Temperature affects battery performance more than most people realise. Charging at the wrong voltage for the ambient temperature damages batteries — slowly for lead-acid, rapidly for lithium. Victron offers several temperature sensing options, from built-in sensors in their Smart batteries to standalone devices that share temperature data across your system. This guide explains what each option does, where to place sensors, and when temperature sensing is essential versus optional.
Why Temperature Sensing Matters
Lead-Acid Battery Temperature Compensation
Lead-acid batteries (flooded, AGM, and gel) have a well-documented relationship between temperature and ideal charging voltage. At 25 degrees C, a typical 12V absorption voltage is 14.4V. As the battery gets warmer, that voltage should decrease; as it gets colder, it should increase. The standard compensation coefficient is approximately -16.2 mV per cell per degree C — which works out to roughly -3 mV per degree C for each volt of nominal battery voltage.
Without temperature compensation, a 12V battery charged at 14.4V in a 40-degree C engine bay is effectively being overcharged. Over months, this reduces battery life through water loss (flooded) or dry-out (AGM/gel). Conversely, charging at 14.4V in a cold UK winter (-5 degrees C) means the battery never reaches full charge, leading to sulphation.
Lithium Low-Temperature Protection
LiFePO4 batteries must never be charged below approximately 5 degrees C. Charging cold lithium cells causes lithium plating on the anode, permanently reducing capacity and potentially creating internal short circuits. This is not gradual degradation — it is immediate, irreversible damage.
Victron's lithium battery management systems (BMS) use temperature data to block charging when the battery is too cold. Without a temperature sensor connected to the BMS or charge controller, this protection cannot function. For lithium systems in the UK — especially in unheated boats, caravans, or garages — temperature sensing is not optional. It is essential.
Temperature Sensing Options
1. Built-In Sensors in Smart Batteries
Victron's Smart Lithium batteries have an integrated temperature sensor within the battery's built-in BMS. The Lithium SuperPack range also includes internal temperature monitoring. These built-in sensors require no additional wiring or configuration — they work automatically.
The built-in sensor measures the internal cell temperature, which is the most accurate reading for charge control. However, this data is only available to the battery's own BMS. To share this temperature data with MPPT controllers or inverter/chargers, you need either a GX device (Cerbo GX) or a VE.Smart network.
2. Smart Battery Sense
The Smart Battery Sense is a small standalone device that measures battery voltage and temperature at the battery terminals. It communicates wirelessly via Bluetooth to create a VE.Smart network with compatible Victron chargers and MPPT controllers.
- Measures: voltage (0-70V) and temperature (-40 to +50 degrees C)
- Connects via: Bluetooth VE.Smart networking (no cables to other devices)
- Attaches to: battery terminal bolt (ring terminal lug connection)
- Power: CR2032 coin cell battery (lasts approximately 5 years)
- Best for: systems without a GX device where you want temperature compensation on MPPT chargers and mains chargers
The Smart Battery Sense is particularly useful for small to medium campervan and caravan systems where a Cerbo GX might be overkill. It pairs with SmartSolar MPPT controllers and Smart IP22/IP65 chargers, automatically adjusting charge voltage based on temperature.
3. SmartShunt Temperature Sensor Input
The SmartShunt (500A, 1000A, or 2000A) has an auxiliary input that can accept a temperature sensor. This is a separate purchase — a small 10k NTC thermistor probe that connects to the SmartShunt's Aux terminal.
- Probe type: 10k NTC thermistor (Victron part number: ASS000001000)
- Placement: attach to battery terminal or battery case surface
- Data sharing: via VE.Smart networking (Bluetooth) to MPPT controllers, or via VE.Direct to a GX device
Using the SmartShunt's temperature input is efficient because the SmartShunt is already connected to the battery for current measurement. Adding the temperature probe means one device handles both state-of-charge monitoring and temperature sensing. The downside is that the Aux input can only be used for either temperature or midpoint voltage monitoring — not both simultaneously.
4. MultiPlus/Quattro Temperature Sensor
The MultiPlus and Quattro inverter/chargers have a dedicated temperature sensor input. Victron supplies a specific temperature sensor (part number ASS000001000) that connects to the unit's terminal block. This sensor directly controls the unit's built-in battery charger — adjusting charge voltage based on temperature without relying on any external communication.
For systems where the MultiPlus/Quattro is the primary charger (e.g., shore power on a boat or grid-connected home backup), this direct connection is the most reliable method. It does not depend on Bluetooth or VE.Smart networking.
