Power Budget and Runtimes
Edit on GitHubWorked runtime math for every mode, cell capacity and temperature scenario
Power Budget and Runtimes
Overview
Runtime is the product of three numbers: cell capacity, average current draw and temperature derating. This page works through the math so you can predict battery life for your exact configuration.
Current Draw by State
| State | Current |
|---|---|
| Deep sleep | 10 uA |
| TX active (+17 dBm) | 120 mA |
| RX (SEARCH) | 40 mA |
| OLED | 6 mA |
| GPS tracking | 25 mA |
| GPS acquiring | 30 mA |
BEACON Worked Example
Configuration: 10 s sleep, 100 ms TX burst, GPS off, OLED on during TX.
Per 10 s cycle:
Sleep: 10 uA x 9.9 s = 0.099 mA x s
TX: 120 mA x 0.1 s = 12 mA x s
Total per cycle = 12.1 mA x s
Average = 12.1 / 10 = 1.21 mA
Runtime on 2000 mAh = 2000 / 1.21 = ~1650 hThe datasheet estimate (~65 h at 10 s sleep) assumes the full payload takes ~45 s to transmit, so TX dominates. Short payloads and longer sleep stretch runtime dramatically.
Runtimes by Mode
| Mode | Sleep | GPS | Runtime (2000 mAh) |
|---|---|---|---|
| BEACON | 10 s | Off | ~65 h |
| BEACON | 60 s | Off | ~175 h |
| SEARCH | - | Off | ~44 h |
| EMERGENCY | - | On | ~12 h |
Temperature Derating
| Temperature | Capacity multiplier |
|---|---|
| 20 C | 1.0x |
| 0 C | 0.85x |
| -10 C | 0.7x |
| -20 C | 0.5x |
At -20 C a 2000 mAh cell behaves like 1000 mAh. Recompute your worst case with the multiplier.