Mar 2, 2010
Palpatine I sent some questions to Tesla Motors asking about strategies for extending the life of my battery pack. I was looking for more tips beyond just plugging in and recharging to standard mode each day.
I received a very detailed response from Dan Myggen and he gave me permission to post it here.
�
Mar 2, 2010
Palpatine This is what I have started doing based on my research and talking with Tesla Motors.
I set my Tesla to recharge at 6 am so that it finishes and balances right before I leave the house each day. That way my car spends more of it's time during a 24 hour day significantly below full standard. It is only briefly at that 87% charge level each day. The goal should be for the car to finish charging and balancing about 30 minutes before you leave in the morning.
If you plug your car in each night when you get home (perhaps 6 pm) then it is likely topped off quickly and then spends all night at the full standard charge level. This is not a good thing. We want to minimize the amount of time the cells are fully charged.
If I know I am not going to be driving my Tesla for a few days, then I will just leave it in standard mode at something less than full standard. I am fine with allowing it to get down to 90-150 ideal miles without recharging.�
Mar 2, 2010
Tdave Thanks James. Fascinating. Sounds like 90% SOC Standard mode is pretty safe for the battery. So in other words, using Standard Mode and just plugging it in whenever is a pretty good strategy. And it happens to be the default for most people. That's good news.
I'd be interested to know just how much better your strategy is compared with the mindless strategy I stated above. In other words, what's the difference in pack life?�
Mar 2, 2010
Palpatine I read a study about these laptop batteries that quoted the loss of capacity per year when kept at certain temperatures and charge levels.
When kept fully charged at 40 degrees celcius then the loss in capacity approaches 15% to 20% per year.
When kept closer to 50% SOC and at 25 degrees celcius then the loss in capacity is about 4% per year.
When kept at 50% SOC and 10 degrees celcius then the loss in capacity is about 2% per year.
If I recall, Tesla states that they expect the average user to be at 65% of their original capacity after 100,000 miles. I am hoping that my strategy keeps my battery pack with much higher capacity over time.
It is an easy change to make. Just select a specific time in the morning for the charging process to start. 5 am is likely a good target for most people.�
Mar 2, 2010
Tdave Cite, please.
I thought it was supposed to be 80%. I sure hope I'm right and you're wrong.�
Mar 2, 2010
Palpatine I think it was in the SEC filing for the IPO.�
Mar 2, 2010
Tdave Something else I've wondered. When range suffers due to battery age, will we see that predicted in some display number? In other words, will "ideal miles" show something lower and lower when fully charged?�
Mar 2, 2010
ChargeIt! Yeah, that's what I too had heard in the early days ...
(And, James, thanks for posting this! Very useful.)�
Mar 2, 2010
Palpatine Registration Statement on Form S-1
Risk Factors. This section typically has the worst case scenario to warn potential investors. So this might be worst case predictions to cover themselves.
Page 16 (top)
The range of our electric vehicles on a single charge declines over time which may negatively influence potential customers� decisions whether to purchase our vehicles.
The range of our electric vehicles on a single charge declines principally as a function of usage, time, and charging patterns. For example, a customer�s use of their Tesla vehicle as well as the frequency with which they charge the battery of their Tesla vehicle can result in additional deterioration of the battery�s ability to hold a charge. We currently expect that our battery pack will retain approximately 60-65% of its ability to hold its initial charge after approximately 100,000 miles or 7 years, which will result in a decrease to the vehicle�s initial range. Such battery deterioration and the related decrease in range may negatively influence potential customer decisions whether to purchase our vehicles, which may harm our ability to market and sell our vehicles.�
Mar 2, 2010
Tdave Well geez, that's disappointing. When I bought I was thinking 80% after 100k miles or 7 years was pretty good, and that I'd be able to let it go longer, probably down to 70% or so before I'd start to care. Now I find out that will happen BEFORE 100k miles and 7 years. Hmph!
Maybe someone will post some suggestions on how to make the batteries last longer. Oh wait!
�
Mar 2, 2010
Palpatine So knowing the best strategy for long term health of the battery pack, it seems easy enough to make a few common sense changes to daily charging habits. This could easily improve your odds of having 80%+ of your original capacity after 100,000 miles.�
Mar 2, 2010
doug Why don't they just change the software so that, in addition to the charge timer and the current limit, the user is allowed to set a target SOC.�
Mar 2, 2010
Tdave Is there much benefit, if I charged only to 75% instead of 90%? It would nice to have quantifiable comparisons of the benefits of these things. Something more than just it's better. If I get another 2 months of battery life after 7 years, it's not worth the trouble for me to worry about it. If it's another 2 years of battery life, well that's a different story.�
Mar 2, 2010
Palpatine I think it will likely result in you having about 10%-15% more battery capacity after 100,000 miles. If the average Tesla owner will have 60%-65% after 100,000 mile by merely charging in standard mode every day (plug and forget), then the obsessive compulsive Tesla owner (that would be me) should be able to improve on that number.
The basic guidelines on laptop cells is a good guide. A few percentage points of preserved capacity per year can add up significantly over 5-7 years.�
Mar 2, 2010
Palpatine Excellent idea for a firmware update. They need an advanced user screen with some of these options.
