I'm building a small RC offroad vehicle that should have one engine per wheel, with the rotation being determined by the current state of the stearing.
I planned to use BLDCs but found that the cheap ones without sensors are not very well suited for slow running, at least not easily with available electronics.
So now I'm looking for steppers. The typical CAD ones need to much voltage, want to run the thing using 2S LiPo battery 7.3V so rather 5V motors. The typical cheap ones sold with small arduino boards have a 1/64 gearing and run to slow. I'd need something capable of running between 50 and 500 rpm. I know, rather fast for 5V steppers. But I currently think it's the most realistic and economical setup.
Any recommendations? Another solution would be gearing for my BLDCs, but the ESCs are rather expensive and I'd prefer something simple at the wheels, not a stack of things.
Steppers are a poor choice for your application. They are not efficient so waste a lot of battery power. Much better would be DC gear motors. They can run at low RPM (depending on gear ratio) and can be controlled through motor drivers with an Arduino running PWM. If you need positioning with them, they can be obtained with encoders. Check out Pololu's line of motors and motor drivers.
Hm, I once built an arduino powered controller for brushed motors, just using the internal PWM on an H-bridge. I was very disappointed on the speed range. Of course full throttle works fine but slower movement quickly stops turning. Nothing I'd be satisfied with a offroad vehicle.
I also would like to have high torque at slow speed, so that it's possible to carefully climb obstacles.
But on the same time it should also be possible to go on road with "some normal" speed. Of course not like a racing buggy, but at least faster than the ants beside the road.
I'm fine if the 7,3V 4Ah LiPo is empty after 10 minutes. And if required I can use two. That should be enough for medium size steppers.
Could you give links to the brushed and brushless motors and driver modules that you tried ?
The PWM by an Arduino board has a fixed frequency, and that might not be the best frequency. I think that a DC motor with feedback/sensors/encoders would be best for your project. From 50 rpm to 500 rpm is not a big range.
Stepper motors are for exact positioning and waste power doing that. Many modules can set the microstepping, but for a large range you would need a automatic switch between microstepping for slow speeds and full step for high speeds. For higher speeds, it gets harder to put enough current into the stepper coils. Stepper motors are current driven, so 5V (or 7.3V) is too low, you need 12V or 24V.
If you try to push the usage of stepper motors, then you will find that they are indeed a poor choice for your application as groundFungus wrote.