Einhell Westfalia Adapter

Acknowldgement

The Einhell part of the adapter is roughly based on the Battery Adapter Einhell Power X-Change General Purpose V2 by Hans. 

Warning

The original battery has exposed contacts which pose the risk of accidetial shorts. The Power X-Change batteries with recessed contacts are much safer in this regard. In order to keep the Einhell battery safe, this adapter is intenionally designed to be fixed to the tool and only allow easy swapping of the Einhell battery, not the Adapter itself. I strongly discourage to attach a battery to the adapter with exposed contacts (i.e. the adapter not mounted to the tool. Shorting the contacts may severely damage the battery and potentially risk fire and/or hazardous outgasing. After Assembly, take extra care to check that the are no shorts in the cabling and the wires are secured so that there is no change for shorts to occur later.

Printing

All parts can be printed with a 0.6mm nozzle and 0.25mm layer height. Both the Einhell and the Westfalia interface parts may require some support dpending on the brindging and overhang capabilities of the printer.

Additional parts

• 10x M3x20 sunk-head screws
• 4x M3x16 sunk-head screws, M3x14 would also work
• 3x M3x10 sunk-head screws
• 9x M3 threaded inserts (e.g. from https://cnckitchen.store/)
• Insulated wire (AWG 15 / 1.5 mm²)
• 2x 6.3mm spade connector (e.g. https://www.aliexpress.com/item/32800318960.html)
• 2x sheet metal 1mm for contacts, 24x20mm² cut to shape
• Optional: 2x 1.5 mm² wire end sleeves and crimping-tool
• Optional: 2x 6.3mm spade connector and matching counterpart

Required tools

• Soldering iron
• Crimping tool for spade connectors
• Crimping tool for wire end sleeves (optional)

Post-Processing

After printing, the highlighted surfaces need to be cleaned as good as possible from leftover support structures:

After postprocessing, add the heat-inserts to the westfalia adapter:

To increase the strength of the part, add 4x M3x20 sunk-head screws and 4x M3x16 (or M3x14) sunk-head screws alongside the sliding rails:

Wiring

For the Einhell part of the adapter, standard 6.3mm spade connectors work great. The Westfalia part however requires contacts with 1 mm thickness, which need to be cut from sheet metal in this form:

A word on tolerances: The tap with 8mm width can be longer than 12.71 mm but should not exceed 15mm. The contact tap width should be within 4-6 mm. To the end of the contact tap (right side), a champfer should be added to all surfaces to assist mating.

After cutting, all edges need to be deburred and and sanded smooth. The flap neds to be bent by 45°:

Obviously, the wires need to be soldered to the contacts before installing the in the adapter. One way of doing this is to crimp on end sleeves and solder those to the end of the contact taps:

Now the contacts are ready to be installed in the adapter:

For better servacibility I added pluggable contacts to each wire, which is completely optional. The contact clamp is held in place by a M3x10 sunk-head-screw:

After adding the Einhell adapter and cutting the wires to length, the spade connectors are crimped on:

Before sealing the wire channels with PLA or hot glue, it's a good idea to do a last check for continuity and shorts.

Final Assembly

The latch needs to able to slide effortlessly in its channel; later it will be secured with 2x M3x10 sunk-head-screws, but since it prevents the adapter from sliding off the tool, you'll need to be able to remove it without it getting stuck:

Disclaimer

I designed this to not have to dispose of a completely fine tool just because the BMS in the rechargable battery is broken and there are no spare parts available. If you make this, be aware that you will operate the tool outside the manufacturer's intention and something may break, possibly with other consequences. In any case, you may loose any warranty you might still have. Make this at your own risk and be aware of potential risks involved. And feel free to share your make, feedback is always welcome.