Ted, I know you are reading this. Why can't we get a screen to set a user defined charge stopping point? Either by SOC or ideal miles?
Or perhaps give us a lower default point to stop charging. Perhaps 3.9 or 4.0 volts.�
Mar 2, 2010
doug Yeah, some quantitative data would be nice. But certainly, such an option in the firmware would be a heck of a lot less trouble than setting the charge time and rate in the hope of interrupting the cycle at the desired SOC, as has been suggested. Would also give the system a chance to balance the cells.
As James suggests, it should be an advanced option. If customers want it, they should just do it, unless there is a compelling reason not to.�
Mar 3, 2010
bolosky Timed charging
I decided to try to set my Roadster so that it starts charging late at night rather than as soon as I get home, with the thought that that way it won't be sitting around at a full standard-mode charge all night. The idea wasn't to try to get it to a partial charge, just to have it start later.
I've never used timed charging mode before, so maybe I did something wrong. I got home, parked the car and set it to start charging at 4AM. I plugged it in and it started charging immediately. I got back into the car and again set it to charge at 4AM. It stopped charging and put up a note saying "scheduled charging at 4AM" or something like that.
This morning, I got to the car and it hadn't charged. It had a screen that said "plug in cable" or something, even though it was plugged in. I switched it to "charge on plug-in" and it started charging, but it only added 2 ideal miles in the time it took me to take the garbage to the curb.
Luckily, I have enough charge to get me through the day, so it's no big deal. Still, it's annoying.
Has anyone else had problems like this? Any suggestions?�
Mar 3, 2010
ChargeIt! It could happen (possibly buggy firmware) when you change the time of charging or stop and restart charging (sliding the grey switch on the connector off/on) that it won't "take". In that case the safest method is to actually disconnect from the port and most importantly close the cover. Re-open after a few seconds and start over. Better yet, make all the adjustments you want while the cover is closed then re-connect.
Edit: don't know why it started for 2 miles then stopped (unless you were "full" or in storage mode, or another bug symptom). But closing the cover basically tells the firmware to "let's start over".�
Mar 3, 2010
JRP3 I wouldn't be surprised of the 60-65% after 100k/7years is a worst case estimate for the SEC filing, and real world results will be better.�
Mar 4, 2010
malcolm I understand that the car needs to be plugged in in order to perform cell balancing, but if I'm reading correctly it only seems to do this after a Standard charge.
Why not after any (non Range/Performance) charge?
I guess we need more charge settings and names to go with them:
Range / Performance - Standard - Medium Commute - Short Commute - Economy - Obsessive/Compulsive - Storage
:biggrin:�
Mar 4, 2010
WarpedOne And don't fortget KISS!�
Mar 4, 2010
Palpatine I had this same issue.
Set the time to charge in the car.
Then after that has been set, open the charging port and plug in the car.
If the car is already plugged in when you are messing around with the time, it is not reliable for actually starting at that time.
This is a bug in the firmware. If the car is already plugged in when you are messing with that timing setting, it doesn't always notice that you have set it to start charging at a certain time.
Opening the charging port door (and plugging in) after this has been set seems to be the key to the car noticing your settings.�
Mar 4, 2010
eledille This reminds me a lot of how I charge my NiCd-car. The Norwegian electric car enthusiasts have done a lot of thinking and research into how we can improve the lifetime of our batteries.
Flooded NiCd batteries are balanced by overcharging. As soon as each cell has reached full SOC it will start to burn off excess charge by electrolysing the water in the electrolyte, which slowly disappears as hydrogen and oxygen. Those cells that reach full SOC early will consume more electrolyte. So the cells will be balanced electrically, but will in the process get imbalanced electrolyte levels - and they must absolutely not run dry.
The cells also self-discharge at slightly different rates, and self-discharge is greatest at high SOC, so leaving the battery at a full SOC causes more imbalance.
We want to keep the battery balanced while also maximizing the time between electrolyte top-ups. Minimizing the number of balancing charges and time spent at high SOC is good. This seems, through an entirely different mechanism, to lead to exactly the same treatment the Roadster wants.
I avoid charging if I can. If I have almost enough charge, I will just charge the needed amount using a timer. When it's down to about 20% SOC, I will let it charge completely to balance the pack (driving at a very low SOC is bad for NiCds). I also use a timer to start the charging as late as possible. An added bonus is that the batteries perform a little better right after charging.
This will easily cut the time spent at high SOC by 90% or more. I gather the Roadster has a built-in timer, which makes it easier.
But this really ought to be implemented in firmware. The necessary input parameters are the range target for the charging session and when the car must be ready. Use of profiles linked to geographical position would make the setting of the parameters very convenient - in most cases all that would be required is a single OK to confirm the profile that was used the last time.�
Mar 4, 2010
ChrisC Fantastic thread! Thanks James for the post you started it with.
