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Battery packs, a decision factor?

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So for one the BMS cooling trigger is around 45 or 50C which doesnt trigger in hot climates (as the pack is at 30-32Cish normally) and secondly, when the pack is at 30C you get A LOT more heat related degradation than i.e. at 10-15C which is what the pack sits at most of the time if you dont live in the tropics.

Target operating temperature while driving is 45C - which however doesnt occur all day long but only while you are driving.

Having your batterypack sit at 32C 24/7 is definetely not good for the battery and unfortunately even when you store your car at 40% in the heat, thats still worse than a car sitting at i.e. 100% when its at 5C.
While I see your argument in long temperature exposure while parked, it is not what research into Li batteries supports. See below chart and paper.
  • Most degradation occurs during the charge/discharge cycle, ie during chemical reaction process.
  • More degradation occurs in colder temperatures than hotter temperatures. Especially if car driven or fast charged without preheating.
  • The upper temperature where problems start is above 50C and it gets worse higher you go. However from Figure B even at 250 cycles, degradation at 35C is only 7%.

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While I see your argument in long temperature exposure while parked, it is not what research into Li batteries supports. See below chart and paper.
  • Most degradation occurs during the charge/discharge cycle, ie during chemical reaction process.
  • More degradation occurs in colder temperatures than hotter temperatures. Especially if car driven or fast charged without preheating.
  • The upper temperature where problems start is above 50C and it gets worse higher you go. However from Figure B even at 250 cycles, degradation at 35C is only 7%.



thats complete nonsense. heat is a killer for batteries. it is very clear that most degradation occurs during storage NOT during charge/discharge cycles.
Cold temperatures are protective for the battery.
 
Just to add fuel to the fire:

1. Candleflames' battery is presumably Panasonic NCA (2019?)
2. The MIC LR and P models are (I believe) LG NCM 811
3. My Zoe is NCM622.

There are quite a lot of differences, in particular with degradation, temperatures, cycles. I have not researched NCA particularly (because I don't have it). You cannot generalise from one article about a non-specified chemistry (at least I could not find the chemistry quoted) to specific Tesla cells.

Just one small example. I could not understand why my (and other) recent Teslas almost always preheat the battery to 43degC for 25kW JOLT chargers. Seemed crazy and I assumed it was that the Tesla software did not bother to cancel pre-heating at low charge rates. WRONG! The real truth is that NCM degrades at a much slower rate as temperature rises above 35degC. So, even though they chew up 6.5kW preheating from an available 22kW, significantly decreasing the charge rate, Tesla is actually reducing battery degradation by doing this!

So I am quite prepared to believe Candelflames degradation rate, particularly for NCA chemistry. I believe we will get more cycles out of NCM and even more still from LFP. So far, ZOE SOHs are tracking well for a cycle life of 1,400 at 80% SOC. I shall be happy if my Tesla gets somewhere between 500 and 900 (or more) cycles for NCM811.
 
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Just to add fuel to the fire:

1. Candleflames' battery is presumably Panasonic NCA (2019?)
2. The MIC LR and P models are (I believe) LG NCM 811
3. My Zoe is NCM622.

There are quite a lot of differences, in particular with degradation, temperatures, cycles. I have not researched NCA particularly (because I don't have it). You cannot generalise from one article about a non-specified chemistry (at least I could not find the chemistry quoted) to specific Tesla cells.

Just one small example. I could not understand why my (and other) recent Teslas almost always preheat the battery to 43degC for 25kW JOLT chargers. Seemed crazy and I assumed it was that the Tesla software did not bother to cancel pre-heating at low charge rates. WRONG! The real truth is that NCM degrades at a much slower rate as temperature rises above 35degC. So, even though they chew up 6.5kW preheating from an available 22kW, significantly decreasing the charge rate, Tesla is actually reducing battery degradation by doing this!

So I am quite prepared to believe Candelflames degradation rate, particularly for NCA chemistry. I believe we will get more cycles out of NCM and even more still from LFP. So far, ZOE SOHs are tracking well for a cycle life of 1,400 at 80% SOC. I shall be happy if my Tesla gets somewhere between 500 and 900 (or more) cycles for NCM811.
I have the 2019 Panasonic NCA 78.8kwh battery.

I have only 50kw dc chargers where I live and my car also uses both motors to generate 7kw of heat stealing 7kw of charge rate.

