LM3914 battery voltage monitor

How it works

The LM3914 compares the input with ten thresholds and lights the corresponding LED. The resistor network and trimmer set the displayed voltage range. Calibrate using an adjustable supply and a separate voltmeter rather than relying on an unknown battery.

The old text confused voltage with state of charge and reversed the mode connection. TI specifies pin 9 connected to V+ for bar mode; leaving it open selects dot mode in the basic single-driver application.

On the bench

The historic 11.89–12.65 V scale is only an approximate voltage indication for a nominal 12 V lead-acid battery. Load, recent charging, and temperature affect the reading; do not label it as an accurate capacity percentage.

Resources & provenance

Rewritten from the original circuits/msr/r3j19ns_msr003.php page. Component values and historical performance claims have not been independently bench-tested. The circuit figures have had their watermarks removed.