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Discussion Starter · #1 ·
I've noticed over the past week that my electric mileage has been getting better and better. I drive the same commute every day, which is exactly 12.0 miles going and 11.9 miles returning. For the first 900 or so miles of this commute, when I return home my battery miles remaining have been consistently 20, meaning I expended 30 miles of battery range to drive 24 miles. Over the past 5 or so commutes, however, my mileage has been getting better and better. This improvement is not only evidenced by returning home with up to 24 miles of battery range left, but also by the fact that my charger is requiring only 10.2 KWh instead of 11.8 KWh to recharge the battery.

Today, a new milestone: my 12.0-mile inbound commute consumed only 11 miles of battery range, leaving me with 39 miles of battery range remaining :)

I should note that my commute includes 4.0 miles of highway driving at > 65 mph.

What's causing the improvement? In order of my estimated likelihood:

- The weather has been cooler and this morning for the first time in recent memory the outside temperature never exceeded my cabin setting (73 deg F), so the A/C compressor remained off.

- My driving techniques to maximize range are steadily improving. I never use hill mode and generally minimize the use of the accelerator and brake.

- The ambient temperature (about 72-83 deg F) may be in the battery's sweet spot for optimal performance.

- As the battery "breaks in", it is accepting more charge. This seemingly unlikely hypothesis is supported by the fact that when I completely drain the battery, I now get more charge than I used to (now > 21 KWh; used to be about 19.5 KWh).

- Henrik Fisker is personally flying out to every Karma and charging our batteries while we are at work to increase the apparent range of his masterpiece.
 

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That's great to hear! Wonder what the actual engineering reason might be... But I'm guessing it has most to do with ambient temperature and your driving style.
 

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I noticed that my most recent drive over the weekend - 32 actual miles, left us with 17 miles on the battery when we arrived home. I was impressed how much battery life was left. Temperature was hot at about 85 degrees on average, but I followed the advice of some of the Fiskerbuzz members and did my best to keep the gen/accelerate needle in the middle.
 

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I just want to confirm a few things with you folks, as I would love to get a little more range as I come back from my dealer with my 6.28 installation tonight:

Are you eschewing Hill mode entirely? Only using it as part of a stopping sequence (similar to a downshift, then going back in to D after you stopped), or leaving it H1?

I am really trying to get my head around why the regeneration of Hill mode, if used only as part of a breaking sequence wouldn't be a net benefit. (maybe it creates more resistance during the acceleration/maintenance throttle?

Thanks for your help. If I can get just 5 more miles of range, I can get home entirely in stealth. And, Friday I am going to the America's Cup in SF, and will have to burn fuel to get there, and i'd like to use as much electric range as possible.
 

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rex said:
I just want to confirm a few things with you folks, as I would love to get a little more range as I come back from my dealer with my 6.28 installation tonight:

Are you eschewing Hill mode entirely? Only using it as part of a stopping sequence (similar to a downshift, then going back in to D after you stopped), or leaving it H1?

I am really trying to get my head around why the regeneration of Hill mode, if used only as part of a breaking sequence wouldn't be a net benefit. (maybe it creates more resistance during the acceleration/maintenance throttle?

Thanks for your help. If I can get just 5 more miles of range, I can get home entirely in stealth. And, Friday I am going to the America's Cup in SF, and will have to burn fuel to get there, and i'd like to use as much electric range as possible.
Nice use of the word eschewing!
 

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rex said:
I just want to confirm a few things with you folks, as I would love to get a little more range as I come back from my dealer with my 6.28 installation tonight:

And, Friday I am going to the America's Cup in SF, and will have to burn fuel to get there, and i'd like to use as much electric range as possible.
In the spirit of the Americas Cup, you may try attaching a spinnaker to the front of the car for the drive.:D
 

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Discussion Starter · #8 ·
If you are skilled at regulating your braking and accelerating, I believe it's better to NEVER use Hill mode. The problem with Hill mode is that sometimes you don't want to brake as much as it decelerates you. If you decelerate more than necessary, you recover more energy per mile, but you give that back and more when you accelerate to compensate.

Best is never brake and never accelerate, but that tends to not be practical if you want to actually get somewhere :)

Next best is to minimize accelerating, which necessarily implies minimizing braking as well.
 

