Understanding the influence of a dc-dc booster in battery life

[FBMinis]

I am not sure what will make my 5V device work longer:

- 4xAA alkaline (2400mAh each);
- Same type of AA but in a 2S2P configuration with a voltage step-up module (blue one - https://www.aliexpress.com/item/1189492730.html)

The load consumes 300mAh during 2min, then is cut from power for 58min.

[wasedadoc]

Is your load happy with the 6 Volts that 4 cells in series can produce?

The current supplied by each cell will be almost the same in each case.  The current into the step up converter will be close to twice the current out.  But it is coming from two pairs of cells in parallel instead of four cells in series.

No step up converter is 100% efficient so loss there.  OTOH the step up may still be able to give 5 Volts out when the cells are more discharged then when using 4 in series.

[TomKatt]

No step up converter is 100% efficient so loss there.  OTOH the step up may still be able to give 5 Volts out when the cells are more discharged then when using 4 in series.

That's an excellent point and likely immensely complicated to figure out other than through experimentation. 

[tunk]

For 4xAA, I guess it depends on what voltage range your device can run on:
New alkalines are around 1.6V and fully discharged, they can go below 1V.
If it e.g. cannot go below 5V, you will waste around half the capacity.
And a step-up module may have some (significant) quiescent current.

[FBMinis]

Is your load happy with the 6 Volts that 4 cells in series can produce?

Probably safer with 3xAA 

[wasedadoc]

Is your load happy with the 6 Volts that 4 cells in series can produce?

Probably safer with 3xAA 

But those will not give 5 Volts.

[JeremyC]

I am not sure what will make my 5V device work longer:

- 4xAA alkaline (2400mAh each);
- Same type of AA but in a 2S2P configuration with a voltage step-up module (blue one - https://www.aliexpress.com/item/1189492730.html)

The load consumes 300mAh during 2min, then is cut from power for 58min.

You should consider “step up down” type of converter. Efficiency is in range of 95%.
Below is link to an example:
https://www.ebay.com/itm/384316104430?hash=item597b065eee:g:srMAAOSwQX9iBwDC&amdata=enc%3AAQAHAAAA8EJi%2FcgwI0knZTcPR8cxpVk%2BPXS8scNBjL8TMKX59T23ulTKV8%2BpTwN6NAy33TMZDBs6xbinGGAII%2BHdacYKF75o8L6JEm04rYmxIa9aojfD2peSwVc2vzdGHVbf7j17f8BYCioDUbUxE%2FzKrTQhZRXtH3mPieHEV%2F%2Bn8%2BLIOxsjBcPQofHVQ%2FlkmH04DlmQzNFZxtRAmJnwpyXV04Zqqs1mfdUjiGMRkRYLUaGqadgDPIzzeja8LLrr1TFAEy14%2Fj4Pp5SCdo6aD%2B1jNXE5F6pAs%2BxBkU1j4RNl6Ph98YJvCt%2Bks7AbBLDs3fOBTY8YcQ%3D%3D%7Ctkp%3ABk9SR57qjOfKYQ