Rechargable 18650 Battery Holder for Hunter Douglas Blinds

Our house has a lot of these Hunter-Douglas blinds, each one of which gobbles down 12 AA alkaline batteries every 6 to 18 months.  I finally got sick of it and designed a holder for a five 18650 Li-ion stack so when they are out of juice I can just recharge them.

It's not super-pretty, but the pack and wiring are all hidden behind the shade, right under and towards the rear of the shade's housing.  I take advantage of it not being super-pretty to allow me to use whatever leftover filament I want to get rid of.  One battery pack is about 85 grams, so a roll of filament is enough for 11 or 12 sets.

Print with the solid ends down (I think you'll need to flip one of the two halves in your slicer).  It should print OK with no supports.  I recommend 0.2mm layer height for the cleanest bottom parts where the terminals go and the cleanest threads at the top.   I use 0.3mm for the middle part (most of the print) to speed up the print.  I've been printing with 3 walls and gyroid infill, but 2 walls would probably work just as well; I should try that next time.

Assembly: Insert the terminals, insert the batteries.  Then solder the 1A fuse to the negative terminal, and the other side of the fuse to the black wire (which should go to the outer conductor of the bullet connector.  Crimp a female spade connector to the red wire, and connect it to the positive terminal of the battery pack.  I use electrical tape to tie down the wires and keep them from being stressed.  

To recharge the batteries, pull the spade connector off the positive terminal, untwist the two halves, and remove & recharge the batteries.

It should be pretty clear how the battery pack is mounted.  Print two of the “Battery Holder Holders”.  I find it easiest to put the big hook of the holders under the battery pack, and then slide both holders up behind the blind, where they should appear behind the top of the blind, where you can then press them into the lip on the top.  

Here's where I sourced the parts (you may be able to find better/cheaper alternatives):

Battery Terminals: https://www.aliexpress.us/item/2251832639324517.html

Fuses: https://www.amazon.com/dp/B081Y8M4ZP

Barrel connectors: https://www.aliexpress.us/item/3256801843520446.html

Spade Connectors: https://www.amazon.com/dp/B0CJQ8PN7P

I think that's it - leave a comment if you have any questions.