4 picks with specs, filters and a calculator to find the right size.
A shunt-based monitor counts every amp-hour going in and out. It’s the only accurate fuel gauge for lithium, whose voltage barely changes until it’s nearly empty.
Your phone is the display. It shows state of charge, current and time remaining in the VictronConnect app, can watch a second battery, and is IP65 rated.
Best for: Clean installs where you check the battery on your phone.
Check price on Amazon (paid link) Specs from bimblesolar.comA dash-mount screen showing voltage, current, power and remaining capacity, with high and low alarms. It works with AGM, gel and lithium. Bluetooth is an optional add-on.
Best for: Anyone who wants a gauge they can glance at.
Check price on Amazon (paid link) Specs from renogy.comA round dash display plus Bluetooth to the VictronConnect app. A second input watches a starting battery, midpoint or temperature, and a built-in relay can trigger an alarm or shut off a load.
Best for: Boats that want a dash gauge and a phone app, and watch two batteries.
Check price on Amazon (paid link) Specs from powerwerx.comA low-cost shunt monitor with a color screen and a phone app that logs voltage and current over time. Pick the 400 A version for a trolling motor or inverter.
Best for: A budget gauge for lithium or AGM.
Check price on Amazon (paid link) Specs from homeof12voltonline.com.auNo products match those filters. Try clearing one.
Pictures are our own illustrations, not photos of the actual products. Specs come from the manufacturer or retailer listing linked on each card and were checked in October 2026. Models and prices change, so confirm details on the listing before you buy. As an Amazon Associate I earn from qualifying purchases.