-
Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
if it is colder out and you are at >90% or much lower it is weak until the car is warm. at 60% if it is 50F out my regen is a little light at first
maybe this?
djp
Model 3 Performance
I think it was Elon's polite way of saying that if you charge to 100% every day you'll kill the battery life and won't have any regen.
Two facts are very clear:
Tesla gives the user the option to adjust the charge limit down to 50%. If there was no positive effect on the battery they would not add that feature. There is must be a positive effect to charge the battery only to 50% instead of 60% or 70% or higher.
If charging to a lower state of charge had a negative effect on the battery, Tesla would mention it in the manual. Clearly they don't make that statement anywhere. Quite the opposite, they do say they charging to 100% all the time does have a negative effect on the long term battery life.
By just looking at these facts it's pretty straight forward to see that it is better to charge to a lower state of charge. Below 50% the difference must be so small that it's not worth it.
The Model S manual does not mention anything about battery balancing. So everything regarding this is speculation. Tesla has sent an official email explaining calibration limitation of the estimated range display. They specifically mentioned shallow charge cycles can make this estimate less accurate and charging/discharging towards the far ends (full and empty) recalibrates the estimate.
With that in mind I really don't understand how people always bring up balancing and charging to a higher level would re-balance the pack. Tesla has explained why charging to a higher level after many shallow charges can 'bring back' miles. It's not balancing. Why do people keep ignoring this and rather go with the theory of balancing?
Tesla gives the user the option to adjust the charge limit down to 50%. If there was no positive effect on the battery they would not add that feature. There is must be a positive effect to charge the battery only to 50% instead of 60% or 70% or higher.
If charging to a lower state of charge had a negative effect on the battery, Tesla would mention it in the manual. Clearly they don't make that statement anywhere. Quite the opposite, they do say they charging to 100% all the time does have a negative effect on the long term battery life.
By just looking at these facts it's pretty straight forward to see that it is better to charge to a lower state of charge. Below 50% the difference must be so small that it's not worth it.
The Model S manual does not mention anything about battery balancing. So everything regarding this is speculation. Tesla has sent an official email explaining calibration limitation of the estimated range display. They specifically mentioned shallow charge cycles can make this estimate less accurate and charging/discharging towards the far ends (full and empty) recalibrates the estimate.
With that in mind I really don't understand how people always bring up balancing and charging to a higher level would re-balance the pack. Tesla has explained why charging to a higher level after many shallow charges can 'bring back' miles. It's not balancing. Why do people keep ignoring this and rather go with the theory of balancing?
Unfortunately, this is less clear than it should be because the slider was really so that the EPA rated range wasn't averaged between the two, the way it was in the Leaf. The new Leafs now only allow 100% charging. My take is that the 50% level is mainly for storage. Mostly I charge at 80%.
Then why are there balancing circuits in the battery? There's a whole discussion on this with pictures showing them.
MarcG
Active Member
Can you please expand on this? I'm still a bit confused as to what's best for the battery and what to avoid... thanks.
PS: added my data to the spreadsheet listed in the OP. Nice work to whomever created and maintains it!
I suppose deep discharge cycles trigger a recalibration but there are many instances of this not working for some folks. Same for charging to 100% and letting it dwell for several hours (for those who think the pack is out of balance). Some seem to think it's entirely a balancing issue (qwk is one) but there really isn't sufficient evidence to sustain this.
Yes the slider was a loophole to avoid the EPA rating to be lower. But while the slider idea was about tricking the EPA rating, the range of the slider was selected to make sense for the battery.
Oh I'm not saying there is no balancing happening. There certainly is! There is just no evidence and technical reasons why balancing is only happening above 90% as some claim. Many people here say you have to charge to at least 90% to re-balance your battery to gain miles back. There is no evidence for that and no reference from Tesla either. There is an official reference from Tesla about why you do gain miles back when charging to a higher level and it's range estimate calibration, not balancing. That's all I'm saying.
I hope someone else can find the email again. Basically what Tesla wrote in an email was this: It is more difficult to determine the exact energy in a Lithium battery when it's partially charged. The car has an algorithm to determine how much energy is left in the battery. Of course it gets all kind of data from the battery itself, but it's not 100% accurate. If you partially charge and discharge the battery the error adds up and the estimate gets less accurate. Obviously, Tesla wants to be on the safe side so it will estimate on the lower side to prevent the driver to be stranded. When the battery charged fully the data from the battery allows a better estimate and the algorithm is re-calibrated. This explains why people that have been charging only to a lower level and then switched back to 100% see their range estimate go back up.
