My inverter keeps shutting down under load
Two causes cover nearly all of it, and the first one surprises people because the batteries look fine on the meter.
What actually works
Undersized or long cables between battery and inverter drop enough voltage **under load** that the inverter sees a flat battery and protects itself. Measure voltage at the inverter terminals while the load is actually running — not at rest, not at the battery.
A well pump or compressor draws 3–5× its running watts for a second or two. The inverter's surge rating, not its continuous rating, is what has to cover it.
A high-resistance connection does the same thing as a thin cable and gets hot doing it. Check them by hand for warmth after a heavy load — warm is a warning.
If the cables are the problem, a bigger inverter does nothing except draw more current through them. Measure before you buy.
Run the numbers
- Wire size & voltage drop → — free calculator, works offline.
- Battery runtime → — free calculator, works offline.
Also searched as
inverter low voltage shutdown · inverter overload · inverter beeping · power cuts out when pump starts · inverter trips · surge watts