How I Turned an E-Ink Reader Into a Victron Battery Monitor

Description and use

A low‑power, always‑on wall display that updates hourly with Victron battery status, eliminating the need for a phone app and preserving the original Victron setup.

Problem

Need a low‑friction wall display that shows Victron battery status without pulling a phone or app, while the device spends most of its life asleep and has no continuous network connection.

Outcome

A low‑power, always‑on wall display that updates hourly with Victron battery status, eliminating the need for a phone app and preserving the original Victron setup.

Workflow

• 1. Place a single‑line file on SD card with HTTPS URL of Victron JSON endpoint (optional second file for interval).
• 2. On boot, firmware checks for file; if present, arms a wake timer (default 1 hour).
• 3. When timer fires, device wakes, joins saved Wi‑Fi network, and downloads JSON.
• 4. Parse JSON; if valid, cache it on SD card and render screen with battery level, voltage, solar, load, 48‑hour chart, QR code, and timestamp.
• 5. After rendering, device enters deep sleep again.
• 6. If button pressed, device skips UI and shows Victron screen immediately, then arms timer. If USB plugged in during sleep, timer is re‑armed to avoid drift.

Evidence

The screen doesn’t need to know anything about Victron, no API token, no installation ID. It makes a single HTTPS request to a tokenized address and gets back a short payload: state of charge, voltage, solar, load, a timestamp, and 48 points for the chart.

Source

If the Victron file is present, I skip that paint entirely. The same module the timer uses runs instead, so the first Victron screen doesn’t wait an hour.

Source