Battery Discharge

I am wondering how much faster (if at all) a battery will discharge when using a step up voltage regulator. I have circuit that draws 100 mA with an operating voltage of 5 V. Now if I power this circuit with a 5 V, 2000 mAh battery and no voltage regulator, I should have 20 hours of battery life, correct? However, I want to power my 5 V, 100 mA circuit with a 3.7 V 1000 mAh battery with a voltage regulator that will step up 3.7 V to 5 V. Will my battery life be 10 hours or significantly less than that? How do step up regulators typically affect battery life?

Thanks for any help, I am new.

akafoury:
I am wondering how much faster (if at all) a battery will discharge when using a step up voltage regulator. I have circuit that draws 100 mA with an operating voltage of 5 V. Now if I power this circuit with a 5 V, 2000 mAh battery and no voltage regulator, I should have 20 hours of battery life, correct?

Yup, that's right. (although the battery voltage will drop over time of course)

However, I want to power my 5 V, 100 mA circuit with a 3.7 V 1000 mAh battery with a voltage regulator that will step up 3.7 V to 5 V. Will my battery life be 10 hours or significantly less than that? How do step up regulators typically affect battery life?

If the converter was perfect (i.e. it took no power itself), then you would just look at the power required:

5V * 100mA = 500mW

The 3.7V battery has to supply this same amount of power, so we can work out what current is needed to do that by:

Amps = 500mW / 3.7V = 135mA

In reality the converter will take around 10% of the power for itself, say 15mA in this case

so you would need 135 + 15 = 150mA.

so you would expect your 1000mAh 3.7 V battery to last 1000 / 150 = 6.6 hours

Yours,
TonyWilk