I'm not sure it did this with the older firmware, but I've noticed that if you do a range mode charge that regen comes back gradually. I saw the "no regen" light on the dash, but I was still getting 10 or 20 kW of regen. I'm not sure whether it was at full regen (~36kW) when the light went out.
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I'm not sure it did this with the older firmware, but I've noticed that if you do a range mode charge that regen comes back gradually. I saw the "no regen" light on the dash, but I was still getting 10 or 20 kW of regen. I'm not sure whether it was at full regen (~36kW) when the light went out.
S-2000 Roadster
#1244
I have noticed the same thing. It seems reasonable to me for regen to come back gradually, but I fully expect the NO REGEN lamp to stay on until the limitations are completely gone.
In contrast, I would hope that the system would not limit regen torque without warning the driver via the NO REGEN lamp. In other words, I hope that vfx was imagining regen limitations that were not actually occurring (it's actually rather difficult to predict how much regen to expect, since the torque depends upon vehicle speed, position of accelerator, and rate of change of accelerator position).
As for the topic, I've decided to try Storage Mode since I rarely drive more than 10 miles a day. My rough calculation is that Storage Mode should provide 98 miles of range, which is way more than I need. If I need to go beyond 100 miles, it's almost 100% certain that I'll also need to go beyond 200 miles, and thus I'll need to do a Range Mode charge right before leaving for my trip. For a point of reference, I spent about $500 on gas last year in my 30 mpg Honda, so you can see that my average was only slightly above 10 miles per day.
One potential caveat that I see is related to "showing off" the car. I understand that it's bad for the battery to pull a lot of current quickly when the charge level is low. My plan is to retire from giving people free 0-to-60 demonstrations, at least when I'm driving around on a Storage Mode charge. This will probably save me from getting a ticket anyway.
Does anyone have new thoughts or experiences to add to this thread?
The no-regen light DOES shut off BEFORE full regen power is restored after a range-mode charge. I could believe regen would be a little less if SOC is really high due to a low-current standard-mode charge. Using the digital KW meter on the VDS would be a way to really confirm.
S-2000 Roadster
#1244
S-2000 Roadster
#1244
I just took my Roadster out for my first drive after deciding to try out Storage Mode. What really surprised me, when I finally switched the VDS to the right screen, was that I was apparently driving around in Storage Mode. I had no idea that there was a Storage Mode for driving. I thought that I read that the Roadster would automatically pop out of Storage Mode as soon as you exceed 0.1 miles, and then it would be back to Standard Mode.
I did not test whether the Roadster would still be in Storage Mode by the time I got back home to my garage. I did not want to continue driving in Storage Mode, so I switched to Standard Mode by pressing the battery icon on the VDS until I got past Range Mode, Performance Mode, and then finally to Standard Mode. Since others have reported that the car would not stay in Storage Mode, I was rather surprised by this.
Update: Upon reviewing the manuals, it seems that the Roadster does not revert to Standard Mode until the charging port door is opened after driving 0.1 miles. Therefore, I guess it is expected that the car would be driving around in this mysterious Storage Mode until it is connected to a charging system again.
Any comments?
I did not test whether the Roadster would still be in Storage Mode by the time I got back home to my garage. I did not want to continue driving in Storage Mode, so I switched to Standard Mode by pressing the battery icon on the VDS until I got past Range Mode, Performance Mode, and then finally to Standard Mode. Since others have reported that the car would not stay in Storage Mode, I was rather surprised by this.
Update: Upon reviewing the manuals, it seems that the Roadster does not revert to Standard Mode until the charging port door is opened after driving 0.1 miles. Therefore, I guess it is expected that the car would be driving around in this mysterious Storage Mode until it is connected to a charging system again.
Any comments?
S-2000 Roadster
#1244
Well, Range Mode is only 24 miles more than Standard Mode, and I seem to recall that it takes more than 12 miles for the NO REGEN light to extinguish. At that point, you're practically back to Standard Mode anyway, or at least within 4% or 5%. Hardly seems worth a whole new charging mode.
Mitrovic
Member
I had a chat with my Tesla Ranger. He does not suggest to use the storage mode. He says that with storage mode the cells get "unbalanced".
S-2000 Roadster
#1244
My immediate thought is: What's wrong with being unbalanced? How does that compare to reducing the life of the batteries by keeping them charged on the high side? I realize that Standard Mode does not keep the cells full, and even Range Mode does not charge cells to the manufacturer's maximum, but the longest life comes from Storage Mode. In other words, I would like to understand more about the benefits of balancing and the detriments of unbalancing before making a decision based on that.
