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gnochi, what is your advice on the following? I'm awaiting arrival soon of a Panamera E-Hybrid. Questions:
(1) is there any way to best optimize the new E-battery pack? In another thread, somebody said they were doing three full charges and three full depletions of the E-power battery pack to optimize the battery for best performance. Any validity to this?
various people on the Tesla forums have done this over time sometimes to minor effect - LiON batteries of various chemistries don't suffer "memory" effect previous battery chemistries were known for - a few deep discharge are recharge cycles won't hurt, but the general consensus on the EV forums (Bolt & Tesla) is that you shouldn't need to worry about this.
(2) I've seen it written above that it's not good to constantly fully charge such car batteries; is this true, and is there a difference to this answer in BEV vs. PHEV?
It is known to be bad to fully charge a LiON battery to 100% and then let it sit over time and keep it at 100% - charging the battery to 100% and then using it with in a reasonable amount of time does not have any appreciable effect. If you're going to leave the car for a long period of time (weeks/months) you should not keep the battery at 100% while you are away
(3) What would your recommendation be to prolong the life and range of PHEV batteries like in the Panamera E-Hybrid, from a driver/owner perspective? I'm mainly interested in having and maintaining driving-range (mileage) capacity to the highest possible level. I plan to use electric extensively for commuting in city driving, and hybrid/ICE power for outside cities.
PHEV batteries tend to be small (hence their limited range) - and trying to optimize the battery's capacity won't have nearly as much effect as driving style - for maximizing range speed is the killer - why is speed the killer because after about 45 mph aerodynamic drag takes over as the _MAJOR_ consumer of power - and it has a velocity-squared component - if you want to maximize range for any particular charing session you will have a far greater impact driving slightly slower vs. any gymnastics at trying to manage the battery…
according to the internet the 2018 Panamera has a 14.1 kWh battery (vs. a Tesla 100 kWh battery) - 14.1 kWh @ 3.3 miles/KWh = 46.5 mile range BEST case - probably less https://electrek.co/2016/09/09/porsc...lectric-range/
it all comes down to wh/mile - to get 3.3 miles per kWh of battery you have to drive at 303 wh/mile - in my Tesla 303 wh/mile = 62 mph on a flat level surface no wind, 70 mph = 383 wh/mile on a flat level surface which is 2.6 miles/kWh - 80 mph = 438 wh/Mile = 2.2 miles/kWh
optimizing battery charging and worrying about it will at most get you 2-6% - and you won't even be able to tell - however driving at different speeds and accelerating hard will have a 20-40% impact on battery life.
driving style HAS much more impact on battery range vs. any charging behaviors - you'd be surprised how much further you can drive with slower acceleration/more regenerative braking, and shaving 1-5 mph off your speed.
basically one or two hard accelerations and the associated greater load on battery to feed the EV motor will have way more affect on your range for that driving session vs. anything you could do in attempting to manage your battery charging sessions.
(4) Do you know if Panamera E-Hybrids have heated batteries at all for cold weather? And do you have any idea if Porsche E-Hybrids use both E-batteries and ICE for heating and air-conditioning the cabin, depending on whether the ICE is running or not? I wonder if there's a way to optimize the E-battery capacity better in cold or hot weather where the heater/AC is needed heavily.
Thanks!
I don't know the answer to this question - I would hope Porsche thermally manages the battery - for them not to do so will dramatically lower it's lifespan.
basically with a 14.1 kWh budget there isn't much to be lost/gained in battery charging management, and the Porsche battery management software will do a better job than you can anyways - if you want to maximize range in an EV or ICE car speed/acceleration/braking is the killer and has a much greater impact than most people realize.
basically at 50 mph my Tesla is a 400 mile beast
60 mph 320 miles
70 mph 260 miles
80 mph 212 miles
if I'm gentle on acceleration I can go forever, if I hit it hard off of every light I suck up battery at an alarming rate…based on how I drive my 26 miles commute it either 8 kWh or 18 kWh - all depending on driving style…
My Tesla P85D has 50,xxx miles on it and is 3.5 years old - it has lost 2% battery capacity in that time - or 1.7 kWh = 1.7 kWh @ 3.3 miles/kWh = 5.61 miles "lost" over the life of the car - charging to 90% most days, supercharging 3-5 times month, and 100% charge session infrequently…that "lost" battery capacity is about 2 0-60 sprints @ 3.2 seconds each - i.e. launching the car from two stop lights at full acceleration has way more affect than 3.5 years of battery capacity loss…I can "save" way more than 1.7 kWh driving 68 mph vs. 70 mph on longer trips and have virtually _NO_ impact on my travel time.
charge the car, don't worry about it, if you want to maximize range drive slightly different.
here is the range vs. speed graph for a Tesla 85 kWh battery RWD (not AWD) - after about 30 mph the decline in range is all attributable to increase aero-dynamic drag.
