Parasitic Loads Audit: Keep the "Always-On" Crew Under Control
One device isn't the problem. Ten tiny ones are. Here's how to find and fix the silent battery killers.
1) Measure, Don't Guess
- Use an inline DC wattmeter at the 12 V fuse panel or a clamp meter on the negative return.
- Log idle draw for 5 minutes with everything "off." That's your baseline parasitic load.
2) Build the Standby List
| Device | Standby (W) | Hours/Day | Wh/Day |
|---|---|---|---|
| Smart Lock | 0.2–0.5 | 24 | 4.8–12 |
| Cell Router | 2–6 | 24 | 48–144 |
| Temp Sensor Hub | 0.3–1 | 24 | 7–24 |
| USB Chargers (idle) | 0.1–0.5 | 24 | 2–12 |
3) Kill What You Can, Schedule What You Can't
- Add a master switch or smart relay for the router; turn off overnight.
- Use motion or door triggers to wake subsystems only when needed.
- Remove vampire chargers from 12 V sockets when not in use.
4) Cable/Converter Efficiency
Bad bucks waste power as heat. If your lock circuit feels warm at idle, upgrade the converter or shorten the run. Use the Energy Calculator with real numbers.
5) Verify the Win
Repeat the meter test. Your new baseline should drop. If not, something's still quietly partying on your battery.
Parasitics don't have to be scary. Name them, measure them, schedule them — then enjoy more boondocking days without touching the generator.
Related Reading
- Boondocking Battery Math — Calculate your power needs.
- Energy Calculator — Model your actual system.