Uneven battery use

To be honest, I'd say what you experienced is not all that uncommon. The same thing happens in a vehicle with a gas engine as well. Even in my own Prius C I see the same thing two or 3 times a week. Multiple factors are involved. Wind direction, heat on or off, the ability to maintain a constant speed vs getting on or off the throttle. Even the smoothness of the pavement. (we have many here that are rock/chip seal) These rock chip roads give me worse mileage than a regular paved road.

Maybe some Prime drivers can pop in and give you a heads up if they are experiencing this as well.

 

Any elevation changes one way versus another?

We’re you waiting awhile to get out of the concert?

I wouldn’t be worried about this as you’ll just charge your Prime back up and you’ll never know what happened.

When I do short trips around town, I notice a slight difference in battery charge percentage due to many factors, but I just plug it in when I’m home and then the charge resets.

I just drive it.

 

The same route but on the to and back from usually have quite different driving conditions unless you live totally flat land with no wind. As @Raytheeagle pointed elevation difference is a big factor. Wind direction is another. The temperature difference between the 70s and the 60s is also a factor. Especially for short distance round trips, those variations effect can be some times very big.

For my routine commute of 18 miles oneway, my morning commute always takes more EV. When I do all 100% EV, it is 60% in, 40% back is usual.

 

The don't call them "guess o' meters" for nothing.

 

What he said.
You are putting too much faith in what the "meters" are telling you.
If you look hard enough you will find other "discrepancies" too.

Did you get this car to worry about.......or to have reliable economical transportation ?

 

is the gauge linear?

 

Comparing SOC % displayed on MID to the real SOC % read by Hybrid Assistance App, it is linear.

 

why don't you let your battery go dead?

 

My situation when I go to work I don't use much EV as I get a lot of downhill and regen quite good. On my way home EV drains fast; ie: uphill.

 

Don't worry. So many factors to calculate. Dropping my daughter at school 6 miles away. All downhill. Only use between 5% and 10% of the battery. On the way back up the hills 10% to 18% used uphill for those 6 miles back. Winter. 12 miles will use over 50% of the battery.

The GOM meter is not linear.

 

He said it was mostly flat ground. I interpreted that to mean no high elevation hanged, but perhaps just few hills?

 

i think you can google the elevations

 

Well, he quoted percent numbers, by which I presume he means that he has the MID display showing actual battery percent charge level, in which case it’s not GoM-accuracy question, let alone a “guess” of any sort.

 

Gag! Writing on the fly... Try that again...

He said it was mostly flat ground. I interpreted that to mean no big elevation change, but perhaps just meant “not hilly”?

 

I can't find anywhere in OP's comment mentioning road being "flat". Did I miss that comment before he edited, maybe?

 

That elevation difference would result in large difference in EV efficiency. I am not surprised to see almost four times more battery power to come home uphill. BTW, the elevation difference between start and finish can be near zero, but if you have hills in between you can have difference in EV efficiency. Low grade uphill is better on EV, if you have steeper uphill on one way, you will be penalized more.

 

All Prii are very sensitive to the elevation difference between start and finish.

I have an empirical rule of thumb that for my Gen3, 10,000 feet of elevation gain (+/- about 15%, depending on load) is equivalent to a gallon of gasoline. I.e. that much climb costs an extra gallon of fuel compared to the same distance on the flats, while that much descent can save a gallon of fuel if it is shallow enough to avoid braking losses.

With this rule applied to a Gen3, a 0.1% grade will cause about a 5% MPG difference between ascent and descent, at common highway speed. The Gen4 is somewhat more efficient, which causes the underlying math to produce a somewhat wider spread percent. Electric battery use should show a similar difference.

282 feet in 3.6 miles is a 1.5% grade. This is huge when figuring Prius MPG.