Battery capacity vs miles/kwh discrepancy

[dtyegian]

I own the 2016 eGolf SE with quick charge package. I just drove 84 miles, started with a full charge and ended with the turtle icon (basically empty). My question is the discrepancy between the calculated miles/kWh under the "Car" menu (4.3 miles/kWh) and the actual usage (capacity 24.2 kWh; if I used 24 kWh for 84 miles => 3.5 miles/kWh)? That's a 20% difference! Does the car show the turtle when there is still an additional ~4 kWh in the battery (24.2 kWh - (84 miles/4.3) = 4.5kWh)) such that I could continue to drive ~15 more miles? Other other drivers noticed this difference as well?

 

[miimura]

The stated capacity of 24.2kWh is the total gross capacity of the battery cells. You cannot use it all. There is some reserve at the top and bottom to prolong the life of the battery pack. Most people find that they can use about 20kWh from full to empty. So, your experience is normal. I would not expect to be able to go more than a mile or so with the Turtle light on.

 

[JoulesThief]

I own the 2016 eGolf SE with quick charge package. I just drove 84 miles, started with a full charge and ended with the turtle icon (basically empty). My question is the discrepancy between the calculated miles/kWh under the "Car" menu (4.3 miles/kWh) and the actual usage (capacity 24.2 kWh; if I used 24 kWh for 84 miles => 3.5 miles/kWh)? That's a 20% difference! Does the car show the turtle when there is still an additional ~4 kWh in the battery (24.2 kWh - (84 miles/4.3) = 4.5kWh)) such that I could continue to drive ~15 more miles? Other other drivers noticed this difference as well?

Describe your route and how fast you drive. This car is more an urban 35 to 40 mph Blvd crawler, not a 75-80 mph diamond lane HOV vehicle wasting all it's battery capacity pushing air out of the way. You might try using less consumer power sucking items also, as this car has maybe 1/10 the range of a VW TDI. Battery stored energy is very low energy density compared to hydrocarbon based fuels.

 

[dtyegian]

Thanks for your explanation Miimura. That does sound reasonable in terms of gross battery capacity vs usable battery capacity. And I'll be sure to watch out for the turtle; no more driving on Empty as I do in an ICE car.

 

[f1geek]

Miimura knows his stuff. I get about 20 kWh usable capacity out of my 2015 e-Golf, based on my calculations, as I've never seen the turtle icon.

 

[JoulesThief]

Thanks for your explanation Miimura. That does sound reasonable in terms of gross battery capacity vs usable battery capacity. And I'll be sure to watch out for the turtle; no more driving on Empty as I do in an ICE car.

I usually get a warning light in dash for reduced power and one of the eco modes being employed to save the battery when about 18 mile of range is left on the battery. I usually try to get a full recharge immediately before my next driving trip. This seems to help increase the range of a battery charge by a few miles per recharge, vs recharging the day before and letting it sit overnight with a full recharge. Some of the charge seems to disappear when doing so.

 

[johnnylingo]

I would not expect to be able to go more than a mile or so with the Turtle light on.

I've lived dangerously and ridden a good 2 miles with it on, and pulled in to my driveway with an estimated 2 miles left. I'd assume it comes on at roughly 5% battery remaining. Eco+ mode gets forced at around 10% battery and it's basically the car's way of telling you to get the heck of the highway and find a charger. This has happened to me a couple times when I'm under 5 miles from home and I wish there was a way to override it, because being stuck at 55 mph on a 65 mph highway isn't fun.

 

[JoulesThief]

I would not expect to be able to go more than a mile or so with the Turtle light on.

I've lived dangerously and ridden a good 2 miles with it on, and pulled in to my driveway with an estimated 2 miles left. I'd assume it comes on at roughly 5% battery remaining. Eco+ mode gets forced at around 10% battery and it's basically the car's way of telling you to get the heck of the highway and find a charger. This has happened to me a couple times when I'm under 5 miles from home and I wish there was a way to override it, because being stuck at 55 mph on a 65 mph highway isn't fun.

Get off the freeway when it goes into any Eco mode, and keep your speed down on surface streets to increase your range. About a month ago, on a cold day, I couldn't find a EVSE available in Malibu to add some charge while in town there for a couple of hours. I tried to make it back to a 24kwh charger and the last 3 miles were all uphill. Killed my battery, I pulled in with 2 miles of range left. Not my idea of something I ever want to do again, the remaining miles was dropping like a rock the last 3 miles, I did not think I was going to make it. Speed was only 45 mph going up hill, in eco +. Going slower probably got me there instead of stalled on the hill going up.

16.02kw added in 51 minutes, on a ChargePoint 100+ 24kwh CCS. Probably an 88% SOC. Battery was taking on 20kwh almost the whole time a few minutes at 21kwh. Charge rate never dropped. Battery probably got warmed up or hot, going up that hill, slowing the take rate down. Mimura says that these are not true DC quick chargers, and are easier on the battery.

