Battery fully depleted

You need some battery to be able to start the car, so you would not want the battery to run down to zero. Also, it is not good for the life of the battery to deplete it completely.
I suspect that your old car behaved in a similar manner, but it may have displayed the information differently.

 

Do you know that the more depleted the battery, the worse mileage you'll get? If you can manage 7 bars consistently, you'll get way better mileage than trying to drive a couple of miles on EV.

 

The amount of pure EV mode seems to make little difference to fuel efficiency. You can have the ICE running, but the EV still driving the wheels. If I've got the temp set for 22 deg when it's 12 outside, it'll generally start the ICE thinking I want the heater to run. The ICE will also run to warm up the engine - with the heater turned off, the drive from my house is possible to initially be in EV mode if I don't have the heater on and there are no cars driving in my street, but I've noticed that, even with a full battery, if I happen to accelerate slightly faster and it starts the ICE, the ICE won't switch off till the engine is warmed up properly, which is probably to protect the ICE. Same thing if it comes on for the heater.

It does sometimes seem to have a mind of it's own, but times when the ICE has come on when I didn't see it "needed" to, have been trips where I've had quite amazing litres/100km.

 

sounds right to me, if you want more ev, get a pip.

 

Gen3s do the same.

 

When researching when considering buying my Prius, I read that using the ICE in conjunction with EV mode, your battery life will be better, whereas trying to force it to stay in EV isn't going to help your battery. Deep discharge and charge cycles don't do them any favours either, and the Prius is designed to still have a considerable charge when the indicator shows it's almost empty to ensure a long life. The jury is still out on Li-ION batteries, but it seems likely a similar, but maybe less pronounced effect will occur (tho they're more expensive to replace)

There are some quite technical threads in PriusChat if you want to do more reading - they specifically relate to earlier models, but should still be applicable:
Understanding NiMH hypercycles (to prolong Prius HV battery life) | PriusChat

The Five Stages of Prius Hybrid Operation | PriusChat

THE NEW TOYOTA PRIUSTHE REBIRTH OF THE PIONEER