Powering motors with PSU for rapid prototyping

I am trying to simulate running 10-12 motors using two batteries and a power expander. I have a small PSU and the motors stall very early. An example is 4 high speed motors connected to a 1/35 gear train and the motors can’t even turn the wheel. I believe the PSU isn’t generating enough current but I’m not sure how much the battery set up can actually provide. I’m pretty sure the current limit of my PSU is 3A and that is why it is stalling, I need confirmation and a guide as to what current max I can run. I’m guessing if each motor is maxed at 2A and I have 12 it should be around 24A? Can the batteries supply that? Does 3000mAh mean I can run at 12A for 15 minutes or 24A for 7.5 minutes? Can someone please explain how I can do this, I am just trying to bypass having to program and run through the cortex while prototyping.

I’ve included a pic of the model and motor modules I designed and am trying to test.

The opposing module polarities are reversed so that the motor rotations are combining to rotate the wheel. I tested them individually to ensure the rotations are correct.
.33 motor module.JPG
launcher prototype.JPG

Some answers.

3A PSU for even one motor is marginal, startup current is >4A and will cause many PSU’s to current limit and drop the voltage. There are some threads where we discussed this before. For a bench PSU I would usually try and find something rated at 20A or more, but that can get expensive. There are some much cheaper dedicated power supplies ( not variable) that can do this for < $100.

I’ve seen batteries momentarily output 40A, look on the forum for Quazar’s battery test, he show the performance of the 3000mAh battery at a couple of different loads.