like to elaborate on the answer already given. I manufactured and sold the first digital speed control in the US in 1992. I was told that someone in Switzerland made one in 1991. My first model did not have a low voltage cutoff but at that time there was no point. The NiCd batteries that people were using then don't mind being run flat. This was a 0-24 volt and 60 amp continuous current brushed motor control. When I got my Warp9 I used one of the prototypes I still have to spin it up. My second controller was intended to be used with a class of racer called Speed 400. These planes weighed between 9 and 14 ounces in race trim and their straight and level speed was a little over 100mph on about 100watts. This second control was capable of operation up to about 15 volts and 15 amps and weighed about half an ounce. It also had a circuit that could power the radio receiver and servos from the flight pack instead of their own battery. (Think of this as a DC-DC converter.) This circuit ended up being called a BEC (Battery Eliminator Circuit). The problem with BECs is that if the flight pack voltage drops below about 5.5v the radio stops working and the plane will crash. So I incorporated a low voltage cutoff that would stop the motor when the flight pack reached a preset voltage. You would then have a few minutes in order to land before the radio dropped out.
This particular feature has been incorporated in one form or another in pretty much all the motor controllers since then. It was a no brainer to modify this feature to protect battery from over discharge instead of protecting the radio from failure.
There is one exception to the use of a low voltage cutoff and that is with the RC helicopters. Almost nobody uses the low voltage cutoff because if you cutoff the power to the rotor the heli will crash unless the pilot is very skilled in auto rotations and the heli is in an attitude with some altitude to allow recovery.
I stopped manufacturing my controls in 1994 when I started consulting with AstroFlight and designing circuits and writing code for them. The main reason I did this was the business was ruining the hobby for me and I was at the point where I needed to hire some people or do something else. I chose to continue to enjoy the hobby and let someone else do the stuff I didn't enjoy.