u/According-Town1031 — reddlx

Hi!

I’m a beginner building a portable lamp project and I could use ideas or suggestions (different module, power-bank style board, wiring tricks, whatever has worked for you).

Hardware

Battery: 4× 18650 in parallel (effectively one big 1S pack, ~3.7–4.2 V).
Charger: common TP4056 USB board with protection (TP4056 + DW01A + MOSFETs, B+/B−, OUT+/OUT−).
Boost: XL6009 from OUT to ~12 V for a 12 V LED strip.
LED: N-channel MOSFET + PWM from ESP32 DevKit.
MCU supply: planning a buck (LM2596-class) for ~5 V into the DevKit.
Motion: NEMA 17 + TMC2209 (StepStick); VMOT from the same ~12 V rail, logic from the ESP32.
Wiring: 20 AWG from charger OUT to XL6009 IN (replaced thin Dupont).

What happens

B+/B− on charger: ~3.8 V (looks healthy).
Battery only, USB unplugged, XL6009 on OUT:
- OUT+/OUT−: ~0.95–1.0 V
- XL6009 IN: same ~0.98 V
- XL6009 output: ~0.8 V (no real boost).
With USB plugged into the TP4056, IN of the XL6009 often looks much better and things improve a lot.
Continuity: B+ to OUT+ beeps strong; B− to OUT− does not beep (seems like the protected path isn’t happy).

What I already tried

MF72 inrush NTC in series: OUT+ → NTC → XL6009 IN+; OUT− to IN− straight. Same collapse — OUT still ~0.98 V, B+ ~3.86 V.

I’m not looking for one “magic” answer — any ideas are welcome: another charger/protection topology, power-bank IC boards (e.g. 5 V out + second boost to 12 V), 1S BMS with heavier discharge, precharge, etc. Photos / exact readings I can add if useful.

Separate small doubt: I never touched the multi-turn trimmer on the XL6009 (12 V adjustment). Could that alone explain IN stuck at ~1 V and OUT ~0.8 V, or is that only for setting output after the converter has a normal input?

Thanks.