Understanding battery capacity with solenoid application

Question

I am working on early stage of product design and was hoping I could get some guidance/ help.

My product will use between 12 and 15 individual, small (less than 1" diameter) rotational, self-returning solenoids.

I do not yet know the force requirements, but anticipate they will be relatively modest.

When power is applied to the solenoids, they will rotate (45-90 degrees). When power is cut, they will need to return to their starting position.

There will be a single power on/off switch and we want all the solenoids to always engage and dis-engage together.

I am hoping that its possible to run all of the solenoids from one battery or set of batteries.

The solenoids would be engaged for approximately 5 seconds at a time. I am trying to understand power requirements and and also to figure out how many times could the set of solenoids be engaged before batteries are drained

The Solenoid I am looking at requires requires .93w

If I use a single D battery with 13,000 mAh capacity to power all 15 solenoids in the device, does that mean I should be able to power the 15 solenoids in the device approximately 931 times (13,000/15/.93)

I do not understand how to take into consideration that the solenoids will be powered up for only approx. 5 seconds at a time and how the hourly value in the mAh should be considered.

Thank you very much,

Jonathan

Answer 1

You're some of the way there in your thinking. To operate, each solenoid needs to be connected to a 5 V power supply. You say its a 0.93 W solenoid so it will draw around 0.186 A from that supply (P = V x A).

So to operate 15 at once, you need a power supply capable of providing 5 V at 2.79 A. That's a steady-state current, a sort of 'up and running' value.

Your 1.5 V 'D' cell supplies about 1.5 V nominal, which will drop under heavy load to a lower voltage. Therefore you could connect 4 in series to get 6 V, giving you some margin if the battery voltage drops.

The problem is that a typical alkaline cell won't give you 2.8 A peak. Revise your question to detail the battery you have and I can expand on this further.