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rex said:
I just want to confirm a few things with you folks, as I would love to get a little more range as I come back from my dealer with my 6.28 installation tonight:

Are you eschewing Hill mode entirely? Only using it as part of a stopping sequence (similar to a downshift, then going back in to D after you stopped), or leaving it H1?

I am really trying to get my head around why the regeneration of Hill mode, if used only as part of a breaking sequence wouldn't be a net benefit. (maybe it creates more resistance during the acceleration/maintenance throttle?

Thanks for your help. If I can get just 5 more miles of range, I can get home entirely in stealth. And, Friday I am going to the America's Cup in SF, and will have to burn fuel to get there, and i'd like to use as much electric range as possible.
Although this article primarily speaks to maximizing fuel economy in conventional ICE vehicles many of the techniques, suggestions and science here apply to maximizing Stealth range as well:
http://en.wikipedia.org/wiki/Fuel_economy-maximizing_behaviors
 

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I've really started to minimize my hill mode use. Its really only effective for long downhill runs where momentum and 5,300 pounds of beauty (and I'm not referring to myself), can carry the car through the friction of the hill mode. Also, I love the advice given earlier to try to keep the "needle" on the display right in the middle as much as possible. I tend to drive like a granny when I do that but a Karma driven slowly gets even more attention than all of the crazies out there!
 

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So to get the most mileage keep the middle in the middle and ONLY use hill mode when coming to a stop so that you are not over decelerating?

Another question: when I run out of batter and move into gas, my electric range is not climbing from 0. I thought the car was supposed to recharge the battery as driving as to get some battery mileage back as you run in gas. Does one have to ACTUALLY hit the paddle and shift into SPORT to do this or should it be doing it?
 

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RE: > 1:1 driven:battery miles!

bigdaddyo811 said:
Another question: when I run out of batter and move into gas, my electric range is not climbing from 0. I thought the car was supposed to recharge the battery as driving as to get some battery mileage back as you run in gas. Does one have to ACTUALLY hit the paddle and shift into SPORT to do this or should it be doing it?
In the production Karma the ICE does not charge the battery sufficient to increase the range under any regimen. It's a little convoluted, but here are the details:

In Stealth mode the car is driven solely from the battery. When the battery reaches 0 miles of range remaining (approximately a 15% state of charge) the ICE kicks in to generate sufficient electricity to propel the car, but it does not charge the battery above it's current level.

In Sport mode, the car is driven from a combination of electricity created by the ICE/generator and from the battery. Sport Mode will draw down the battery until it reaches approximately 26 miles of range remaining, and then it will charge the battery sufficient to hold this level. If sport mode is engaged when the battery is below 26 miles, sport mode will hold the level of the battery at the time of engagement. It does not charge the battery above it's current level under either circumstance.

The pre-delivery "Roadshow" cars operated differently. The ICE/generator was calibrated to generate enough electricity to both power the vehicle *and* increase the range of the battery by charging. In the Roadshow cars if you had 0 miles of range but drove in Sport mode for a sufficient duration you could increase your battery theoretically back to full charge. This was changed for the production vehicles. Exactly why isn't perfectly clear to me, but my understanding is that the emissions and fuel economy profile of the ICE when running in the Roadshow mode was insufficient, so a decision was made to alter the operation of Sport mode. I understand that the intent of ICE/Generator is to be a range extender, and is not an efficient way to recharge the vehicle, but like many owners here I would love to have an option to go into a "Sport Plus" mode that would allow me to increase my battery range on those occasions where I felt that was important, even if my MPG and emissions suffered.

The only way I'm aware of to increase the range of the battery without plugging it in is through the use of brake regen and Hill mode. If you are in Stealth mode only, and using Hill mode, the car can generate enough electricity during long downhill coasts to increase the range of the battery. Just driving around in Hill mode all the time won't do it though; the energy required to get to the top of the hill is greater than the energy recovered by hill mode. The trick that some have discovered is if you use Sport mode to get to the top of a hill, switch into Stealth mode (with Hill engaged) and coast to the bottom of the hill, and then re-engage sport mode you will then maintain the "new" battery level. By doing this multiple times, or by descending a sufficiently long hill, you can work your battery level back to 26 miles remaining. Of course this is more of a trick than a useful driving strategy.


