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Old 01-24-2017, 11:55 PM   #1 (permalink)
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Question Stealth driving or Sport driving with 0 EV miles?

I did a search on this and didn't find anything. I thought I asked this, maybe I just meant to ask or made a side comment in another thread...IDK.

So I am driving along in my sweet ride boom I have 0 EV miles, the ICE kicks in and I am left wondering do I engage Sport? Do I just continue to drive in Stealth?

I have switched to Sport if I gain 1 EV mile to capture it. I don't think I have ever reached 2. Does it make any difference driving on 0 EV miles in Stealth vs Sport?

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Old 01-25-2017, 01:11 AM   #2 (permalink)
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Sport Mode's programming is to hold at whatever percent State Of Charge (SOC) the battery is at (provided it is under 50% - below 50%/27 Stealth, it lets the SOC drop at around half the normal rate). Without Sport Mode, the programming will let the battery drop down to 15% before it automatically engages the ICE to push the battery SOC back to up to the safety minimum 15% any time it gets below that and does it's best to hold it there.

So, in your scenario. I would engage Sport. It may not help, but it might. Here's how/why ...

As a general rule, I do not really like being at 0 (unless I'm almost pulling into my driveway). I always feel like I'm not taking advantage of having a battery backup should my ICE fail for any reason. So, on a long trip, I try to engage Sport as soon as I get to 27, and hold it there until I'm close enough to my house and choose to use up the last of my EV miles close to home (or at least to a place to plug in). The reason for keeping it at 27 is that the car will accelerate better when the battery is at or above 50% SOC. So, on a long trip, I try to keep it up there to maintain performance until I'm close enough to a charger to let it use the rest of my EV miles.

In your scenario - you just noticed you were at 0 without realizing ... If you engage Sport, it is possible for the Re-Gen Brakes to push a Stealth mile or two back into your battery (i.e. raise your POC up around 17%). If you see your Stealth mile count pop up from 0 to 1 (usually happens after some hard braking in Hill Mode 2 or a downhill run), you can flick Sport mode off and immediately turn it back on. This has the effect of "locking in" that extra backup electric mile. Sport Mode will now maintain 17% (1 Stealth mile) of charge. And, maybe you can do it again and get to 2 miles (18-19%). This can happen because the computer used the generator during cruise to get you back to 15%/your last locked SOC -- and then you braked or went down hill and the ReGen system added even more power back into the battery. Coming back to AZ from CA once, I forgot to engage Sport at a rest stop, and blew all the way down to 0 going up into the CA mountains. But, by the time I got home, the Regen braking had put 4 miles back on my battery because I stayed on Sport Mode after that and locked in those miles every time I saw the number creep up.

What does that buy me? Maybe 4 miles of emergency EV only travel if my ICE were to fail. So, honestly, not a lot. But, not nothing.

Lastly, I have a weak cell that drops me from 12 to 0 Stealth miles in around 10 seconds. And, while my Stealth miles might say 0, I probably have closer to 30% of my KWh still in the battery. But, one of my cells is reporting a small (but large enough) voltage variation to make the computer say 0 Stealth Miles. In that situation, I really have more power in the battery than the Stealth Miles number reported by computer says, and that extra power can help me accelerate ... If I engage Sport mode it does wind up holding my battery at that higher SOC regardless of the Stealth Mile indicator. I know this because of the number of hours the car recharges back to 50.

Basically, the car wants to protect you from dropping below 15% -- but if you're accelerating up a mountain (I live up a small one) or if you have to accelerate a couple of times in rapid succession without having "cruise time" to build the charge back up, you can wind up with a battery dangerously below that. So, any time I get near 15% ... I do what I can to try to get back above that for that little extra margin and make the car hold itself there if I can.

This only applies to a stock Fisker. FYI - PowerSource does sell an aftermarket product that can let you put the car into modes that makes the ICE run harder and use gas to generate power above the stock modes and make the car recharge enough to make the Stealth miles go UP.

