Acceleration uphill with low battery

Is this a Gen4 PRIUS?

PWR Mode or ECO mode make no difference - full accelerator is the same, just the modulation between. I've never noticed that happening. But then, I'd probably be using RADAR Cruise at that stage, and speed has never dropped off. Maybe someone who lives in mountainous regions might have experienced this.

Did the battery charge up again after that?

There isn't something jammed under the accelerator pedal - eg a rolled up carpet?

 

They can get a bit slow on a steep upgrade. That's why they make climbing lanes on most mountain roads.

 

You're avatar isn't saying: You've got a 4th gen Prius? What year? With 10,000 miles on the odometer?

With third gen, and I think it's the same with 4th: you NEVER see 1 bar on the hybrid battery state-of-charge display; two bars is the minimum. At least, in normal operation. If you've got a near-new 4th gen displaying 1 bar (and low power), I would check in with dealership, could be a dud battery.

The one bit of info in your avatar: you're 119 years old. Seriously........

 

Took me a bit of exploring to figure out, but to fill in the car info on your avatar, mouse-over your username at top-right of a Priuschat page, then click on personal details. That's assuming you're on a computer, it's a little different on a phone, but the same thing, personal details:



Yeah, if it's struggling on hills and dropping to one bar, that is not normal. Two bars is the normal bottom-out, and at that point the engine will start running (even when stopped), to help charge it up. If that behaviour persists I would contact the service department, see what they say. No warning lights though??

 

generally on the highway, the battery stays pretty full until you hit a big hill, then it will come into play if the engine needs assistance.

one bar does seem wrong, i have never seen less than 2 on any of my pri, but i don't have gen 4.

 

I occasionally see one bar displayed under the following circumstances: Cold start of engine. While it is in warm-up phase it tends to use only battery for locomotion (slow speeds), thus depleting it to one bar before it starts charging. Is this abnormal? Got one more week on my warranty but can't imagine any other response from the dealership other than to blow me off, declaring the behavior as normal.

Edited for typo.

 

maybe gen4 is different

 

Yeah, maybe dips a little deeper into the reserve, or the it's just the display that's different.

There was a thread, back a few years, and early gen 4 owner was having some sort of hill climb issues. I think the title had the name of a specific location, some canyon road or something??

 

Ain't Google wonderful:

Loss of Power on Canyon Road!!! | PriusChat

 

But 6% isn't that steep. My Gen3 doesn't max out on 7% climbs, though I don't have such hills with 70 mph PSLs for testing.

 

On my G4 it will hit one bar when depleting the battery. This at 20% SoC, according to my ScanGauge.

 

6% isn't much to a new healthy car. 5% is a threshold used by many road planners when deciding whether to include a climbing lane. At 5% you can get away without, depending on traffic. At 7% nearly every road would benefit from an extra lane for lower power-to-weight ratio'd vehicles.

 

While that data is certainly true, there's a bigger picture here, which means PWR mode can make a big difference.

In fact, I'd go so far as to say that could be the problem.

So driving in PWR (versus ECO) mode means the power demands on the hybrid synergy drive will be generally greater, by virtue of the fact the accelerator is effectively being pressed "harder" at any given moment, other than when pressed to the floor, like you pointed out. Conversely, regen is also likely to be higher as there's a statistically greater chance of having to slow down from a higher speed (as you've accelerated more quickly, so more like to be traveling faster).

In short, the battery is probable being discharged and charged more aggressively and more frequently in PWR mode, for most drivers.

Combine that with the warmer time of year and you are far more likely to end up with the ECU reducing battery use to prevent overheating. I've only ever experienced this when in PWR mode on winding country roads and driving like I wish teenagers didn't.

You first notice the battery fan getting audible. Then quite obviously loud. Although maybe not that obvious at higher/noisier road speeds. Then you notice the ICE revving up high when slowing down or braking, just like it would in B mode, because it's using engine braking instead of regen. This is when the ECU is using protective measures to help prevent the battery temperature increasing further. And at this point, you get very little, if any, assistance from the electric motor. It's very noticeable, especially when going uphill, and/or accelerating at high speeds.

 

The 2ZR-FXE engine can produce about 98 HP. Mostly that's enough for getting the car around in ordinary circumstances.

If you want to accelerate extra hard, or climb a hill extra steep or extra fast, the physics of the situation can require more than 98 HP. In those situations, the battery is used to give you extra power (up to a total, from all sources, of 134 HP or so).

The battery can only do that for so long. Less long if it is below full charge to begin with. When it gets to the lowest charge state the car is allowed to use, it stops chipping in, and at that moment you notice your car changing to a 98 horsepower vehicle trying to climb a grade fast.

It is a normal thing to happen. If you notice it happening a lot with your Prius and not with other comparable Prii on the same grade at the same speed, then it could indicate something reducing your engine's power output.

 

I should note that climbing a 7% grade at 70 mph, in a half-loaded Prius, takes 46 HP to climb up out of the gravity well. This is in additional to the other power needed to drive at 70 mph on the flats.

How much HP is needed for a flat 70 mph? Something under 40? (I haven't looked at the relevant ScanGauge display in a very long time.) That should still leave a Gen3-4 Prius engine (98 and 96 HP) with a small margin on low altitude hill climbs even after the battery is depleted. Though a Gen2 (78 HP) may struggle, as some (but not all Colorado readers) have reported.

P.S. All ICE-based cars lose power in the thinner air at high altitude, so margins are much narrower in the Rockies than down here near sea level.