To step up or to step down...that is the question!

Hi,

I have a question for an "Arduino to go"...so to say :) I want to avoid LiPo cells since they are not that save as simple NiMH cells and more difficult to get.

First choice: Take three NiMH cells in serie and power the Arduino Pro Mini (3.3v) via GND/Raw. There is (I dont know the details)-converter on the Arduino which will make 3.3v from that by cutting off everything which is too much.

Second choice: Take one or two NiMH cells and a extra DC-DC step-up boost converter (OUT:3.3v) and power the Arduino Pro Mini via GND/Vcc.

I know that there more efficient and less efficient boost converter... Which solution tends to be more efficient based on the principle of generating the needed voltage?

Is there any cheap but recommended DC-DC converter which generates 3.3v from one or two NIMh cells?

Thank you very much in advance for any help! Best regards, mcc

www.pololu.com has 1-cell boost converter modules that would work. They also have step down converters if you want to use 2 or more in series.

Hi,

thanks for your reply CroosRoads,

what do you think is better regarding of the efficiency: To step up or To step down?

Thank you very for much any help in advance! Best regards, mcc

Stepdown is usually better, but it all depends. An oversized buck converter could be worse than a micro-power boost converter. Batteries usually last relatively longer at low current drains then at high current drains. Pololu is one of the only sites that has efficiency graphs and idle current data for it's converters. I support them (buying stuff) for that reason. If you know the peak/normal/sleep currents of your setup, it shouldn't be that hard to work things out yourself. Leo..

Are you more concerned about safety or about conversion efficiency? Can you describe the environment where you plan to implement your project? and your power draw?

There are protected 18650 Li-ion cells that are safe for most projects. + They have more protection than NiMH and the capacity than 3x NiMH cells combined and also they are easier to get these days and they are cheaper than 4x eneloops and they weigh less than 3x NiMH cells and they have lower self discharge than typical NiMH.

So in short, 18650 cells are safe and more efficient than NiMH. :)