I've noticed that, upon arriving home after a drive in Storage Mode, my Roadster warns me to keep the car plugged in while in Storage Mode. Then, as soon as I open the charge port door the computer resets from Storage Mode to Standard Mode. That sure makes the warning go away, but it's pretty funny to watch this behavior. Tesla Motors surely did not intend for people to drive in Storage Mode, nor did they test this much for usability.
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There are instances of lost range for people driving in storage mode due to the pack balance being off too much. Nobody knows Tesla's batteries better than Tesla, so I would follow what they recommend.....
Using storage mode every day.
Sorry I haven't gotten to this thread sooner... :smile:
Using storage mode for daily driving is not the best idea. Here's why:
The graph shows the deeper the discharge, the lower the number of cycles. Notice at 10% dod, you get 7000 cycles. At 20% we would expect 3500 but only get 3300. At 40% we expect 1750 but get 1470. So if your daily drive uses 10% it's better to go from 80% to 70% than 40%-30%. If you know you are going to be doing a lot of miles driving, charge it fully in range mode and use it immediately. As Tesla recommends: keep the car in standard, plugged in and charging for daily use. If the car won't be used, drop the SOC to 40%-50% and use storage mode, but before you use it, charge it back up in standard. Keeping your car fully charged in standard seem to be the best compromise.
Sorry I haven't gotten to this thread sooner... :smile:
Using storage mode for daily driving is not the best idea. Here's why:
The graph shows the deeper the discharge, the lower the number of cycles. Notice at 10% dod, you get 7000 cycles. At 20% we would expect 3500 but only get 3300. At 40% we expect 1750 but get 1470. So if your daily drive uses 10% it's better to go from 80% to 70% than 40%-30%. If you know you are going to be doing a lot of miles driving, charge it fully in range mode and use it immediately. As Tesla recommends: keep the car in standard, plugged in and charging for daily use. If the car won't be used, drop the SOC to 40%-50% and use storage mode, but before you use it, charge it back up in standard. Keeping your car fully charged in standard seem to be the best compromise.
S-2000 Roadster
#1244
Thanks for the graph.
Is Storage Mode 40%? My Roadster still just barely dropped to around 50% after several days of Storage Mode. I thought that Storage Mode kept the SOC at 50%. If I'm only going to use 5% to 10% of my ESS each day, it seems like I would be best to charge to 55% or 60%.
My question about that graph is whether it actually represents the same testing conditions. The term "depth of discharge" implies that all testing was done starting with a full battery and then discharging to the value shown on the graph. But that's not the same as starting with a 50% charge and discharging only to 45% or 40%. It all depends upon whether "depth of discharge" is an absolute or relative measure. It could be that there are plenty of cycles when using Storage Mode and only discharging a total of 5% to 10% per day, making the lifetime towards the high end of that graph on the left.
I remember reading that Li-ion batteries have a certain number of charging cycles, regardless of whether you count a cycle as a single 100% discharge and 100% recharge or as two 50% discharge and 50% recharge sessions. At first I thought that this graph might disprove that tidbit of Li-ion folklore, but then I realized that it all depends upon how you define "number of cycles." Does that graph count a 50% charge as a full cycle? Does it count a 10% recharge as a full cycle? I would expect the graph to be decreasing, as shown.
In other words, do you have a link to the study that produced that chart?
Hmm: If you never use your battery, i.e. if you always have 0% depth of discharge, does that mean you can attain an infinite number of recharge cycles?
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S-2000 Roadster
#1244
I looked at the numbers from that graph in a spreadsheet and then again in a graphing application. I discovered a few things. First of all, if you change the DoD axis to logarithmic, the graph becomes a straight (linear) line. Second of all, that graph is almost exactly 1/x, with a scaling factor to represent the estimated number of 100% discharge plus recharge cycles.
In other words, if you assume that the general description of Li-ion batteries is correct, in that you get a certain number of full discharge and recharge cycles, regardless of whether you achieve a full cycle by 100% discharge and 100% recharge or two separate sessions of 50% discharge and 50% recharge, et cetera, then the expected number of partial cycle events should be a/x, where 'a' represents the number of full or complete (100%) cycles.
