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As I said in the last post you could do it with an odd number (5s3p pack of 60 volt modules can be charged at 300 V as is or at at 900 V as a 15s1p) but clearly if you are going to split into 2 equal pack then the total number of cells is going to be even.
This gets us into the perennial discussions as to what the capacity number represents. Is it the charge capacity or the discarge capacity? Is it from max safe to min safe or 80% or 78.65% of (max_safe - min_safe), at what charge/discharge rate? What is important to us is that the car deliver nominally the rated miles. Rivian has said that the 300 mile pack performed "better than expected" in the recent rally,
I've been wondering the same. The chat session indicated that it was slightly less to enable it to fit in the truck, which would indicate the physical size needed to be reduced, which would indicate fewer 21700 cells were used.
The capacity (energy) rating is likely what you refer to as "discharge capacity" and is the amount of energy the cell/battery can provide.
Discharge capacity is the number that EV drivers (and almost all others that use batteries to power things) will be primarily concerned with, and hence that is the metric battery and EV manufacturers use.
Tesla has never listed battery capacity for any of their vehicles (the old 70, 85, 90, 100 designations did have a loose correlation).
Not so sure.
If you knew anything of what the engineers perspective is there would be no doubt. There are a couple of standards out there for battery testing (and probably more that I don't know about). ASTM has a couple, SAE a couple more but they are not specific to traction batteries. The industry would benefit from some standards for traction battery testing and I have little doubt that it is being discussed somewhere. Establishing a standard is a lengthy process. Protocols have to be promulgated and then tested within and between labs in order to be certain that inter and intra facility CVs (variations) are small enough that the results are meaningful. When the standard passes these tests it is then up to organization to adopt the standard and, in turn, for industry to accept it.
If you had the engineer's perspective you wouldn't ask such a naive question and you probably won't understand the answer but as my overall goal here is to promulgate information I'll give it anyway. Capacities are determined by recording battery voltage and current between the "empty" and "full" voltages. For specification purposes (at this point the manufacturer of the cell is free to do what he wants) and in any adopted standard particular charge and discharge profiles are imposed (e.g. charge at 0.2C until Vx, is reached then at Vx until current drops below Iy at 20 °C. ). In the vehicle the conditions are, of course, whatever conditions the vehicle is being charged or discharged under.
Neither Tesla nor the form factor of the battery have anything to do with this. Tesla does record this data and use it both in navigation management (range prediction) and battery health monitoring and I hope, and expect, Rivian will do the same.
The engineers at the OEM will demand of the battery supplier whatever testing they want done on the cells that are to be delivered. In addition to that the OEM will do his own testing. If you recall the early days of Rivian their advertising (if you can call it that) heavily emphasized battery testing.
I'm an engineer. I recognize good engineering when I see it. So do other engineers. Tesla dominates the BEV market today in no small measure from business acumen but primarily because they have good engineers. But for whatever reason they do dominate. The rest of the industry hopes to equal their success. At this point in time Tesla sets the standard and so becomes the de facto standard.
I quoted from 4 different spec sheets from four different manufacturers. None even hint at "Charging capacity". All give ratings in the form of the how a battery performs when being discharged.
Evidently you think that proves something. What?
Sometimes the lack of answer is an answer in and of itself.[/QUOTE]
In the first place I didn't ask that question. What I did was comment that unless we are given the measurement protocol attached to a a kWh rating (and we aren't), including the direction of current flow (i.e. whether it is a charge or discharge capaacity) the number is meaningless.
Really? Seems to me that you did:
Battery and vehicle manufacturers specify the amount of energy a battery can provide to the user.
Ahh. Perhaps English is not your first language.
Well I don't know of any that specify either capacity any more. But Tesla used to have a capacity sticker on its battery packs. The number on that sticker was closer to the charging capacity than the discharge capacity of the X I had in those days. To be honest I don't remember whether Tesla put battery size in their specs or not in their sales lit in those days but I'm pretty sure they don't now. But I had the big X which, it was widely accepted, had a 100 kWh battery and that's what it took to charge it. In driving it delivered more like 92 kWh. In any case what does this have to do with anything? No direct question was ever asked. The post that led to your tirade was:
The implied question is moot as his car doesn't have a 135 kWh battery. It has a 300 mile battery and mine doesn't have a 180 kWh battery. It has a 400 + miles "Max Pack". It's pretty clear that the OEMs aren't going to put out kWh numbers any more and I'd guess it's because they have seen samples of what people who think they know a lot more about batteries than they do can do with such numbers.
Audi, BMW, Chevy, Ford, Honda, GMC, Jaguar, Mini, Mercedes, Nissan, Toyota, Subaru and Volvo come to mind. I'm sure I missed a few. (and none of these have ever mentioned anything vaguely related to "Charge Capacity")
No, Tesla never gave kWh as a battery spec. And your battery took much more than 100 kWh to charge if you go by Teslas official testing. And unless you discharged your "100 kWh" pack at a steady C rate indicated by the battery manufacturer from full voltage to cutoff voltage at the specified temperature after charging in the specified manner, you should expect a different number
That battery capacity can indeed be measured and quantified. Is it important? Since that is the metric that degradation warranties use, yes.
