Ferrex (Aldi) 20V Battery Adapter by Thinger13

Last crawled date: 2 years, 11 months ago

This is a battery adapter for Ferrex (Aldi) 20V and 40V (2 x 20V) Litium battery packs to supply e.g. a TS100 soldering iron.
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Update 15 June 2021:
It would be nice to have a cute little voltmeter to check whether the battery has reached the lower discharge limit. But it should not be connected to the battery all the time wasting capacity. Adding a switch would make the design complex.
So I designed this voltmeter module as a separate item (see the first 5 pictures). It is still a bit of a hack. It contacts the battery through the tips of a pair of the infamous 2.9 x 9.5 metal sheet screws while you press the voltmeter onto the battery contacts (it is not screw-on, it is press-on). The wires of the voltmeter are "cold welded" to the screws (similar to the wire-wrap technology of the Apollo-aera). The former adapter cover receives a number of additional holes to let the screws pass through.
I uploaded the new cover. The voltmeter module itself (including the updated .scad file) has not yet stabilized. I am working on it.
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The B2+ contact on the battery is 20V positive, B2- is 0V (ground).
The 40V battery version is composed of two internally separated 20V "half-packs", independently accessible through the B1 and the B2 contact pairs. On the 40V version my adapter draws power from the B2 half-pack only, i.e. the nominal supply voltage is still only 20V and the usable capacity is only half of the 40V battery pack's total capacity.
Caution:
Use only the genuine Ferrex battery charger! Never charge the battery through this adapter. The battery may catch fire or even explode. This adapater completely ignores the temperature sensor accessible via the middle contact ("T / ID"). The temperature sensor is a safety device used by the genuine Ferrex charger during chargeing.
Drawing too much current from the battery pack or a short-circuit most probably WILL (!) lead to fire and/or explosion! I have no profund knowledge of the maximum allowable current. It may be around 10A, but this is just an assumption. There are no maximum current specs on the Aldi or Ferrex website. Again this adapter completely ignores the middle contact ("T / ID") possibly used by genuine Ferrex tools to sense dangerous battery temperatures. You are using this adapter at your own risk.
There may be no battery discharge protection in the battery pack to avoid discharging the battery below a safe minimum and subsequently become dangerously unstable while being recharged. Such protection circuits may be located in the Ferrex tools. So it is up to you to stop discharging before the safe minimum voltage level is underrun. The safe minimum voltage per 20V pack may be around 5 x 2.5 = 12.5V, but please do not call me to account for this figure.
Disconnect the adapter from the battery when not in use in order to prevent accidental short circuits.
If you intend to modify the adapter to use both battery packs of the 40V battery pack in parallel (e.g. to access the full battery capacity of the 40V version still at 20V output to the cable), then you should have profund knowledge about the possible consequences, e.g. consequences of both half-packs having different charge levels, whereupon the half-pack with the higher charge level will try to charge the other half-pack trough your connecting cables at possibly excessive current levels. You may add a high-current diode (> 30A) to each half-pack as a protection against this situation. But what if a diode is becoming a short circuit by accident? I strongly suggest to abstine from such modification.
Using this adapter may void the warranty of your Ferrex battery pack.
To make the cable strain relief work as intended, the width of the circular cable trench must tightly match the cable diameter (current default is 3.5 mm) in order to create some friction. You may have to modify the parameter "d_cable" in the OpenSCAD source file and re-create the .stl file to match your cable:
Download and install OpenSCAD from openscad.org
Open the .scad file in OpenSCAD
Modify the value of the "d_cable" variable according to your cable's diameter
Render with "Design/Render"
Export with "File/Export"
Feed the exported file to your slicer and print
The sheet metal screws are 2.9 x 9.5 mm. The AMP contacts are the red 6.3 mm type. The blue type is too big. I use a piece of double-sided Velcro (TM) to secure the cable when not in use.
Here you may find more information about the Ferrex battery pack:
https://www.youtube.com/watch?v=H9Mb5_nCVeohttps://www.youtube.com/watch?v=2d6iggXptNc
But I am not the author of these videos, so I cannot take any responsibility. I haven't opened my battery pack, so I cannot confirm or deny anything here. And please consider that Ferrex may change the battery cell type between production runs.