I always presumed that Tesla never bothered to program in slow DC charging as the american engineers assume everyone just supercharges.
The primary reason for the heating is that a hot battery can accept a higher charge rate...

NCM batteries degrade much faster once temperature rises above 25C. To say that NCM batteries degrade slower once its above 35C is just not scientific.
 
by subtracting my capacity from the starting capacity of 77.8 kwh. Or alternatively you can just subtract the kms and multiply by the rated wh/km. Adding 22km of range as 2019 technically has 521km not 499km, which are hidden before degradation puts it below 499 km.
Just wondering, have you recalibrated your cars battery? (Charge to 100%, empty to 0% and recharge to 100%)

 
Just wondering, have you recalibrated your cars battery? (Charge to 100%, empty to 0% and recharge to 100%)


yeah, I do deep discharges every 2-3 months because I have to do long distance travel in rural QLD.
That said, last time I did it in November I have noticed that my voltage is too high (true SOC 6% but the voltage fits more with 10%, so I might have a little bit more range than indicated, so perhaps 12-13% degradation rather than the 16%).

Next step is to charge the car frequently to 90% and let it sit there - I live in the tropics so im not gonna do that just yet but I will move somewhere colder next month so I will do it then in March to april when it gets frostier and then we will all find out if I get some range back. My car very rarely spends anytime above 70%. Tbh it only really does so during long distance travel and it doesnt sit there.
My car only gets very shallow circles around 40-60% when im not traveling.

However, there is someone up here who got their car at the same time and they charge to 90% everyday and they have even more degradation (over 20%).
 

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You got that completely backwards, where do you get that information?

Your analogy of batteries seems to be based on storing food in a fridge ;)

yes, you store batteries in the fridge when not in use. Thats how you store batteries. ?? Im not sure if you are trolling.
Coldness slows down the internal reactions.

It also does that for the LFP batteries - the difference is that the LFP battery has a unique reaction which forms a protective film on... cathode or anode I cant remember which prevents degradation. So its actually desireable for them to sit at 90-100% at high heat to speed up this reaction.
 
yes, you store batteries in the fridge when not in use. Thats how you store batteries. ?? Im not sure if you are trolling.
Coldness slows down the internal reactions.

It also does that for the LFP batteries - the difference is that the LFP battery has a unique reaction which forms a protective film on... cathode or anode I cant remember which prevents degradation. So its actually desireable for them to sit at 90-100% at high heat to speed up this reaction.
I just tried but my car wont fit in the fridge
 
This US Dept of Energy paper is interesting. 34 pages so too long to reproduce here. However, here is a link. They do observe that there can be differences between manufacturers so one has to be careful generalising. They tested over a three year period and did NCA (earlier Teslas), NCM 811 (MIC LR and P) and LFP (MIC SR+). They used 18650s but the real focus was on the characteristics of each chemistry.


Here are their conclusions. However, I suggest reading the whole paper, or at least pages 1-13:

"Commercial Li-ion batteries based on NMC, NCA, and LFP chemistries were cycled with varying temperature, depth of discharge, and discharge rate. The capacity and discharge energy retention, as well as the round-trip efficiency, were compared. The dependence on each cycling variable was analyzed qualitatively as well as by analysis of variance. Key insights from this work include:

1) Even within manufacturer specified operating ranges, the equivalent full cycle count at 80% capacity varied up to thousands of cycles depending on the conditions.

2) LFP cells had the highest cycle lifetime across all conditions, but this performance gap was reduced when cells were compared according to the discharge energy throughput. The latter metric factored in the lower capacity and lower voltage of the LFP cells, illustrating the importance of identifying the appropriate metrics for each application.

3) The RTE can vary up to 10% among fresh cells depending on the cycling conditions and can decrease over 5% as a cell ages. LFP cells generally had higher RTEs at all conditions and for all cells, RTE consistently decreased with increasing discharge rate.

4) Based on the current work and a review of previous commercial cell studies, trends in temperature, depth of discharge, and discharge rate dependence are chemistry specific. Variable dependence in one chemistry should not be broadly extrapolated to all lithium-ion batteries.