5. GX Device Temperature Inputs
The Cerbo GX can receive temperature data from multiple sources:
- Directly connected temperature sensors — the Cerbo GX has inputs for up to four temperature probes
- From connected devices — SmartShunt, Smart Battery Sense, and Smart batteries all report temperature to the GX via their respective communication protocols
- VE.Can BMS — the Lynx Smart BMS reports battery temperature via VE.Can
The GX device acts as a central hub, making temperature data available to all connected products and displaying it on the VRM portal for remote monitoring.
Comparison of Temperature Sensing Options
| Option | Cost | Wiring Required | Data Sharing | Best For |
|---|---|---|---|---|
| Smart Battery (built-in) | Included | None | Via BMS to GX | Victron lithium users |
| Smart Battery Sense | ~GBP 30-40 | Ring terminal to battery | Bluetooth VE.Smart | Small systems without GX |
| SmartShunt temp probe | ~GBP 15-20 | Probe to SmartShunt Aux | VE.Smart + VE.Direct to GX | Systems already using SmartShunt |
| MultiPlus/Quattro sensor | ~GBP 15-20 | Probe to MultiPlus terminal | Direct (charger only) | Shore power / mains charging |
| Cerbo GX temp inputs | ~GBP 15-20 per probe | Probe to Cerbo terminal | Full system via GX | Larger monitored systems |
Where to Place Temperature Sensors
On the Battery Terminal
The recommended placement for most sensors is directly on the negative battery terminal. This gives the most representative reading of the battery's temperature. The Smart Battery Sense attaches here by design (its ring terminal goes under the battery terminal bolt). For NTC probe sensors, use a cable tie or thermal adhesive to secure the probe against the terminal.
On the Battery Case
If the terminal is not accessible, the side of the battery case is an acceptable alternative. Place the sensor midway up the battery — not on the top (which may be warmer due to charging heat) or the bottom (which may be cooler due to floor contact).
Avoid Placing Sensors
- Near heat sources — do not place sensors next to an inverter, engine, or exhaust. They will read high and suppress charge voltage
- In direct airflow — a sensor in a ventilation path may read lower than the actual battery temperature, causing overcharging in summer
- On the battery room wall — ambient air temperature is not the same as battery temperature, especially during heavy charge/discharge cycles
VE.Smart Networking for Temperature Sharing
VE.Smart networking allows compatible Victron devices to share battery data wirelessly via Bluetooth. In a VE.Smart network, a temperature source (Smart Battery Sense, SmartShunt with temp probe, or a Smart battery) broadcasts its readings. Other devices on the same VE.Smart network — typically MPPT controllers — receive and use this data.
Setting Up a VE.Smart Network
- Open VictronConnect and connect to the temperature source device
- Go to Settings > VE.Smart Networking
- Create a new network or join an existing one
- Repeat for each device that should participate (MPPT controllers, chargers)
- All devices on the same network share voltage, current, and temperature data
VE.Smart networking has a limitation: it uses Bluetooth only and has a range of approximately 10 metres in open space (less through walls or metal enclosures). For larger systems or installations where Bluetooth range is a problem, use a GX device instead — it gathers temperature data via wired connections and distributes it to all connected products.
When Temperature Sensing Is Critical
- Lithium batteries in any unheated space — UK winters regularly drop below 5 degrees C in garages, boats, and campervans. Low-temperature charge protection is mandatory
- Lead-acid batteries in hot engine bays — temperatures above 35 degrees C accelerate degradation without voltage compensation
- Systems relying on shore power charging — the MultiPlus charges for long periods at high current, so incorrect voltage causes more damage than brief solar charging
- Any system without a GX device — without a GX to coordinate, individual devices need direct temperature data via VE.Smart networking
When Temperature Sensing Is Optional
- Indoor systems at stable room temperature — a home battery system in a heated utility room stays close to 20-25 degrees C year-round
- Systems with Victron Smart Lithium batteries — the built-in BMS handles its own temperature protection
- Very small systems — a single 100Ah AGM battery charged by a small MPPT in a well-ventilated space may not justify the cost of a sensor, though adding one is still best practice
For more on how temperature data flows between devices, see our communication protocols guide. To understand the SmartShunt and its Aux input options, read our product naming guide. And for choosing the right accessories and sensors, check our accessories guide.
