What to consider when powering multiple devices in parallel?
The book you're studying is very good, however I am not sure it covers in a straightforward manner the parallel connection of different devices (where a device could contain many additional circuits).

Consider just the first five devices you mention:


Device 1: 24V 1A
Device 2: 24V 1.35A
Device 3-5: 24V 0.046A (ea.)


Since they require the same voltage, you can connect them in parallel. The power supply will need to be able to supply their sum total current requirements, ~2.5A (plus additional for inrush current).

If these devices are tolerant of lower voltage, they will try to pull more current to compensate (assuming they aren't just resistive loads like heating coils or something).

Recalculating the current to maintain power for the first five devices:


Device 1: 24W, @18V = 1.33A
Device 2: 32.4W, @18V = 1.8A
Device 3-5: 1.1W, @18V = 0.061A (ea.)


Adding the two motors:


Device 6-7: 11.7W, @18V = 0.65A (ea.)


Summing all the current requirements results in ~4.6A, which isn't much more than the 4.4A you originally cited as your total requirement.



I thought it might be helpful to go through and add up all of the device requirements, but in this case, I don't think the problem necessarily lies with the power supply (unless it cannot handle >4A) or voltage differences. Per Ron Beyer and Simon B's comments on your question, I'd suggest adding flyback diodes to the motors to protect the other devices, and double-check your wiring to ensure you haven't simply made a mistake.