I am currently designing a device that is intended to be used outside the car and supplied by car 12V socket (also during the drive).

The question is: Are there any specific requirements for example international standards related to this kind of devices? Is there any EMC certification required before allowing the device to be sold?

Usually in case of devices designed for automotive market, OEMs define this kind of requirements, it's a little bit different story since the device could be used in any car/truck and is not an actual car part.

I am aware that the device should be both protected against potential supply line disturbances [cold cranking, over-voltage etc.] and also not generate any disturbances/conducted emission backwards. But how to define actual limits?

I believe most of modern cars 12V sockets are filtered and protected against potential short circuit / conducted emission, but this cannot be guaranteed right?

  • 1
    \$\begingroup\$ By "12V sockets" do you mean the traditional cigarette lighter socket? I don't think you can expect any filtering at all on such a socket, just a fuse. \$\endgroup\$ Commented Aug 1, 2018 at 20:12

1 Answer 1


Yes. ISO 7637-2. The device must protect against test pulses 1 - 5 for a 12v system. Google it and you will find a lot of information.

  • \$\begingroup\$ Can you expand on this answer a bit? If I understand correctly, the ISO document specifies testing of a device to be installed in a vehicle but does not specify any testing of the vehicle itself...is that right? Can you talk about whether/how this standard is used in practice by device manufacturers? \$\endgroup\$ Commented Aug 1, 2018 at 21:39
  • \$\begingroup\$ A vechile has a lot of potential transients, such as a fully charged alternator being disconnected. The standard is there such that it assumes (mainly for older vechiles) there is little to no protection and you must protect accordingly. Pulses 1 - 5 represent various fault conditions. Most manufactures use fuses and TVS line regulators to protect the system and pass the standard. \$\endgroup\$
    – user160063
    Commented Aug 1, 2018 at 23:08

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