As I understood, 12-V car system refers to automotive system that runs with a 12-V battery. What are the basic differences between a 12-V and a 24-V (actuators, ECU...) ?

  • \$\begingroup\$ Basically the difference is 12V more and lower current to reduce wiring costs. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Oct 1 '17 at 17:17
  • \$\begingroup\$ That, and 24V systems are scarce as hen's teeth in passenger cars. Large trucks (and maybe buses) use 24V, but I don't know of any common passenger car that does. \$\endgroup\$ – JRE Oct 1 '17 at 17:23
  • \$\begingroup\$ Trucks, some large agricultural stuff, earth moving etc \$\endgroup\$ – Solar Mike Oct 1 '17 at 17:24
  • \$\begingroup\$ In the early/mid naughties there was a lot of talk about automotive moving to, IIRC, 42V for the reason of thinner cables. I remember various IC manufacturers looking at designing and maybe even coming out with higher voltage parts specifically for this purpose. Not sure why it never happened. \$\endgroup\$ – DiBosco Oct 2 '17 at 13:07

24V is used on trucks as the starter needs enough power for the big diesels : approximately 1000A. If that was at 12V then it's double the current which means thicker cables.

The disadvantage was that the bulbs needed longer filaments for 24V and the vibration (road and engine) caused them to fail often, this was helped by supported filament bulbs so that they lasted longer, now LEDs have helped even more.


In the automotive industry every single cent saved could be worth millions to a company because of the large volumes. Higher voltages saves copper by reducing the cable area. But for a small car 12V is usually the standard. Trucks usually use 24V. Working for a company that makes ECUs* we make the main regulator cover the whole range if it's used for both cars and trucks. Sensor inputs/outputs, voltage protection etc, are usually handled by mount options on the PCB.

* Electronic Control Module NOT Engine Control Module

  • \$\begingroup\$ So basically, can we use the same ECU for both 12 and 24V system ? Is it because of different voltage, ECU parts ( microcontroller, drivers, memory IC ) are different ? \$\endgroup\$ – TonyJ Oct 1 '17 at 18:53
  • \$\begingroup\$ @TonyJ i think Dejvid means those ecu's that are common use not all of them. \$\endgroup\$ – Solar Mike Oct 1 '17 at 18:59
  • \$\begingroup\$ If it's not stated by the manufacturer I wouldn't try 24V on a 12V unit. We might be speaking about different things here. I was writing about Electronic Control Units, not Engine Control Units. Some units can handle both 12V & 24V but definitively not all. If a unit is sold only for 12V it might be more cost effective to not cover 24V. \$\endgroup\$ – Dejvid_no1 Oct 1 '17 at 19:30
  • \$\begingroup\$ Given that any raw car battery voltage with its transients is unfit to feed LSI ICs directly, it would be unusual to find different MCU/memory parts - the power supply parts and indeed the drivers would be more likely different... \$\endgroup\$ – rackandboneman Oct 1 '17 at 22:14
  • \$\begingroup\$ @rackandboneman Exactly. \$\endgroup\$ – Dejvid_no1 Oct 2 '17 at 3:26

No major difference it is only that 12 volts drew double current of 24 volts , means u sing less cable cross section diameter with 24 volts.


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