Long Inclines And Battery Drain

Maximum speed limit here is 110km/h or just under 70mph so never had this happen to me even on the longest steepest hills

 

This is fascinating. Two red bars is the lowest battery SOC that I have seen.

If you don't have any warning lights on, then there will be no stored DTC and hence your dealer won't take any action.

I wonder if your use of 85 octane is related to the lack of power; this would have caused the engine to run with retarded ignition timing as compared to 87 octane.

 

I have had mine go to purple bars climbing steeply in the Sierras and Death Valley. I had all the speed needed for the road considering the steepness and curves. I was more concerned with the long downhills overcharging the battery!

I'm not sure if you have a problem or not. Your car is a bit young yet and may improve with more miles.

Lee

 

i get my car down to one bar once in a while, and what happens even if you do full throttle acceleration is the engine would charge the battery, once it goes down to 1 bar your car will be so slow.

 

I think it depends on both the grade and the chosen speed. Some folks here report charge gain on long grades.

My personal commonly used roads include a three-mile uphill stretch on about a 4% grade with a 55 mph limit. If I enter with six bars and travel about 52, I quite quickly go down to two, and sometimes even one. If I hold back to 48 mph, I can preserve three pretty often.

People have reported some pretty significant moding, so these effects may not be monotonic in either speed or grade.

As discharging on a long uphill is energy wasteful (the energy is guaranteed to be replaced from the engine, not from regeneration), I sometimes wish I could hit a hint button marked "long upgrade". We easily notice that trips including a round trip up and down this grade give us much worse mpg than our other trips in town.

 

i have! passing through 80.. i think.. above colorado. just before you have to cut right. there is this really really long pass.

i learned that you shouldn't floor it.. and just mildly gain energy as you climb up.. it will start out slower but in the end you should end up with a higher amount of assist. so.. 3/4 petal or so instead of the full throttle.. and since this petal is complicated (just barely touch the high rpms on the ICE)

but yeah.. i too was stuck at 55-60mph in a 70 zone... slow lane for me! haha.

You still get decent gas mileage in the end. (shrug)

 

85 octane is used in higher climates. it's needed to be that way. if you talk to the dealers, they'll say the the prius needs 85 in your area!

 

Maybe if you fill it with premium it'll balance the octane out?

 

You don't want to "balance the octane"; 85 is the correct octane at high altitudes. Switch back to 87 when you get back to lower elevations.

Tom

 

Well, since he is now - assumingly - in a "normal" altitude area with a half of a tank of low octane gas... filling the rest of it up with a high octane gas may balance the octane enough to ensure performance and drive-ability.

 

Ricochet: I have experienced the exact same situation on one trip through Colorado on I-70 through the Rockies. It happened on two different particularly long and steep climbs. However, I never saw zero battery bars. In my case the battery level dropped to 1 or 2 bars, and cut out the electric motor assist. The ICE and transmission were working hard and did sound louder than normal. Once I reached the summit of those 2 passes, batteries started charging, and everything was back to normal. So, I think what you and I saw was normal Prius operation under very extreme climb conditions.

 

85 octane is correct for high altitude, above 5000 feet or so. Buy plain old 87 octane when you get back to lower elevation.

The battery dropping and the engine roaring are completely normal when going up long inclines. After all, the battery cannot provide infinite energy, so the engine revs up to provide the necessary power. The computers won't let the engine redline or harm itself, and they take care of the batteries also. Just drive it. Don't be afraid to floor the gas pedal when it seems necessary.

(But *don't* run out of gas. That's one of the few things that are easy to do that can cause a lot of expensive damage.)

 

Here in AZ, I'll pull the 7% 12 mile grade going up North and get down to a single bar. I've ran it twice. Both times with 2 adults and 2 kids and the A/C on. I can maintain my usual 85-90+ while going up it. Not the best for fuel economy but road trips are fair game for me. I drive extremely conservatively during every other time... but once I'm on a road trip all bets are off.... luckly I only go on a couple of road trips a year.

 

Right, but that assumes sea level pressure altitude. Octane requirements change with pressure altitude, unless you have a supercharged or turbocharged engine. Thin air changes the characteristics.

Tom

 

Correct. I'll just add a bit. Octane in very simple terms is how difficult the fuel is to ignite. The higher the number, the more difficult. So visualize this. The air/fuel mixture is injected into the engine, the piston compresses this mixture. If it gets too hot in the cylinder there's a chance for the fuel/air mixture to ignite sending the piston back down. This is not supposed to happen. The piston is supposed to make it's way up and the air/fuel is supposed to be ignited by the spark plug. If this "pre-ignition" happens, you need a higher octane fuel to make sure the mixture doesn't ignite prematurely.

When you're in the mountains you'll notice less power (unless you have a supercharger/turbocharger). This less power is a result of less air. Less air means the potential for pre-ignition is slightly less and therefore you can technically run a lower octane (since pre-ignition is less likely).

On the flip side of all this, this is why most supercharged/turbocharged engine require higher octane fuel (because more air is forced in there). In addition to this higher octane fuel these engines will have a lower compression ration than their normally aspirated versions (to reduce the fuel pre-igniting due to the higher pressure) if the engine is to run on pump gas.

 

I just returned from a east to west coast round trip. I experienced the same thing on rt 70 going thru southern utah. At one point I had no bars and running on engine alone. It would not let me go above 55. Those gradual inclines really make this car work hard. I averaged 36mpg on that stretch from vegas to green river utah. Once I got on the Denver side of the mountains I never had this happen again. On the whole trip according to my notes. I averaged 45.2 mpg. The car was a great road trip car.