Operating time measurement of self-made air purifier

The 12cm fan I bought is 0.25A at 12V, so I can use it most efficiently if I have a 12V AC adapter.
But I wanted to mobilize the air purifier, so I would either prepare a 12V battery or boost the mobile battery to 12V. I chose the latter because I didn’t want to mess up too much.

The configuration diagram looks like this.

I measured the current at each point.

The boost circuit I bought was quite inefficient. I can not help because it is about 250 yen with 5 pieces.

https://rover.ebay.com/rover/1/711-53200-19255-0/1?mpre=https%3A%2F%2Fwww.ebay.com%2Fsch%2Fi.html%3F_from%3DR40%26_trksid%3Dm570.l1313%26_nkw%3D%2BMT3608%2BDC-DC%2BStep%26_sacat%3D0&campid=5338483311&toolid=20008

rover.ebay.com

If such a power bank is used, the efficiency drops further because two booster circuits are connected.

My 18650 cylindrical lithium-ion battery was 3000 mAh in the display, but when I used this mobile air purifier as the ability, it was 3 and a half hours.

11.1 Wh as 3.7 V 3000 mAh.
It runs out in 3.5 hours.
If I trust the battery display to be 3000 mAh, 3.2 Wh.
If it is 2.85 W with one boost circuit, there may be about 3000 mAh of this green 18650 lithium ion battery!
That’s a surprise.