50 mph = solid 330 miles range
70 mph = iffy 240 miles range
Thanks, Dave, for those helpful answers to my questions. I indeed tend to be light on acceleration when in all-electric mode driving around the city on my commutes. I'll enjoy the 462 hp out on the open expressways, but no need to worry about the sports-car aspect of it in heavy traffic, when I can save tons of gas, hopefully. I'm not quite ready for an all-electric car because I do too much long-distance and rural driving with no access to electric charging. Ideally, I'd love a PHEV in a Macan or Panamera (or Cross Turismo) that could go 50-100 mph on all-electric but still have good gas range also. I guess, from my reading of the above discussion, that with current battery limitations, despite the notable improvements in the last few years, it's more likely that Porsche and Volvo (and others that have sporty cars or SUVs) will max out around 15-20 kWh in PHEVs?
As for your graph with the Teslas in speed vs. range, it's interesting that the range for the Model S peaks around 20-22 mph. Why is it lower at 10-15 mph than at 20 mph?
I think that ICE cars also peak at some value around 25-35 mph, with worse mileage below that.
there is some minimal power required to just move - but you don't cover much distance at slower speeds, so the amount of power being used is not efficient - as you increase in power you go further for the same input of kWh's - then after you get to 30 or so MPH you have to start overcoming aero-drag and adding power to increase speed - so you go less distance…
Dave and gnochi, Can I get your thoughts on the following, please?
At the beginning of the charge there is 0 mAh stored and at 105 minutes, when charging starts to slow down, the cell has stored about 3000mAh. Between 105 minutes and the end of the recharge, at around 180 minutes, the energy intake slowly decreases to 3000-3200 mAh. Thus, less than 10% of energy is accumulated in the last 75 minutes of charging. When applied to electric cars, you’ve probably noticed that the charging rate slows down as the battery fills. Now you have the explanation, related to the characteristics of the lithium-ion cells.
To estimate the number of cycles that the cell can undergo in its lifetime, we charge it at a maximal current of 0,5C and discharge at a current of 1C at 25 degrees Celsius and then we count the number of charge/discharge cycles until the cell degrades down to 70% of its initial capacity (2250mAh). In the case of these cells, the number is about 500 cycles.
500 cycles? But that’s (relatively) low! Yes. But what is not shown on the spec sheet is that when you partially charge and discharge, degradation of the battery capacity is reduced. Thus, you can do over 40 000 charge/discharge cycles when going from 30% to 70% only. Or over 35 000 charge/discharge cycles from 20% to 80%; 28 000 cycles from 10% to 90%; 15 000 cycles from 8% to 92%, 7500 cylces from 6% to 94%, and the capacity reduction goes faster and faster, finally reaching 500 cycles when recharging from 0% to 100%.
This explains the partial cycling strategies implemented by car manufacturers: GM limits the cycle from 17% to 80% of energy storage levels for the Volt. Nissan limits maximum charge level of the LEAF to 90% (4,15V). Tesla invites owners to limit the maximum load to 90%, and recommends avoiding deep depletion of the battery pack. All these strategies work well and significantly increase the number of battery cycles. When I manage the power levels of my own Tesla, I try to keep my maximum load below 90% and avoid depleting below 20%. Following this practice since the purchase of my Tesla, I have seen no capacity degradation. My wife’s 2012 Volt shows no degradation either. In fact, no Volt has yet shown degradation below 70% of the initial capacity which would have resulted in a warranty claim. In conclusion, we can trust the reliability of our Lithium batteries!
I agree with cometguy- as long you aren’t doing 0-100% daily charging the longevity of LiON batteries is well with the life span of most vehicle ownership cycles and beyond!
there is some minimal power required to just move - but you don't cover much distance at slower speeds, so the amount of power being used is not efficient - as you increase in power you go further for the same input of kWh's - then after you get to 30 or so MPH you have to start overcoming aero-drag and adding power to increase speed - so you go less distance…
The other loss is called the rolling resistance power loss which is a function of the vehicle's weight, type of tires, and vehicle speed.
This can be expressed as P = K x W x V, where K is a constant related to the tire, W is the vehicle weight, & V is the vehicles speed.
At speeds less than about 40-50 mph, the rolling resistance loss is usually greater than the drag loss. With the Tesla MS vehicle
and its weight (~ 4500), the rolling resistance power loss is significant. The drag power loss is basically, P = K x D X V^3, where D is the drag coefficient.
Dave and gnochi, Can I get your thoughts on the following, please?