These kinds of charging strategies and SOC considerations are going to be common knowledge 10 years from now, just as most people currently know about things like octane numbers, engine knock, choke, blue exhaust, etc. For now, it's just us on the bleeding edge who get to watch this knowledge base accrue�
Mar 5, 2010
malcolm Ok. Here's an idea:
The car could offer the following recharge profiles:
Range/Performance
Standard
Custom 1
Custom 2
Custom 3
Custom 4
Storage
All profiles except Range/Performance and Storage carry out cell balancing after the recharge has finished.
As mentioned earlier, Storage isn't really a recharge mode, you just set it and the car gets on with the job of keeping the battery happy somehow. Cell balancing is redundant(?) for Range/Performance - I'm guessing you can't shift charge between "full" cells.
For a given mode the system displays recharging start and end times; owners choose which one they prefer to set.
The Range/Performance and Standard settings recharge the battery to a non-adjustable charge level. Owners can only set the recharge current and (by default) the "finish charging/cell balancing by XX:XX am/pm". This way, if the car happens to be at a different location, owners don't have to work out a new start time. Also if the time needed for charging/ cell balancing changes as the battery ages(?) this will not be noticed.
Hopefully they can sort out the problem of the car not recognising settings if the charge port is open etc.
Owners can decide if they need the recharge (or recharge/balance) period to end immediately prior to departure (recommended for Range/Performance) or if the end should come just before higher daytime electricity prices start or to coincide with some on-site renewable energy source etc.
The system would need to alert owners if the chosen recharge current is too low to achieve the necessary charge and cell balance within the set time. Owners can then make necessary adjustments.
Since the car remembers recharge settings for a given location it could also have the ability to record the mileage between key locations including those which don't offer recharging. The car could learn your typical mileage and preferred driving style. It knows where you live, it could know where you work and how you get there
The owner may choose to allocate settings for particular regular journeys or just daily or weekend mileage to one of the four Custom profiles.
As before, these allow the owner to set the start or finish time and recharge current. In addition, the charge level can also be set anywhere from 80% to 20% in 5% increments by the owner and (if the profile's auto-optimise setting is on) this could be gradually adjusted by the car using its knowledge of the route, your driving and maybe things like seasons of the year (which would affect average battery temperatures).
Obviously all four of these profiles could be allocated with very similar or very different settings between one or maybe more regular drivers.
It would be useful if the default names could be changed (USB keyboard?) from Custom 1, Custom 2 etc to things like Home2Work, Recharge@Work, FridayNight etc for easy selection.�
Mar 5, 2010
bolosky I tried this and it worked fine last night. I think from now on I'll leave it that way, there's no need to let it sit at full standard mode charge overnight when I'm sleeping.�
Mar 5, 2010
eledille The greatest benefit of an updated firmware with more advanced charging options would be that the car would be able to balance its battery once the range target is reached without bringing it to a high state of charge. Convenience is nice, but as I understand it, balancing cannot currently be done except by completing a full standard mode charge.
I think users should not have to worry about SOC. By telling the software what range you need and when, the car would be able to select the optimal SOC target within those parameters.
Assume for instance that battery deterioration at 20 deg C is lowest at 40% SOC, while at 30 deg C, 30% SOC is better. If the user specifies a needed range of 35 miles, the car is free to select the optimal SOC target. Input the needed range, let Tesla choose SOC target.
The idea of several customizable profiles is good, but there should also be a choice for setting one-off charging parameters, so you don't have to modify one of your profiles to do that.
By linking to geographical position, I was thinking that the car might present a choice between those charging profiles that have been used at that location previously. It probably also knows the time and date, so it might even suggest the correct profile for weekends when plugged in at home on a friday evening.�
Mar 7, 2010
LAB I was in a showroom last week and the current ESTIMATE for a battery replacement is somewhere between $30,000-$40,000. Is this correct? Also, if the battery is reduced in capacity by 60-65%, at least it is still functioning which is not what I was led to believe is the case after 100,000 miles.�
Mar 7, 2010
Palpatine You could lock your battery replacement cost at $12,000 by purchasing the option from Tesla. In reality, the cost will likely drop within 5 years and the real cost will be lower. Or the battery you get in 5 years may actually provide 400-500 miles of range. The technology and the pricing is improving every year.
Most people would be fine with 120 ideal miles of range in standard mode. I know that I am fine with that most days. Within 5 years we will have more recharging options out in the wild.�
Mar 7, 2010
tennis_trs It looks like a previous post had said reduced to (instead of by) 60-65%.�
Mar 9, 2010
LAB If I understood the battery warranty correctly, it does not guaranty a replacement, only a warranty against being defective from year three on to 100,000 miles or 7 years. And I was mistaken in that the battery life is reduced to 60-65% not by as pointed out by tennis trs.�
Mar 9, 2010
ChargeIt! I think you are confusing a $5,000 ESA (Extended Service Agreement) for 3 additional years (years 4-6 if your original Warranty is 3 yrs, or years 5-7 if original warranty is 4 yrs) vis-a-vis the Battery Replacement Agreement ("BRA" :tongue
The BRA actually does guarantee a replacement battery between years 3 (or 4) and 10. If after 7 yrs it's the pre-paid $12k; if earlier it's an additional $2k/yr; if later it earns a $1k refund/yr.
