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Range Loss Over Time, What Can Be Expected, Efficiency, How to Maintain Battery Health
- Thread starter KK_RedM3
- Start date
navguy12
Active Member
I wonder if Tesla is going to factor in a baseline calendar aging rate for all cars, which it seems like they may already do for cars with LFP batteries. The displayed range in Teslas with LFP batteries ticks down with alarming consistency over time, so much so that you can guess the age of them to within a few months. I find it hard to believe those batteries are all aging nearly identically and suspect they are using some standard curve as a baseline and adjusting it slightly based on BMS measurements.
Because of the flat voltage curve in LFP I bet that it's much more difficult for the BMS to reliably get capacity measurements, and a generic aging curve might be more accurate on average.
If the LFP battery regularly gets charged to 100% and gets down to under ~15% or so (when the voltage curve is less flat), the BMS may be better able to measure capacity.
But there may be many cars that rarely get discharged low enough for that.
AlanSubie4Life
Efficiency Obsessed Member
I wonder whether it now includes effect of internal resistance increasing over time or something. But it seems like that would have already been accounted for too. (But maybe not! Sometimes the heat losses don’t all seem to be counted…it’s unclear to me how much of the mismatch of energy drawn from the battery, per the trip meter, vs. the delta in rated miles use, is due to heat loss…or is all of it?)
I don’t like the term “estimated battery range” used, because the estimated battery energy display does not have units of range. It’s energy.
So it’s confusing. It makes me not sure if they are referring to that display or the energy app calculations!
I don’t like the term “estimated battery range” used, because the estimated battery energy display does not have units of range. It’s energy.
So it’s confusing. It makes me not sure if they are referring to that display or the energy app calculations!
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Didn't you answer this questions yourself?
As far as anyone knows, age is not a currently used to estimate degradation. That job is handled by the BMS measuring electrical properties of the battery. However, it is clearly ideal to anchor battery degradation on age because that is the primary degradation that drivers will see. Esp. with the proliferation of low-usage drivers who only cycle between 70-80% (or similar), there is no way for the BMS to know total capacity either LFP or ternary cathode chemistry.
PACEMD
Active Member
Yes, never download an update, ever! Not worth the risk. I'm still on MS-DOS, mostly sh*t-driving on stilts.........Should we delay downloading the update because we don’t want to lose range
Strumming on the old banjo.........
I was thinking it was neither the battery icon range or the energy app range. I was thinking it was the trip computer calc range when you enter a navigation destination. There were updates last year that said it would start to account for temp, wind, humidity, elevation etc. So my thought was that the trip computer now will add degradation into it. Seems like maybe BMS and trip computer calc never shared this info?
With all my long distance trips, I think the trip computer does good job with final SoC estimation at destination. Well see what it does.
With all my long distance trips, I think the trip computer does good job with final SoC estimation at destination. Well see what it does.
On a long trip last summer, I saw the trip computer estimate have some significant errors in both directions (on the order of up to 10%). This could be significant if you plan to arrive at a Supercharger or your destination at a low state of charge.
I think I have about 5% degradation on the vehicle. If you are seeing up to 10% difference, then maybe that is your degradation that isn’t being accounted for upfront? And will be now?
Also, When you say 10% do you mean in absolute or as a ratio of final SoC? Both 10% vs 20% SoC and 9% vs 10% SoC are 10% “difference” and just trying to understand which you meant.
For me if driving 200+ miles to next supercharger, I end up about 2-3% Absolute SoC difference. Like nav will say 17% at initial trip start and I arrive with 14% instead.
In absolute terms. On a ~700 mile trip home, I had a planned Supercharger stop initially estimated at around 15%, but got there at around 6%. But on the final leg home, I Supercharged enough so that the estimate was to arrive home at around 10%, but actually got home at around 20%.
Note that this was Supercharging to about 50-60% for the fastest trip.
Thanks for this. Does this refer to charging before a trip or leaving a car sitting? In other words, if I charge to 80% before a road trip, or when I'm going to be out running errands all day, will that quicken my degradation?
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