Poleshoes - Insulated Terminals For 12V Lead Acid Batteries

I like to use old 12V car batteries for all type of projects which require more portable power than what is reasonable available with small rechargeable NiMH or Lithium-Ion batteries. One problem I had, is how to cleanly connect the cable to the battery. The usual battery clamps are do not provide insulation of the battery poles, rather they even increase the exposed metal surface which is prone to produce (potentially very hazardous!) short circuits.

So the aim of this little project is to generate insulated battery terminals that can be used to connect cables to standard 12V lead acid batteries. The terminals are designed for applications in which 12V car type batteries are (ab-)used to power low current applications up to about 20A charging resp. load currents. An example of such a project is using an old car battery to store energy collected by a solar panel.
These pole shoes provide a good and stable electrical connection as well as they insulate to open poles to prevent accidental short circuits.
To connect the end of 1.5mm2 insulated stranded wire to the terminal, strip the insulation at about 20mm and insert the end of the wire into the vertical hole until the insulated part is even with the horizontal hole. Then insert the bare copper part through the hole into the inside of the pole shoe and split it into the strands, so as to optimally contact the battery pole on a large area. For even better hold of the cable, I make a small knot into the very end of the insulated part of the wire, after it passed the first hole. Push the pole shoes firmly onto the conical battery poles and fasten them by means of two M3x12 screws and the corresponding nuts.
I recommend printing the positive pole (+) using red filament and the negative pole (-) using green or black filament.
Update 2014-08-05: I uploaded updated versions of the files, which take explicitly into account that the cone of the minus pole is slightly smaller than the con of the plus pole. There are now also a "+" or a "-" signs engraved on the top of the pole shoes.
Update 2014-08-06: I just uploaded an improved version of these pole shoes which directly incorporates a fuse holder, avoiding the risk of a cable melt-down due to an accidentally shorting. I strongly recommend using either the fused version on at least one pole or else integrating some external fuse right into the power cable.