One sentence in the BRA that worries me a little is
What locality requires this ? And how much is that additional expense going to run ?
Also, what happens if your Roadster is totaled and you choose not to repair/replace it ? Refund ? (If you choose to replace it (like Ian) is the BRA transferable ? If you choose to replace with a Model S .... )�
Mar 9, 2010
vfx This is pretty important.
�
Nov 4, 2011
daniel My reading of the "additional cost" for a "replaced battery" means that when they replace your battery, they get to keep the old one. If you insist on keeping the old one and the law is on your side, then you pay them for the old battery which you are keeping. IOW, the $12,000 BRA includes the provision that the old battery belongs to them.
Just my reading. I am not a lawyer.
The long quote in the OP says that "most" of the benefit of storing the pack with less than a full charge is realized at 87%. I read this to mean that there is little benefit from storing it at a lower SoC.
As far as degradation time, I think it will take me 20 years to put 100,000 miles on my Roadster. That's 5,000 miles a year, which is typical for me. I expect this car to have more than enough range for my needs until I am too old and arthritic to be able to get in and out of it. At that time I'll trade it in for a Model S, or whatever.�
Nov 4, 2011
Robert.Boston I'm thinking that all these old batteries will be mighty valuable, ganged together, as a grid-level storage device. Degradation won't matter, as long as the operator knows what the usable level is.�
Nov 5, 2011
daniel At grid level the total number of available used EV batteries will probably be insignificant for a very long time. But in a home-based PV system that is not grid tied, where weight is not an issue, and size is much less of an issue than in a car, a used EV battery with 50% of its original capacity will definitely have value. And even for recycling, dead batteries may have some value.�
Nov 5, 2011
JRP3 Even without solar a used pack could make a nice house sized UPS for emergencies, and maybe even take advantage of dual rate metering for time shifting. Charge the pack at a cheaper night rate and then use that energy during the higher day rate, or allow the smart grid to tap it for load leveling for a fee, at some point. Lots of possibilities. The LiCo cells that Tesla uses have the highest recycling value at this point of any of the Li chemistries.�
Nov 5, 2011
surfingslovak Interesting, I wonder if this was perhaps due to the high cost of cobalt. Be it as it may, I wanted to direct your attention to Tom Moloughney's blog. Tom is one of the MINI-E pioneers and he posted a very thoughtful comment on the plugincars.com article about battery care a fellow Leaf owner wrote couple of months ago.
Tom leased his MINI-E as part of a field trial by BMW and since there was no mileage limit, he subsequently proceeded to drive the car into the ground. His battery pack is based on 5,088 laptop-format cells manufactured by Molicel in 2008. Tom reportedly charged his MINI on average twice a day through its 12 kW onboard charger. And he charged it to full whenever possible. Based on the ratio of usable to rated capacity, a full charge likely corresponded to about 88% of true pack capacity, which is comparable to standard mode in the Roadster.
Given what we know about lithium-ion batteries, Tom should see about 6-10% reduction in battery capacity after 27 months and 50K miles. Well, the surprising thing is that there is hardly any degradation at all. Tom is not able to measure battery capacity directly, but he keeps track of the ideal range predicted by the car. Based on this data, he claims to be experiencing about 2% range reduction, which is surprising to say the least.
The reason I'm bringing this up is simple. I like the err on the side of caution and the battery care guide from Dan Myggen posted earlier in this thread helped me to understand how to treat the battery conservatively. Admittedly, Tom's experience with the MINI is a bit extreme, but it gives me the confidence that the lithium-ion pack in my car has the capacity to perform well beyond my expectations.
How is this relevant to this thread? If Tesla recommends to routinely charge the car in standard mode, they will base their battery life estimates on that. They will likely be conservative, which means that there is a good chance that we will see better results in the real-world. And if you treat the pack conservatively, you could improve upon that further. The question is then, do you really need to do that or would you be satisfied with the longevity you are getting by following the standard charging protocol.�
Nov 5, 2011
JRP3 Basically. The lithium isn't worth recovering at this point as far as I know, nor is the aluminum, which are sold as slag, but the copper and cobalt are. (To be clear the lithium and aluminum are not disposed of, they are just not extracted from the slag as distinct elements. The slag does have industrial uses.)Agree. If you just follow the standard recommendations I think you'll do better than expected anyway in most cases.�
Aug 3, 2014
marco2228 Does anyone know, to what the Roadster is being discharged in:
a) Standart mode
b) Range mode
and at what current these voltages are measured?
I know I read it somewhere bud don't find it anymore.�
Aug 3, 2014
djp Depends on how hard you punch the accelerator. Resting pack voltage is 412V in Range mode and 403V in Standard mode.�
Aug 3, 2014
marco2228 I think the voltages you mentioned are the resting voltages after charging the car?
What I am looking for are the low cutoff voltages after the discharge�
Aug 3, 2014
dhrivnak I believe they use a Coulmb counter (a measure of current) and standard mode draws you down to 13% where range mode drops you to 0. Note I think there is still about 5% in the batteries but that is locked out to reduce the chance of bricking.
