Energy Displays

[ajdelange]

I think I'm going to have to let go of that mentality on long trips anyway since I've got a young kid now. Might as well charge the vehicle when we stop for potty/snack breaks.

You'll learn to think in terms of the three B's: Battery, bladder, belly.

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[Trandall]

You'll learn to think in terms of the three B's: Battery, bladder, belly.

If only there was an algorithm to get them all sinked up.

 

[ajdelange]

For whatever strange reason I enjoy optimizing my driving efficiency and look forward to strategizing charging stops on long trips.

I don't think it's strange at all but I'm an engineer. It's interesting (to engineer types) and helps pass the miles by on long trtips.

I cringe when I ride with my wife she goes from the gas directly to the brakes every time we need to slow down or stop!

There are two women like that?

Doesn't she know the car will coast for peat sake!

Be sure you set regen to fulll and see what happens. Mine never hits the brake now (even when she needs to) and her driving is much smoother.

 

[Autolycus]

Well, we can't really have endless "which oil is better" debates like most automotive forums, so we need to find something to debate!

But we can still argue about cleaning and detailing products and methods!

 

[sub]

I selected let the user choose, but miles(or km) / kwh is objectively the wrong choice for a real-time consumption gauge.

Miles / gallon works with a gas vehicle because the gallons term never approaches 0, even when you are coasting you are burning fuel.

But in an EV, kwh can not only approach 0, it can cross zero and go into the negative. Which is a mathematical problem. Not only is it impossible to divide by 0, but when you cross the 0 kwh mark, you jump from infinity to negative infinity.

During light regen, your miles / kwh is -1,000,000,000,000,000,000,000,000,000 Which is impossible to graph, and is very difficult to interpret.

-0.00000000001 kwh / mile is easy to graph and is quite easy to interpret: you are very slowly charging the battery.

I can understand wanting to make the units feel more familiar to people who are comfortable with miles / gallon. But the laws of math and physics trump perceived convenience.

 

[ajdelange]

Miles / gallon works with a gas vehicle because the gallons term never approaches 0, even when you are coasting you are burning fuel.

How about when you are stopped? Then the miles accumulates in any time increment are 0 and the gallons or kWh used are also 0. 0/0 is an indeterminate number in either case. The Mach E seems to indicate 99 miles/kWh when the car is stopped for charging. Tesla, which used Wh/mi indicates 0 until the car starts to move and then sometimes indicates a huge number (e.g. 1999) for the first tenth mile. This quickly averages down but often stays quite high because the accumulators start accumulation when you go into drive and the battery is being drained at that point even though you may not start moving for a minute or 2. I call this the "departure tax".

But in an EV, kwh can not only approach 0, it can cross zero and go into the negative. Which is a mathematical problem. Not only is it impossible to divide by 0, but when you cross the 0 kwh mark, you jump from infinity to negative infinity.

During light regen, your miles / kwh is -1,000,000,000,000,000,000,000,000,000 Which is impossible to graph, and is very difficult to interpret.

-0.00000000001 kwh / mile is easy to graph and is quite easy to interpret: you are very slowly charging the battery.

This alone should be sufficient to put the last nail into the coffin lid of miles/kWh displays but I fear the trend is in the other direction. Tesla seems to be, as they often are, bucking the trend by using Wh/mi.

I can understand wanting to make the units feel more familiar to people who are comfortable with miles / gallon. But the laws of math and physics trump perceived convenience.

A lot has to do with the scaling. My Lexus runs on nominally 0.056 gal/mi. That's not a very useful way of displaying the consumption. In an airplane it would be displayed as 20 lbs/hr (at 60 mph). Then it occurred to me that perhaps the mi/kWh display was stimulated by the desire that it resemble the old "efficiency" gauges that used to be installed on ICE cars. They measured manifold vacuum. If you were rolling along at cruise and took your foot off the gas the vacuum zoomed towards 30" - the efficiency was extremely high. OTOH if you floored it the vacuum dropped to near 0". The efficiency was very low.

In another thread here I begged for Wh/mi displays and someone came back with what I supposed to be the efficiency display from the Rivian. I has a line indicating the average over the last 30 minutes labeled in mi/kWh and a y axis labeled "more efficient" above that and "less efficient" below. Clearly the driver had backed off the skinny pedal a few times as the graph shows saturation at a constant level at the top for a good part of the time. Did he go into regen? Would he like to know if he did and if so how far? I'm starting to get a very bad feeling about this. I hope Rivian is watching here, will take note of these concerns and listen to its engineers.

For years I've been assuming that Rivian's engineers are at least as smart as Tesla's and that we would thus get cockpit info at least as good as what Tesla gives. Perhaps Rivian's engineers are smarter than Tesla's and have figured out that they'll sell more trucks by dumbing their product down to better meet what the hoi polloi are familiar with.

 

[jwardell]

Here are the two displays I find I want to see at all times: Instantaneous battery wattage, and pack temperature.

WIth the choice of thousands, they are the two I like to watch while driving, and have front in center in front of me on my dash:

Power of course is great to see when you hit the pedal, but it's also great to see how much you are sucking at a steady speed in various situations. It's even useful when not driving, to see how much AC or heat is taking, or how much charge power is going into the battery.

Battery pack temperature communicates how the car will perform, and why...as it falls below room temperature your regen gets weaker and none if it's below freezing. You can also see if the battery is warm enough to accept full speed DC charging, or if it's limiting the charge (or more often, the charger).

But ultimate there are thousands of signals I occasionally am interested in...I can always log them all and graph them later on the computer but nothing is better at experiencing things live and seeing how all the systems and sensors react to various situations. EVs are a lot of fun for data nerds

 

[ajdelange]

What's that a picture of?

I too would love to see battery temperature and kWh remaining but there is no way I know of to get either of these numbers before me in the current X I am driving. Tesla seems as determined as any of the other manufacturers to hide real battery capacity info from the diver. And I have noticed that the latest software version has taken the numbers off the power meter.

 

[Dark-Fx]

My preferred units would be Gigajoules per fortnight.

 

[Autolycus]

My preferred units would be Gigajoules per fortnight.

I prefer gigawatts per 88 miles per hour.

 

[Scott]

For whatever strange reason I enjoy optimizing my driving efficiency and look forward to strategizing charging stops on long trips.
I cringe when I ride with my wife she goes from the gas directly to the brakes every time we need to slow down or stop! Doesn't she know the car will coast for peat sake!

This. So much this.

I am both more aggressive and more efficient than my wife. I constantly get 10% better gas mileage in our ICE and have a similar gain in our EV.

 

[jwardell]

What's that a picture of?

I too would love to see battery temperature and kWh remaining but there is no way I know of to get either of these numbers before me in the current X I am driving. Tesla seems as determined as any of the other manufacturers to hide real battery capacity info from the diver. And I have noticed that the latest software version has taken the numbers off the power meter.

You can tap into the CAN and get everything you can imagine. Then view it on a phone app, or one of my little displays there, or log and analyze later.
My battery display now shows me temp, cell balance, max regen and max discharge, again all values describing performance.
This is why I'm waiting to see if Rivian spits out data over CAN through an OBD port, or we can find it elsewhere, or if it's all ethernet as rumored. I'm determined to tap in

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