battery ?

You should be OK. The car's computer is very protective of the battery and won't let it even get close to a complete discharge. When one or two purple bars are showing the battery still has a 40-45% charge. I suppose all bars could disappear (I've never seen it, even climbing a mountain), but again, you're still at 40% charge.

See this for a discussion on the relationship between the battery display and state of charge. The discussion is somewhat technical, but the graphics clearly tell the story.

EDIT: One more thought. As you make your own climb up the mountain and the battery display drops to one or two bars, the ICE (internal combustion engine) may seem like it's revving higher and the car producing less power. That's the result of the car protecting the battery. The lower the charge, the less the battery gets used, so the car ends up running mostly or exclusively on the ICE. It's only a 1.5L engine, so it will be really working to get you over the summit.

 

you have a 2008 prius
maybe the hv bat still needs to get to its optimum working condition

 

The bars indicate the condition of the high-voltage (HV, or traction) battery. There are two easy ways to completely drain the HV battery:
1. run out of gas and keep driving until the car stops
2. shift the car into "N" (neutral) and leave it running until the HV battery drains (the car does not recharge the HV battery when in "N").

Both of these are abnormal ways of using the car. If you remember not to do these things you will never drain the HV battery.

When driving to Big Bear floor the gas pedal as needed. The engine roar is completely normal; it is merely providing the power required. The computers will not let it harm itself.

 

Don't worry about the battery, I have had my Prius for about a year and sometimes see the purple bars, but have never seen them completely missing.

The engine will rev higher when the battery is low or cold, but that is normal. Before owning the Prius, I had a Civic Hybrid for almost 5 years, and even though the hybrid systems are completely different, it behaved the same way. When the battery meter was at the bottom the engine had to rev higher to keep up speed on long hills and it's poor little engine was only 1.3 liters.

By the way as I have said several times on this forum. The Prius is MUCH nicer than the HCH.

 

And neither of these ways will completely "drain" the HV battery. They will take it down to 30% minimum. The car will then shut off until you stop doing such silly things.

 

Two of my Japanese Prius friends saw 18% SOC.

Ken@Japan

 

What were the circumstances?

 

I'm going to be a bit picky here. For 'may seem' substitute 'is'. On a single carrigeway I check that the SOC is out of the purple and in the blue before overtaking as less power is available. (This is normally on the horrible, A9 up to the Highlands of Scotland.)

 

Both 1 and 2 cases as richard schumacher stated.
On case 2, he did that intentionally to see the results.

Ken@Japan

 

Golly, you and Evan?!

 

I was glad to find this thread! I've owned my beautiful white 2008 Prius, Package #3 for 12 days and only today did I see the battery go down to two purple bars. Was wondering if I was in trouble. (The circumstances were that I had idled the car in a parking lot for a while listening to the radio with the air conditioning on, and then got stuck in a traffic jam for about 20 minutes where I was stopping and starting and going only about 3-4 mph when I was moving.)

After 12 days I have 1,035 miles on the car and am getting 50.9 to 55.8 mpg on the MFD. Very happy with the car.

 

And I'm glad you did too! We appreciate those like you who spend just a little time with the search function after first coming aboard. Questions like this about the battery are among the more common ones around these parts.

Welcome to PriusChat and Prius-dom!

 

I've posted it before but I'll say it again for those who get worried when the engine roars.
Climbing out of Hope B.C. on the Coquihalla, driving like I owned an SUV and oil refinery with cruise set at 115 km/hr, on the steepest portion I saw the engine at 5000 RPM. Funny, passing SUVs with V8 engines. Boy were they pissed. I -still- got 4.6 l/100 km on that tank.
I've never seen the engine go faster than 5000 RPM. It's the reputed "red line" for the current Prius, though I suspect it's more of a "yellow line". The SOC didn't drop during this, though it only lasted 5-10 minutes.
At any rate, the car will protect itself.