Voltage is not a good measure of the state of charge in Lithium batteries.�
Aug 3, 2014
marco2228 Ok, I am not sure about coulomb counting. Sure, it makes sense as it's counting the energy, that is being charged into or discharged from the battery. But how do you take aging into account? I think there has to be defined high and low cutoff voltage.
I am asking because I charged my ESS with an external Brusa charger when I had it out of the car. Now as it's back in the car, the car is confused because it doesn't know about the external charge.
I drove approx. 500 km since then, but still have a max. range of 255 km and a CAC of around 151. That doesn't fit.�
Aug 3, 2014
djp I think the min is around 3.6V, but I've never been down to zero. The CAC is fixed regardless of SOC. Try charging with the onboard charger to see if that resets the range estimate.�
Aug 3, 2014
JRP3 They certainly do use voltage for max and min SOC. Plus LiCo has a steeper charge/discharge curve where voltage more accurately reflects SOC than some other lithium chemistry.�
Aug 3, 2014
slcasner I don't have information about the absolute SoC when discharged, but I wanted to know the relationship between the displayed SoC in Standard mode vs Range mode. Since in my normal driving I manually record the Standard mode SoC as observed on the VDS into Tom Saxton's EV Logger, I plotted those data points (Y) against the full-scale (Range mode) SoC as recorded in my collection of log files downloaded from the car (X). For my car at least, I find that 0% Standard corresponds to 10% Range and 100% Standard corresponds to 87.5% Range. I believe the points far from the line in this graph are the result of manual data entry errors that I did not chase down.
�
Jan 1, 2015
sethr I always plug in and do a Standard charge on getting home for the day, and let it do a charge the next day even if I'm not driving that day. It's what Tesla says to do... Do you not plug in, or do you plug in and immediately hit "stop charging" (while the port light is still pulsing blue)? I guess my other question is whether there such a thing as cycles that are TOO shallow. TIA, and Happy New Year to all!�
Jan 1, 2015
djp I plug in once or twice a week, and will stop charging around 50% if I'm not doing a long drive the next day. My commute is only a few miles, so it usually takes a week to drop to 35%.
Tesla recommends plugging in nightly to avoid bricking the battery. There's a real risk of destroying the Roadster pack if you let the charge drop to zero. The Model S does a better job of protecting the pack by disconnecting all systems when the charge drops too far.
There is no cycle too shallow, and the battery degrades more slowly at lower SOC and in cool temperatures. It's a marginal difference on the Roadster though, Tom Saxton's battery study shows that mileage is the biggest factor in battery degradation. The pack can also become unbalanced if it doesn't spend time in Standard mode, you're fine charging nightly.
With the higher capacity 3.0 pack there's less of a need for a full charge, so I'd prefer a Model S style charge slider to maximize battery life. If I buy the upgrade I expect it'll be my Roadster's last pack - the longer life I can get out of it the better.�
Jan 1, 2015
spaceballs There is no such thing as too shallow for DOD.
My only thoughts is the wear on the mechanical relay contacts, and charging port/cable contact wear though if you do charge it often.�
Jan 1, 2015
wiztecy I also follow the same SOC habits djp has adopted and always target 50% SOC:
My case is a little different since my Roadster is my daily commuter for a 70 mile round trip. From Friday evening to Monday morning the Roadster is around 50-60% SOC from my last commute run. Monday morning I start the charge 3-4 hours before I leave on my 220/30amp MC240 so that its ready 30 minutes to 1 hour before I leave work. That gives ample time to balance with my standard mode charge.
Driving to work my SOC drops from 82-84% down to about 72-75%, where it sits away from the sun or any direct heat while I work.
Then 8 hours has elapsed and I head on home, when I arrive home from my 35 mile trip back the SOC is now around 60-65% and a little lower if I had to do some errands/etc. If the ESS temp is greater than 26C, I initiate a cool-down on the ESS until it drops to 26C or lower, then shut down the cool-down. With that I don't want to pump a charge really in the pack unless I need it since I'm above 50%SOC, if I'm below 50%SOC I'll pump in some charge.
After that, the whole cycle starts again where the Roadster is ready to start charging 4-5 hours before I leave. If its Friday evening from my return home from work (don't work weekends), I initiate the cool-down if needed. And then removed the charge plug. That way the SOC stays around 50-60% over the weekend, and then put the charger plug back on Sunday night. If I had a larger pack I'd probably do a standard mode every 2 days then and still keep the SOC close to 50%.
Just plugging the Roadster in and allowing it to charge in standard mode is easier for some people. Managing the SOC like djp and I do, it's a little bit more work. But after you get into the habit its not all that bad. However adopting this habit does limit wear on the mechanical parts of the system like the contactors. Spaceballs is correct about adding more wear to the contactor and other parts. For myself I save 2 days / week of the contactor/system being used, for djp he saves about 5 days / week of wear.�
Jan 1, 2015
tomsax OVMS Advanced Charge Control
OVMS offers many of the advanced charge control options requested by various posts on this thread. You can set a desired end time and charge level, as well as ask for a cooldown charge that uses minimal energy to cool a hot battery battery pack.
