What Is a Battery Relay and How Does It Work?
A battery relay is a voltage-controlled switch placed between the battery and the load. It monitors battery voltage continuously. When voltage falls below a programmed disconnect threshold, the relay opens and cuts power to the load. When the battery recharges to the reconnect threshold, the relay closes and restores power automatically.
This protects batteries from reaching a state of deep discharge, a condition that reduces capacity, shortens cycle life, and in lithium systems, can trigger Battery Management System (BMS) lockout.
The Victron Energy BatteryProtect series operates on this principle with precision. Disconnect and reconnect thresholds are programmable via a rotary selector or, on Smart models, via the VictronConnect app over Bluetooth.
Key protection functions:
Low Voltage Disconnect
- Cuts power to connected loads when the battery voltage falls below the preset threshold, helping prevent excessive battery discharge.
Automatic Reconnect
- Automatically restores power to the load once the battery voltage recovers to a safe level.
Alarm Output
- Provides an early warning signal before the low voltage disconnect activates, giving you time to reduce power consumption or recharge the battery.
Load Shedding
- Prioritises essential circuits by disconnecting non-critical loads first in multi-circuit power systems, helping extend battery runtime for critical equipment.
Standard BatteryProtect vs Smart BatteryProtect | What's the Difference?
Both protect your battery bank from deep discharge. The difference is in configuration and monitoring capability.
Standard BatteryProtect
Configuration is done via a physical rotary dial with preset voltage thresholds. No Bluetooth, no app connectivity. This is the right choice when the system is fixed, the settings are set once during installation, and remote monitoring is not required. It is simpler, lower cost, and highly reliable.
Smart BatteryProtect
Adds Bluetooth connectivity and full VictronConnect app integration. This allows you to configure disconnect thresholds, monitor real-time battery voltage, review historical data, and receive alarms, all from a smartphone. The Smart variant also supports integration with other Victron devices on the VE.Smart Network, enabling system-wide communication without additional wiring.
Choose Standard when: installation is straightforward, settings won't need adjustment, and budget is a priority.
Choose Smart when: you want remote visibility, adjustable thresholds without physical access, or you are building a larger Victron ecosystem.
Victron Energy BatteryProtect Models Available at Volts Energies
We stock the complete Victron Energy BatteryProtect range across all voltage classes and current ratings.
- 12/24V — 65A: Entry-level protection for smaller loads on 12V or 24V systems. Suitable for lighting circuits, small inverters, and auxiliary loads on RV and marine installations. Available in both Standard and Smart variants.
- 12/24V — 100A: Mid-range option for moderate load circuits. Well suited for 12V systems running mid-size inverters, refrigeration, and combined accessory loads. Available in both Standard and Smart variants.
- 12/24V — 220A: High-current protection for demanding 12V and 24V applications. Handles large inverters, high-draw DC loads, and multi-circuit systems in off-grid cabins and larger marine vessels. Available in both Standard and Smart variants.
- 48V — 100A: Designed for 48V battery banks, the standard voltage class in modern off-grid solar systems and larger lithium battery installations. Available in both Standard and Smart variants.
All models are DIN-rail mountable, feature an integrated alarm output, and carry CE and UL certification.
Where Are Battery Relays Used in an Energy System?
Battery relays are not a single-application product. They appear at multiple points in off-grid and mobile power systems wherever a battery bank feeds an unmonitored or non-critical load.
Off-Grid Solar Systems
In an off-grid home or cabin, a BatteryProtect is placed between the battery bank and non-essential loads, lighting, appliances, entertainment systems. Critical loads like the inverter-charger may be wired separately without a relay, while discretionary loads are automatically shed when the battery is low.
Rv And Motorhome Systems
A BatteryProtect protects the house battery from being drained by accessories while the vehicle is parked. It prevents a dead battery that would disable lighting, water pumps, and heating overnight.
Marine And Boating
On a vessel, a battery relay protects the house bank from auxiliary loads, bilge pumps, navigation electronics, lighting, ensuring the starter battery and critical systems always have sufficient charge.
Vehicle Dual-Battery Systems
In ute, 4WD, and van conversions, a relay isolates the auxiliary battery from the chassis battery, protecting both from reciprocal discharge.
How to Choose the Right BatteryProtect for Your System
Sizing a BatteryProtect is straightforward. Follow these steps:
- Identify the loads you want to protect the battery from, list each load and its current draw in amps
- Add the amperage of all loads that could run simultaneously
- Select a BatteryProtect rated at or above that total draw
- Match the voltage rating to your battery bank: 12V, 24V, or 48V
- Decide between Standard and Smart based on your monitoring requirements
Do not underrate the relay. A BatteryProtect running above its current rating will overheat, trip prematurely, or fail. Always size with some headroom above your calculated peak load.
Integrating BatteryProtect Into a Victron Energy System
The Smart BatteryProtect communicates directly with other Victron devices over the VE.Smart Network. This enables coordinated responses across the system, for example, triggering load shedding when the solar charge controller reports low state of charge, or logging battery voltage data alongside MPPT output in the VictronConnect app.
For installations using a Cerbo GX or Venus GX monitoring hub, the Smart BatteryProtect data feeds into the GX device for centralised system overview on the VRM portal.
Standard BatteryProtect models do not support VE.Smart Network but remain fully functional as standalone protection devices in any 12/24/48V system.
Why Buy Battery Relays from Volts Energies?
Volts Energies is Canada's largest online retailer of renewable energy equipment. We have supplied Victron Energy products to off-grid homeowners, marine installers, and vehicle builders across Canada for over 20 years.
Every BatteryProtect we sell is sourced through authorised Victron Energy distribution channels. You receive the full manufacturer warranty, Canadian-compliant documentation, and free shipping on orders over $297.
If you are unsure which model is right for your system, or how to wire a BatteryProtect into an existing setup, contact our team before purchasing. We will give you a direct answer based on your actual system, not a generic recommendation.
FAQs
Can I use a BatteryProtect with a lithium (LiFePO4) battery?
Yes. Victron BatteryProtect units are compatible with lithium battery systems. On Smart models, you can configure voltage thresholds to match the specific discharge curve of your LiFePO4 battery. However, a BatteryProtect is not a substitute for a Battery Management System (BMS), both serve different protection functions and should be used together in a lithium system.
Can the BatteryProtect handle inductive loads like motors and inverters?
No. The BatteryProtect is rated for resistive DC loads only. It must not be placed in series with inverters, motor controllers, or other inductive loads. For inverter protection, use a dedicated inverter relay or configure load shedding at the inverter level.
What happens when the BatteryProtect disconnects?
The relay opens and all loads on the protected circuit lose power. An alarm output (if connected) triggers before disconnect to give a warning. Once the battery recharges to the reconnect threshold, either from solar, a charger, or the alternator, the relay closes automatically and restores power.
Can I use a 12/24V BatteryProtect on a 48V system?
No. Voltage rating must match your battery bank. Using a 12/24V model on a 48V system will damage the unit. Select the 48V-100A model for 48V battery banks.
Does the Smart BatteryProtect require the internet to work?
No. The Bluetooth connection operates locally between the device and your smartphone via the VictronConnect app. No internet connection is required for configuration or local monitoring. Internet is only needed if you want to access data remotely through the VRM portal via a GX device.
Can I use two BatteryProtect units in parallel to increase current capacity?
Victron does not recommend paralleling BatteryProtect units. If your load exceeds 220A, a different disconnect solution, such as a relay integrated with your BMS or a dedicated high-current contactor, is the appropriate approach.
