@tiefpunkt@social.tchncs.de i’d go with multi cell, which would let me use a linear regulator if it turns out that a buck caused problems. With protected 18650 cells charging is easy, just use either a balancing bms intended for power tools, or a usb step up charging module. See pinned thread in my profile https://s.click.aliexpress.com/e/_mMoMTLH https://a.aliexpress.com/_mLtVDYf