Estimated Range Prediction / Energy Used Calculation

[Boatguy]

The more relevant question is what raw data would you, or others, like to see, and how will you process it to produce a more accurate range forecast? If it can be done I certainly want to support it and take advantage of the improvement.

I started this thread with exactly what you are asking. An energy used readout on the trip computer, onboard info, or eDrive display. Counts up from zero, accounts for regen, shows me exactly how much of my 18.8 kWh I have used since my last full charge.

I know you are a frequent poster here so you're probably aware of the technical manuals available to download. Study the graphs and text on pages 180-182 of the High Voltage Components document and I think you'll see a better explanation of what I was trying to communicate about non-linearity and why absolute SOC would probably trip up a lot of drivers.

 

[juniorbeep]

Something I realised the other day was if you have a rex and go to the section in the menus where you can switch on "Hold state of charge" there is actually a percentage figure of the battery remaining. To me this is much more accurate than the bars and if you are driving you can see how far you have driven and how much battery percentage is left. If i'm down to 50% and done 45 miles I know I'm going to get about the same in the second half of my journey... assuming I don't change my driving too much.

 

[KurtEndress]

Study the graphs and text on pages 180-182 of the High Voltage Components document and I think you'll see a better explanation of what I was trying to communicate about non-linearity and why absolute SOC would probably trip up a lot of drivers.

Are you pointing out that the last kWh (5.3% SOC) isn't as useful as the first? While it's true the power won't come as fast, it should get you just as far. I don't think it should come as a big surprise that there is limited performance at very low power levels.

Even an ICE might sputter and lose power as it sucks the tank dry. The process is a little more gradual with an EV.

 

[noakey]

The more relevant question is what raw data would you, or others, like to see, and how will you process it to produce a more accurate range forecast? If it can be done I certainly want to support it and take advantage of the improvement.

I started this thread with exactly what you are asking. An energy used readout on the trip computer, onboard info, or eDrive display. Counts up from zero, accounts for regen, shows me exactly how much of my 18.8 kWh I have used since my last full charge.

Bottom line is I mostly ignore the range remaining indication next to the blue bars. I wish I could turn it off. However, I'm finding the Blue Bars are actually pretty reliable indicators. In my case, each bar gives me at least 20 miles. So I use that then look at my distance to go. I made a long trip today of almost 200 mi in my BEV and this method worked very well for me to know that I was able to reach each destination on my trip.

Once again, the Navigation color warnings (Red and Yellow) are mostly inaccurate because they use the calculated range value to key off. On my 1st leg, when the range went to 71 miles after 1 minute of driving, the NAV came up and told me I won't get there (74 miles away). I made it with 1 Bar remaining (20 miles by my estimate). Interestingly, the range readout said 15 mi.

A great trick is to tank it down the motorway to work (26 miles) using up 50 miles range, then at the end of the day with 42 miles range, poodle home and arrive home with more range than you started with (44)..

 

[Boatguy]

Study the graphs and text on pages 180-182 of the High Voltage Components document and I think you'll see a better explanation of what I was trying to communicate about non-linearity and why absolute SOC would probably trip up a lot of drivers.

Are you pointing out that the last kWh (5.3% SOC) isn't as useful as the first?

I'm pointing out that BMW defines SOC in both "absolute" and "relative" terms and that in absolute terms, restricted driving begins at 15.7% which means the really accessible battery capacity s about 16kWh which may help the OP understand what he's seeing when he's charging.

It's really laid out quick clearly in both text and graphics in the technical document I referenced in an earlier post.

 

[KurtEndress]

I'm pointing out that BMW defines SOC in both "absolute" and "relative" terms and that in absolute terms, restricted driving begins at 15.7% which means the really accessible battery capacity s about 16kWh which may help the OP understand what he's seeing when he's charging.

Where do you get your 16 kWh figure from?

Yes, BMW does reserve some of the gross battery capacity of 21.8 kWh (page 72) and presents the i3 user with a usable 18.8 kWh capacity. The absolute SOC references the full 21.8 kWh gross capacity and the relative SOC the user sees is calculated from the 18.8 kWh usable capacity.

Since the user is always presented with the relative SOC, the other absolute figure might as well not exist. The fact is that the Rex switches on at 6.5% relative SOC and it’s just a minor trivia fact that this is 15.7% absolute SOC. Since you can’t access that last hidden 10% absolute, it doesn’t matter for range purposes. Range is calculated on the 18.8 kWh usable, not the 21.8 kWh total.

