Re the quiescent current - it depends on the chip and switching frequency. Low quiescent draw is becoming pretty common (and usually a variety of other things like burst mode and pulse skipping for low/intermittent loads) but if the core oscillator is super high frequency because everything must be tiny (including the inductors and capacitors), well, parasitic gate charging losses are proportional to F... You can make a stupid efficient SMPS pretty easily if it runs at 50 or 100 KHz. At 4MHz it's a harder ask.
-- Erik On Tue, Oct 21, 2025, 2:50 PM B9 <[email protected]> wrote: > That looks great, thanks for the link! > > The one you linked is the same seller as the one you tested, right? I'm > always suspicious of stuff on Amazon these days. No idea if it's going to > do something out of spec, not work at all, or simply catch on fire. > > I am surprised that the design is such that the cable itself is drawing > non-negligible current from the USB battery. Have you measured actual > wattage? I thought most buck/boost chips had low "quiescent current" modes, > but I'm no expert. > > If it was designed poorly, the conversion to 6V might be inefficient and I > suspect you'd actually get better battery life by just using the 5V from > the USB directly. > > Even with an ideal circuit, I'm curious how much extra life, if any, one > gets by increasing the voltage to 6V. The lithium ion voltage curve is > mostly a flat line and then a precipitous cliff at the end. That's why you > can't trust the red low power light on your Model T to give enough warning > with LiIon batteries. What's more LiIon batteries have an internal > discharge cutoff point to prevent damage due to low voltage. > > Or so I've read. (This is not my field of expertise and I do appreciate > any corrections.) > > --b9 > > > > On October 21, 2025 1:19:24 PM PDT, Scott McDonnell < > [email protected]> wrote: > >> I am going to bet that somebody already found this, but I will tell the >> group about it just in case. >> >> If you are looking for a power adapter to run your M100 from a USB battery >> bank, this is the ticket: >> >> https://www.amazon.com/dp/B0BJDRV4H5 >> >> Boost to 6V and it is already center negative so you don't even need to >> crack it open and flip the wires. >> >> Of course, you can run the M100 from the 5V directly, but you will get more >> life out of this as the M100 shuts down at 4.8V from my understanding. >> >> The only drawback is that it will draw power from your battery bank the >> entire time it is plugged in since it draws enough current by itself to keep >> the battery bank turned on. >> >>
