Last summer it was a very hot day and I was driving my 2013 Prius up a long winding highway. After a while acceleration slowed and the car was losing power and speed. When it got to 30 mph I pulled over which was scary because there was barely any room on the side of the road. I had the car towed to my destination and then to a mechanic. He checked the codes - all was fine - and suggested I drive off and not worry about it. Well, I drove off, the car works fine, but I do worry about it. I had one sort of similar incident on another long hill, but the car maintained speed at 40 mph and I was able to get over it. All mechanics are stumped because no codes have showed up. I'm afraid to take the car on trips that involve hills now. Previously it made it up the grapevine (going from SF to LA), so I don't know if something has happened which prevents it from going up long hills now.
Simple soultion. Your car is most likely overheating. I was in th same boat. The car would drive 1000 km on highway like a piece of cake but would stumble down to 20 km/h on a long hill drive. The car had two main issues. Radiator needed flushing. Plus there was some air in cooling system. Get ur radiator and water pump looked at and u will be good to go Posted via the PriusChat mobile app.
How steep and how long was the hill, and how fast were you driving? There might well be no codes, if what was happening was the normal operation of the car. Your gasoline engine can produce 98 HP maximum. If you are driving up a steep enough grade at a speed that requires more than 98 HP, then the battery is chipping in the whole time. But that can only last as long as the amount of charge in the battery. If you have something like a ScanGauge or the Torque app connected in your car to show you the actual battery state of charge in percent, and you see it steadily dropping while you're climbing the hill, watch how close it gets to 40%. The magic switch flips just below 40% state of charge: the battery will stop contributing then, and suddenly you find yourself driving a 98 HP car up a steep hill, and your speed is going to drop to whatever a 98 HP car can do there. If that's what's happening, and it used to not happen under those same circumstances, it could just be that the battery is older now and its capacity's a bit lower, but not that anything is really wrong besides that. If you have something showing you the state of charge, you can sometimes pace yourself, and pick a little lower speed for driving up the hill so the battery will still be at least 40% at the top. I nearly had the same experience the time I let my sister drive my Gen 1 up Afton Mountain. She was driving, and I was watching the SoC drop on the ScanGauge, but luckily our exit came just as it was hitting 40%. The Gen 1 could do just fine up that same ascent, at the speeds *I* would drive.
How does the battery last driving on the grapevine. I previously had problems with the battery lasting the whole way up the grapevine going south. My battery would go all the way down and my gas engine would get louder ascending the grapevine going south. I made it over but then I replaced the battery with a project lithium and have no problems ascending hills anymore.
These tales puzzle me, because my traction battery state-of-charge normally remains constant on long uphills taken at moderate speed. (Of course it initially drops rapidly when I'm forced by a traffic jam to creep up a hill with engine off.) Battery current, as shown by ScanGauge, does not change from what is shown in level stretches. Besides, the battery simply does not contain enough usable energy to be a significant factor on long climbs. Specifically how long and how steep, or how high overall, is the "Grapevine" thing Californians like to talk about?
