Battery for the NB-IoT

I would like to power my NB-IoT board from my car cigaret-lighter but with a battery in between, so that when the car stops (and power goes down) the arduino and the NB-IoT boards keep running (doen’t have to be long, only long enough to send out their position for a couple of times).

So I think my setup should be the following: Cigaret-lighter => battery (or some sort of capacitor) => arduino and NB-IoT
The battery in this case would be charged by the car when driving but powers the boards untill empty.

Is there anyone who can recomment the right hardware for this purpose? And what durations could I expect running on the battery?
This is what we sell as Sodaq.
It comes with a coin cell, if this is no enough then you can connect a lipo :slight_smile:
Batteries can be charged by solar and/or usb.