Thank you for the long and thoughtful reply. It was a pleasure to read. I don't have the time to address all of your points.
jlsoaz said:
I agree with the points as to some of the concerns with liquid coolant vehicles. Whether the coolant is water or something else, the potential concerns include safety and complexity/cost. As an aside that I have made at least once before, I'm curious as to what is being done by various manufacturers to investigate some sort of solid-state cooling (and energy harvesting) though it's known to be inefficient so maybe it just inherently is not that useful for pack cooling.
Solid state cooling is very inefficient so is just inherently not that useful for pack cooling. Might change in the future, this is an active area of research.
jlsoaz said:
I've seen you write:
"...As for keeping an EV longer than the battery warranty, I'm past the battery warranty, have about 90% capacity and all bars. People in moderate climates, most of the USA, should be able to exceed the warranty easily. Hot climates like Phoenix are the risky place: if you just miss the warranty too bad, if you just hit the warranty you should be good to go for another warranty period...."
To what degree does your opinion take into account the differences in extremes in various places deemed "moderate"? And what is the best way to define "moderate"?
I'm not sure if this is the best definition of "moderate climate for an EV", but I'll propose some definitions and feel free to suggest alternatives.
A cool climate is a climate for which a commuting EV will never have a reasonable TMS turn on to cool the battery. Ever. Plus areas with less than 1% added battery life for a TMS. Seattle WA, Norway, much of Canada. Portland OR. Buffalo NY.
A moderate climate is one for which a reasonable TMS will provide between 1% and 20% more battery life for a commuting EV. Portland, OR or Maine. Florida. Salt Lake City, UT.
A hot climate is one for which a reasonable TMS will provide more than 20% more battery life for a commuting EV. Phoenix AZ, Los Vegas NV, Palm Springs CA and similar: generally an area of the Southwestern USA where summer temperatures are over 90 for well over a hundred days a year, and over 100 for a month or more.
A commuting EV mostly drives between work and home. Notice that the early BEVs, with EPA ranges of ~80 miles and No Worries Ranges of about 35 miles could only handle a fraction of all commutes.
A reasonable TMS has a cooling threshold above the likely condensation point of water. Depend on details, this might range from 30C to 40C.
Battery life is likely modeled by Arrhenius's equation with an activation energy such that the rate doubles for every increase in temperature of between 7C and 10C.
https://en.wikipedia.org/wiki/Arrhenius_equation
A weak point of the above definition is places that are fairly warm all the time, but do not often get over 100 F. While battery life isn't much improved by a TMS, it is likely to be shorter there. Florida and Hawaii, for example.
Another weak point is accounting for the range of driver behavior. Fast starts heat the battery. Hills and high speeds heat the battery. Parking in the sun, on hot pavement vs cool garages. Miles driven and recharging times and rates.
And yes, the percentage thresholds are just picked. Perhaps there are better ones.
jlsoaz said:
However, I think we have some of our disagreement in mulling over whether Nissan made (in the past) the right engineering compromise decisions (whether right is defined as "for Nissan", "for some customers" or both) and whether it is doing so now, and, once those decisions are made, whether it is making the right decisions in how it then presents the product to customers. Perhaps, for example, if it knows or strongly suspects that the latest iteration of its cooling will not hold up well in some of the hotter areas, maybe, as a matter of customer satisfaction, it should decline to sell the vehicle into those markets. Or, maybe the right decision is to go ahead and sell it, but with a much different marketing campaign, and different warranty terms. I don't know that different warranty terms would be legal. Are federal warranty terms necessarily homogeneous and does this make it more difficult in product development to make engineering cost/benefit compromise decisions that are focused only on some climates?
"For Nissan", the LEAF was designed for the wrong group of users. The car wasn't designed for many of the people that ended up buying it.
Something with higher range, higher performance, and of course a TMS would have been closer. Maybe even a two seater.
I was closer to the target market, I wanted commuting only.
I suspect that the newer batteries are likely to hold up enough to prevent an expensive warranty problem for Nissan. Time will tell, and there hasn't been enough time yet.
jlsoaz said:
Separately, I think that there may be matters in business where, adding everything up, it is simply not a good idea (regardless of considerations as to which customer group is being served) to make a particular engineering compromise. [[edited]: In this case, I thought Nissan's decision in the past to go with air cooling was on that line of being generally debatable regardless of target customer. As to now, about six years later, I'm wary, and question if it is still generally debatable.[/edited]]
Still, to be sure, upon re-consideration, perhaps I have incorrectly downplayed some aspects in this matter and it does indeed seem worth explicitly acknowledging and saying that from the point of view of customers who don't want the expense and (in their view) not very useful feature of having liquid cooling built in, then it is good from their point of view to see EV companies offering the less expensive, less complex tech.
One size fits all doesn't.
A range of EVs for different people is far more likely to meet needs.
jlsoaz said:
It is inherently a somewhat complex topic in some ways (IMO) and so there are some qualifiers to this -
1) vehicles are re-sold throughout the country and so it raises the question of knowing what you are buying. Do you want a Leaf that spent years in hotter portions of Texas but then ended up in North Dakota? Or do you at least want to be advised accurately of its earlier days?
2) what is the mileage and previous climate experience of a battery pack. I just spoke to an industry participant on this point. In the old days, it may have been easier to roll back odometers on gasoline cars. What measures can be taken to prevent the equivalent of illegal odometer rollback in battery packs.... i.e.: so that used buyers have full transparency.
3) once a vehicle is released into the wild, the use-case, even within a single-owner household, may change and (for example) it may be driven more frequently on long trips leading to more frequent quick-charging and thus to some need to be concerned about engineering to address the heat questions.
1) Knowing what you are buying is likely just knowing the current capacity of the battery pack. See point (2). If battery life is Arrhenius's equation driven, the way the pack got to that state isn't meaningful.
2) It is a complex problem to solve: How know what the real capacity of the battery pack is? I would propose a history readout of capacity estimates that isn't changeable, in "write once" memory.
3) Tires are speed rated. Driving faster than the speed rating may cause the tire to fall apart, perhaps leading to death. In the case of a well designed passive battery, the battery just loses capacity faster. And maybe that's ok, if you know it isn't going to be a habit.