 

[bob95825]

This is an interesting discussion.

Once, I calculated the wrong distance to my home. To cut the story short, the "Miles left" indicator went to 0 about 2 miles from my home and I kept driving in the right lane thinking that the engine is going to cut off soon but it never did. So basically I drove 2 miles after the panel was showing 0 miles left and battery fully depleted. I took pics, but can't find them right now.

So I'm guessing that starts using the 2 to 4KW reserve once indicator says 0 miles left.

 

[f1geek]

Since your e-Golf was operating in Eco+ mode, I suspect you were getting around 4-5 miles/kWh efficiency. If you got an additional 2 miles after hitting "0" on the GOM (Guess-O-Meter), then you probably used less than 0.5 kWh of energy to get to your destination. Also, don't forget that the GOM reading is not the same as the "fuel gauge". What was your fuel gauge reading when the GOM said "0"? I suspect that the VW engineers wrote the car's software to completely shut off the drive system before you damage the battery (I've watched videos where people ran the car to battery depletion and the vehicle will shut off), so I'm suspect that you were able to dip into the ~4 kWh reserve.

Also, did you observe the charge rate once you plugged in? Were you getting 7.2 kW? Or was the rate slower? Thanks!

 

[bob95825]

I was getting 6m/kWh Once I realized I was going to be short, I was driving really really carefully.
The last 2 miles going home is where my efficiency actually goes down, so I probably did use 0.5kWh.
Fuel guage needle was below zero.
My car has a 3.6kW charger but I don't remember any major change in the charging time on my level 2 charger at home.

I've actually run to below 5 miles left 4 or 5 times in the last 2 months that I've had it.

I checked again and looks like I didn't take pics but made a video in the last half mile (once I was off the main road). So I'm attaching the screen grabs from my phone.

 

[Nonyaz]

One of the first things I did when I got my egolf was to run it down to turtle and do some laps around my block, I don't remember the exact number but I remember driving a substantial amount of miles past 0 (15 comes to mind, but don't quote me on that), on the way down it gradually limits your power and speed to where at the end you're going brisk jog pace. It will cut out, and then you can shut it off and restart it for as many times at it will let you, I hard to restart it about 3 times to crawl 100 ft, then up my driveway, luckily I made it up. Basically being on turtle doesn't scare me now that I've done that experiment, it'll get me home, just very slowly.

 

[JoulesThief]

One of the first things I did when I got my egolf was to run it down to turtle and do some laps around my block, I don't remember the exact number but I remember driving a substantial amount of miles past 0 (15 comes to mind, but don't quote me on that), on the way down it gradually limits your power and speed to where at the end you're going brisk jog pace. It will cut out, and then you can shut it off and restart it for as many times at it will let you, I hard to restart it about 3 times to crawl 100 ft, then up my driveway, luckily I made it up. Basically being on turtle doesn't scare me now that I've done that experiment, it'll get me home, just very slowly.

None of this running low is very good for the long term life of a very expensive to replace battery. Any German car, when ANY gauge is running in the red, RED means STOP and fix the problem, you are doing damage. Whether it's overheating a cylinder head, running too many RPMS on the tachometer, or discharging the battery too deeply. Don't drive or run the car when the gauge is in the red, if you can help it, with a simple little bit of foresight and planning your recharging, or slowing down long before it reaches that zone, to extend your range.

 

[Nonyaz]

None of this running low is very good for the long term life of a very expensive to replace battery. Any German car, when ANY gauge is running in the red, RED means STOP and fix the problem, you are doing damage. Whether it's overheating a cylinder head, running too many RPMS on the tachometer, or discharging the battery too deeply. Don't drive or run the car when the gauge is in the red, if you can help it, with a simple little bit of foresight and planning your recharging, or slowing down long before it reaches that zone, to extend your range.

I do as I please. The fraction of the percent of battery life I squandered was well worth the knowledge to me, piece of mind ya know?

 

[JoulesThief]

None of this running low is very good for the long term life of a very expensive to replace battery. Any German car, when ANY gauge is running in the red, RED means STOP and fix the problem, you are doing damage. Whether it's overheating a cylinder head, running too many RPMS on the tachometer, or discharging the battery too deeply. Don't drive or run the car when the gauge is in the red, if you can help it, with a simple little bit of foresight and planning your recharging, or slowing down long before it reaches that zone, to extend your range.

I do as I please. The fraction of the percent of battery life I squandered was well worth the knowledge to me, piece of mind ya know?

You'd fail as a pilot of a plane. And lose your license by the FAA. Really, doing this on public streets is a health hazard and a nuisance. Try it on a closed course, not public roads.