In other words, charging to a lower level is in no way bad for the battery nor does it cause individual modules to get out of balance. It's just the algorithm that gets less accurate. Not only is there nothing to worry about in terms of battery health, it also does not mean you are losing range. It is just the estimate that is showing you less.
My only problem with that is you are implying someone who charges->discharges 90->70 would be worse off than someone who exercises a greater portion of the capacity, say 70->30 each day. Experience tells us that the owner charging to 90 each day sees higher range, but at the probable cost of accelerated degradation.
I have a model S 85, one year old and 20k miles. Even though it fully charges to "260" miles vs. 265 when new, I have computed actual battery capacity and it looks like I am getting only about 72-74kwh which is a 15% degradation over one year. Fully charged, the battery is at "rated miles" and 100%. The trip meter does a pretty good job of showing total kwh used. So, multiply kwh used by rated miles used (not miles driven!) and divide by the fully charged miles to get fully charged capacity. I did this also using "percent charge" and got the same results.
I have done this for two trips of ~200 miles (with about 40 rated miles remaining) and that is how I got the 72-74 khw value.
I suspected the reduced capacity because even at 300 wh/mi I was chewing through "rated" miles faster than actual miles.
BTW I typically use 20-30 kwh between charging to 80%, only fully charging when going on long road trips, about 5-8 in the last year.
Anyone else seen this kind of capacity loss?
I have done this for two trips of ~200 miles (with about 40 rated miles remaining) and that is how I got the 72-74 khw value.
I suspected the reduced capacity because even at 300 wh/mi I was chewing through "rated" miles faster than actual miles.
BTW I typically use 20-30 kwh between charging to 80%, only fully charging when going on long road trips, about 5-8 in the last year.
Anyone else seen this kind of capacity loss?
MarcG
Active Member
Be careful in comparing 72-74 kWh to 85 in calculating degradation. There is only about 75 kWh available for driving in a brand new 85 kWh pack, the rest being reserved for conserving the battery at super low states of charge (SoC) and preventing it from being "bricked" (become unusable whereby it won't even charge anymore).
In my experience, the most I ever got was 75.2 kWh by calculating it the same way you did - and driving nonstop from 100% to 0.8% SoC, with less than 1,000 miles on the odometer, confirmed that (see below snapshot).
My "total energy since last charge" number was 74.6 kWh, and I had 2 miles remaining. Charging to 100% yielded 252 miles at the time, in range mode the whole time (P85D with early 6.0 release). And 74.6*252/(252-2)=75.2 kWh.
Anyway, this means that your 100% yielding 260 miles was based on only an available capacity of 75 kWh.
So even if you are at just getting 72 kWh of total available driving capacity, that's still only about 4% degradation - not 15% - from the original 75 kWh of a brand new pack.
PS: Welcome to the forum, I just noticed this is your first post! :biggrin:
Last edited:
No, that's not the case. The 85 kWh battery has 75.9 kWh usable capacity (before going into reds) to begin with when it is new. There is a graph in the middle of THIS page explaining usable battery capacity before rated range goes below zero.
Using the proper information, my battery has degraded somewhere between 2-3% over the last calendar year.
mknox
Well-Known Member
260 vs. 265 is pretty good, actually. After 2.5 years / 60,000 miles, I am seeing about 240 on my car. Secondly, the Trip Meter actually does a pretty poor job of showing kWh used from the battery. It will not account for any usage when the car is off, for instance the much talked about Vampire drain. It really only tracks the amount of energy drawn from the pack when the car is on and running. I see quite a discrepancy from what I measure at my car's charging circuit via a sub-meter and what the car is telling me.
That graphic has been circulated several times around TMC. It is nothing more than informed speculation. Some folks have been able to pull close to 80 kWh while others only 70 kWh on a full charge. My guess would be that the range algo was poorly calibrated for those that only made it 70 kWh and if they had continued driving past "Charge Now" they would've had usable capacity remaining.
Similar threads
- Question
