Buyer's guide
Best Battery Monitors & Shunts for Off-Grid
A battery monitor is your fuel gauge. With LiFePO4 it stops being optional, because the voltage stays nearly flat from full to almost empty, so you cannot read the charge level off a voltmeter. A shunt monitor counts every amp going in and out, which is the only way to know your real state of charge. Here are the ones worth installing.
Quick picks
How the picks compare
| Model | Shunt rating | Display | Bluetooth / App | Best for |
|---|---|---|---|---|
| Victron SmartShunt 500A | 500A | Phone only | Yes (VictronConnect) | Most builds |
| Victron BMV-712 Smart | 500A | Head unit | Yes (VictronConnect) | A wall display |
| Renogy 500A Battery Monitor | 500A | Backlit LCD | No (wired) | Renogy systems |
| AiLi Battery Monitor | 350A | Round LCD | No (wired) | Tight budget |
| Victron SmartShunt 1000A | 1000A | Phone only | Yes (VictronConnect) | Large 48V banks |
Victron SmartShunt 500A
Shunt: 500A / 50mVDisplay: Phone (no head)App: VictronConnect (Bluetooth)
The SmartShunt is what most off-grid people end up installing. It is a shunt with Bluetooth built in and no display head, so your phone is the screen. It tracks state of charge, amp-hours used, current, voltage, and time remaining, and you program it for your bank in the VictronConnect app. If you do not need a panel-mounted screen, this is the one to buy.
What we like
- Accurate coulomb counting, the real fuel gauge for LiFePO4
- Reads everything in the VictronConnect app over Bluetooth
- Talks to other Victron gear over VE.Smart networking
Worth knowing
- No physical display, you need your phone to read it
- You have to enter your battery settings to get accurate SoC
Victron BMV-712 Smart
Shunt: 500A / 50mVDisplay: Round head unitApp: VictronConnect (Bluetooth)
The BMV-712 is the SmartShunt with a round display head added. You get the same accurate state of charge, amp-hours, current, voltage, and time-to-go, but you can read it from a wall-mounted screen without pulling out your phone. It also has Bluetooth and an aux input that can watch a second battery, like a starter battery, or temperature.
What we like
- Wall-mounted display plus the same VictronConnect Bluetooth app
- Aux input monitors a second battery voltage or temperature
- Same trusted Victron accuracy and history tracking as the SmartShunt
Worth knowing
- Costs more than the SmartShunt for the added screen
- The display head needs a panel cutout and a data wire run
Renogy 500A Battery Monitor
Shunt: 500ADisplay: Backlit LCD headRange: 10V to 120V
If you are already running Renogy panels and a Renogy charge controller, this is the easy match. It is a shunt with a backlit display head that shows voltage, current, consumed power, and remaining capacity, and it has programmable high and low voltage alarms. It does not have Bluetooth, so it is wired-only, but the screen is clear and the price is friendlier.
What we like
- Bright backlit display reads voltage, current, power, and capacity
- Programmable high and low voltage alarms
- Wide 10V to 120V range covers 12V, 24V, and 48V banks
Worth knowing
- No Bluetooth or app, you read it at the screen only
- SoC tracking is less refined than Victron's
AiLi Battery Monitor (350A)
Shunt: 350ADisplay: Round LCD headRange: 8V to 120V
The AiLi is the cheap coulomb-counter that a lot of DIY builders start with. It is a shunt with a small round LCD that shows state of charge as a percentage, amp-hours remaining up to 999Ah, voltage, current, and power. It is not as polished as the Victron and the menus take patience to set up, but for a small van bank it does the one job that matters: counting amps in and out.
What we like
- Real coulomb counting at a budget price
- Shows SoC percent, amp-hours, voltage, and current on the LCD
- Handles 12V through 48V banks up to 999Ah
Worth knowing
- No Bluetooth, and the setup menus are fiddly
- Build quality and support are basic compared to name brands
Victron SmartShunt 1000A
Shunt: 1000A / 50mVDisplay: Phone (no head)App: VictronConnect (Bluetooth)
Same SmartShunt, bigger shunt. The 1000A version is what you want when a 48V cabin bank can pull serious current through a large inverter. It works exactly like the 500A model in the app, it just has the headroom so you never max out the shunt. Victron also makes a 2000A version for very large systems if you need even more.
