Acceleration problem up long hills

This is normal operation of the hybrid system once the traction battery reaches minimum charge (~40%, 1 purple bar on the battery meter on the energy flow screen) and the electric drive stops assisting. There's likely nothing wrong with the car.

On long climbs, it's common for the traction battery to reach minimum charge. The gasoline engine does not have much horsepower or torque on its own, without the help of the electric drive, so the car becomes quite lethargic at this stage until the grade lessens and the traction battery is able to recharge again.

It sounds like this is the first time you have experienced this. It may be that the state of charge of the traction battery just happened to be lower than normal before the start of the climb, so it reached minimum before cresting the hill.

There are different thoughts of how to reach the top of climbs without the electric drive cutting out. One is to approach the bottom of the hill with quite a bit of speed and let the speed gradually decrease as you reach the top. If the climb is long and steep enough, there may be no practical way to crest it with charge remaining...just limp over the top on the gasoline engine (I try to keep it below an estimated 4000 rpm to reduce engine wear--I don't like to let it scream) and then recharge on the way down.

 

I edited to "There is LIKELY nothing wrong with the car." after you quoted it. How many miles are on the car? It's possible that the traction pack is losing some capacity. See if it becomes a habit for it to go to minimum on your next trips over this hill. If it only happened this one time, it's probably just a chance thing that the charge level happened to be lower before you started climbing.

You might monitor the charge level on the energy flow screen more diligently and make note of the level when you get to the hill, how quickly it depletes as you climb, and how the charge level changes in other driving.

I like the screenname. It reminds me of the credits on Car Talk. I'd probably be Major Payne Diaz.

 

With that odometer reading, it's possible that the traction pack is losing some capacity. It may not be close to failure though--you might be just fine for that road trip.

Also pay attention to the sound of the traction pack cooling fan. It runs at high speed when the pack is under stress. The vent is located high on the passenger side, rear seat bolster. It helps to have a rear seat passenger listen for it, but when it's really churning, you can hear it from the front seats.

Here in Colorado, just about every trip over the mountains depletes the traction battery, regardless of route or technique but I think some give it more pedal than others once the electric drive cuts out. I take it pretty slow but there are definitely Pri drivers that fly over the passes. Maybe they get to the top so fast, the traction battery doesn't have the TIME to deplete. I don't know which way is best.

 

Snoqualmie Pass has both a shallower slope, and much lower elevation (i.e. high barometric pressure and better ICE power), than the Colorado mountain roads. I hope other Washington GenII drivers chime in, but I'm not aware of them having the same problem with limited power and speed on Snoqualmie that some GenII owners report for I-70 in Colorado.

 

What is the car's maintenance? What have you done to the car so far? Last time you changed the Inverter coolant, trans fluid etc?

 

185,000 miles on mountain roads...yes, you can be certain the traction battery has reduced capacity by now. The behavior you see is normal for that level of use.

 

With that odometer reading it is also highy likely that the ICE has lost some of it's capacity too. Using a bit more oil than it used to ? Put new plugs in it lately, air filter, put Techron in the gas ? It might just be getting old but neglecting needed routine maintenance can make matters even worse.

 

When was the last time that the engine air filter was changed? I suggest you remove the filter, inspect it (the bottom side is the side that collects dirt) and replace as needed.