Parkside X20V TEAM LED Floodlight Adapter

Motivation & Design

I had a couple of heavily-modified “100W” 12V LED floodlights bought some time ago from AliExpress.

Upon arrival I've discovered that they are closer to 40W than 100W, which is probably a good thing since the LED chips aren't driven too hard.

The unpleasant part was the lack of proper cooling - the manufacturer actually used a few drops of hot glue as a thermal interface between the LED PCB and the metal frame, and compared to the 230V mains version there's no thermal regulation that would limit the current if the PCB got too hot. If used as-is this would limit the lifespan of LEDs severely.

So I stripped the paint both sides of the metal frame and added a couple of beefy heat sinks on a thermally conductive silicone caulk. The PCB was placed on a standard thermal compound. The rather useless CCA wire was replaced with a barrel jack socket.

More detailed description of how I modified the floodlight is out of scope for this project, as this design may be used with any floodlight that accepts DC up to 30V.

Since Parkside X20V battery provides … well … 20V DC, it cannot be connected directly to the floodlight, so some power conversion is needed.

I had some experience with XR-131 LTC3780-based DC-DC converters. They are:

• rather cheap
• quite efficient
• able to operate in constant current (CC) mode, which can be used to regulate the power
• with integrated undervoltage protection

They do require some modification for this particular project, so do not attempt replicating this design unless you have a soldering iron and basic soldering skills.

The assembly also requires a power supply with adjustable output voltage to correctly setup the undervoltage protection and a voltage meter to set up the output voltage.

Parts Required

• 1 x XR-131 LTC3780 board. Sold for 6-7 EUR on AliExpress.
• 1 x WH148 pot. The converter board uses a 200k multiturn trimmer pot for current adjustment in CC mode, but my floodlight maxes out its current at ¼ of the 200k range, shifting to 12V CV mode, so I chose a 50k pot instead. This way there's more adjustment range, but your mileage may vary. Do not go over 220k however. This design assumes no pin near the shaft to hold the pot in place, be sure to pick a similar pot or modify the STL/SCAD if using a different one.
• Heat-shrink tube that fits the pot terminals.
• 2 x XINYA XY2500 508 PCB-mount connectors. Not strictly needed if you plan to solder input and output wires to the PCB.
• 1 x 3mm red LED. Used for signalling fault condition like disabled output or low battery.
• 1 x 3mm green LED. Used for signalling enabled output. Useful for diagnostics when the floodlight itself isn't working, but power is available.
• 1 x 9x14mm SPDT switch. When closed the board will disable the output and vice versa, so an SPST can also be used, but "ON" and “OFF" will be inverted.
• Heat-shrink tube that fits the SPDT/SPST switch terminals.
• 750k ¼W resistor to add hysteresis for undervoltage protection.
• 2 x 2-pin 2mm female crimped wire connector for LEDs. 
• 1 x 2-pin 2.54mm PCB header + ca 7-10cm crimped wire connector for the switch.
• 1 x 3-pin 2.54mm PCB header + ca 7-10cm crimped wire connector for the CC pot.
• 2 x ~10cm 1.5mm² wire + 6.3mm male blade terminals for battery connectors; try to use red and black wires to distinguish polarity.
• 15-20cm DC coaxial cable for output connector; should be no less than 0.75mm² for each pole.
• 3 x M4 nuts. One for floodlight mount, two for battery adapter mounts.
• 2 x M4 20mm bolts for battery adapter mounts.
• 1 x M4 12mm countersunk bolt for floodlight mount.
• 4 x M3 10mm countersunk bolts for case cover.
• 4 x M3 square nut for case cover.
• 4 x M3 6mm bolts for PCB fastening.
• Neutral silicone caulk and/or hot glue.
• Cyanoacrylate glue (Superglue).

LTC3780 Board Modification

1. Screw terminal blocks are desoldered and either replaced by top-accessible PCB-mount terminal blocks or directly by input and output wires. The design makes no room for side access.
2. The middle multi-turn pot is replaced with a 2.54mm 3-pin header.
3. The unpopulated 3-pin ON/OFF pin header placeholder is populated with 2.54mm 2-pin header aligned near the edge. I've used a 3-pin header, because I had only those lying around. Regardless only the two bottom pins are used to enable/disable the output.
4. The SMD LEDs are desoldered and replaced with crimped 2mm connectors. A drop of glue is recommended after soldering as the wires get bent and eventually snap off due to fatigue.
5. The boards I had were with a dangling power inductor. A drop of neutral silicone caulk fixed the problem.
6. The converter will start flickering when approaching the threshold set by Vcut (i.e. undervoltage protection voltage), so to remove the flicker a 750k resistor may be added between pins 5 and 7 of the LM358 opamp. This value can give a hysteresis range of ~0.8V, which allows decisively turning off the lamp once the battery is discharged in operation, but also not limit its useful capacity if used intermittently. You may want to experiment and choose a value that suits you best. Larger resistance value decreases the hysteresis range, lower value increases. Based on my experiments a 470k resistor gives ~1.5V hysteresis. The resistor once soldered should be protected from dangling using a drop of hot glue or silicone caulk.

