nema17 stepper window shades, 150mAh LiPo?

I want to use several stepper motors to control several window shades in a home. I want to daisy chain the controllers with RS485 over cat5, and also use the cat5 for power. Due to the max wattage safe for cat5, there is a limit on how many motors can run at the same time. My first thought was to run them in sequence, but that really won't do the project justice when I press the button for the first time.

My next idea is a tiny LiPo battery and charging chip on each controller. Since the motors only run for a minute, something really small would work. 150mAh is the smallest I can find, and the price is so low I am done looking for anything smaller. In theory, as long as the motors draw from the batteries, many of these controllers could charge at the same time from the cat5. (at least 10-20 of them depending)

  1. I am curious how much current I can draw from a tiny 150ma LiPo battery (the C rating is not listed on ebay). Would I be safe using a 1.2 amp stepper motor from one of these?

  2. are cheap ebay lipo batteries a safe option for my application? They will be near direct sunlight for years, being in the window. the heat scares me to some degree.

  3. am I better off with a capacitor? or lithium ion?

example 150mAh Lipo:
http://www.ebay.com/itm/3-7V-150mAh-130-210-UP-RC-LiPo-Battery-AKKU-SH-V-MAX-6020-Syma-S107-S108-S026-/370936708495?pt=Radio_Control_Parts_Accessories&hash=item565d8cfd8f

Thanks in advance,
Mike

Do you really need stepper motors? They use just as much power when they are stationary as when they are running.

What sort of window shades are you talking about - how do they work?

I wouldn't by LiPos that unless they have a C rating and are supplied by someone who will take responsibility if they burst into flames if used within the specification.

How often do the motors need to run for 1 minute? Will there be enough time to recharge the small batteries?

Why does the size of battery matter?

What voltage batteries are you thinking of? And will that voltage be sufficient for the motor?

What stepper motor drivers boards are you planning to use?

What stepper motors are you planning to use?

What, exactly, do you mean by daisy-chaining the controllers?

...R

The small gear motors that Pololu sells (and you can find elsewhere) are actually designed for window shades. With a DPDT relay and limit switches (scroll down) you can do as well or better than a stepper motor.

Your battery is designed for a small helicopter. Guess that it flies for 10 minutes at best, so it should be good for a 900ma current draw (150ma over 60 minutes =~ 900ma over 10 minutes). But I wouldn’t hang LiPos around my house – even the small risk of fire is just too much. Suggest you stick with NiMH or Lithium Ion AA cells or such.

LiPo's should never be charged unattended, and should be charged on a fire-proof surface. That completely
rules them out.

I like the fact that they report back if someone manually adjusts the shade

They don't.

Stepper motors have no feedback system. Systems using steppers must be designed so that they cannot / will not be moved by external forces.

...R

how about a AA lithium ion like this? it says 50w circuit max? if that's even close to accurate, I'm sold on the battery size of AA.

http://www.ebay.com/itm/3-7V-1200mAh-ICR-14500-AA-Li-ion-Rechargeable-Battery-for-Flashlight-D9-/400650939179?pt=US_Rechargeable_Batteries&hash=item5d48a82b2b

miketedeschi:
how about a AA lithium ion like this? it says 50w circuit max? if that's even close to accurate, I'm sold on the battery size of AA.

Those specs are overly generous; that would be a 13A discharge. Compare to: Tenergy 14500 3.7V 800mAh Li-Ion Rechargeable Battery - Tenergy which is rated at just 160ma discharge.