ICE Starts when Battery Bars are even more then Half, Is is Normal?

That's quite normal. Since your Prius doesn't have a plug, it seeks out the most efficient opportunities to recharge the pack. It will start the engine when the power load is at a balance where some of the resulting output can be used to generate electricity.

Note the at the plug-in model does the very same thing when in HV mode. It took takes advantage of the engine.

Also, keep in mind that some of the generated electricity will be consumed immediately and the fact that the energy-flow from the system will change rapidly & often. Watching the screen, you can see it happening anywhere from 10 to 20 times per minute. That's the result of having a PSD (Power-Split Device) connecting a gas-engine with 2 electric-motors.

The dynamic nature of that design is often not realized by new owners... who question why the heck the engine started. You're not alone. That is indeed what's suppose to happen.

If that makes sense, now consider the other goal of reducing emissions. It seems counter-intuitive to run the engine without having first exhausted the battery. Keeping the emissions from engine exhaust low requires heat. That heat is used by the catalytic-converter to cleanse the exhaust. When the engine runs, its own heat that it creates is used for the cleansing. The heat is retained by the coolant.

It's an interesting cycle of one feature taking advantage of another.

 

Yes, its normal. The ICE will be incorporated in 99.9% of all driving situations. After all, the system is called Hybrid Synergy Drive, implying both systems are used to complement each other.

 

And incase you need a 3rd vote: Yes, it is normal.
The primary means of propelling the car is the gas engine; the battery is always secondary.
If you had a plug-in model, the battery is primary until it gets below a certain point.
It does NOT work that way with a conventional hybrid. It seems that a really LOT of people have trouble understanding that.

 

Also, depending on your location, in cold weather the engine may start occasionally due to the climate control system calling for heat, which comes from the engine.