I've replaced the batteries in my keys but the car still says low battery

I have replaced my key fob batteries on a couple of occasions but it still indicates that the battery is low. Am i missing something here that i should do after installing new batteries?

Why am I getting a battery charge failure warning light in my Rover 75?

I'm having battery charge problems with my Rover 75 CDTi. I get dashboard warnings that all go away when you charge the battery, but return twenty miles afterwards.

Is it safe for a battery to be permanently connected to a mains charger?

Is it safe for a Honda Jazz battery to remain in the car and permanently connected to the mains via a smart charger through the winter?

Is it safe to connect a battery to a 'smart' mains charger all winter?

I see that you replied to Brian Joslin's question "Is it safe to connect a battery to a 'smart' mains charger all winter" in the negative, but I thought that is exactly what they are designed to do (although...