A few years back I started having a problem where when I would make an ascent of any length, say, a mountain pass or long incline, the battery would completely drain, i would begin losing forward momentum and the speed would start dropping. Eventually I would have to pull over, wait for the battery to recharge and start going again. I attributed this to the age of my battery (2008) and sure enough, the battery eventually crapped out on me, gave me the big red exclamation point and I bought and new one from Green Tech auto and had them install it. Everything seemed fine, gas mileage went back up and I was happy. However, yesterday I made a trip across the state and sure enough as I reached the summit of Snoqualmie pass, it did it again. Granted, it didn't happen as soon and was not as severe, but it still happened. I have been pulling my hair out for a few years now trying to figure this out and no one seems to have an answer. Anytime I have asked the dealership they tell me the battery tests fine.
it's the battery. when did green tech install it, and how many miles have you put on it? what is the warranty? a rebuilt battery is made up of some new cells and mostly older, that have been balanced. but that does not mean one of the older cells won't crap out sooner than later. as the cell(s) degrade, power output degrades until you finally get the red triangle. the reason the dealer said it's fine is because they do not understand the battery or electricity in general. toyota does not have a standard testing procedure to show the battery as 'good' or 'bad', because a battery constantly degrades from when it is new, and the point between good and bad is arbitrary, and set by the engineers in the software. when it crosses the line, you get the triangle, but it was only a little bit better before it crossed the line.
I see that Greentech sells remanufactured batteries and "new" batteries that are made up with a full set of new cells rather than the old ones in remans. I would guess that you got a remanufactured one. If you did and it was more than a year ago, I think you beat the averages. +1 to @bisco's comments. The dealer won't tell you it's bad till you see that big, nasty red triangle and they can read the codes that triggered it. Right now, I'd classify it not as "bad" but as "failing." Greentech has two different warranties on the remanufactured batteries, 12 and 24 months. Warranty on a new one is 48 months, which is GREAT. If you're still in warranty, you should check with them.
Actually I did buy the new battery, I want to say it was about a year ago I will have to verify. It was a 3 year warranty, installed for $2500. If you all think it is the battery then I will definitely give them a call.
Having never driven a Prius over Snoqualmie Pass, I don't know if what you experienced is just that it demanded more than the system could deliver or if it's getting weak. Long steep grades at high speed do require lots of help from the battery and it could just have been more than the battery can deliver.
Washington State. I-90 over the Cascades. I've never been to that part of the state, but would like to see it.
Actually, when I first got the car in 08 my kids were still young and I was driving to Ellensburg and Spokane several times a month and it always powered right over the pass in cruise control at 75 with no problems. It wasn't until the oem battery started aging that this began.
you can ask them, but like toyota, they likely won't do anything until it throws a code. if not the battery, it's probably the engine or tranny. how many miles on her? have you done all the recommended maintenance? after that, you have to start trial by elimination.
Just about to hit 260,000 and I'm religious with the maintenance. I have an envelope with the multi point inspection from every single oil change/ maintenance ever done on it.