Knowledge base
Does a CAN Bus Module Drain Your Car Battery?
A new accessory needs a measured answer
An added electronic module consumes energy, but its effect on a parked vehicle depends on the complete installation. A flat battery after fitting auxiliary lights is a reason to investigate, not proof that the CAN interface is faulty. Equally, a product described as plug-and-play should not be assumed to draw no current.
The useful questions are whether the vehicle reaches its intended sleep state, what the complete installation consumes in that state, and how those results compare with the vehicle manufacturer’s diagnostic specification. Avoid applying one universal current threshold or waiting period to every vehicle.
Sleep mode is a design feature, not a product measurement
CAN components can support low-power operation and wake-up detection. For example, the Texas Instruments TCAN1167-Q1 documentation describes sleep and standby functions that can reduce node power consumption. That explains a possible engineering approach; it does not establish the standby current of a complete accessory built by another manufacturer.
For Highbeam X, request the specification and installation guidance for the exact part number. Do not infer a measured standby-current figure from the general description of a CAN transceiver or from another module’s datasheet.
What to give the installer
Record when the problem began, how long the car was parked, the battery’s condition, the accessory part number and any other recent work. Ask the installer to document the vehicle state and elapsed time for each measurement, and to check the power and ground connections against the installation instructions.
A comparison before and after isolating an accessory is useful only when the vehicle has returned to comparable conditions. Disconnecting components can itself change the network state. Let the workshop choose the appropriate current-measurement method; opening a battery circuit or using an unsuitable meter range can interrupt vehicle systems or damage the meter.
Keep the diagnostic findings with the installation record. A repeatable measurement under specified conditions is more useful than a general assurance that a module is unlikely to cause trouble. The Styrestrøm FAQ provides the route to product support.
Questions before installation
Does a CAN interface use no power when parked? No. Request the relevant standby specification and verify the installed system.
Is one normal current value valid for every car? No. Use the vehicle-specific test conditions and limits.
Should I disconnect the battery to test it myself? Follow the vehicle service procedure and have a qualified installer choose the measurement method.