Solar Sizing for Low Power Displays
An E Ink project often needs tiny energy, yet it can fail when solar sizing is guessed. This calculator helps convert screen behavior, sleep current, refresh energy, battery capacity, and local sun hours into practical design numbers. It is useful for shelf labels, weather tags, garden signs, dashboards, mailbox indicators, and simple outdoor sensors.
Why E Ink Changes the Estimate
E Ink screens usually draw power during updates. They may use very little energy while the picture stays still. That makes duty cycle important. A device that wakes once each hour needs a different panel than one that refreshes every minute. Sleep current also matters because it runs all day.
What the Tool Measures
The tool estimates daily watt hours, adjusted load, required panel watts, panel output, battery reserve, autonomy, and charge time. It includes efficiency, controller loss, temperature derate, reserve percentage, and safety factor. These options help you test a realistic build before buying parts.
Planning Better Solar Projects
Start with measured current whenever possible. Use a multimeter or power monitor during sleep and active periods. Then enter the local peak sun hours for the worst useful season. A winter value is safer for outdoor signs. Add reserve for cloudy days, aging cells, dust, cable loss, and imperfect mounting.
Reading the Result
If daily panel output is higher than adjusted demand, the setup should maintain charge in average conditions. If the balance is negative, increase panel watts, reduce refresh frequency, improve sleep current, or choose a larger battery. A bigger battery gives autonomy, but it does not fix poor daily charging. The panel must replace the energy used each day.
Common Input Choices
Use conservative defaults when data is uncertain. Many panels produce less than their label rating. Batteries also lose capacity with age. For unattended displays, a margin is not waste. It is protection against dim weather, dirty covers, and longer update cycles.
Useful Design Advice
Keep wiring short. Avoid shaded locations. Place the panel toward the best sun angle. Use a charge controller suited to the battery chemistry. Leave extra capacity for cold weather, display changes, and firmware updates. Review the numbers again after field testing, because real projects always vary.