Note: The REx starts at 6.5% relative SOC; the "driving with restricted power" happens below 1.9% SOC relative. Something else happens at 0.4% and below which is listed as "safety reserve for REx start". So there may be a little of that 18.8 kWh that is difficult or impossible to use, but it's a small fraction of a kWh.

 

[ultraturtle]

Something I realised the other day was if you have a rex and go to the section in the menus where you can switch on "Hold state of charge" there is actually a percentage figure of the battery remaining.

Sadly, that feature is not available to us Yanks, nor is the SOC display in that menu item.

 

[Chrisn]

I look at this very simply. The care cannot know the future (how I will drive, will I drive up a hill (although it COULD know this via current Nav route)), but I can. A numeric SOC or kWh remaining display would be very helpful when I know that my recent driving will not be similar to future driving. The blue bars help, but a number would be even better. Just give me a split screen widget to should more data. Simple.

 

[Boatguy]

I'm pointing out that BMW defines SOC in both "absolute" and "relative" terms and that in absolute terms, restricted driving begins at 15.7% which means the really accessible battery capacity s about 16kWh which may help the OP understand what he's seeing when he's charging.

Where do you get your 16 kWh figure from?

Yes, BMW does reserve some of the gross battery capacity of 21.8 kWh (page 72) and presents the i3 user with a usable 18.8 kWh capacity. The absolute SOC references the full 21.8 kWh gross capacity and the relative SOC the user sees is calculated from the 18.8 kWh usable capacity.

Since the user is always presented with the relative SOC, the other absolute figure might as well not exist. The fact is that the Rex switches on at 6.5% relative SOC and it’s just a minor trivia fact that this is 15.7% absolute SOC. Since you can’t access that last hidden 10% absolute, it doesn’t matter for range purposes. Range is calculated on the 18.8 kWh usable, not the 21.8 kWh total.

Note: The REx starts at 6.5% relative SOC; the "driving with restricted power" happens below 1.9% SOC relative. Something else happens at 0.4% and below which is listed as "safety reserve for REx start". So there may be a little of that 18.8 kWh that is difficult or impossible to use, but it's a small fraction of a kWh.

Yes, we're in agreement with what the technical docs say. The only ambiguity, at least I can't find a definitive reference, is whether SOC's are with respect to the Gross or Net battery capacity. My assumption was Net and I multiplied .85 (~ 1-14.2% when restricted driving kicks in for BEV) to get the 16kWh. If it's Gross, then a more accurate .86 x 21.8 = 18.8 which is probably no coincidence as the usable power in a BEV.

It's clear that at least some drivers want to see an SOC number, not bars, and to do their own range calculation. Seems like it would be pretty simple for BMW to make that a display option for those who want it. Personally I don't feel strongly about it, but I wouldn't want to see it as always displayed because I prefer less numbers in the display for my wife. But if it's a display option it's certainly not a sum zero game and won't bother me.

 

[fdl1409]

It is all there, you can read out SOC and kWh capacity in a hidden menu of the board computer. Plus battery temperature and other data. Was discovered and reported about in Facebook by one Chad Hogan. Use at own risk.

On the small display there is a button for trip reset on the left side.
Press and hold this for 10-12 seconds - you are in.
Press through until option 4 "Lock", then press and hold for about 4 seconds until "Number"
Your individual number you get by adding up the last 5 digits of your VIN. My VIN is 71776, so my number is 28.
Press through to your number, then press and hold again - you are in the menu.
In 13 you find SOC, absolute and momentary battery capacity, REx fuel capacity and others. In 14 you find battery temperature und others. And so forth.

Unfortunately you have to go through this every time you start the car.

Frank

 

[noakey]

It is all there, you can read out SOC and kWh capacity in a hidden menu of the board computer. Plus battery temperature and other data. Was discovered and reported about in Facebook by one Chad Hogan. Use at own risk.

On the small display there is a button for trip reset on the left side.
Press and hold this for 10-12 seconds - you are in.
Press through until option 4 "Lock", then press and hold for about 4 seconds until "Number"
Your individual number you get by adding up the last 5 digits of your VIN. My VIN is 71776, so my number is 28.
Press through to your number, then press and hold again - you are in the menu.
In 13 you find SOC, absolute and momentary battery capacity, REx fuel capacity and others. In 14 you find battery temperature und others. And so forth.

