Just discovered something wild with the Oukitel WP5 and now I can’t unsee the potential. I got it for the massive battery and ruggedness, but it turns out it can act like a pocket UPS + LTE router for a Raspberry Pi via OTG reverse charging. I’ve got a Pi Zero W running off the WP5’s battery while the phone shares mobile data over USB tethering. It’s surprisingly stable.
What I did:
- Plugged a simple USB‑C OTG adapter into the WP5, then USB‑A to micro‑USB into the Pi Zero W.
- In Developer options, set Default USB configuration to USB tethering (so it auto-enables when something enumerates).
- Disabled Wi‑Fi/Bluetooth on the phone, left LTE on, Battery Saver enabled, screen off.
- The Pi gets 192.168.42.x over RNDIS and can route traffic out through the phone’s LTE.
Observations:
- With an inline USB meter, I’m seeing 5.08 V no load, dipping to 4.82 V at 0.6-0.7 A. No brownouts on the Zero W; a Pi 3B+ complains.
- Runtime with the Zero W idling and light LTE use: battery drops 3-5%/hour depending on signal. Roughly a workday+ in decent signal, much less in poor signal or with camera workloads on the Pi.
- Heat is modest; the WP5 gets warm but not scary even after a few hours.
The catch:
- As soon as I plug wall power into the WP5, OTG power cuts (phone switches from host to device), the Pi dies, and it becomes just a charging phone. I tried a Y‑OTG “charge‑while‑host” cable and a small powered OTG hub-still no luck. Seems like the WP5’s kernel/PMIC won’t do host+charge simultaneously.
Questions for anyone who’s tinkered with this or knows MediaTek/OTG quirks:
1) Is there any known way (root, kernel, EngineerMode, specific hub) to keep the WP5 in OTG host mode while also charging the phone, i.e., true pass‑through so it can be a real UPS? Does the WP5 support ACA/BC1.2 charge‑through or any PD DRP trick that a particular USB‑C hub can trigger?
2) Is there a safe method to bump the OTG current limit on this device? I’m fine staying at ≤700 mA for the Pi Zero, but curious if there’s a hidden cap that can be raised without toasting the PMIC.
3) Long‑term wear: anyone run reverse‑charging 24/7 on a WP5? Any signs of accelerated battery degradation or PMIC throttling over time?
4) Automation tips: best way to auto‑enable USB tethering on boot or when an OTG device is detected? I’m using Tasker/MacroDroid, but every once in a while after a reboot it stays on “charging only” until I replug.
If pass‑through is impossible on stock hardware, I’m thinking:
- Use the WP5 only as the modem and power the Pi from a tiny DC UPS, then bridge via USB or Wi‑Fi (kinda defeats the single‑brick idea).
- Use a very low‑power SBC (Zero 2 W still ok?) plus aggressive power management to maximize WP5 runtime.
This feels like a super practical rugged off‑grid setup for sensors/cameras, but the pass‑through limitation is the bottleneck. Would love to hear if anyone has cracked host+charge on the WP5 (or any specific hubs/cables that make it work), or if there’s a firmware toggle lurking in MTK EngineerMode I should try.