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I think that as batteries go bigger, charging becomes more important. After about an honest winter, highway speeds, real world range of 220-250miles per charge (where Tesla is right now) I'd pay more to get faster charging than a bigger battery. It has diminishing returns so I don't think it is very feasible to build 400-500 mile range EVs. You are pretty much tugging along unneccesary weight at some point.
However with Tesla's NCA chemistry, although energy density is amazing they compromise on charging C rates and IR. So do you think this could pose a threat to Tesla's superiorness in the long run vs. other makers?
250-300 mile range is all you need and the 'other' cells will reach that sometime in the future. (ZOE already has 45kWh gross pouch cell pack, Bolt has 60kWh etc.) Also cycle life can be dropped in list of importance as batteries get bigger as a 28kWh Ioniq would have double the cycles in same mileage vs. a 2013 Model S 60, even less cycles with the new 100D.
So I feel like going into the future, towards early 20s, cycle life and energy density can be dropped in favor of thermal qualities, IR and C rates charging/discharging. What are some of your more educated thoughts?
However with Tesla's NCA chemistry, although energy density is amazing they compromise on charging C rates and IR. So do you think this could pose a threat to Tesla's superiorness in the long run vs. other makers?
250-300 mile range is all you need and the 'other' cells will reach that sometime in the future. (ZOE already has 45kWh gross pouch cell pack, Bolt has 60kWh etc.) Also cycle life can be dropped in list of importance as batteries get bigger as a 28kWh Ioniq would have double the cycles in same mileage vs. a 2013 Model S 60, even less cycles with the new 100D.
So I feel like going into the future, towards early 20s, cycle life and energy density can be dropped in favor of thermal qualities, IR and C rates charging/discharging. What are some of your more educated thoughts?
If Tesla is committed to slow charging high density battery technology for the next decade or more, they have to fight the competition with long range. Selling point would be that you'd only charge away from home on road trips over 300 miles long. Normal range cars would have the quick charging selling point, but you'd be charging up a lot when on the road, potentially spending more time waiting in line for a charger than actually charging.
With low cost, high density batteries, they not only CAN make long range cars, they may HAVE TO. Face deforming acceleration is possible when sticking in large motors, but smaller motors suffice and offer better range.
Short range city cars may be a possible market for Tesla's battery tech. Low pack cost for a decent weight and range. Basically competing with the entry level BEv's on the market today. Downside would be even lower charging speeds than those cars are getting today. A 30kWh Tesla pack car is going to be not-so-great on the occasional road trip, while fine for metropolitan non-taxi use. The other brands' offering with similar range will spend less time charging.
With low cost, high density batteries, they not only CAN make long range cars, they may HAVE TO. Face deforming acceleration is possible when sticking in large motors, but smaller motors suffice and offer better range.
Short range city cars may be a possible market for Tesla's battery tech. Low pack cost for a decent weight and range. Basically competing with the entry level BEv's on the market today. Downside would be even lower charging speeds than those cars are getting today. A 30kWh Tesla pack car is going to be not-so-great on the occasional road trip, while fine for metropolitan non-taxi use. The other brands' offering with similar range will spend less time charging.
JRP3
Hyperactive Member
As packs get bigger the charge speed per mile also increases because the amount of energy delivered per unit of time is increased. A 50kWh pack charging at 1C is taking 50kW, a 100kWh pack charging at 1C is taking 100kW.
Not necessarily true since motor loads in a vehicle are always changing. One motor may be operating in it's peak efficiency range at say 45 mph while another is at peak efficiency at 75 mph.
cycle life can be easily extended by building buffer on top and bottom (see the Volt example - they have so huge buffers that they see 'zero' range degradation even after well over 100k miles on battery) - this is well known property of Li-Ion batteries - the closer you stay to the middle of the capacity in your cycles the more cycle counts you can get out of the pack.
If I was Tesla I would go that direction - increase raw battery capacity (and margins) without telling people to and at the same time change chemistry to be able to accept higher Cs. Also having a cap at the top lowers the charging taper (see software limited S60D).
I bet with small changes S90D with 120kWh pack should be easily capable at accepting 250kW (2C - see Nissan Leaf or i3 packs already accepting 2C today) and yet give you same long time stability today's S90D has.
JRP3
Hyperactive Member
How do you put additional battery capacity in a vehicle, not charge extra for it, and increase margins?
Higher C rate chemistry means lower energy density chemistry, i.e. heavier packs and less range.
Agree. I'd take a 200 mile EV over a 400 mile EV if it can charge to full >2x as fast.
gavine
Petrol Head turned EV Enthusiast
Lower the cost per kWh. That's what the gigafactory is doing. When capacity is at $100 per kWh, the extra "hidden" capacity will be inconsequential in terms of its affect on margins.
JRP3
Hyperactive Member
Increasing margins are a result of lower costs, not hiding pack capacity. Yes lower pack costs minimize the impact, but whatever the pack costs, hiding some capacity does not increase margins, it lowers them.
Roughly, to cruise: 2kW/km, 105 km/h = 210kW overhead. That 2kW/km could be 3, who knows.
I'm with you on the suggestion, though. Overhead wires for the long straight highway sections, and battery buffers sufficient for off-highway and local delivery. Trolleybus technology has been around for a very long time, and I think we'll see more of those first with the push for electrification taking hold.
You mention winter..., depending on climate, that range can be cut nearly in half. Add towing, hitch cargo box usage, roof mount racks, etc, and you take another significant hit.
