Very simple, yet functional and handy jig to hold your batteries while spot-welding. Saw something similar being sold on e-shops. Fits 1x1 to 8x9 set of batteries. multiple parts can be joined together to increase width or length of entire bracket.
I've used 8mm anchor style bolts in the construction, though I think regular 8mm screw could do just fine as well.
Printed that @120mm/s as the quality doesn't really matter much for such a thing.