As others have mentioned, this is normally because of the right HA being the Bluetooth master. If by chance, the hearing in your right ear is worse than your left, this can also increase this issue. Though with this latter case, your fitter can switch your left HA to be the master.
Recently I have also noticed that If my HAs are connected to both my phone & my mac simultaneously, the right HA will drop even faster, as much as 20% lower battery than the left HA by the end of the day. Because of this, I have started only connecting it to my computer when needed.