5) In the 15 to 35°C temperature range, the capacity fade rate increased with increasing temperature for LFP cells but decreased for NMC cells, indicating different dominant degradation mechanisms. These results illustrate the value of varying multiple temperatures within a normal operating range rather than looking solely at extreme temperatures. The gap in preferred conditions for LFP and NMC cells has implications for battery thermal management. A survey of the literature and the results here suggest that LFP cells are more suited for lower temperature applications.

6) The NMC and NCA cells exhibited a stronger dependence on depth of discharge, with greater sensitivity to full SOC range cycling than LFP cells.

7) Battery degradation models would benefit from the incorporation of larger data sets and reporting values with a standard deviation. Most models are evaluated against a single experimental data set, but a comparison of the degradation data in this study to previous commercial cell cycling studies shows the variation possible even under the same conditions."
 
Going back to the original question: Battery packs, a decision factor?
No, money is.. if you've got the money get the LR or Performance. If you're tight on money then get the SR+ but don't justify buying one over the other due to the battery tech as the battery management which Tesla does is a bigger factor than the chemistry.

Either way the car is fine. Your habits will change with a electric car vs a petrol car so total range is mainly irrelevant anyway and if it a critical factor, then pay the extra for the long range/performance.

Oh but.. What does the premium models like the Model S or the models have when they come out before cost cutting comes in? Nickel
 
You wouldn't pick one over the other on chemistry alone, but for me and I'm sure many others it certainly factored into my choice. Ultimately range, performance and audio won, but personally, I'd rather have LFP chemistry all things being equal.
 
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I think LFP batteries in cars is a short term thing due to the lower density.
Range is an issue. If you look at the history of ICE cars, back in 1980, the top selling car (commodore) had a range of about 400+ km per tank. Everyone was ok with that. Fast forward to 2021, the equivalent family car (Camry) has a range of 800+ km. Fuel tank capacity hasn't changed, efficiency has.
EV's will go the same. 400km now, 800km in the future (within 10 years) as battery tech improves. LFP isn't the answer.
 
I think LFP batteries in cars is a short term thing due to the lower density.
Range is an issue. If you look at the history of ICE cars, back in 1980, the top selling car (commodore) had a range of about 400+ km per tank. Everyone was ok with that. Fast forward to 2021, the equivalent family car (Camry) has a range of 800+ km. Fuel tank capacity hasn't changed, efficiency has.
EV's will go the same. 400km now, 800km in the future (within 10 years) as battery tech improves. LFP isn't the answer.
New battery tech that actually gets to market takes ages. Take 4680, firstly it's really only a number of incremental improvements on a ternary Lithium battery, they have probably been worked on them since 2018 or earlier by the fastest moving company in the world and we will still not see them in cars here in Australia for sale probably until 2024 or later. Most other companies will take 10 years minimum from concept to market of new battery tech and not mass production at that.

LFP makes a lot of sense right now, lower density aside (lower Wh/kg & Wh/L) which albeit has already improved a lot lately more than people realise, the tech has a lot of upsides, cheaper, safer, highly efficient and powerful, minerals are easy to source and abundant and low pollution (potential recyclability is good)

If I was already set on a super fast 4wd sedan (M3 long range) then it likely wouldn't have swayed me to 'downgrade' but i'm super happy it's coming with the battery on the base model Tesla it's quite a bonus for the cheap version to have such tech.
 
New battery tech that actually gets to market takes ages. Take 4680, firstly it's really only a number of incremental improvements on a ternary Lithium battery, they have probably been worked on them since 2018 or earlier by the fastest moving company in the world and we will still not see them in cars here in Australia for sale probably until 2024 or later. Most other companies will take 10 years minimum from concept to market of new battery tech and not mass production at that.
There will be incremental changes. Take ICE from the 1980's to now. The petrol tank has stayed the same capacity. Whether thats by choice or design, but 800km range is where its at. Assuming investment in improving ICE slows down now, I dont think it will get much better than that.
First step to greater efficiency of ICE was the 'overdrive gear'. No longer needing to have the engine screaming in 3rd on the highway. A few years later carburetors were replaced by fuel injection. The more efficient A/C, more gears, front wheel drive, better tyres, better aerodynamics. All small stuff, but all contributors.
EV's will go the same way 4680 is a small step of many.

I also got a Long Range, because I think it will stand up to the test of time as battery range improves toward 800km.
Plus Australia is a 3rd world country regarding charging infrastructure, so any diversion off the hume highway needs it.