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Voltage guesses the state of charge; a shunt counts it

The best battery monitors for 2026

A battery monitor answers one question — how much is left — and the two ways it can answer differ in kind. A voltage-only meter infers the state of charge from the terminal voltage, which is a fair guess for a rested lead-acid battery and a poor one for lithium, whose voltage barely moves between eighty and twenty percent. A shunt-based monitor puts a calibrated resistor in the negative lead and counts every amp in and out, which is arithmetic rather than inference, and it is what makes a lithium bank legible. The shunt rating in amps must exceed the largest current the installation can draw, inverter surge included. Accuracy is published as a percentage, and it depends on the battery capacity being entered correctly — a monitor is only as right as the capacity it was told. Supported chemistries and the Peukert setting decide whether the count is corrected for the way lead-acid batteries lose capacity under load. Then the display or app, the alarms and relay outputs that can shed a load automatically, the monitor’s own consumption — it runs all year — and what the installation requires: all negatives through the shunt, without exception, or the count is wrong from the first day. We compare measurement method, shunt rating, accuracy, chemistries, display and app, alarms, self-consumption and installation requirements.

Every machine on this shelf, side by side

  1. Renogy 500 A shunt monitor, 12/24/36/48 V, programmable alarm

    shunt-based counting · 500 A shunt · accuracy described as high, no figure · LiFePO4, AGM, sealed, gel and flooded · display included · no app named · programmable high and low voltage alarm · self-consumption not published · installation requirements not described

    A 500 A shunt battery monitor for 12 to 48 V systems with a programmable high and low capacity alarm, custom battery parameters and a memory that survives a power interruption.

    Best for: A bank whose chemistry is unusual enough to need custom parameters.

    ≈ £54 / €59

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  2. ECO-WORTHY 300 A shunt monitor, 3.5-inch colour touchscreen, 0.5 mA

    shunt-based counting · 300 A shunt · accuracy not published · chemistries not named, custom parameters supported · 3.5-inch colour touchscreen with adjustable brightness · no app named · voltage, current and temperature alarms · 0.5 mA self-consumption, PUBLISHED · installation requirements not described

    A 300 A shunt monitor with a 3.5-inch colour touchscreen and a published self-consumption of 0.5 mA — the only self-consumption figure in this catalogue.

    Best for: A system where the monitor itself must not be part of the standing drain.

    ≈ £61 / €60

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  3. Victron Energy SmartShunt 300 A 50 mV, Bluetooth, no display

    shunt-based counting · 300 A, 50 mV shunt · accuracy not published · chemistries not named · NO display — the phone is the display · VictronConnect over Bluetooth · alarms not described · self-consumption not published · VE.Direct plus a second connection for a second battery, midpoint or temperature sensor

    A 300 A shunt monitor with no display of its own, reading out over Bluetooth to VictronConnect, with a VE.Direct port and an input for a second battery or a temperature sensor.

    Best for: An installation already using Victron equipment, where one application covers everything.

    ≈ $70 / £60 / €67

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  4. SENTORISE 0–500 A shunt monitor, 8–120 V, IP68, buzzer alarm

    shunt-based counting · 0–500 A shunt · accuracy not published · chemistries not named · LCD showing SOC, voltage, current, power and time remaining · no app named · buzzer alarm every 10 seconds at a user-set level · self-consumption not published · IP68 waterproof and dustproof

    A 0 to 500 A shunt monitor for 8 to 120 V systems rated IP68, with an LCD showing state of charge, voltage, current, power and time remaining, and a user-set low-capacity buzzer.

    Best for: A boat or an exposed locker where the display itself will get wet.

    ≈ $68 / £70 / €80

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  5. Redodo 500 A shunt monitor, 8–120 V, M8 terminals, backlit LCD

    shunt-based counting · 500 A shunt, M8 connection · accuracy not published · LiFePO4, lithium-ion, AGM, gel and lead-acid · backlit LCD · no app named · flashing display and buzzer every 10 seconds at a set threshold · self-consumption not published · 0–9999 Ah capacity range

    A 500 A shunt monitor for 8 to 120 V systems with M8 terminals, five named chemistries, a capacity range to 9999 Ah and a backlit LCD with a buzzer alarm.

    Best for: A large mixed-chemistry installation where the terminal size has to be known in advance.

    ≈ $88 / £81 / €83

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