Motorbike 12V to 5V efficiency

Hello and sorry if my question makes some experienced electricians a little confused.
Meaning i dont know almost nothing.
So i want (create a project)
to connect in my 12V motorbike (when the ignition is off-onother not relative topic)
a processor like arduino pro mini for me the noob.
So when motorbike is locked then through some regulator i will take 5V
for all the night to be used in my alarm project.
Now my problem is that (forgot the alarm and ignition)
…my problem is that my pro mini will use VERY SMALL amount of amperage
(the 8 hours that user lets say sleep having the pro mini on throught regulator)
And as i saw in step-down regulators …the efficienty is VERY bad (the most bad from specs)
when amperage is very small.
Below image “need efficienty in low amps”

So…finally the question for anyone that have time and can answer surelly to a noob like me.
a)Am i wrong in my understanding
and EXIST some PERFECT for this occasion pololu regulator
(and if yes please answer whitch exactly)?
b)Am i good in my understanding but because i am not a 'from study-lesson’electrician
the answer to my problem is something ELSE ? linear regulator?
c)My genaral design-thinking of how i can implement my project is totally in-appropriate(electrically)
and better use special batteries for processor …(at least when it is powered down)

I hope my question is understandable.
PS…assume arduino will be always in power down mode …so assume processor consumes
LESS than 1 ma throught the regulator from 12V
(just wake up every lets say 10 minutes and…checks something…)

Thank you in advance.


You are correct that switching regulators are generally less efficient at lower output currents than they are at higher ones. To maximize efficiency at the low end, you can select a switching regulator with a maximum output current close to the maximum your application needs and use it in power save mode. If you only expect to your Arduino to ever draw a few milliamps, our D24V5F5 or D36V6F5 regulators might be appropriate. Both of them operate in power save mode with low currents.

The efficiency of a linear regulator is mainly determined by the input and output voltage and will be at most Vout/ Vin. For your case going from 12V to 5V, that is around 40% efficient, so I suspect a low power switching regulator is generally still going to be better for your application.


Very well…this (those diagrams) was all i need.
(Just didnt think it about …to check those “60% – 95%” …meaning
…i was looking high eff regulators ignoring the amperage)

Claire and team.