The main drawback of BikeCompanion, or GPS cycling apps in general, compared to a physical bike computer, is battery life during your rides.
Today, on recent high-end smartphones (such as the Samsung Galaxy or iPhone), you can record activity over 9 hours.
However, there can be big differences with less recent or lower-range smartphones.
Additionally, external factors like cold weather or lack of network coverage can drain and deplete the battery quickly.
If you have the problem of limited autonomy when you ride, then a simple and inexpensive solution is to purchase an external mini-battery.
For simplicity, I recommend buying a case with a grommet + a 10000mah battery, all for 30€:
https://www.amazon.fr/gp/product/B094Y1R46V/ref=ewc_pr_img_1?smid=A1J6IDEM095KAU&psc=1
AND
https://www.alltricks.fr/F-41498-bagagerie/P-1685802-sacoche_de_cadre_zefal_z_adventure_t1_noir
Another solution is to buy an external mini-battery with no cable.
They fit directly onto the bottom of the phone, are very light (less than 100g), and generally have a capacity of around 5000 mah.
Buying a mini-battery like this doubles the phone’s autonomy at a cost of €10-15.
Be careful with this model: on some phones, the mini-battery connected directly to the phone can “jump” and come off the hook due to speed and shock/vibration.
There are also bike mount that directly integrate external batteries (induction or wired), as shown here.
or lamps with large built-in batteries and a cable to connect them to the phone, as shown here.
With integrated lamps and batteries , as shown here