Lithium batteries have taken over as the primary battery chemistry from applications ranging from consumer electronics to electric vehicles and all kinds of other things in between. But the standard lithium ion battery has a few downsides, namely issues operating at temperature extremes. Lead acid solves some of these problems but has much lower energy density, and if you want to split the difference with your own battery you’ll need to build your own lithium iron phosphate (LiFePO4) pack.

[Well Done Tips] is building this specific type of battery because the lead acid battery in his electric ATV is on the decline. He’s using cylindrical cells that resemble an 18650 battery but are much larger. Beyond the size, though, many of the design principles from building 18650 battery packs are similar, with the exception that these have screw terminals so that bus bars can be easily attached and don’t require spot welding.

With the pack assembled using 3D printed parts, a battery management system is installed with the balance wires cleverly routed through the prints and attached to the bus bars. The only problem [Well Done Tips] had was not realizing that LiFePO4 batteries’ voltages settle a bit after being fully charged, which meant that he didn’t properly calculate the final voltage of his pack and had to add a cell, bringing his original 15S1P battery up to 16S1P and the correct 54V at full charge.

LiFePO4 has a few other upsides compared to lithium ion as well, including that it delivers almost full power until it’s at about 20% charge. It’s not quite as energy dense but compared to the lead-acid battery he was using is a huge improvement, and is one of the reasons we’ve seen them taking over various other EV conversions as well.

Syringes are pretty ergonomic, but when manually dispensing flux and solder paste it doesn’t take long before one wants a better way. [Elektroarzt]’s flux and solder paste dispenser design uses 3D-printed parts and minimal hardware (mostly M3x20 screws, and an optional spring) to improve handling and control.

How does it work? The ratcheting lever mechanism is similar to that of a hot glue gun, where an arm slips into notches in a rod when pressed down, driving it forward and never backward. In the process, a larger lever movement is translated into a shorter plunger travel, enhancing control.

The types of syringes this tool is meant to be used with have a plunger tip or piston (the rubber stopper-looking part, in contact with the liquid) inside the loaded syringe, but no plunger shaft attached to it. This is common with syringes meant to be loaded into tools or machines, and [Elektroarzt]’s tool can be used with any such syringe in a 10 cc size.

It’s an attractive design, and we like the way syringes top-load as well as the way the tool is made to lay flat on a tabletop, with the lever pointed up.

Want truly fine-grained control over your extrusions? Then check out this dispenser which really lets one dial in small amounts. You can also go motorized, and let a small PCB and stepper motor do the work.

EDM (Electrical Discharge Machining) is one of those specialised manufacturing processes that are traditionally expensive and therefore somewhat underrepresented in the DIY and hacker scenes. It’s with great delight that we present EnderSpark, a solution to not one but two problems. The first problem is how to perform CNC operations on hard-to-machine materials such as hardened metals (without breaking the bank). The second problem is what to do with all those broken and forgotten previous-generation Creality Ender 3D printers we know you have stashed away.

To be honest, there isn’t much to a cheap 3D printer, and once you ditch the bed and extruder assembly, you aren’t left with a lot. Anyway, the first job was to add a 51:1 reduction gearbox between the NEMA 17 motors and the drive pullies, giving the much-needed boost to positional accuracy. Next, the X and Y axes were beefed up with a pair of inexpensive MGN12H linear rails to help them cope with the weight of the water bath.

The majority of the work is in the wire feeder assembly, which was constructed around a custom-machined aluminium plate. It’s not lost on us how the original RepRap bootstrapping concept could be applied here: a basic frame made externally in a low-cost material, then using the machine to cut a much thicker, stronger copy for its own upgrade. The main guide nozzle is an off-the-shelf ruby part surrounded by a 3D printed water-cooling jacket. To maximise power transfer from the wire into the electrically conductive workpiece material, the top part of the wire feeder, including the wire itself, is one electrode, and the entire bottom part of the frame is electrically isolated from it. The bottom part pulls the ‘consumed’ stock wire through the nozzle above and keeps it under tension, sending it onward to the waste spool.

Electrically speaking, the project is based on stock Ender electronics, with an additional power driver stage to send capacitor-discharge-derived pulses down the wire from the 48V power supply, up to 10A, generating the needed tiny sparks as the wire is advanced into the electrically grounded workpiece. Industrial machines operate around twice this voltage, but safety is a big issue with a DIY machine. Not to mention 48V and water don’t make the best of friends. Speaking of water, it needs to be de-ionised to reduce dielectric loss, but ionic contamination will build up over time, so it needs to be regularly changed.

Software-wise, the machine is running on G-code, so all that is needed is a custom plugin for Fusion 360 to turn the extracted toolpath (they’re using the Wazer water cutter profile as a basis) into G-code, with knowledge of the material. There aren’t too many variables to play with there.

In the future, a few things are being considered. Adding closed-loop control of the pulse energy would be straightforward, but controlling the horizontal feed rate would be a little trickier to implement with a pure G-code approach. We’ll keep an eye on the project and report back any advances!

If you’re thinking you’ve seen this sort of thing before, you’re right. Here’s another DIY EDM machine, and another, and finally, a Kickstarter we covered a while back that converts any 3D printer into a wire EDM.

Thanks [irox] for the tip!