Weakened Hybrid Battery

This community was very helpful with advice on whether I needed to worry about my original water pump so I'm going to ask about my weak hybrid/traction battery.

I make several trips a year from Las Vegas to Southern California, which is a 4.5-5 hour trip through mountains and desert landscape. A good portion of the trip is made through uninhabited land in 100+ degrees, where you don't want to experience a break down.

My car is 10.5 years old, it has brand new tires, there are no leaks, the engine isn't burning oil, fluids are fine, EGR is clean, and I have a new inverter. The concern is the traction battery, which is giving me around 42-45 mpg for a tank, from an average of around 50 mpg during it's peak. Dr Prius has my battery at around 38% left in it's estimated lifetime, they recommend a new battery when it hits 30%.

My question is what happens if my traction battery dies when I'm in the middle of nowhere? I've read that I can limp along with the engine, but how far can I drive the Prius just using the ICE engine? Can I make it up mountain passes and how fast can I drive? Or does the Prius just become a regular ICE car and can be driven like one until I get a replacement battery?

(I'm leaving this week during a heat wave, so I'm hoping to hear something reassuring. I'm anticipating getting around 47 mpg (calculated) for this trip. TIA)

 

Uh oh. My morning drive to the local park usually gives me 60 mpg. This morning, I achieved 33 mpg. I quickly did a full battery test via Dr Prius and received a battery warm warning. I’ll update later but I’m getting more concerned.

does anyone know what the battery warm warning means?

Update: I'm going to get a new OEM battery installed. The prices that I have been receiving have a big variance between the different dealers in different states close by to me so it pays to shop around. I'll update this later about the experience in getting a new hybrid battery.