Lead Acid battery charging.

I have smart chargers and energy monitors, so when I put my car on charge I can see if charge complete from my bedroom.

However first with Kia car with 95 Ah battery, and then with mobility scooter with 2 35 Ah batteries I have noted as the battery continues to charge the time between low rate and higher rate becomes less.

this is the mobility scooter reached a point now where the two rates are changing that rapid that they merge together on the display the same with Kia battery the spikes get closer and closer together the longer it is on charge for. Now I have very little info on the mobility scooter charger, but the Lidi charger used on the Kia does tell you what is does, at 14.4 volts it drops charge rate to 0.1 amp, and at 12.7 volt it increases it to 0.8 amp, I would have expected as the battery gets more and more charge the decay time would increase, but it seems the reverse is true.

Now with the other car, there were very few spikes and it in the end dropped to zero charge rate, switching back on at 11:40 every day for a few minutes, clearly the car does something at 11:40. So with the Kia I assumed either a drain on battery by the car, or battery getting too old, don't remember this happening in the summer.

But when the mobility scooter did the same, then I started to wonder what is going on. Any ideas, in both cases the chargers say can be left one 24/7 365 days of the year with no problem.