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?
My 2013 Prius is having these issues too, no warning lights or codes. It loses a lot of power under load (failsafe mode) and the engine revs way too much uphill. It has almost 213,000 miles on it. I cleaned the EGR and changed the oil and engine coolant a few months ago. And I am not sure how to safely check the hybrid battery or the inverter due to high voltage.
Was that ever not true on the same hills? To some degree that's normal behaviour, compared to most other cars.
Please start a new thread in the Gen 3, Care, Maintenance and Troubleshooting sub-forum. It is much better doing it that way so you do not have information scattered across multiple threads like you are doing. I made the same request on May 8th in another thread that you posted in.
I took the liberty of bolding your "taken at moderate speed" part, which is key. The "Grapevine" thing I don't know about. In Virginia there is a section of expressway that passes through Rockfish Gap, and I know about that. In ➡this post⬅ a decade ago I told a little story involving Rockfish Gap, my old gen 1, and my sister. A couple things to know about gen 1. It had a 70 HP engine (for some reason I wrote 71 in that old post, but no, I have the NCF in front of me right now, it says 70). That's less than the 76 HP they eked out of the same basic engine in gen 2, and it's a lot less than the 98 HP of the larger engine in gen 3. That 70 HP from the engine could be electrically boosted up to 97 combined horsepower (under the best RPM conditions), using up to 27 HP from the battery. (The corresponding gen 3 figures are 98 HP from the engine, 134 combined system HP, meaning up to 36 HP from the battery.) Whether the battery does or doesn't "contain enough usable energy to be a significant factor on long climbs" depends a little on what you call significant. An as-new gen 3 battery, starting at the usual 60% state of charge, could give you the max 36 HP for about 35 seconds before reaching 40% where the boost cuts out—taking only the battery capacity into account (in practice, complications like heat management come in, and I've really never seen anything like max output sustained for that long). An as-new gen 1 battery, which was larger, could give you 27 HP for about 64 seconds in the same conditions. As for Rockfish Gap, when I would drive that stretch myself in my gen 1, observing the posted speed limit, the battery never contributed much. That ascent, taken at moderate speed, could be handled within 70 HP from the engine alone. But when I let my sister drive, the battery had to contribute. It did not contribute the maximum possible, but only (as I wrote in that old post) "10 to 20 amps or more pretty much the whole way up". Obviously, I was just glancing now and then at the ScanGauge, and don't have a datalog. Those amp figures, at the higher gen-1 battery voltage, come out like "4 to 7 HP or more all the way up". So it takes something like 74 to 80 HP to go up that stretch if you drive like my sister. An as-new gen 1 battery starting at 60% can give you 7 HP for about four minutes, or 4 HP for seven minutes—long enough that you definitely can be making some climbs of noticeable length with the battery pitching in the whole way. If the battery does get down to 40% and you lose those extra HP in mid-climb, you'll definitely notice; your speed is going to drop then to whatever the engine output can sustain on its own. Now, remember that the gen 1's combined rating of 97 HP is less than gen 3's 98 HP rating for the engine alone. So, a gen 3 could make that same climb and still maybe slightly charge the battery, even with my sister driving.* Nevertheless, I'm sure that even for gen 3 there are stretches of road where sustained battery contribution can be needed, when driven hard enough. * I'm neglecting whatever the weight difference is between the generations.
