THE BMW ActiveE FORUM

[ydoc]

I understand that the top part of the ActiveE battery graph shows the consumption in real time one minute increments, but what does the bottom half of the graph show? -- is it illustrating power being recaptured in the regen process? Over the same time period as the consumption figures? What are the units on the graph labeled "10" and "20"?

see picture below...

[woof]

I was hoping someone would ask this question, as I believe the graph on the bottom, while apparently supposed to show energy recouped by regen, doesn't show that at all, or shows it incorrectly.

Note the numbers marking the axis on the left grow down--from zero in the middle to 20 at the bottom. More regen would be a bigger bar grown downward (like a stalactite). But on stretches of highway where I very carefully drove with out using ANY regen (the charge/ready/eDrive needle NEVER swung to the left over a 15 minute period), the bars are always full, from the middle to the bottom. Just like the far right 4 bars in the picture above. So where there is NO regen you would expect NO downward bar, but instead there is a full downward bar.

Other times where i've used lots of regen, I get very short bars. So I think the graph is backwards from what is expected, and the units on the axis are incorrect, or the plotting of the values in the graph is incorrect.

I've also noticed that while not moving, the graph doesn't update. So you cannot sit still and wait a minute or two to see a graph of 0 regen, 0 eDrive.

[ydoc]

Originally Posted by woof

I was hoping someone would ask this question, as I believe the graph on the bottom, while apparently supposed to show energy recouped by regen, doesn't show that at all, or shows it incorrectly.

Note the numbers marking the axis on the left grow down--from zero in the middle to 20 at the bottom. More regen would be a bigger bar grown downward (like a stalactite). But on stretches of highway where I very carefully drove with out using ANY regen (the charge/ready/eDrive needle NEVER swung to the left over a 15 minute period), the bars are always full, from the middle to the bottom. Just like the far right 4 bars in the picture above. So where there is NO regen you would expect NO downward bar, but instead there is a full downward bar.

Other times where i've used lots of regen, I get very short bars. So I think the graph is backwards from what is expected, and the units on the axis are incorrect, or the plotting of the values in the graph is incorrect.

I've also noticed that while not moving, the graph doesn't update. So you cannot sit still and wait a minute or two to see a graph of 0 regen, 0 eDrive.

woof,

A new idea based on the point you have just raised -- could the numbers on Y axis below the zero line in the middle be negative numbers, i.e., 0, -10, -20? Thoughts?

[woof]

Originally Posted by ydoc

woof,

A new idea based on the point you have just raised -- could the numbers on Y axis below the zero line in the middle be negative numbers, i.e., 0, -10, -20? Thoughts?

They can be looked at that way...power flowing IN to the batteries (charging) being negative with respect to power flowing OUT from the batteries.

The units are mls/KWH, so yes, charging miles would be negative--putting miles back into the battery, so to speak.

I believe this graph is supposed to show the 1 minute accumulation of the what the charge/ready/eDrive needle shows instantly. With "negative" charge (needle to the left of center) being graphed below the 0 line, and "positive" eDrive (needle to the right of center) being graphed above the 0 line, divided into distance moved over that minute (so it's not just showing energy in KWH, but efficiency in miles/KWH)

I still think the charge part is being graphed incorrectly.

[nilsbunger]

It's actually correct, but it's really unintuitive. It makes much more sense in European units (kwh/100km). You can actually change to those units in the settings.

First, the x axis is time. With most recent at the left. One bar is 1 minute long.

The charging bar is, as woof and others said, the total energy captured through charging over each minute.

Seems easy, but iit looks unintuitive because:
1) the scale is different than the top bar.
2) larger bar down means *less* charging
3) the units are weird.

An example should help:

In city traffic, the charging bar might be short, indicating -5miles per kwhr. This means if you did the same amount of regenerative braking for 5 miles, you'd make 1 kwhr of electricity. If you regenerate less, te number becomes more negative, eg -20 miles per kwhr.

It seems pretty convoluted to me.

But if you go to European units, the equation is flipped, so 5 miles per kwhr becomes like -12kwhr per 100 km. Those units are better because you can add the bars together for aggregate consumption, which you can't do with miles per kwhr. And a bigger number means more.

[woof]

Originally Posted by nilsbunger

It makes much more sense in European units (kwh/100km)...But if you go to European units, the equation is flipped, so 5 miles per kwhr becomes like -12kwhr per 100 km. Those units are better because you can add the bars together for aggregate consumption, which you can't do with miles per kwhr. And a bigger number means more.

Thank you! That explains it. When the units are kWh/100km it makes more sense.

I still consider this a bug in the display. Changing the units requires a change in how the graph is drawn, and this wasn't done.

I'd still prefer just to have a graph of kW (or maybe even kWh) vs time, rather than efficiency vs time. How much power/energy used is more interesting and informative than how well it was utilized.

[nilsbunger]

I will second that! It feels like someone was told to convert the screen to US units, and they did exactly that, but they forgot to think about the usability of that info.

[Dominik]

Yes this is the old MPG vs Liter/100km issue. This clears thisng up. Thanks!

[chuckhawley]

This is a mind-numbing terrible display. It seems like what you want to know is how much you've consumed, and how much you've "regened" per minute of operation. A single stacked column graph would show this easily, but I haven't thought through all of the permutations. Each minute, I'd want to know how much I consumed in watt-hours or some other metric, and how much I have saved. An interesting question would be whether it would be more informative to separate accessory loads from "driving" loads. I'd like to see the impact of the A/C for example. In fact, just having two numbers showing accessory loads (5 sec average) and driving loads or charging (5 sec average) would be very informative.

Current bar graph is virtually useless to modify one's behavior.

[nilsbunger]

I agree the default is useless in the US. But you can change it to kWHr/100km in the "Settings/Units" panel, without changing over the whole car to European standard. I did it, and it makes the display much more useful once you get used to the units.

Originally Posted by chuckhawley

This is a mind-numbing terrible display. It seems like what you want to know is how much you've consumed, and how much you've "regened" per minute of operation. A single stacked column graph would show this easily, but I haven't thought through all of the permutations. Each minute, I'd want to know how much I consumed in watt-hours or some other metric, and how much I have saved. An interesting question would be whether it would be more informative to separate accessory loads from "driving" loads. I'd like to see the impact of the A/C for example. In fact, just having two numbers showing accessory loads (5 sec average) and driving loads or charging (5 sec average) would be very informative.

Current bar graph is virtually useless to modify one's behavior.