Lexel you're absolutely right! The XAL7070 and 7030 have essentially identical pads so I made the pads fit both inductors, so you can choose whatever you want. Some pills like the Convoy S2+ have a lot of space so it definitely makes sense to go with the big inductor. Others have less space and I've verified it works OK with the smaller inductor too. But like you mentioned, the 7070 helps in reducing DC losses (and thus also less likely to cause the inductor to drop inductance due to heat), and that we can use more inductance for less ripple and less RMS current losses and switching losses!
As for the capacitors, yes definitely larger and higer voltage rating with better dielectric is more desirable. In fact I did change some of the pads to 1206 before I sent it off for fab last week. Since the inductor is so fat, it's also possible to stack MLCCs on top of each other. Currently I have 94uF on both the input and the output at 16V, though we could do something like a 138uF 10V on the input and 66u 25V on the output, and more with stacking. Finally, I also found some nice bronze springs from Kaidomain which have a ~5mm top and ~8mm bottom. The high drain cells all have fairly large flat tops so I'm planning to try to use those springs in reverse (since my spring pad is very small to save space), but I suppose it doesn't really matter since we'll need to bypass them anyway.
Well the way I have it set up should work just fine I hope with perhaps a change in a resistor or two. The LDO max input is above 2S, and my battery voltage divider also takes this into account so it's a simple firmware change to have it running with 1S or 2S with auto-detection. The downside however is that because this driver is fairly specialized for the application, for best performance ideally one really needs to configure it for either 6-7V out or 12-14V output. For example, if I really wanted to drive a 6V LED hard, I'd choose input and output caps specifically for that purpose which would not work well for a 2S input. Likewise for 2S operation, I can choose a larger value inductor for less ripple and a more regulated output with lower peak switch current. So in short, it can work, but it will not be near optimal. That said, if you're just planning to run at fairly low power levels (<20W), I see no major problems.
Hello Clemence! Yes thanks also for your help in getting Nichia LEDs to the community! I ordered some from you recently so hopefully I'll get to pair one of the 144s with this project.
Thanks for your kind words! For soldering, it depends! Typically for stuff like this I use a stencil and reflow it in an oven, but for one-off small boards like these (at least for now), I typically use hot air for the stuff with pads underneath, or in this case, the big indutor too. The rest I either use hand-placed solderpaste with a needle and hot air it, or use a tiny tip soldering iron and needle tweezers. Typically I do this under magnification.
Thanks MRsDNF! I hope to get this inside a flashlight soon when the host and boards arrive, and when I finish whatever firmware I'm working on right now.