Hello, thanks for reading my question.
I made a motorized camera slider with a 1.5 amp NEMA 17 stepper, a 28BYJ-48 – 5V stepper motor and the arduino nano. I am not sure about the exact current draw of the system, but it must be around 1 to 1.5 Amps. At the moment it is powered with a 3amp, 12V DC power supply. It works great and all, but I want to take it outside. Therefore, I am looking into batteries and the shop where I usually buy my electronics sells a lead acid battery rated 7.0Ah/20Hr.
Suppose my system runs at about 1.3 amps; does this mean it will last for a little more than 5 hours?

Do you maybe have better suggestions for powering my system?

 

7Ah @ 1.3A discharge is 5.3Hours, ideally you don't want to go below 11V.

 

What matter is how you are driving the stepper. If you are using a current chopper, then I would measure the current at the power supply side. This will be mostly a DC current (with some minor ripple) and you can use a conventional DMM to get an idea of what the system's RMS current is. That is the current the battery will see. Not the motor current, which is usually much higher than the power supply current.

Now, if you are not using a current chopper, then that is a completely different matter... Either way, if you measure the power supply current, that is what the battery will see!