If you're planning to build an off-grid power system for your caravan or 4WD, one critical component that you shouldn't overlook is the shunt. Specifically, a smart shunt is a device that plays a crucial role in monitoring the energy created and used by the power system.
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What is a Shunt?
A shunt is designed to measure the energy flow from the battery into or out of the system. They are installed on the negative terminal of a battery as they measure the real-time voltage of the system and the current draw to and from the battery.
A smart shunt will compare this data against the parameters set in the battery monitor to accurately determine the charge, remaining energy and power consumption. This information can then be accessed by the user via the battery monitor to effectively monitor the system.
Essentially, a shunt will measure the flow of current across the terminals and a smart shunt completes the calculations required to accurately determine the state of charge of the battery. This is made more accurate by correctly setting up the battery monitor.
How does a Shunt work in an Off-Grid System?
A shunt can be installed within a power system to effectively monitor the battery state of charge. To operate effectively, shunts need to be installed as close to the battery as possible and have minimal interfering connections to enable accurate data transmission. Additional shunts can be added to the system to monitor the state of charge of secondary devices, however the shunt with largest priority is the one connected to and monitoring the battery.
Shunts are used to trigger a response in order to maintain or save battery charge; for example, if the battery state of charge has depleted below a predetermined threshold. The mechanism within the shunt that acts as the ‘trigger’ is usually a relay contact that is often located on the body of the shunt component. It can also be located on the regulator or inverter that the shunt is reporting the battery state of charge to.
Common actions that a shunt can trigger include:
- Starting and/or stopping an auto-start generator
- Sending a communication (via SMS, email or SNMP) to
alert the system operator or monitoring system of the
condition of the battery
- Commence a partial shutdown of the load. For example,
when essential and non-essential applications are
separated into different circuits, the shunt can temporarily
shut down non-essential circuits to lessen the use of the
battery until the battery can recover its state of charge.
Most lithium-ion batteries have an integrated Battery Monitoring System (BMS). BMSs vary between battery type and brand.
Some lithium battery BMSs are simple and don’t offer access to the information it collects and monitors. In these instances, It is recommended to include a shunt so the battery monitoring information can be viewed and monitored easily.
Some lithium batteries include a Bluetooth interface that connects to the battery BMS, allowing you to view battery information from your phone or device when you are within range.
Whether you have a simple lithium setup or a Bluetooth connected battery, however, the level of battery monitoring access varies and neither option allows you to set up monitoring triggers. The inclusion of a shunt is the best way to set up battery-connected actions based on real-time data, without requiring user involvement.
Check out the video below to see how we include a Victron Battery Monitor in this Off-Grid Motorhome
Why it’s Important to Include a Shunt in your Off-Grid System
Smart shunts are important to include in your off-grid system because they allow you to accurately monitor your battery status against the parameters of your battery (which you would predetermine when you set up the system).
With the help of a battery monitor, you can easily view the amount of current flowing in and out of the battery and the battery's state of charge, which is crucial for managing battery life and preventing overcharging or undercharging. This information can be used to adjust charging and discharging settings to ensure optimal battery performance and longevity.
A smart shunt can help protect the lithium battery from damage due to over-discharge or overcharge. When the battery reaches a predetermined low voltage, the shunt can signal the charging system to stop discharging the battery, preventing damage. Similarly, the shunt can signal the charging system to stop charging the battery once it reaches full capacity, preventing overcharging.
All in all, a smart shunt optimises your energy efficiency by monitoring (via a battery monitor) the amount of energy being consumed by appliances and other devices connected to the battery, allowing for a more efficient use of power and longer battery life.
A smart shunt also allows you to troubleshoot your system, which can be especially important if you are off-grid and unable to seek assistance. A smart shunt will help determine and display any possible issues which you can attempt to resolve immediately. If you don’t have a smart shunt installed and your battery isn’t operational, it can become very difficult to rectify while off-grid as you won’t have access to your battery’s data.
Shunted Battery Monitor Recommendations
There are several types of shunts available on the market, each with its own unique set of features and capabilities. Some shunts can be integrated with mobile apps, allowing you to monitor your power usage from your smartphone or tablet. Others can be programmed to send alerts when the battery bank's state of charge reaches a certain level, or when power usage exceeds a certain threshold.
Victron SmartShunt 500A/50mV
The Victron SmartShunt is an all-in-one battery monitor. The SmartShunt connects via Bluetooth to the VictronConnect App on any smart device acting as the display for this component. This allows for convenient access to all monitored battery parameters, like state of charge, time to go, historical information and much more directly from a smartphone or tablet. Alternatively, the SmartShunt can be connected to a device, such as a Cerbo GX, that will read the monitoring information and provide a touchscreen display from within your vehicle. The Victron SmartShunt is available in different sizes for various load sizes.
Enerdrive ePRO+ Battery Monitor (with Shunt)
The Enerdrive ePRO Plus is a comprehensive battery management system designed for off-grid applications. It comes with a precision shunt that accurately measures the flow of current in and out of the battery, as well as the battery’s state of charge and other critical parameters. The system includes a backlit LCD display that shows real-time battery information such as voltage, current, power, state of charge, and historical data. The ePRO Battery Monitor has the ability to monitor individual circuits for a precise and specialised monitoring system.
Victron BMV-712 Smart Battery Monitor
The Victron BMV-712 is a high precision battery monitor. This battery monitor measures the voltage and current of a singular battery bank to calculate power and state-of-charge. It can be paired with a secondary temperature sensor to measure the temperature of the battery. The BMV-712 includes built in Bluetooth for easy data transfer to any smartphone or Bluetooth-receptive device.
In summary, if you're building an off-grid power system, a smart shunt is a critical component that you shouldn't overlook. By accurately monitoring your energy usage and optimising your power consumption, you can ensure that your power system remains operational and reliable, even in remote locations where access to external power sources or assistance may be limited.
Springers Solar | Brisbane's Most Experienced Caravan Solar Installer
Springers Solar is an established, family-owned solar specialist company based in Lawnton and Capalaba in Queensland, Australia. We offer over 20 years of industry knowledge and experience, offering services and products ranging from installations and batteries, inverters and chargers, solar panels, lighting, and more. We cater to private and commercial clients offering auto and electrical solutions. Springers Solar offers a wide range of products complete with design and installation by our 60+ team of dedicated in-house project managers, engineers, and installers. We have installed solar for over 5,000 happy customers and have become a top choice for solar installations on a national scale.
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