OVMS doesn't change what the firmware does, it just does the equivalent of entering custom settings on the touch screen and then starting the charge. So, if you set an SOC limit, you'll miss out on end-of-charge balancing. For this reason, I don't recommend using the SOC limit; I personally prefer allowing Standard mode to run to completion.
You can set these advanced charge options for up to four locations.
I have our Roadster configured so that when I plug in at home it:
The actual charge end time can vary by 30 minutes, plus the charge time predictor that determines the start time is only an approximation and subject to variation based on starting pack temperature, ambient temperature, air circulation, etc. So, I recommend setting the end timer at least 30 minutes before you need the car.
- Immediately cools the pack down to 80� F, if needed.
- Charges in Standard mode at 32A, timed to complete around 7 a.m.
Using the charge end time setting is also nicer to the grid, since it will distribute both the start time and end time of the charge, which is much nicer than having a bunch of EVs all start charging right on the dot of midnight, 1 am, 2 am, etc.�
Jan 3, 2015
dsm363 If the car is just used on weekends is the recommendation still to charge in standard mode?�
Jan 3, 2015
djp Standard mode daily is fine, but if you want to be OCD about battery life you could plug in on Friday and Saturday nights only. The pack is better off siting at a lower SOC during the week, and it won't lose enough charge over five days to damage the battery (unless you run it down right to zero on Sunday).�
Jan 3, 2015
wiztecy I presume you mean keeping it plugged in to charge in standard mode every day?
If that was my driving habit, I'd try to keep it around 60-65% SOC when your done driving it after a cool-down (if needed) come Sunday night. Keep in mind the pump and the Roadster will drain some of the ESS for monitoring / pump necessities. Then monitor your SOC throughout the week to ensure it falls between 50-60% come Friday night/Saturday morning (4-5 hours before you need it) when it'll begin to charge for your Saturday's use. I would plug it in again Saturday night if you plan on driving hard, punching it and aggressively or if you're using the pack for longer drives / pulling the pack down below 50%. If you're only doing short drives and easy on the accelerator, no need to plug it in. Again monitor if you need a cool-down. Then on Sunday night, if the ESS is higher than 65% SOC, that's fine and no need to plug the Roadster in. If below 50% I'd put enough charge into the ESS to bring it up to 60% so I'll settle in around 50% come Friday. Note that in the summer your pump will be working more, so be aware of that and you will have to monitor your SOC to ensure you're still falling into the 50% SOC range come Friday.
I'm doing the same thing right now over the New-Years vacation, almost the same duration unplugged, 4 days. I last used the Roadster Wed. evening, didn't need a cool-down since we have the arctic cold in California now and it was left at around 57% SOC. I just checked now, Sat and its around 53%.
Do whatever works for you. Keep in mind that when temps drop, such as in the winter, the battery cells don't get as stressed as much as they do in the summer when sitting. Summer is the time where adopting this habit really helps them out.�
Jan 6, 2015
sethr wondering about balancing behavior
So, I did not plug in and charge to standard immediately after driving for a few days, and let my SOC go down. Took one more trip, leaving at 50% SOC, and I ended up arriving home with a bit less than 30% (45 ideal miles - found out that the battery bar changes from green to yellow, a fact that is nowhere in the manuals). I charged to standard charge at my usual leisurely 24 amps, and was surprised to see the ideal miles ending up at 198! Looking at the info screens, I noted that the battery was balanced after less than 15 minutes. It wasn't for about another hour before the ideal miles dropped, to 186. It then stayed there for at least a few hours, at which point I went to sleep. In the morning it was down to 184, but that part's typical. I am just wondering - is the pack really balanced when the grid is all 0's? Or is this some sort of recalculation of ideal miles, in which case I wonder why it takes so long? Any thoughts? TIA�
Jan 6, 2015
wiztecy Yes, its balanced to the exactness of what the grid represents which means its good to drive and battery is in good care. However a grid with 0's & 1's does not show the precision of balance in mV. On my Zero motorcycle in their supplied application I can see the deviation in mV the bricks are out balance from one another, and that's more precise. But for what we have for feedback 0's & 1's are better than nothing.
The miles get recalculated as the pack balances, as long as you don't turn the key on after the standard mode or better charge is completed. Out of the 3 packs I've had experience with, each one had their own unique behavior with balancing, ideal miles calculation and CAC. My 1st pack would charge up to 198-200 ideal miles in standard, but then settle in to the mid 180's, my second pack that replaced the 1st only charged up to 168 miles, when it stopped it just settled in to 165 miles. Since that pack never reached full capacity in CACs it replaced I then had a 3rd pack. That one currently charges up to 187 ideal miles, and settles in to about 179-182. The latter pack has the best CAC out of them all, but a lower ideal miles result (even after doing the recalculation) compared to the 1st pack. I'd rather have a higher CAC than ideal miles so I'm fine with that. It also goes up and down some, I went down as low as 152.15 CAC, currently at 153.20, and hit has reached as high as 160.
