Fleet Managers may worry that telematics devices can drain a vehicle’s 12-volt battery. In reality, these devices are engineered to draw very low current - typically around 80 milliamps (mA) - when the vehicle is off, and many enter a low-power sleep mode during inactivity to further preserve battery life.
When it comes to battery drain, instead of telematics being the culprit, telematics can in fact help to reveal the reasons why your 12-volt battery is going flat.
How telematics collects battery data
Telematics devices are connected to a vehicle’s battery either directly, via the vehicle’s CANbus (Controller Area Network bus), or via the OBD port in that vehicle. Data is collected to provide insights into vehicle performance, battery health, and other key metrics.
How telematics devices use power
Smartrak customises its devices (power management settings) to have minimal draw on a 12-volt battery. Telematics devices are designed with smart power management features and operate in different modes including Online Deep Sleep Mode which uses 11mA + 1 mA with the CAN Control assuming it’s also asleep.
For example, Smartrak’s Nextrak device draws just ~12 mA in deep sleep mode and up to ~130 mA when actively transmitting. The actual consumption depends on device settings like update frequency, sleep mode configuration, and external sensor use.
When might a telematics device drain a 12-volt battery?
It’s important to note that a telematics device’s draw on a 12-volt vehicle battery can vary widely. Settings on a telematics device are often customisable, and many devices can be configured to enter deep sleep automatically after a period of inactivity. Features like frequent GPS tracking, always-on cellular connections, or wake-on-motion settings will all increase power draw. If a vehicle sits unused for days or weeks a low standby current from the telematics unit can drain the battery over time.
When is a battery “flat”?
It may surprise you that a 12-volt lead-acid car battery is actually 12.7+ volts at resting. 12.7 volts is considered 100% capacity while 12.1 volts is half capacity (50% State of Charge), and a flat battery is 11.3V or lower.
Voltage
State of Charge (SOC)
Startability
12.7+V
100%
✅ Easy start
12.3V
~75%
✅ Usually OK
12.1V
~50%
⚠️ Risky
11.8V
~25%
❌ Often fails
11.3V or lower
<10%
🚫 Dead battery
12V Lead-acid Battery State of Charge vs Voltage
12-volt batteries in EVs and ICE vehicles
ICE vehicles typically use a 12-volt battery to power all electrical systems.
EVs have a 12-volt battery for low-power electronics (lights, infotainment, door locks, safety features) and a traction battery (high-voltage or HV battery) to power the motor and main vehicle functions like heating, cooling, and charging.
How to measure a 12-volt battery charge
Beyond telematics, there are other ways to measure battery charge, including:
Multimeters allow for direct measurement of the battery's voltage
Battery testers often provide more information than a multimeter, such as the battery's cranking amperage and state of charge
Telematics devices, including Smartrak’s vehicle tracking devices, offer an optional API “Device health check” that pulls through vehicle battery data. Note that Nextrak and OBD-II also monitors the real-time EV battery traction battery charge data.
Vehicle issues diagnosed through 12-volt battery data
By tracking 12-volt battery voltage levels, Fleet Managers can detect anomalies that may indicate underlying issues.
ICE vehicle issues diagnosed
The following are some real-world examples where 12-volt battery data has helped diagnose issues in ICE vehicles.
Phantom battery drain - hidden electrical fault - A vehicle’s battery consistently showed low voltage readings, even after full charges. Telematics data revealed overnight power drain, despite the ignition being off. Diagnostics uncovered an improperly wired aftermarket accessory continuously drawing power.
Starter motor failure - slow cranking alert - Telematics recorded consistent voltage drops during ignition, even though the battery appeared healthy. Maintenance logs noted repeated slow start issues, which were traced to a failing starter motor drawing excessive current.
Key-on (using accessories) without the engine running -Telematics data revealed frequent use of accessories (e.g., lights, infotainment) with the engine off, leading to battery drain. Fleet managers implemented driver training and automatic shutoff systems to mitigate this issue.
Temperature-related battery performance drops - A fleet operating in extreme cold experienced unexpected battery failures. Telematics data flagged sudden voltage drops during early morning startups, correlating with low temperatures. The solution was to implement insulated battery covers and scheduled pre-heating to mitigate cold weather effects.
Fleet-wide battery health monitoring - proactive replacement - Aggregated voltage data across a fleet revealed that some vehicles consistently operated at lower voltages. Telematics insights predicted which batteries were nearing end-of-life, allowing for proactive replacements before failures occurred.
EV issues diagnosed
The following are some real-world examples where 12-volt battery data has helped diagnose issues in EVs.
Phantom drain (parasitic loss) - Excessive battery drain while parked can be caused by always-on background systems such as thermal regulation, connectivity modules, or software updates including a vehicle’s third-party apps communicating back to the vehicle manufacturers.
Charging interruptions - A sudden stop in charging is often due to charge station faults, damaged cables, or restrictions from the vehicle's battery management system (BMS).
Slow charging speeds - Often caused by a degraded traction battery, poor environmental conditions, or EVSE (charging station) limitations.
State of Charge (SoC) reporting errors - Incorrect charge readings may be due to faulty sensors or software miscalculations, which can be diagnosed through voltage trends and anomaly detection via telematics.
EV Traction battery faults caused by 12-Volt battery issues
On the flipside, a faulty 12-volt battery can cause issues in an EV. Although EVs rely on a high-voltage traction battery for propulsion, a weak or faulty 12-volt battery can prevent the vehicle from operating altogether. Here are common problems tied to the 12-volt system:
Vehicle wake-up and control systems: The 12-volt battery powers essential control units, including those that manage the traction battery. If the 12-volt battery is flat, the EV may fail to start or appear completely unresponsive—even with a fully charged traction battery.
Charging system dependencies: Most EVs recharge the 12-volt battery via the high-voltage traction battery through a DC-DC converter. If this converter fails, or the 12-volt battery is compromised, the vehicle may not charge or operate correctly.
High-voltage safety interlocks: Critical safety systems rely on a functioning 12-volt supply to engage or release interlocks. A failed 12-volt battery can disable access to the traction system or force the EV into restricted mode.
Monitoring battery health with Smartrak’s Solutions
There are several ways Smartrak's solutions can assist with monitoring 12-volt vehicle battery health.
Telematics
Our AVL GPS trackers perform a battery diagnostic check every four hours
Fleet Managers can set up battery notifications and be alerted when a battery is low or has gone flat
A Battery Status Report is available through our telematics system
Battery status can also be viewed in Smartrak’s maps interface by hovering over a vehicle to see individual details
Telematics can be used to collect not only battery data, but key on/off, idle time, booking period, and more. This data contributes to Smartrak’s Utilisation Report, and Trip Report which are useful tools for homing in on underutilised vehicles, and vehicles with long periods of non-usage.
If GPS tracking is not installed, PoolCar reports can provide insights into vehicle usage and optimisation. This helps to identify vehicles at risk of 12-volt battery issues due to infrequent use.
Smartrak customers can find further information in our Self Help resources.
Conclusion
By monitoring 12-volt battery health through data, fleet managers can detect hidden non-battery issues before they lead to breakdowns or other issues. If you do not have access to telematics battery data, try adding regular battery checks to your maintenance calendar and/or trickle charge key vehicles or ATVs, specialist vehicles, and call-out vehicles.
By leveraging data and running reports, fleets managers can improve vehicle reliability and operational efficiency, and monitor and manage battery health - along with eliminating a telematics device as the culprit of 12-volt battery drain.
Get in touch to find out more about how our solutions can help manage 12-volt batteries in your fleet.