At the beginning of the charge there is 0 mAh stored and at 105 minutes, when charging starts to slow down, the cell has stored about 3000mAh. Between 105 minutes and the end of the recharge, at around 180 minutes, the energy intake slowly decreases to 3000-3200 mAh. Thus, less than 10% of energy is accumulated in the last 75 minutes of charging. When applied to electric cars, you’ve probably noticed that the charging rate slows down as the battery fills. Now you have the explanation, related to the characteristics of the lithium-ion cells.
To estimate the number of cycles that the cell can undergo in its lifetime, we charge it at a maximal current of 0,5C and discharge at a current of 1C at 25 degrees Celsius and then we count the number of charge/discharge cycles until the cell degrades down to 70% of its initial capacity (2250mAh). In the case of these cells, the number is about 500 cycles.
500 cycles? But that’s (relatively) low! Yes. But what is not shown on the spec sheet is that when you partially charge and discharge, degradation of the battery capacity is reduced. Thus, you can do over 40 000 charge/discharge cycles when going from 30% to 70% only. Or over 35 000 charge/discharge cycles from 20% to 80%; 28 000 cycles from 10% to 90%; 15 000 cycles from 8% to 92%, 7500 cylces from 6% to 94%, and the capacity reduction goes faster and faster, finally reaching 500 cycles when recharging from 0% to 100%.
This explains the partial cycling strategies implemented by car manufacturers: GM limits the cycle from 17% to 80% of energy storage levels for the Volt. Nissan limits maximum charge level of the LEAF to 90% (4,15V). Tesla invites owners to limit the maximum load to 90%, and recommends avoiding deep depletion of the battery pack. All these strategies work well and significantly increase the number of battery cycles. When I manage the power levels of my own Tesla, I try to keep my maximum load below 90% and avoid depleting below 20%. Following this practice since the purchase of my Tesla, I have seen no capacity degradation. My wife’s 2012 Volt shows no degradation either. In fact, no Volt has yet shown degradation below 70% of the initial capacity which would have resulted in a warranty claim. In conclusion, we can trust the reliability of our Lithium batteries!
This was posted today on the Panamera E-Hybrid discussion thread by somebody who just got his new car:
"When I was at the LA Driving Experience my instructor told me the car always keeps a reserve of battery power for the rapid acceleration or hard driving where the car needs both the batteries and the gas engine. Not sure how many miles that translates to??"
So perhaps this battery reserve is around 5-10 percent of total capacity? More? Any idea?
And this perhaps means that one can run the battery capacity down to "zero" in terms of what the car says for all-electric driving, but still not be down to zero (and thus, not degrading the long-term battery capacity so much when doing so)?
In the first graphic, the blue & green lines' labels need to be reversed, i.e. the blue line is the rolling resistance losses which are a direct function of speed.
The green line represents the losses of motor controller, which increases very little as speed increases, i.e. the motor controller is very efficient.
What is interesting to me is total consumption between 15-20 mph is about 150 wh/mile - which is about 6.67 miles per kWh - making a car with a 100 kWh battery a 650 mile range beast - after that is all aerodrag.....having lived with EV’s for a while it always amazes me how much further I can drive if I just shave 2-4 mph from my speed if I’m trying to extend range....
In the first graphic, the blue & green lines' labels need to be reversed, i.e. the blue line is the rolling resistance losses which are a direct function of speed.
The green line represents the losses of motor controller, which increases very little as speed increases, i.e. the motor controller is very efficient.
Your statement is incorrect- the graph labels are right.
Rolling resistance increases in direct proportion to speed if you’re measuring in watts. The graph scale, however, is in watt hours per mile. The energy needed to turn the wheels the ~790 revolutions needed for every mile is nearly constant regardless of whether you’re turning them slowly or quickly.
For the same reason the drivetrain and controller losses do increase- they are transferring more total energy to go one mile as speed increases, so even if the % loss is constant (not quite) it’s a percentage of an ever greater number as speed increases. Hence per mile that loss goes up with speed.
Your statement is incorrect- the graph labels are right.
Rolling resistance increases in direct proportion to speed if you’re measuring in watts. The graph scale, however, is in watt hours per mile. The energy needed to turn the wheels the ~790 revolutions needed for every mile is nearly constant regardless of whether you’re turning them slowly or quickly.
For the same reason the drivetrain and controller losses do increase- they are transferring more total energy to go one mile as speed increases, so even if the % loss is constant (not quite) it’s a percentage of an ever greater number as speed increases. Hence per mile that loss goes up with speed.
Yes, it's energy (Wh) consumed per distance (mile) as a function of vehicle speed, my oversight. The slope of drivetrain losses graph may represent the MS/MX
for their induction motor/controller versus the more efficient M3 with a PM motor, i.e. smaller slope for the M3. Obviously, different BEVs will have different values
for the vertical axis. Typically the efficiency of the MS is about 235/250 Wh/mile, i.e. not that great. The M3 should be about 10/15% better.
04-23-2018, 02:21 PM