And yes, I've seen the ideal miles drop some after the balancing was fully completed and all 0's. As for how long it takes to balance, it all depends the state of your bricks and how out of balance they are. They do go through changes. The latest pack I have goes through many changes, its very sensitive if I charge 2+ times without allowing it to fully balance. That appears to throw a couple bricks off and it'll take a minimum of 2 hours to balance, sometimes a few days of balancing for 3+ hours each day. But when its fully balance it takes 15 mins tops to complete.�
Jan 6, 2015
heychubs This might be a silly question, but does the amperage matter when charging, if you wanted to maximize the life of the battery? Does trickle charging it with the spare mobile connector (15A) work better to extend the life, than using the 30A UMC? My commute to/from work is about 70 miles a day. If I plug in as soon as I get home from work with the spare mobile connector, I will have a full standard charge in about 14 hours. That works out perfectly for me. Just wondering if that is better than 30/40A charging.�
Jan 6, 2015
tomsax Even charging at 240V/70A (16.8 kW) is very nice to the Roadster's battery. To gauge the level of charge, divide your charge rate (in kW) by the pack size (in kWh). This is the "C" value for the charge rate. For lithium ion, staying below 1C is considered good for battery longevity. 16.8/55 = 0.3C. That's already so far below 1C that it's not clear there's a measurable benefit for lower charging levels.
Martin Eberhard says Tesla chose to stay below 0.5C for the Roadster.
A Bit About Batteries | Blog | Tesla Motors
By comparison, Supercharging an 85 kWh Model S at 135 kW is 1.59C.
Still, I like slow charging the Roadster because it's nicer to the grid and maybe a tiny bit nicer to the battery pack. For the Roadster, higher charging rates are more efficient. I charge at 32A because that's the slowest I can charge without giving up efficiency, and it's still much faster than I typically need to get a full charge overnight.
Tesla Roadster Charging Rates and Efficiency - Tom Saxton's Blog
Charging at 120V is not only much less energy efficient, it causes the coolant pump to run much more than with faster charging rates. There's anecdotal evidence to suggest that owners who normally charge at 120V go through coolant pumps pretty frequently, like 3 replacements in 5 years. Our coolant pump died after just over 5 years and 42,000 miles with most of our charging done at 238V/32A.
Having Tesla replace the coolant pump costs $400 for the pump and $300 for labor. You can buy the pump online for $100 (Bosch PCA 12V Part number 0 392 022 002), but I wouldn't let anyone but a Roadster service tech do the swap because you have to bleed the air bubbles out of the coolant lines. It's not difficult to do, but Chris at the local garage probably isn't going to know how to do it. I don't know if Tesla will install a pump that you bring in yourself, but if you happen to know a former Roadster service tech...
The connector to the pump can go bad after years of use. I think I have the part number for that. I'll post that, too, once I've confirmed it. It's an inexpensive fuel injection connector, $12.50 on Amazon, but I'm sure Tesla will sell you one for much more.�
Jan 6, 2015
heychubs Thanks for the info Tom. Both blogs were interesting reads. I never even thought about the excess cooling the ESS needed when slow charging... I guess I'll use the higher amperage charging option as much as possible.�
Jan 7, 2015
GVTesla What heychubs says: thanks for the info Tom!
I can acknowledge that out pump still lasts after approx. 40K miles, with all charging being done at 230V/10-32A (usually 13, fair amount 16 and some occasional 32A when i need fast recharge).
As for 'overhead', I noticed some overhead too depending on the Amperage. When charging at 230/13A I gain some 14 KM per hour. At 32A this is close to 40KM/hour which is slightly better.�
Jan 7, 2015
Chris Lockfort Tesla Roadster Charging Rates and Efficiency - Tom Saxton's Blog�
Jan 7, 2015
pharma5 Higher voltage/amperage charging is def better - not just based on all the excellent efficiency info from Tom, but also for temperature management of the pack (apologies for any redundant info below...).
When using 120V 15amp or lower, the system will allow pack temp to float higher, up to 40 degC, until it gets near completion of charging. At that point the compressor and front fans kick on, bringing the pack temp down to eventually settle a full charge at 25 degC. In contrast, the compressor and fans stay involved and hold the temp lower the whole way when the extra volts/amps are there.
This is pretty invisible in the winter, but a hassle in summer (esp in a garage). Having lived with trickle charging for 3 yrs, it works but I wouldn't recommend it over using more juice.
- - - Updated - - -
Thus far pump still intact (knock wood).:frown:�
Jan 8, 2015
GVTesla Excellent blog, thx for sharing the link.�
Jan 11, 2015
Volta So, here is my general charging routine, as a relative newbie. I drive to/from work each day, a 70 kms (44 mile) round trip. I charge using a normal 13A plug, dialed down to 10A, overnight at home. Charging from around 10 PM to 7 PM puts back in the 70 kms I used the day before.
So, I charge overnight to around 70%, drive 35 kms to the office, at which time the battery is around 55%. The car is then parked in secure underground parking from around 8 AM to 8 PM standing at 55%. By the I time get home, the battery level is around 40%. I plug in after dinner, and the car charges back from 40% to around 70%, ready for the next day's trip.
I don't use the car at the weekends, so on Friday night through Sunday night, I leave the car at 40% (she seems to lose next to no charge sitting for 2 days), then charge Sunday night for Monday morning, per the above.
