Toyota Prius - Depleted Battery Power in Mountains


Asked by Jun 01, 2015 at 11:34 AM about the 2009 Toyota Prius Liftback

Question type: General

Has this happened to you?  We were driving on Highway 70 through the Rockies and
climbing to the Eisenhower Tunnel at 11,000 feet.  On our way up the mountain,  the car's
battery ran out of power near the summit and we crawled to the top on the gasoline
engine only.  It made it, but,   I wasn't happy about it.   We stopped along the way to
charge us the battery and it worked for a while,  but,  the thing got depleted really fast.   
Not sure I want to do that again.   Soon as we reached the top, the car resumed to normal
operation and its fine.  No apparent damage to the hybrid system.   HAVE ANY OF YOU

7 Answers


I have not experience this but have a friend that has. He didn't get to the bottom of it by the time I last spoke to him, but I await an answer on here. My hunch is that it could be to do with the electric engine having to work harder to regulate the temperature, if it was either very hot or cold.


The temperature was in the 30s when we went through on one occasion and in the 40s on another. Did it twice and both times, we watched that graph on the dash just go to nothing. Then, we crawled up the summit around 25 miles per hour, not a secure feeling at all. That little engine was working pretty hard. Did not overheat, but, seemed to strain. Not doing that again, we're done taking it up that road again. My Subaru Outback would have been better going up that mountain pass! Even so, it's hard for a lot of cars. We saw people even struggling more than our Prius, but, they were in some much older vehicles.


Yes, I would definitely be interested to know about your friends experience.

Harry Shaw

just a thought, but when in the mountains it suggests putting the drive in B mode which is like gearing the car down which will make the motor turn over faster and might help keep the battery charged!


Gassipiper - interesting theory, I'm impressed that you thought of that! Did you find this in the owners manual? All I can say is that you might expect the car to do this automatically on a steep grade, that's what automatic transmissions are supposed to do, correct? The Toyota Prius is marketed as a "CVT transmission ", but, it's technically a "power sharing transmission ", which uses CVT like technology, but, not like a conventional CVT. Their "hybrid synergy drive" as its called, should have made adjustments automatically. Tell me, am I missing something here? Anyway, I have to say that either way, the 1.5 litre Four just worked so hard on this climb to just over 11,0000 feet, I don't think I'm going to do that again. It did make it, but, we slowed down to about 25 miles per hour near the top. I guess my point is that it's just too much for this car, two people and luggage. First time we went through it was normal temperaturea, I really don't think that makes a big difference.


Gassipiper, found this interesting, see rid_camry_prius_b_mode_braking_brake_fade_downgrade_failure_.a spx


Here's the most salient point of the Web link I sent you just now, "So essentially, you should ignore B mode, unless you are driving down a mountain. It is not used for towing, snow, up hills, or any other time when you would use the low gear in a normal car."

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