12-point-something volts: half full, or nearly flat? A voltmeter can't tell you. A shunt counts every amp in and out, so it can. How a shunt monitor counts, the one wiring rule that matters, the settings a lithium battery needs, and SmartShunt or BMV-712. Victron's own figures throughout; under three minutes.
Read the guide: Battery monitors: why a shunt beats a voltmeter
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Chapters
- 0:00 Intro
- 0:26 Why voltage lies
- 0:49 How a shunt counts
- 1:11 The one wiring rule
- 1:40 Lithium settings and the dashes
- 2:07 SmartShunt or BMV-712
- 2:25 The guide and the monitors
The parts
Grouped by type: Battery monitors.
Sources
- Victron Energy, SmartShunt manual (Rev 19, 08/2026), PDF pp. 9, 15, 17, 21, 45: victronenergy.com
- Victron Energy, SmartShunt datasheet, p. 1: victronenergy.com
- Victron Energy, Energy Unlimited (book), PDF pp. 4, 18, 22: victronenergy.com
Sources read 7 October 2026.
The +11 A and 62 % readings are illustrations, not measurements; the arithmetic is ours. Check the manual for your own gear.
Voiceover is AI; script and facts checked by NB Camping Equipment.
Transcript
Intro
G'day. In this one we're on battery monitors: why voltage is only a rough guess, how a shunt counts every amp, the one wiring rule that matters, the settings a lithium battery needs, and SmartShunt or BMV-712. 12-point-something volts. Half full, or nearly flat? A voltmeter can't tell you. A voltmeter guesses. A shunt counts. Let's get into it.
Why voltage lies
Voltage moves with the load and the temperature, not just with how full the battery is. Victron's Energy Unlimited: voltage only drops quickly once the battery is almost flat, 80 to 90% discharged. Their words: "To start charging once the voltage drops is simply too late." A voltmeter is still a handy glance near empty. It just can't tell you that you've got 62% left. (Illustration.)
How a shunt counts
The shunt sits in the battery's negative cable, so every amp going in or out passes through it and gets counted. Victron's example: 10 A for 2 hours takes 10 x 2 = 20 Ah out. The monitor keeps the running total and turns it into a percentage and a time to go. What you see is the net. Solar putting in 15 A, fridge taking 4 A: about +11 A. (Illustration.)
The one wiring rule
The shunt must be the only thing on the battery negative. Victron: "Any loads or chargers connected here will be excluded from the battery state of charge calculation." Battery negative to one side of the shunt. Everything else to the other: loads, inverter, chargers, solar. The one people miss is a small earth on the battery terminal: a USB socket, a fridge lead. It works fine, but the monitor never sees it, so the count is wrong.
Lithium settings and the dashes
Victron's defaults suit lead-acid. For lithium: Peukert exponent 1.05, charge efficiency 99%, discharge floor 10 to 20%, and the tail current your battery maker gives. It re-syncs to 100% when the battery is truly full. Victron's 12V example: above 13.2 V, charge current under 4% of capacity, both held for 3 minutes. Three dashes mean it hasn't synced yet. Charge to full and it sorts itself out.
SmartShunt or BMV-712
Same measurement, same accuracy (current ±0.4%, voltage ±0.3%). SmartShunt: your phone is the display, less wiring, no alarm, no relay. BMV-712: a screen on the wall plus the app, with an alarm and a relay. Most touring setups: the SmartShunt 300A.
The guide and the monitors
The full guide has the wiring and the settings to copy, and the monitors are together in the battery monitors collection. nbcampingequipment.com.au, guides.