Printable light weight spacers to replace the heavy steel ones in the battery pack.  For a typical 48V DIY powerbank with 42 modules you'll save 4.6 kg. I'm building mine on a trolly so keeping weight down will make it easier to manage. 42 steel spacers (top and bottom) weigh 5.5 kg, where as 42 PLA spacers weigh just 0.8 kg. I printed 5 pairs at a time on a Bambu P1P bed (256 x 256 mm), which took 3hrs and 104 grams of filament. I used fuzzy skin on the outside edge to reduce warping hopefully/slightly?). These spacers need to be solid under compression so I printed them with 7 bottom and 7 top layers which gives you a sollid object (same outcome as enabling "100% infill"). I chose PLA because it has good stiffness. My prediction is that this battery will never get warm enough to soften the PLA (50°C). The other option is PETG but it's not as stiff (but it does have a slightly higher softening temp). I don't have any fancier material apart from TPU (higher temp tolerance but way softer). Print settings: PLA Orange 0.4mm nozzle 0.28mm layers 7 walls, 7 base layers, 7 top layers - i.e., solid infill (you could specify solid infill directly if you wish) fuzzy skin on outside walls only. To print 5 pairs at a time takes 3 hours on a Bambu P1P printer. You'll need to print 8.4 beds worth. That all comes to 0.88 kg of filament and 25 hours of printing! So... non-trivial. But it looks cool :)