You'll note in my graph that the blue line has a scaling factor of 500, so it lines up with the final figure in the collected data. The green line has a scaling factor of 575, making it line up with the collected data at the 50% DoD point. The orange line is scaled by 775, so it lines up better with the left half of the collected data. In all cases, there is a very close correlation between the collected data and a simple 1/x graph.
This is the long way of saying that there is apparently no effect on the life of the battery based on Depth of Discharge. A given Li-ion technology appears to have a certain number of full, 100% charging cycles. If you fully discharge your battery every time you use it, then you get 500 charging events. If you only use 10% of your charge with each driving session, then you'll have 10 times as many charging events. Or, to put it another way, 10 charging events that bring the battery up by 10% is equivalent to a single charging event that brings an empty battery up by 100%.
The more you use your battery, the quicker it reaches its maximum number of 100% charge cycles. I see no evidence that there is any significant difference how deeply you discharge the battery. In particular, I see no evidence that starting at 80% and using 10% per day with a recharge to 80% is any different than starting at 50% and using 10% per day with a recharge to 50%. There should be exactly the same number of charging events if each one involves an increase in SOC of 10%.
I welcome more data, since I'm obviously working with nothing more than one tidbit of information on Li-ion technology and a single graph of data points taken under incompletely specified test conditions.
In other words, if you assume that the general description of Li-ion batteries is correct, in that you get a certain number of full discharge and recharge cycles, regardless of whether you achieve a full cycle by 100% discharge and 100% recharge or two separate sessions of 50% discharge and 50% recharge, et cetera, then the expected number of partial cycle events should be a/x, where 'a' represents the number of full or complete (100%) cycles.
You'll note in my graph that the blue line has a scaling factor of 500, so it lines up with the final figure in the collected data. The green line has a scaling factor of 575, making it line up with the collected data at the 50% DoD point. The orange line is scaled by 775, so it lines up better with the left half of the collected data. In all cases, there is a very close correlation between the collected data and a simple 1/x graph.
This is the long way of saying that there is apparently no effect on the life of the battery based on Depth of Discharge. A given Li-ion technology appears to have a certain number of full, 100% charging cycles. If you fully discharge your battery every time you use it, then you get 500 charging events. If you only use 10% of your charge with each driving session, then you'll have 10 times as many charging events. Or, to put it another way, 10 charging events that bring the battery up by 10% is equivalent to a single charging event that brings an empty battery up by 100%.
The more you use your battery, the quicker it reaches its maximum number of 100% charge cycles. I see no evidence that there is any significant difference how deeply you discharge the battery. In particular, I see no evidence that starting at 80% and using 10% per day with a recharge to 80% is any different than starting at 50% and using 10% per day with a recharge to 50%. There should be exactly the same number of charging events if each one involves an increase in SOC of 10%.
I welcome more data, since I'm obviously working with nothing more than one tidbit of information on Li-ion technology and a single graph of data points taken under incompletely specified test conditions.
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My working assumption (which could be completely wrong) was that a week of additive 10% drains followed by a 70% recharge would be worse than doing a 70% to 80% "top off" every day.
I also assume (based on no specific data) that draining below 10% isn't good, and charging over 90% isn't good either.
I suppose this depends on a lot of factors... ambient temp, charge rate, etc. And probably differs for different chemistries (e.g.: Leaf != Roadster).
I think there are different angles to what can be "bad":
#1: Capacity reduction in the cells due to 'damage' (like from heat)
#2: Unbalanced cells where the BMS didn't have a chance to equalize them.
#3: Computers start having trouble tracking actual SOC and battery health.
I think #2 & #3 can be "corrected" by switching to a different charging "program" to give the BMS a better chance.
I also assume (based on no specific data) that draining below 10% isn't good, and charging over 90% isn't good either.
I suppose this depends on a lot of factors... ambient temp, charge rate, etc. And probably differs for different chemistries (e.g.: Leaf != Roadster).
I think there are different angles to what can be "bad":
#1: Capacity reduction in the cells due to 'damage' (like from heat)
#2: Unbalanced cells where the BMS didn't have a chance to equalize them.
#3: Computers start having trouble tracking actual SOC and battery health.
I think #2 & #3 can be "corrected" by switching to a different charging "program" to give the BMS a better chance.
Do you know what the condition of the battery is supposed to be after the cycles indicated in that graph? I.e., how much of the initial storage and discharge capability is left?
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