DIS says key's battery is low...

[Johnmed]

Intermittently the boot would not unlock when the key was in my pocket, and DIS would say no key was present (having let me enter the car with key in my pocket) and rarely DIS would report the key's battery was low.

I replaced the battery in the key I had been using, and the low key battery warning continued, again rarely. So I started using the other key, and today DIS told me its battery was low too... So I've bought some expensive Duracell 2032s today and replaced the battery in the key I have with me.

Is it just a coincidence, and both batteries were low, and maybe the battery I had (in one of those blister packs you get, of cheap batteries) wasn't the best, or is something else going on?

John.