Hi. Do you think this will be enough for indoor usage to power a simple temperature sensor ?
What type of battery did you use this module with ?

@dbemowsk this also happened to me. Those fuses are very hard to solder without damaging them. I tried to use alligator clips to act as heat brakes but with no success.
I finally managed to solder them using a third hand and dipping the body in cold water like in this
this video

So in the end it is the fist component I solder on my board. Not very convenient

@flopp : cool module ! This could do the trick. The 0.1 mA could be taken care of by powering the module via a MOSFET controlled by the arduino. It would then power the sensors and the radio only when needed.

Sure ! The newer ones have a battery protection chip. I've tested it and it kicks in at 2.8v.
http://www.aliexpress.com/item/Free-Shipping-10pcs-lot-1a-lithium-battery-charging-18650-with-protection-one-plate-protec-2-in/1876166772.html

Looking at discharge curves I can see that I should be able to squeeze 75% of the battery capacity if I charge it back when it reaches 3.3v. On a low power node this could work.
@flopp The reason I was mentionning 2.8v is because the battery protection module will kick in at this voltage. But you're right, no reason to go this far.

Thanks !

So if I sum up, powering this node with a single Lipo cell will work by connecting the Lipo to the raw pin on the arduino. This will work from 4.2v to 3.4v. This is not that good for the battery life.
Using 2*AA batteries with a boost converter seems a lot easier...
I'm almost giving up on this idea : I liked the flat form factor of the lipos and they were solar pannel friendly. Is there a way to use a voltage regulator from 4.2v to 3.4v and then switch the circuit to a boost converter from 3.3v to 2.8v ?

If the arduino is outputing 3.3v that means that you are powering the arduino with the RAW pin, isn't it ?
If so make sure the linear voltage regulator on the arduino will be able to provide the 3.3v if battery voltage drops below 3.3v (so from 3.3v to 2.8v). I don't think they can boost the voltage from 2.8v back to 3.3v

I'm thinking of building the same kind of board for protyping sensors, also powered by Li-Ion or LiPo cells as I have plenty lying around
The TP4056 board will protect the cell if voltage drops bellow 2.8v. The arduino and nrf24 module should be fine at those values. This might not be the case for all sensors...
However when charging or at 4.2V the nrf24 module will exceed its 3.6V max input power. Did you manage to get your board working ?