Prius Prime 2021 why EV battery stops charging once empty

The technical term for "blank mode" is normal mode.

Thanks for coming back and providing feedback .

 

Just to clarify what @Raytheeagle pointed. There is no Hybrid Mode indicator on the dash. The Blank is the HV mode either without EV range left or switched manually to HV mode by EV/HV switch or switched automatically during EV AUTO function. If it is HV mode (blank mode in your comment) due to depleted EV range, then it will switch back to the EV mode automatically if the traction battery gains enough charges from regen. You will need to recharge the traction battery above 3% SoC on the dash to see the "_%" to be shown again, then you will need additional regen above 6% SoC in the traction battery to go back to EV mode.

Here are composite pictures of changes in display on the dash I demonstrated in another thread to show the regen capability to recharge the traction battery after depleting the EV range. I couldn't find the thread, but if I find it, I will post a link here. The photos show the ascent up to a summit to consume all EV range down to - -% then start the descent to use regen to charge the traction battery. As you can see after the dash indicator change from EV mode to HV (blank mode in your comment), the engine started (shift from the second to the third pic). As I started the descent and regen charged the battery and started show the SoC at 3%. Continuing the descent and regen charging the battery, SoC at 6% the car is back in EV mode. I did not touch the EV/HV or EV AUTO mode buttons during any of this experiment. But I did put the car in B gear during descent so that I can maximize the regen brake capability without using a friction brake.

 

in 17 years, i don't think i've ever seen a new owner so confused...

 

I hope it's not closed. You still seem mighty confused. Actually, it's time to open the manual and correct some of the wrong assumptions you're making. For one thing, any time you're braking using regen or if you're coasting, the car puts that energy into the battery -- in any mode and any state of charge until the battery is as full as the system permits, which shows as 100% on the display. @Salamander_King gave a terrific explanation and the pictures he provided should make it clear. As has been said, "blank mode" isn't blank mode. It simply means that the car is not in EV mode. The only other mode is HV. It may be running with or without the ICE at any moment, but if it doesn't say EV by the speedometer, it's not in EV mode. The EV indicator by the HSI bar is on when the ICE is off whether you're in EV mode or HV mode. Note the charge area (#1) in the picture below. When the bar moves into that area, it's using regeneration to charge the battery. In all modes.

Nice pictures. Great explanation.

 

tough love