Installing a Battery Monitor Shunt: Where It Goes

A shunt is a precise, low-resistance link that a battery monitor uses to measure every amp going in and out of the battery. It goes on the negative side.

1. The one rule

Nothing may connect to the battery negative except the shunt. Every load and every charger negative must connect to the other side of the shunt (the system side). If anything bypasses it, the monitor can't see that current and the percentage will drift.

2. Typical layout

1. Battery negative → shunt (battery side).
2. Shunt (system side) → negative bus bar.
3. Every negative (fridge, lights, DC-DC charger, solar controller, inverter) → bus bar.

3. Size it right

Choose a shunt rated above your highest current, including an inverter at full load.

4. Set it up

After fitting, enter the battery capacity and type in the monitor's settings, then fully charge the battery so the monitor can sync to 100%.

5. Common mistakes

• A charger or inverter negative still on the battery negative post.
• The small sense wire connected to the wrong side.
• Battery capacity entered wrong in the settings.
• Never doing a full charge to sync.

6. Quick summary

• Shunt on the negative, between the battery and everything else.
• Every negative goes through it.
• Set the capacity, then sync with a full charge.
• Read our guide How to Read a 12V Battery Monitor.

Work on 240V AC wiring, including inverter outputs and mains inlets, must be done by a licensed electrician. For high-current DC gear, follow the maker's installation manual and have an auto electrician check your work if you're unsure.

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