Unfortunately you have to go through this every time you start the car.

Frank

Hi frank... hmmm just tried this. I can't get past the 'number' stage... i go to my vin sum and hold.. and get taken back to the original 4 item.menu... any ideals?

 

[fdl1409]

Not really. Works for me and a number of other people. Got your sum right? You have to get to that number, wait for a second or two. then press long. Never fails when I do it.

Frank

 

[RJSATLBA]

noakey - there appears to be some documentation of part of this process towards the beginning of the Displays and Controls document, item 11 in the set of BMW University docs, although there it is in relation to the brake test function.

 

[Boatguy]

noakey - there appears to be some documentation of part of this process towards the beginning of the Displays and Controls document, item 11 in the set of BMW University docs, although there it is in relation to the brake test function.

Page 3 to be specific.

 

[noakey]

noakey - there appears to be some documentation of part of this process towards the beginning of the Displays and Controls document, item 11 in the set of BMW University docs, although there it is in relation to the brake test function.

Page 3 to be specific.

Ah.. Ok thank you. .. will give it another go this morning. ..

 

[Zzzoom3]

It is all there, you can read out SOC and kWh capacity in a hidden menu of the board computer. Plus battery temperature and other data. Was discovered and reported about in Facebook by one Chad Hogan. Use at own risk.

On the small display there is a button for trip reset on the left side.
Press and hold this for 10-12 seconds - you are in.
Press through until option 4 "Lock", then press and hold for about 4 seconds until "Number"
Your individual number you get by adding up the last 5 digits of your VIN. My VIN is 71776, so my number is 28.
Press through to your number, then press and hold again - you are in the menu.
In 13 you find SOC, absolute and momentary battery capacity, REx fuel capacity and others. In 14 you find battery temperature und others. And so forth.

Unfortunately you have to go through this every time you start the car.

Frank

Great post thanks. It does work for me as well, however, I'm not sure it has any value on a drive. Will the menu stay up while driving? I also didn't see an SOC or Energy Used indication in the Unlock Menus?

 

[fdl1409]

It will stay up while driving. And there is a SOC indication in 13. No indication for power used, but absolute usable power left in the battery.

Frank

 

[roperld]

There are several aftermarket SOC meters for the LEAF that hook into the OBDII. I got one right after I leased the LEAF in May 2012 and that is what I watch instead of the battery bars on the LEAF display. It shows usable SOC in % tenths. Some of them even show the battery-modules voltages on an Android app by means of a Bluetooth connection.

 

[mindmachine]

There are several aftermarket SOC meters for the LEAF that hook into the OBDII. I got one right after I leased the LEAF in May 2012 and that is what I watch instead of the battery bars on the LEAF display. It shows usable SOC in % tenths. Some of them even show the battery-modules voltages on an Android app by means of a Bluetooth connection.

According to the owners manual we are told that the OBD2 port is not to be used by anyone other than factory trained technicians. I want to use the port myself but have yet to hear from anyone who has. I asked BMW about using a passive monitoring device for my insurance company, it allows the insurance company to give you a discount based on your driving style, but so far no answer other than at your own risk will probably be the answer.

Anyone used the port or ask BMW about the warning??

 

[ultraturtle]

Anyone used the port or ask BMW about the warning??

I have. You can read a lot of standard parameters, but nothing useful. My opinion only, but I don't believe that reading data from the car poses any concern. Writing it to the car (changing settings) can cause damage, however.

There are several aftermarket SOC meters for the LEAF that hook into the OBDII. I got one right after I leased the LEAF in May 2012 and that is what I watch instead of the battery bars on the LEAF display. It shows usable SOC in % tenths. Some of them even show the battery-modules voltages on an Android app by means of a Bluetooth connection.

Unfortunately, traction battery SOC is not a standard PID (Parameter ID) as defined by SAE J1979. BMW (like many other manufacturers) chooses to not publish its non-standard PIDs, of which SOC is almost certainly one.

It is not difficult to monitor and examine raw output from the OBD II port and sleuth PID codes from it, just time consuming. I was hoping someone had already done that for us, but I have been unable to find the BMW PID for SOC anywhere online.

The goal would be a dash mounted cell phone displaying a large round dial gauge of REx RPM and a digital readout of SOC. Right now, you can display the RPM (its a standard PID), but not SOC.