Marine Battery Monitors and Shunts
Learn how a shunt measures current, energy and state of charge in a LiFePO4 boat battery bank.
LiFePO4 has a relatively flat voltage curve through much of its state-of-charge range.
That means a simple voltage display is not a precise fuel gauge.
A shunt measures current entering and leaving the bank. A compatible monitor can estimate state of charge, amps, watts, amp-hours consumed, time remaining, historical discharge and charging performance.
BMS versus shunt
A Bluetooth battery BMS and a system shunt can complement each other.
The BMS is primarily there to protect the battery.
The shunt is primarily there to measure system energy flow.
Do not assume they are interchangeable.
Make the installation verifiable
A credible marine installation should be inspectable, documented and recoverable after a protection event. The battery label alone cannot show whether fault current, isolation, charging control, mounting and essential services have been addressed.
- Document cable sizes, protection ratings, isolation points, charging settings and BMS warning or shutdown logic.
- Confirm that terminals are protected, equipment is restrained and the location is suitable for heat, water and service access.
- Have the completed system commissioned and retain the drawings, settings, test results and equipment manuals aboard.