Battery Life (switching vs Linear Regulators)

Thread Starter

keyboardcowboy

Joined Dec 31, 2012
25
how does using switching regulators in place of linear regulators effect battery life??
If i use a 7805 to get 5v from 12v (2 Ah) battery consuming a current of 500mA, the battery should last 2A/0.5A = 4 hours RIGHT???, the thing that i do not understand is that the linear regulator is wasting the other 7v in the form of heat, shouldn't this effect the battery life as well??
 

Shagas

Joined May 13, 2013
804
The thing is that when you pull 500mA of current from a 12 volts battery , you are pulling in effect 12 x0,5 = 6 watts of power . Now you can choose what you will be doing with those 6 watts of power .
The voltage regulator wastes 7 x 0.5 = 3,5 watts and there is 2,5 watts available on the output of the regulator .
Basically the battery life is determined by the current pulled from it (in this case 500ma)
It also provides 12 volts , now if you use the full voltage or not is your problem , not the battery's (at least this is how I like to think of it :) )
 
Last edited:

Shagas

Joined May 13, 2013
804
also when I say 'use the full voltage' I mean it in the sense that if you connected the battery say directly to a motor which pulled 500ma then the motor would be using all of the 6 watts provided by the battery .
If you are using a regulator to give you 5 volts then you are in essence 'wasting' 7 of the volts that the battery provided .

In this specific example lets say you had a 12v 2Ah battery and a 6V 2Ah battery .
Both batteries would have exactly the same life span. The only diffrence would be that with the 12v battery 3,5 watts would be wasted in the regulator and with the 6 volt battery only 1/2 watt would be wasted in the regulator .
 

#12

Joined Nov 30, 2010
18,210
I think shagas missed the point. A switching regulator can be in the range of 90% efficient. 12 volts times 1/2 amp with a linear regulator will take 6 watt hours per hour out of your battery. A 5 volt load at 1/2 amp is 2.5 watts, and the switching regulator will use about 2.8 watt hours per hour to do the job.
 

Attachments

crutschow

Joined Mar 14, 2008
25,267
Just to make it clear to the OP as to how this higher efficiency of a switcher helps, a switching buck regulator that reduces the voltage from input to output will take less input current from the battery then it delivers at the output. It rather acts like a transformer to simultaneously reduce voltage and increase current at high efficiency. That is how it improves battery life over a linear regulator.
 
Top