Bosch PSR 14,4 Volt rechargeable battery cases for NiCd to Li-Ion conversion

Since I hate to throw away tools that generally work but could do with some enhancement, I've converted an old Bosch NiCd battery drill to use Li-Ion batteries. I found different models for the battery case that all had some issues and combined them into one model that worked for me and my conversion project. You will need to source the electronics (Lithium cells and charge module) yourself. I got mine from Aliexpress. 

The contact strips were done by using nickel strips which are usually used to connect cells. I wrapped the strips around the 3d printed power_contact_strip and point-welded them together at the rectangular hole of the power_contact and then soldered them to the cells. The power_contact_strips with the nickel contact then are pushed all the way from inside the upper part until you cannot move them any further. I glued mine into the rails with super-glue once they fitted. 

The closing mechanism is genius (it was created by the original creator of the upper part, not by me ;-). The two bolts will be pushed outside into the clip_base and make sure that these are kept within the case. You will need to glue the clip-buttons on top of the clip-base. It's a bit fiddely to assemble initially. But once you have everything assembled, it will work just as well as the original from Bosch.

The following parts need to be printed twice:

• power_contact_strip
• bolt
• clip_base
• clip_button

Extra parts required:

• 4x Li-Ion 18650 cells with ≥ 3000 mAh
• 4S 40A charge electronic (look on Aliexpress or Amazon for 4S 40A, 20A will probably do as well)
  • https://de.aliexpress.com/item/32852015245.html
• Nickel Strips 10mm wide
• Spring 6-7mm diameter 20-30mm long
• Some insulation
• 4x 4x25mm or similar Spax-Screws for the case

With this conversion you will end up with a 14.8V (4x 3.7V) battery which will work with the original 14.4V charger.

Printing:

Nothing special. I used standard settings.

• PETG with 50% infill (probably 15-20% infill will do fine as well but since it's a tool, I thought I increase the infill).

The Photos don't represent the final product but one of the prototypes. The final model is more sleek and mechanically better. I will update the photos when I have access to the drill again.