A shunt-based monitor is the single most helpful power tool you can add. It measures every amp in and out, so SOC is trustworthy.
Options in plain language
- Voltage-only meters: Cheap, but SOC guesses are often wrong (especially with lithium).
- Shunt monitors: Accurate amp-hour counting = reliable SOC.
- Smart batteries: Built-in BMS data; still benefits from a shunt for whole-system visibility.
What to watch daily
- SOC trend, not just one number.
- Overnight draw (fridge + parasitics).
- Charge returned after solar/alternator runs.
Field tip
Set low-SOC alerts (e.g., 20–30%) to trigger “conserve mode” or a re-charge drive before you run into inverter cutoffs.
Product spotlights:
- Victron SmartShunt / BMV-712 (Bluetooth app, deep history).
- Renogy 500A Battery Monitor (good value).
- Iota/Victron app ecosystems for whole-system insight.
Quick setup
- Install shunt in the negative line with all loads/chargers on the “load” side.
- Program battery capacity and chemistry.
- Fully charge once to “synchronize” SOC.