You should plan your battery changes for when you change your pod (not every time you change your pod, but just when the battery is low).
The only thing wrong with your PDM is the internal battery is bad. The internal battery is only used to maintain date and time when you change batteries.
I have a PDM like that, but I haven’t had it replaced. When the battery indicator shows it is low, I just change the batteries at pod change time.
Anyway, this would be worth mentioning to people starting on the pod, that it is best to do battery changes when you don’t have an active pod.