Last edited by JCMorrill; 01-25-2017 at 01:16 AM.
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Old 01-25-2017, 10:33 AM   #3 (permalink)
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Originally Posted by jomak View Post
I did a search on this and didn't find anything. I thought I asked this, maybe I just meant to ask or made a side comment in another thread...IDK.

So I am driving along in my sweet ride boom I have 0 EV miles, the ICE kicks in and I am left wondering do I engage Sport? Do I just continue to drive in Stealth?

I have switched to Sport if I gain 1 EV mile to capture it. I don't think I have ever reached 2. Does it make any difference driving on 0 EV miles in Stealth vs Sport?

For a stock Karma you just keep driving in Stealth. That's what the car was designed to do. There's no need or benefit to putting the car in Sport. There's no difference to performance, regen, battery level, recharging or any other metric as far as I'm aware. Neither mode will add net-new range miles to your battery regardless of Hill mode either.

If you weren't stock and had a PowerSource TOM module you would have other options and modes to consider.

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Old 01-25-2017, 01:48 PM   #4 (permalink)
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Originally Posted by JCMorrill View Post
This only applies to a stock Fisker. FYI - PowerSource does sell an aftermarket product that can let you put the car into modes that makes the ICE run harder and use gas to generate power above the stock modes and make the car recharge enough to make the Stealth miles go UP.
Good explanation but some clarification... Our TOM unit never "makes the ICE run harder." TOM only generates power at synchronous RPM's that operate within the normal range set by the HCU. For example, if you are at WOT you won't generate energy and will likely deplete energy but if you are on cruise at a constant 65 MPH you will generate energy. In many cases this energy will likely be bled off anyway, since it has instructions from the HCU not to bank these miles. This is why sometimes (in stock mode) you hear the engine revving up but see a net negative or 0 KW on the energy screen. Just wasted in heat.

Of course this depends all on RPM, speed, SOC etc.

Will let the users of the TOM chime in if they feel something I said is inaccurate.
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Old 01-25-2017, 02:02 PM   #5 (permalink)
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Originally Posted by jomak View Post
I did a search on this and didn't find anything. I thought I asked this, maybe I just meant to ask or made a side comment in another thread...IDK.

So I am driving along in my sweet ride boom I have 0 EV miles, the ICE kicks in and I am left wondering do I engage Sport? Do I just continue to drive in Stealth?

I have switched to Sport if I gain 1 EV mile to capture it. I don't think I have ever reached 2. Does it make any difference driving on 0 EV miles in Stealth vs Sport?

I recall asking some variant of this question to a Fiker tech. a long time ago, and IIRC, the only difference between Stealth Mode at 0 Miles EV range and Sport Mode is that in Sport mode, the top power output limit imposed by the HCU is slightly higher than in Stealth mode. Otherwise, the two modes, as I understand it, operate exactly the same way in that battery SOC. I used to drive up a steep, windey street at the end of my daily commute with the ICE on, and I could not tell any difference between Stealth and Sport mode for that part of the drive. Of course, YMMV.
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Old 01-25-2017, 02:08 PM   #6 (permalink)
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Good explanation but some clarification... Our TOM unit never "makes the ICE run harder." TOM only generates power at synchronous RPM's that operate within the normal range set by the HCU. For example, if you are at WOT you won't generate energy and will likely deplete energy but if you are on cruise at a constant 65 MPH you will generate energy. In many cases this energy will likely be bled off anyway, since it has instructions from the HCU not to bank these miles. This is why sometimes (in stock mode) you hear the engine revving up but see a net negative or 0 KW on the energy screen. Just wasted in heat.

Of course this depends all on RPM, speed, SOC etc.

