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What do you guys see when charge to 100%?
- Thread starter KG2002
- Start date
cold weather and range is reduced. Also, may take time for the system to fully calibrate itself to recognize full range capacity. In short, you are fine.
AlanSubie4Life
Efficiency Obsessed Member
I assume that when you switch to energy display it shows 100% charge (and doesn't stop at 97% or whatever, which can be a problem sometimes).
My understanding is that Model Y AWDs from 2020 got a software update to increase their rated range to ~326 rated miles (~525km) at 100% charge, assuming a maximum capacity 77-78kWh battery.
That was just a change in the constant.
If my understanding is correct, you're showing 505km at 100% now. If temperature is not a factor (you'd have to make special efforts to make your battery very warm (ideally 30-40C) to rule it out, and simultaneously get it to 90-100% charge), then that would imply you've lost about 4% of your capacity. That would be completely possible for a vehicle that is just a couple months old, but it depends a bit on mileage, etc.
The question, really, is what's the maximum you've ever seen at 90% (at 90%, or extrapolated to 100% from 90%)? Do you have a record of this?
Anyway, the point is that if your battery is cold, you need to be a little careful with the BMS estimate. However, there are ways to rule that out, and if that does not resolve the range issues, and you do a few 100% to 5% discharges with no change in the estimates at 100%, you can pretty much conclude the BMS estimate is basically correct. It is a direct representation of how much energy the car thinks you have available. It can be wrong, but once you rule out the various ways in which it can be wrong, you can conclude it is right.
After all, if you do a basically full discharge (90% of your capacity), and the resultant energy you see is 5% lower than it would be for a brand new (or someone else's) vehicle, and you repeat that a couple times, then that means you don't have that energy!
This is easy stuff to determine. You just have to see how much your car trip meter says you have (continuously measured for a full discharge, no stopping, etc., etc.). On a brand new car, in warmer conditions, you can see 72-73kWh on the trip meter with a 100% to 0% discharge (99% of 95.5% of 77-78kWh). If you're down to 70kWh, you've lost a few %. No big deal; it happens.
Worth keeping in mind these discharge experiments ALSO have to be done in reasonably warm temperatures. The Tesla cold weather FTP 20F test actually results in less energy being drawn from the battery for a full discharge; it's clearly stated in the EPA documents. That's probably partially because a very cold battery has less energy available for use when fully charged.
Also worth keeping in mind that if you're not doing 100% to 5% discharges, the loss of capacity doesn't matter too much. For some people it really matters, for others it does not (though it will affect resale value of the vehicle on the private market).
Did you actually take it on a long drive or just charge it to 100% to see? I ask because there are people that do this -- charge to 100% just to see their range has changed.
I haven't charged my car up to 100%. I try to keep my car between 50-70% SOC.
I haven't charged my car up to 100%. I try to keep my car between 50-70% SOC.
I don't know about you all, but my full charge range is going up and is almost at 350! 
Seriously though, stop obsessing over full charge range fluctuations... you're wasting your time worrying about nothing.
Seriously though, stop obsessing over full charge range fluctuations... you're wasting your time worrying about nothing.
Some cars are meant for driving.
Other cars are meant for charging (and obsessively checking range).
Other cars are meant for charging (and obsessively checking range).
I don't know about you all, but my full charge range is going up and is almost at 350!
Seriously though, stop obsessing over full charge range fluctuations... you're wasting your time worrying about nothing.
Based on what I’ve read, and what I know about lithium battery chemistries, the reason for the fluctuations in full charge range estimates has to do with the BMS’s requirements in order to maintain an accurate calibration of the pack’s true capacity.
To summarize, the BMS needs the MY to sleep for several hours at various states of charge so the BMS has multiple samples points to then build an accurate estimate of the pack’s true capacity. What tends to happen is the user charges the pack to the same state of charge everyday, without allowing enough time at other SoC for a proper calibration.
From my understanding, this is all due to the lithium battery chemistry and it’s flat discharge curve. To put it into perspective, the difference in cell voltage between full and empty is around 1 volt with lithium chemistries, compared to around 4 volts with lead acid. This characteristic makes it difficult to estimate the MY’s full charge capacity, especially when ideal calibration conditions aren’t provided to the BMS.
To summarize, the BMS needs the MY to sleep for several hours at various states of charge so the BMS has multiple samples points to then build an accurate estimate of the pack’s true capacity. What tends to happen is the user charges the pack to the same state of charge everyday, without allowing enough time at other SoC for a proper calibration.
From my understanding, this is all due to the lithium battery chemistry and it’s flat discharge curve. To put it into perspective, the difference in cell voltage between full and empty is around 1 volt with lithium chemistries, compared to around 4 volts with lead acid. This characteristic makes it difficult to estimate the MY’s full charge capacity, especially when ideal calibration conditions aren’t provided to the BMS.
correction..
The cell voltage difference between full and empty is not that large when comparing lead acid to lithium... let me rephrase..
The point I’m trying to make is that the discharge curve of most lithium chemistries is extremely flat in terms of voltage change, specifically between 20 and 80% SoC, when compared to pretty much anything else, such as lead acid.
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Here's something that's more fun: Go on a drive and see what the computer is estimating for your range.
I went up the highest peak around here (Mount Hamilton, 4000ft climb) which is about 19 miles from start from finish. Of course, I had to go back down and I got 5% in regen. The computer was estimating my range as 738 miles! I know it's totally not real...
Oh yeah, my average was 231 Wh/mi over ~87miles of driving.
I went up the highest peak around here (Mount Hamilton, 4000ft climb) which is about 19 miles from start from finish. Of course, I had to go back down and I got 5% in regen. The computer was estimating my range as 738 miles! I know it's totally not real...
Oh yeah, my average was 231 Wh/mi over ~87miles of driving.
How do I know the reduced range is due to the BMS and not due to degradation? As far as I can tell there’s virtually no way to prove what the actual range is because when you go on a long trip you can’t keep your avg. Wh/mi exactly where it’s rated, so how would you know exactly how many miles you should be getting without the computer telling you?I don't know about you all, but my full charge range is going up and is almost at 350!
Seriously though, stop obsessing over full charge range fluctuations... you're wasting your time worrying about nothing.
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