Printing

For this project I used red and black PETG from Spectrum, dried and printed on Prusament PETG settings in PrusaSlicer.

For the box and the cover I used 25% infill, for the floodlight clamp I increased infill to 30%.

For the box and the clamp no support material is needed, but it is mandatory for the cover part.

The attached 3MF has all settings dialed in.

I've printed the bottom part from the design by boorek with 25% infill as well, although the original design suggests 30%.

There are many options for the potentiometer knob, but I chose the KNOB B Φ 15 from the design by Bartosz Niedziałkowski. You may want to add a drop of contact glue inside the knobs, or else they might fall off.

Post-processing & Assembly

1. Crimp or solder the 6.3mm blade terminals onto 1.5mm² wires and assemble the battery connector.
2. Fasten the battery connector to the bottom part of the case using 2x M4 nuts and M4 20mm bolts.
3. Put 4x M3 square nuts inside the pockets for the top cover.
4. Add a drop of cyanoacrylate glue to the nut holder of the top part and put 1x M4 nut inside it.
5. If soldering the input and output wires, strip, trim and connect them to the converter input and output respectively. Skip steps 7 and 15.
6. Fasten the modified PCB inside the bottom part using 4x M3 6mm bolts.
7. If using XY2500 508 screw terminals, trim and connect the input wires to the connectable part of the terminal; the wires should be tinned or crimped in a ferrule in this case.
8. Add heat-shrink sleeves and solder 2-pin crimped wire connector to the output enable SPDT switch.
9. Fasten the output enable switch to the top part. A drop of hot glue or silicone caulk may be added to immobilize the switch in case the port is too large.
10. Add a drop of cyanoacrylate glue to each 3mm LED hole near the switch in the top part and fasten the 3mm LEDs inside the holes. The placement of LEDs doesn't matter as long as you know what they represent. I've chosen the red to be near the edge, so that it lights up next to the switch when it's in “OFF” position.
11. After the cyanoacrylate glue is polymerized trim the LED leads to ~4mm length. Mind the polarity to avoid further confusion. The longer lead is positive/anode.
12. Add heat-shrink sleeves and solder the WH148 pot to the wires with crimped 3-pin female connector.
13. Fasten the WH148 pot to the top part of the case with its pins facing the side opposite of the output screw terminal.
14. Lead the coaxial output cable through the hole near the LEDs.
15. If using XY2500 508 screw terminals, trim and connect the output wires to the connectable part of the terminal; the wires should be tinned or crimped in a ferrule in this case.
16. Connect the switch to the 2-pin header of the PCB, the pot to the 3-pin header, input and output in case of XY2500 508 screw terminals + each of the LED connectors to the corresponding LEDs.
17. Connect the battery connector to the adjustable power supply. The output voltage can be in the range of 10-30V. Be sure to leave the floodlight disconnected from the output. When turned off only the red LED must be lit, when turned on, only the green one. The green may persist for some time after the red turns on because of residual output capacitance, but will nevertheless eventually fade away.
18. Turn the output current pot to maximum and adjust the output voltage trimmer (the closest one to the output) so that the output voltage is 12.0-12.1V for a 12V floodlight.
19. Set the output voltage of the power supply to 16.9V. Start increasing the resistance value of the Vcut trimmer (closest to the input) until the red LED turns on and the green LED starts to fade. Increase the output voltage of the adjustable power supply until the red LED turns off and the green is fully lit. With the 750k hysteresis resistor this should be in 17.5-17.7V range. X20V TEAM batteries should not be discharged below ~17V.
20. Connect the floodlight to the output and test the undervoltage protection. The floodlight should decisively turn off if input voltage is <16.9V and turn on again when the voltage is ≥17.5-17.6V. 
21. Disconnect the floodlight and the power supply, carefully tuck in all wires and put the top part, securing it with 4 x M3 10mm countersunk bolts to the bottom case part.
22. Secure the floodlight to the top part using the top clamp and M4 12mm countersunk bolt.
23. Solder or otherwise connect the floodlight to the output wire. For my modified floodlight I used a barrel jack.
24. Try out the adapter with a charged X20V TEAM battery. A proper discharge test is recommended.
25. Voila! 🫡 😎 👏

Notes

1. The undervoltage protection does not allow leaving the adapter constantly connected to the battery, as the quiescent current of the red fault LED + LTC3780 will slowly drain the battery beyond safe voltage level.
2. I've included an OpenSCAD source file in case you need to modify e.g. output cable hole dimensions. Feel free to use it.