Is there room to charge a "full" battery?

As on nearly all hybrid vehicles, to achieve a reasonable lifespan for the battery on the Prius Prime, Toyota has programmed the Hybrid Vehicle Control ECU to keep the battery state-of-charge in a limited range under most conditions, never allowing the battery to be completely charged or discharged. The meter indications you see are relative to this limited range, not to the true capacity of the battery.

 

is it possible that the engine came on and you didn't hear it?

 

most people report that starting with a full charge and immediately going downhill will start the engine.

 

Yes: it allows engine braking to be used, if there is no more battery capacity available for regenerative braking.

 

The HV ECU won’t allow charging under conditions Toyota considers unsuitable, and remember that they are making a warranty on the HV battery, in some markets, of up to 10 years or 150,000 miles.

This view may provoke some vigorous discussion, but I think it’s reasonable to rely on the battery management and protection features designed into the plug-in hybrid system by Toyota’s engineers, who undoubtedly had access to extensive test data when developing and refining the system’s control strategies and parameters to balance vehicle performance, driving range, fuel economy, and battery lifespan.

 

i agree with the above, but also the possibility that your car is defective, however unlikely. more testing and data is needed on your part, and please report your experiences here.
also, you may want to invest in a scan gauge, which will give you real data, vs the toyota display which is just for interest.

 

I've had it say 29.0 miles when I got in after charging complete and 29.3 when I got to the bottom of the hill near my house.

 

I've experienced something similar as I live near the top of a hill. Leaving in the morning on a full charge (100% battery indicated) the engine does not come on but the battery and range don't change. Also, the engine does not come on! This is <1 mile so I think that the maybe 2% regeneration is OK for the battery. As noted, it then takes more time to decrease from 100% than would be expected.

I think if it was a longer hill the engine would come on to prevent excess charging. I've had this happen on longer downhills.

 

I have a slight downhill in the mornings too and have also observed the EV range in creasing slightly (0.2) and ICE is definitely not running

 

how are you folks determining that the ice is not spinning to burn of excessive charge?

 

You can feel it if you're careful, or you can look at any of about three screens.

 

not sure toyota's screens show when the ice is spinning to burn excess energy, or that it feels the same as combustion.

 

couple thing for me, I would hear it and I also feel a ever so slight vibration when the ICE comes on.

 

during combustion? or have you felt it on a downhill where it is freewheeling to burn off juice?

 

Yeah, I have, and like I said you can feel it and you can see it on the screens in multiple ways.