Let's @#$%ing face it: bearing in mind implied contact losses (and even if don't) the useful voltage window of li-ion cells overlaps operational emitter voltage windows. A multi-purpose 1S/1S driver should be able to accept input voltages from 2.5V, offering regulated output up to at least 3.8V. This means buck and boost.
And another thing: PWM is bad. Since little to no one complains, there's no @#$%ing care about. The usual high frequency (4+KHz) switching of 7135's is the last straw, it causes lower efficiency and much earlier loss of regulation. A proper LC filter at the output of linear regulators can fix these issues, providing proper stable DC to the emitter and doing away with the need to switch on/off faster than our poor 7135s can tolerate. This means an inductor in series with the emitter is required. Can someone bear with me and do some inductor calculations for 1 to 2KHz 7135 PWM frequency? Is this too low frequency to smooth out?
I did something wrong, your calculations look correct. Yes, at higher current the difference would be lower.
Either way, when I see that a different driver enables 5% higher sustained performance and 5-10% better runtime (depending on mode), I stop seeing the less efficient one as a top choice.
It is possible to add external thermal support, but someone needs to write the firmware for it.
For those still waiting for the 17mm boost driver, I’m still working on it. It will look pretty similar to the one made by loneoceans.
But I still have problems with it, and need to solve them.
With the current MLCC shortage, I can’t get the capacitors that I want for the boost driver, they’re all sold out. I will order from mouser soon though, and get the best capacitors they currently have.
I think a user (Jensen) here managed to get either the H1-A or H2-C driver from into an s2+ by somehow mounting it behind/under the pill and, perhaps, grinding down the PCB to get it to fit.
H1-A is, I think, 20mm and boosts to 6v. H2-C is 22mm and boosts to 12v. I think, but I’m not sure, that the H1-A can be modded to higher compliance voltages.
I think I remember something like that, but all I could come up with a quick search was him building an S2+ into a MT-G2 with a H1-A. But yeah, he mounted the driver behind the pill instead of in it:
LOL, both of the boost drivers are still in the works, just on hold at the moment. Schoki is waiting for some components to get in stock at Muser last I heard and LoneOceans just got busy with life but still plans to do more work on it when he gets more time.
I still have a box for of components for prototyping whenever another prototype design is ready.
Very interesting, looks to be based on the same basic setup as the other drivers but impossible to say without seeing the other side.
I am guessing he ran into similar issues to the rest of us or it would be released already. It is proving very hard to get a stable driver in this form factor that can provide enough power for us.