Brent
 

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Excellent write up on the stealth vs. sport modes Brent. Most owners stay in stealth all the way to zero then accept the fact that they'll be on the ICE for the remainder of the trip. Another thing I always found amusing is the "shake" when in Stealth with zero miles on the battery, ICE running, sitting at a stop light and the ICE shuts down and shakes the car. If you don't know what's happening you think someone bumped your car. It reminds you of the uniqueness of this wonderful machine!
 

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LonePalmBJ said:
If sport mode is engaged when the battery is below 26 miles, sport mode will hold the level of the battery at the time of engagement. It does not charge the battery above it's current level under either circumstance.
If you drive down to 0 miles in Stealth mode, then switch to Sport, is the performance different than if you had swtiched to Sport earlier with 5, 10, or 27 miles remaining? If you have 0 miles of range, will the car still draw power from both the battery and ICE when you stomp on the pedal? In other words, does it tap into that 15% SOC remaining, or is that cushion always maintained to preserve battery life?

It could be that the car will use both battery and ICE, even with 0 miles, and use pauses in demand to bring the battery back up to 0 miles (15% SOC).
 

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teslaowner said:
If you drive down to 0 miles in Stealth mode, then switch to Sport, is the performance different than if you had swtiched to Sport earlier with 5, 10, or 27 miles remaining? If you have 0 miles of range, will the car still draw power from both the battery and ICE when you stomp on the pedal? In other words, does it tap into that 15% SOC remaining, or is that cushion always maintained to preserve battery life?

It could be that the car will use both battery and ICE, even with 0 miles, and use pauses in demand to bring the battery back up to 0 miles (15% SOC).
There's no appreciable difference in performance whether the battery range reads "0 miles" or not; the range extender can produce enough electrons to keep the motors happy. I don't know if the car "borrows" from the 15% SOC floor. As far as I know it doesn't, but if it does it's temporary and not noticeable to the driver. This is done for battery life.

Brent
 

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The battery management algorithm (capacity estimation and threshold limiting) could also be learning/adjusting - that would explain sudden, more accurate mapping of estimated miles to travelled miles. I recall the Fisker service guy (not the dealer) mentioning that the algorithms were adaptive.
 

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Discussion Starter · #17 ·
I thought the range prediction algorithms were adaptive as each trip proceeded, but not between trips. Otherwise one would think that my car would learn that my driveway isn't 1 mile long ;)

siliconkiwi said:
The battery management algorithm (capacity estimation and threshold limiting) could also be learning/adjusting - that would explain sudden, more accurate mapping of estimated miles to travelled miles. I recall the Fisker service guy (not the dealer) mentioning that the algorithms were adaptive.
 

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Personal Best: 46 Miles on a full charge at (mostly) highway speeds

As an exercise in range extension, I managed to drive all the way to work today in EV mode, a distance of 46.0 miles according to G-Maps:



The first 5.5 miles and the last 1/2 Mile of the trip are on city streets and the remaining 40 miles are on highway I-280, which tends to be very fast moving. On the highway portion, I kept my speed below 65 MPH, which meant that I was getting passed by fat guys on scooters and every other motorized conveyance (a few of which flashed me thumbs-up anyway before speeding off), but it was pretty impressive to pull into the garage at work without having to turn on the ICE.

Today was a pretty cool, but not cold day, and the drive from San Francisco to Cupertino tends to be generally downhill, but with a couple of large hills along the way. Here's the actual elevation profile:



Given all of this, and the fact that I drove most of the way at 60-65 MPH, I think it is remarkable how close to the 50 Mile range I managed to get on a single charge.

Update: On the return trip, I started with a fully charged battery and to the extent possible, I used the cruise control to keep the speed at 65 MPH. As expected, the battery did not last as long on the return journey during to the rise in elevation, and possibly also due to the lower evening temperatures, and at 42 Miles the ICE kicked in to get me home. Overall, I got 88 miles out of two full charges or 44 Miles average/Charge, which is pretty respectable given the conditions.
 

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Skibum said:
How many miles did the range indicator say you had left when you pulled in?
Zero! I was actually expecting the ICE to start up as I was parking my car but I guess at very low speeds like that you are dipping into the 15% reserve.
 
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