What we like
- Handles the high current of a large 48V inverter
- Same VictronConnect app and accuracy as the smaller SmartShunt
- Steps up to a 2000A version for very large banks
Worth knowing
- Overkill and added cost for a small 12V van bank
- Still no display head, your phone is the screen
How to choose a battery monitor
Start with the shunt rating. The shunt has to handle the most current your system will ever push through it, which on a 12V van usually means a 500A shunt is plenty, while a large 48V cabin bank with a big inverter is happier with 1000A. A bigger shunt does not hurt accuracy, so when in doubt, size up rather than down.
Then decide if you want a screen or your phone. The Victron SmartShunt has no display and uses the VictronConnect app, which keeps the install clean. The BMV-712 and the Renogy add a physical screen you can glance at. If you want Bluetooth and the best state-of-charge tracking, the two Victron units are the pick. If you want a cheap screen and do not care about an app, the Renogy or AiLi will do the job.
Last, make sure it actually counts coulombs. Every monitor here is a shunt-based coulomb counter, which is the whole point. Avoid cheap voltage-only gauges that just show battery volts, because on LiFePO4 that number tells you almost nothing about how full the bank really is. The reason why is in our LiFePO4 voltage chart.
Who should skip this: If your bank is still lead-acid and small, a basic voltmeter gets you most of the way, because lead-acid voltage actually tracks charge level. And if you run an all-in-one solar generator or power station, it already has a built-in fuel gauge, so you do not need a separate shunt. A standalone monitor pays off most on a LiFePO4 house bank you built yourself.
How to wire a campervan electrical system →
Frequently Asked Questions
Do I need a battery monitor for LiFePO4?
Yes, more than you do with lead-acid. LiFePO4 holds a nearly flat voltage across most of its charge, so a voltage reading cannot tell you whether you are at 80 percent or 30 percent. A shunt monitor counts every amp in and out, so it always knows the true state of charge. It is the only reliable fuel gauge for a lithium bank.
What is a shunt?
A shunt is a precise low-value resistor that all of your battery current passes through. The monitor measures the tiny voltage drop across it to know exactly how many amps are flowing in or out. By adding that up over time, it tracks how much energy you have used and how much is left. The shunt goes on the negative side of the battery.
SmartShunt vs BMV-712, which should I get?
They use the same 500A shunt and the same VictronConnect app over Bluetooth, so the readings are identical. The only real difference is the display. Buy the SmartShunt if you are happy reading the numbers on your phone, and buy the BMV-712 if you want a wall-mounted screen you can glance at without unlocking your phone.
Where do I install a shunt?
On the negative side of the battery, between the battery negative terminal and everything else. One small stud connects only to the battery negative, and the main stud connects to all your other negative wires and the chassis ground. Wiring it this way means every amp that enters or leaves the battery passes through the shunt, which is what makes the count accurate.
Can I monitor my battery over Bluetooth?
Yes, with the Victron SmartShunt or BMV-712. Both have Bluetooth built in and connect to the free VictronConnect app, so you can check state of charge, current, voltage, and history from your phone. The Renogy and AiLi monitors are wired-only and you read them at their display screens.
Does a battery monitor protect my battery like a BMS?
No, and that is an important distinction. A monitor only watches and reports, it does not disconnect anything. The protection job belongs to the battery's BMS, which cuts off charging or discharging in a fault. Think of the monitor as the fuel gauge and the BMS as the safety system. You want both.
How accurate is the state of charge reading?
Coulomb-counting monitors are very accurate as long as they are set up for your bank and the battery gets a full charge now and then to resync. Enter your true battery capacity during setup, and let the bank reach full charge regularly so the monitor can recalibrate to 100 percent. Skip that and the percentage slowly drifts.