Hello, I plan to build a battery handheld with a Witty Pi 4 L3V7, a Raspberry Pi Zero 2 W and one protected 18650 Li-ion cell (Keeppower P1835J), with the battery wires soldered to the BAT/GND pads. Before ordering I'd like to check a few points:
1. Does the board have any battery-side protection IC (over-discharge, over-current, short circuit)? Or only the TP4056 over-charge and the MP3423 output short-circuit protection?
2. What happens if the cell is connected the wrong way round? Is there any reverse-polarity protection?
3. Which pin of the PH2.0 battery connector is positive: the one marked "+" near the USB-C connector? Does the red wire of the included cable go to it?
4. Is the battery path to VIN a Schottky diode or a MOSFET? How much lower than the cell voltage is VIN at about 1 A?
5. Is the TP4056 TEMP pin grounded? Can the microcontroller switch the charger off?
6. Does the USB-C connector have 5.1 kΩ resistors on CC1/CC2, so that a USB-C to USB-C charger gives 5 V?
7. How long must TXD stay low before the board treats the Pi as halted?
8. In firmware revision 7, turnOffFromTXD is set after a TXD-detected shutdown or reboot and is never cleared. If a later button or low-voltage shutdown takes longer than the power-cut delay, the board treats it as a reboot and does not cut power. Is that intended? Do you recommend the 25 s delay for a Pi Zero 2 W?
9. If I order now, will I get the new 3.5 mm header (from 10 Nov 2025)? Is the January 2026 STEP file for that revision?
10. With the board on a Zero 2 W, can jumper wires or male pins be pushed into the top of its female header to connect a display and other modules?
11. Is a schematic, or a block diagram of the power path, available?
Thank you!