Presumably, one powers an Arduino board with car batteries for long-term operation away from the power grid.

How can this be done, and what are the most (1) economic, and (2) reliable ways to do this? Specifically, do any additional risks to short the board with an extraneous discharge exist?

  • car batteries are 12.5V most arduinos can take 12.5V, add a fuse/surge protector and you're set Commented Mar 6, 2014 at 12:31
  • Auto batteries are 13.8v optimal, but the actual voltage can vary on its charge condition, physical condition, and power load. While the built-in regulator on most Arduino boards can step this down, it may result in high temperatures (if no heatsink on the on-board regulator); and the electrical noise from the vehicle ignition/devices may cause havoc on data transfers to/from the Ardiuno. A suitably rated buck converter with appropriate filtering would probable be the best choice.
    – Ron J.
    Commented Mar 6, 2014 at 14:06
  • @ratchetfreak I agree with Ron. It'll probably overheat, especially in the summer. Commented Mar 6, 2014 at 22:20
  • @Ron I agree. One thing to note: IIRC the onboard Uno regulator has some sort of heat sink build into the PCB that's designed to cool it from beneath. Commented Mar 6, 2014 at 22:21

6 Answers 6


Use a switching regulator such as the LM2596. You can get a ready board from eBay for about US$1.

Enter image description here

Just set the output voltage to 5 V and feed the Vcc input of Arduino; this bypasses the onboard regulator.

The benefit is that unlike the linear onboard regulator, a switching regulator is very efficient which means less consumption and less generated heat on the regulator. An additional benefit is that it can withstand a higher input voltage (about 35 V for the specified regulator), just in case the circuit is used in a vehicle that has 24 V batteries.

The regulator has already several protections like for short circuiting, overheating, etc.

  • 10 for 11$ right now on eBay. Sounds good to me.
    – 0xF2
    Commented Mar 7, 2014 at 14:19
  • @0xF2 You can get single ones for $0.99 so don't fall for than "cheap" ten piece package
    – alexan_e
    Commented Mar 7, 2014 at 14:29
  • While a better idea than a linear regulator, bear in mind that LM2596 switchers have a quiescent current of around 5ma (possibly more in a given implementation) which is a many times the power consumption of a sleeping or even slowly clocked ATmega. Commented Jan 18, 2015 at 22:46

I'm a big fan of USB car chargers for things like this, or USB buck converter boards that you get from ebay.

  • 1
    Can you please elaborate a bit more about how to attach one of the two or how they work/what they do? Commented Mar 6, 2014 at 22:02
  • A usb car charger normally has a bullet connector (thats what I have always called it) that goes into the cigarette lighter (12v accessory) socket on the car. And it converts it to 5v and you can plug in a usb phone charger or in this case Arduino cable.
    – Joel
    Commented Apr 25, 2015 at 23:24

There is also the higher-end Akafugu breadboard power supply - takes input from 7V all the way to 35V, but costs 11$ apiece in the bargain.

enter image description here



"Practical Arduino book" has a very interesting circuit for this purpose: http://www.practicalarduino.com/projects/vehicle-telemetry-platform

Here is how I've recreated it:

It uses LM2940CT and huge electrolytic cap - even if supply voltage drops, you'll have about a second to shut down your Arduino gracefully (close files on SD properly, and so on).

"Arduino Cookbook" (2nd ed.) has a chapter with examples on how to reduce Arduino's power consumption to absolute minimum - have a look at it, too.

  • 1
    A linear regulator is a poor choice - between this and the one on the Arduino itself, over half of the consumed energy will simply be wasted as heat. All that is really being accomplished here is (possibly) some input protection and moving some of the heat dissipation off board rather than concentrating it all in the on-board regulator. Commented Jan 18, 2015 at 22:48

Two more options - battery pack with convenient pre-made screw holes for Arduino, Raspberry.PI, and Beagle Board:

Smart Power Base

Smart Power Base

Kicking it up a notch - using a cordless drill's 18V battery. The project is meant for R.PI, but it would work just as well on Arduino, as the power supply is USB

Portable PI Power

Portable PI Power

  • images are broken
    – hithwen
    Commented May 5, 2014 at 14:04

Standard car batteries are 12.6 volts there are 6 2.1V cells. AGM batteries (i.e. Optima batteries, some interstates, and many other brands make AGM), in my experience with AGM batteries they are around 12.8 volts (I do not know the technical voltage). Without the car running you do not need to worry about voltage spikes AS LONG AS THE WIRES TO AND FROM THE BATTERY ARE SHORT. When the car is running the serpentine belt turns the alternator which is an AC generator. The alternator is connected to a rectifier to change it back to DC and the unit has a voltage regulator. When the car is running the alternator runs the electrical system and charges the battery. When you connect to the battery while the car is running you are actually connected to the alternator. When connected to the alternator there is a ton of electrical noise, voltage spikes, etc.

I have always had success connecting straight from the battery to the Arduino through its barrel jack connector, I have not tried any analog read function when the car is running. On the Arduino website it recommends 7-12V, however the limits (as listed on the Arduino website below the recommended) are 6-20. I have actually experienced problems with lower input voltages. If you feel uncomfortable just buy a 5 volt regulator and power through the usb.

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