Will let the users of the TOM chime in if they feel something I said is inaccurate.
That's pretty consistent with my experience. In fact, with TOM, the ICE seems to run quieter and less hard than in stock Stealth/Sport modes and actual MPG, based on gas used to refill the tank, is consistently 10% to 20% higher than the number the energy screen readout shows.
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Old 01-25-2017, 02:11 PM   #7 (permalink)
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Originally Posted by LonePalmBJ View Post
For a stock Karma you just keep driving in Stealth. That's what the car was designed to do. There's no need or benefit to putting the car in Sport. There's no difference to performance, regen, battery level, recharging or any other metric as far as I'm aware. Neither mode will add net-new range miles to your battery regardless of Hill mode either.

Brent
That was my experience with the stock Karma also. The car seemed to manage the energy flow fairly well on its own. Most of the time, it is best to let the car figure out what it needs to do.
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Old 01-25-2017, 08:36 PM   #8 (permalink)
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For a stock Karma you just keep driving in Stealth. That's what the car was designed to do. There's no need or benefit to putting the car in Sport. There's no difference to performance, regen, battery level, recharging or any other metric as far as I'm aware. Neither mode will add net-new range miles to your battery regardless of Hill mode either.

Brent
While I agree that the car was designed to generally let you leave it in Stealth mode and drive around without ever thinking about it. And, I agree that stock ICE does not charge the battery ABOVE where it was when you first engaged Sport Mode ... But, it does charge it RIGHT back up to that point while you're cruising. So, if you have been cruising a while at highway speed, and then have a strong stop (like coming off a highway ramp) or down hill run especially while using Hill Mode 2, you absolutely can get enough more charge put into the battery to make the Stealth Mile counter go up by 1. And, I've done the trick of locking in that Stealth Mile (Sport off & back on) at least a hundred times in the last 2 years. It does work. I've gotten my battery back to 27 from 24-26 loads of times. And, a few (careless) times, I've gotten back from 0 to 1 or 2 (once up to 4 on a long trip).

The first summer I had the car, I had my battery indicator go into "red danger mode" on me accelerating up hill for the 2 mile run to my house at 0 Stealth (with the A/C blasting). If I keep a few Stealth miles locked in with Sport Mode, I do not have this problem. It makes sense. The battery is always providing the initial oomph to get you moving and the Genset is paying back that power to the battery levelly over time. So, if you live somewhere flat & cool, maybe you don't ever notice a problem. But, there is a slight difference in how the car performs between the two modes that one can use to advantage. PowerSource has always seemed adamant that acceleration performance is better with higher states of charge.
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Old 01-25-2017, 09:49 PM   #9 (permalink)
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PowerSource has always seemed adamant that acceleration performance is better with higher states of charge.

Higher bus voltage (V) = more power.. P=I*V (Ohms law) if V goes up power goes up, if V goes down power goes down. V is higher at higher states of charge. At 350v+ the car will perform better than at 340.
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Old 02-06-2017, 01:43 PM   #10 (permalink)
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PowerSource has always seemed adamant that acceleration performance is better with higher states of charge.
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Higher bus voltage (V) = more power.. P=I*V (Ohms law) if V goes up power goes up, if V goes down power goes down. V is higher at higher states of charge. At 350v+ the car will perform better than at 340.
For those of us who are not aficionados of Ohm's Law, this video does a great job explaining why a battery provides more power at higher voltage than at lower voltages. This is a promotional video for a product called Batteroo (Australian; go figure) which is designed to maximize the utilization of disposable batteries by keeping the Voltage as high as possible regardless of the battery's charge level. While I have no opinion on whether this product actually works or not, the explanation of why higher V means higher power is very accessible for those of us without an advanced EE degree.

Edited to add: As expected, the actual product appears to be a scam. But the explanation is still pretty accurate.




As I understand it, the same principle applies to Karma's battery in that as the battery drains the output voltage drops, and the overall power output drops proportionally. What this product appears to do is to keep the voltage level constant as the battery drains. You can actually do the same thing with an EV battery, and some other cars have a special circuit that keeps the voltage level constant to allow the car to access the battery's full power regardless of the SOC.

Hope this is helpful.
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