I Turned an Old $60 Android Phone into a 24/7 Edge AI and S3 Server (4.2W Draw)

instead of buying another raspberry pi or letting an old xiaomi redmi 9i rot in a drawer, i turned it into a 24/7 edge ai node and local s3/sqlite storage server running on about 1.2w idle and 4.2w peak. hardware: mediatek helio g25 (8x cortex-a53 cores) 4gb lpddr4x ram emmc 5.1 internal flash + microsd built-in 5000mah battery acting as a zero-cost ups the software stack: rooted android base running a linux chroot with partial wakelocks so android's aggressive lowmemorykiller daemon and doze mode don't quietly murder background processes. speech-to-text: whisper.cpp (base.en) compiled with arm neon simd vector instructions on the a53 cores. llm: llama.cpp running quantized qwen 2.5 (0.5b instruct q4_k_m). memory governor: an in-process jit governor that automatically evicts idle models back to disk after 75 seconds so the 4gb ram never gets oom-killed. storage & db: project-isolated sqlite in wal mode plus an s3-compatible blob store with an in-memory hot ram index. the real headache: grid outages & zombie tunnels the power cuts out roughly once a day here. the phone’s battery means the node itself never shuts down, but downstream chaos was the real killer: the router dies, wi-fi drops, and temporary cloudflare quick tunnels would instantly get killed with http 530s or freeze on stale tcp sockets once the connection returned. to make it genuinely self-healing, i moved to a named tunnel with a persistent domain and wrote a background supervisor watchdog. the second wi-fi comes back up post-outage, it flushes dead socket states, tears down zombie listeners, and resyncs the cloudflare edge worker so the database, storage, and inference endpoints recover without me ever touching the phone. actual numbers: Top comments (0)