I am developing battery based product. In that supply voltage is 5V and total current is 2000mAh. Now if I use 3.7 V or 7.4V lipo battery with DC to DC converter, how much capacity (in mAh) of the battery is required?. How to calculate the battery capacity?

 

It all depends on how much current drain is on the battery from the dc/dc converter. You just measure the current in mA and multiply by hours.

 

You need to think in terms of watt hours. 5volts and 2000 mAh (2 amp hours.) is 10 watt hours. For 10 watt hours from a 3.7 volt cell you would need a 10/3.7 Ah cell = 2.7 Ah (2700 mAh). For a 7.4 volt battery you would need 10/7.4 Ah = 1.35 Ah (1350 mAh) battery. You would also allow for the loss in the voltage conversion. So if the converter had an efficiency of 80% you would need to multiply those values by 1/0.8 = 1.25.

Les.