JB has suggested Li-ion was improving at a rate of 7-8% a year.
We are already at 300+ mile range, and that's within only one step of chemistry improvement, and one step of pack layout optimization. We know the new 2170 cells will allow for another layout optimization, and there's a strong hint that additional chemistry change will also be in play.
Not only is 400 miles not infeasible, I wouldn't be surprised if a Model-S sized pack could be capable of it rather soon.
Not if it sacrifices some other key metric like cycle-life, energy density, or mass efficiency.
Also: cool new word!
Your statements seem at odds with each other. You are stating that bigger batteries help cycle-life, which is true. It also helps overall charge times for a given mileage target, as total energy delivered for a given C-rate increases as pack size increases.
Yet you then state that energy density can be dropped in favor of other characteristics. How are you getting these larger packs in the same space and yet decreasing energy density?
Also: see above regarding the 250 mile range being sufficient.
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Wait, what? There aren't any faster charging cars around from a time-per-mile perspective, are there?
I'm not even really sure what you are trying to say here... that Tesla's current pack chemistry is a limitation if they decide to go with pack sizes even smaller than the 40kW pack they dropped because nobody wanted them?
Well, cutting the battery size in half already reduces the charge time significantly for a full charge (although not >2).
So are you suggesting twice as fast as would have been the case for charging to 50% of the larger battery, or in other words a 2x increase in C-rate, which would therefore be 4X less time to charge as the large battery?
Yes, 200 miles is half of 400 so if it charges twice as fast it would be meaningless since an equivalent number of miles would be delivered.
However, if it charges at >2x the rate of the 400 mile battery you will get 200 miles sooner.
To be clear:
Say 400 mile battery charges in 2 hours. 200 mile battery charges in 1 hour. Same thing.
But now say the 200 mile battery charges in 40 min. I'd take the 200 mile battery over the 400.
However, if it charges at >2x the rate of the 400 mile battery you will get 200 miles sooner.
To be clear:
Say 400 mile battery charges in 2 hours. 200 mile battery charges in 1 hour. Same thing.
But now say the 200 mile battery charges in 40 min. I'd take the 200 mile battery over the 400.
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JRP3
Hyperactive Member
Of course if most of your trips are less than 400 miles, and over 200 miles, you'd be better off with the 400 mile pack. Not charging at all is always faster than charging.
OK, that's what I figured.
I'm trying to figure out if I'd make that trade off. Now I realize that you said "greater thank 2x", so certainly something like 5-10X is a game changer.
But using a 2X increase in charge rate in exchange for a 2X decrease in energy density for example:
All Li-ion chemistries have a non-linear charge curve, as far as I know. That implies a taper as you approach 100%. So assuming that 80% SoC is obtained in 2/3rds the "full C-rate" charge time, that means:
For a 200 mile pack with a 2C charge rate, that's 160 miles in 20 minutes.
For a 400 mile pack with a 1C charge rate, that's 320 miles in 40 minutes.
That means that you could also obtain 160 miles in ~20 mins for the 400 mile pack.
Assuming a 200 mile pack with a 4C rate, that means your 80%/160mile threshold would be reached in 10 minutes. Given that you have to pull over and get in and out of a charging station more often than a larger pack, I'm not sure even that makes the tradeoff terribly useful.
Having done many long trips over the years, I really do think the perfect balance is a "no worry" 275-300 mile range with the ability to comfortably skip at least 1 supercharger at a time. If you think about it, this covers just about every anxiety issue and unexpected charging issue you can come up with. The "no worry" caveat is +5 over highway speed limit + cold weather - 5-10% arrival buffer.
I'd like to think the 100D is almost there if not there already. But it could very well mean an EPA rating of 350 miles with real world usage of 300 using the above restrictions. Anything more than that is just unnecessary for 95% of the people out there. It puts your 100% charge times at 75-90min even with supercharging and adds cost.
I'd like to think the 100D is almost there if not there already. But it could very well mean an EPA rating of 350 miles with real world usage of 300 using the above restrictions. Anything more than that is just unnecessary for 95% of the people out there. It puts your 100% charge times at 75-90min even with supercharging and adds cost.
Right now I'm getting about 280 under good conditions going 5 mph or less over the speed limit, with one passenger (and a dog) so for me the magic Rated Range number would be 400+. That would get me from L.A. to San Francisco without having to stop.
In moderately cold weather (down to the teens), I lose ~1/3rd of my range. That gives your ideal 300 mile car a real-world 200 mile range. Subtract your 10% arrival buffer, and you are at 180 miles range.
I'd suggest that only allowing for 5mph over the limit puts you in the slow lane on many highways. And also not counting elevation, wind, and rain. I'll leave out towing or roof racks.
With 180 miles (or less) of actual range for a good portion of the planet for a significant mount of the year, that's not really enough to skip superchargers in many (most?) areas.
Assuming that you are only going to lose ~14% range of ta 350 mile car isn't realistic for the scenarios I outlined above. I'd say 400 miles starts to get you there.
The issue is that, although it may only be 5% of my overall requirement, when I need it, it's critical. If you are going to convert the world to EV's, then suggesting they need to go rent a vehicle for 1 out of 20 trips (or for their 2-4 vacations/road trips a year), becomes a tough sell.
This doesn't make sense. If you only need 300 miles 95% of the time, don't incur the extra time or expense to charge up to 100%. But when you do need it, you'll be glad to have it.
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