So, the car is never charged above 70% or below 40%, and mainly sits at 55%.
It seems ok, but is there something I should perhaps do differently, assuming I have no other charging options?
I had a couple of thoughts:
1. Should I instead charge up to 80%, let the car sit at work at around 65%, never going below 50%? Just a little concerned that I have seen a couple of people suggest on this site that you shouldn't push it when the battery charge is below 50%. I may perhaps do that on the run home :biggrin:. Sometimes. But is letting the car sit for 12 hours at 65% worse than letting her sit at 55%?
2. I tend to unplug the car in the morning, when she is at 70%, and drive straight off. Should I unplug an hour earlier to allow for balancing? Or does that only happen if you fully charge the car?
3. Is it good for the battery for it to be balanced from time to time? If so, how is it best to do this - fully charge the car from time to time? I could do that at the weekend, quite easily, if it is better for the car. Does the car need to be fully charged for balancing to take place, or will this automatically happen from time to time?
As you can see from these questions, I still have much to learn. So, apologies in advance for my uninformed questions. I stand ready to be enlightened.
Thanks, in advance.
Volta�
Jan 11, 2015
djp @Volta, can you run a 240V circuit to your charging location? As mentioned above, charging at 120V is less efficient and lets the battery reach higher temperatures, which isn't ideal for longevity of the cells. (Edit: sorry I didn't realize you're in Hong Kong and already at 220V - you're fine)
Your charge range is fine. Punching the accelerator at extreme low SOC stresses the battery by drawing more current than at high SOC, but I wouldn't worry about the 40-50% range. The car will limit power when the SOC gets close to zero to protect the battery.
Balancing only happens at a Standard charge or higher. I'd run a balancing cycle about once a month or so. Being unbalanced isn't necessarily a bad thing, but you won't be able to access the full potential capacity of the pack when you need it. Also the longer it drifts out of balance the longer it'll take to bring back into balance.�
Jan 11, 2015
dhrivnak I encourage everyone to add or update your numbers in the Tesla Owners battery study. Now that we are getting some range it would be nice to collect some updated results. Plug In America
Thank you�
Jan 11, 2015
hcsharp I would do this (charge to 80%) for two reasons that are beneficial to your battery. Many people like to talk about how it's better to keep your battery around 50% or so for longevity but they fail to realize that an EV stays cooler when running at a higher state of charge. Keeping your battery cooler is more important than resting SOC unless you leave it resting for several days. The other reason is that it's important to keep your battery balanced, which it won't do very well at 70% SOC. You should charge to 80% (full std mode) and let it sit for an hour before leaving for work. It won't balance if you're charging and just unplug and go.
Letting it go unbalanced for a few days is no big deal. But if you are driving/charging with some cells lower than the others, those cells could potentially wear out at a different pace than the rest of the pack. There's a reason Tesla recommends a full std mode charge every day unless you don't plan to drive it for a week or so.�
Jan 12, 2015
Volta djp/hcsharp: thank you both for your guidance. Very helpful. I can certainly charge my Roadster up to 100% standard (80% full), and then run to down to 85%, where it will stand for 12 hours whilst I work, and run it down to 70% by the time I get home. Charge up to 100% overnight, unplug around 6:20 AM and set off for work again at 7:20 AM. Glad I asked!
Ta.
Volta.�
Jan 14, 2015
Volta So, quick question. To get the benefit of balancing, do I need to hit the 'top off' button and fill her to the very brim (well, the standard mode brim) before unplugging and letting her rest for an hour before driving off? I didn't do so this morning, when the charge indictor showed that charging had stopped overnight (because then I wouldn't have had the hour between unplugging and driving), but if I need to I can do at the weekend, and will generally do that each weekend.
Or, put another way: "to top off or not top off, that is the question ..."
Appreciate any further guidance you can give, hcsharp (or indeed anyone), on this.
Best.
Volta.
�
Jan 14, 2015
djp No need to top off, the balancing program starts as soon as the Standard charge completes. Just set it for a Standard charge, leave it plugged in, and let it rest for a few hours after the charge completes. If you want to run multiple balancing cycles over the weekend you can restart the charge (or top off) to kick off another cycle.�
Jan 14, 2015
Volta Thanks so much, djp. Most helpful. So, am I right to understand, from what you say, that I don't need to physically unplug? Once the charge cycle stops because the pack is full, the pack will automatically start to rebalance even if left plugged in, and that might take a few hours?
Volta.
�
Jan 14, 2015
djp Correct, the balancing happens as soon as the charge cycle finishes - no need to unplug or hit "top off". If the pack is balanced the rebalancing could finish in as little as 15 minutes. If it's out of balance, it could take several rebalance cycles of a few hours each to bring it back into balance. I'd let it sit over the weekend in Standard mode, and restart the charge a few times over the weekend to kick off new cycles.�
Jan 14, 2015
Volta Again, thanks so much djp. How will I know when the pack is balanced? Do I need to check the log, or is there a visible/audible sign which will make me go 'a-hah: the pack is now balanced!'
Volta.
�
Jan 14, 2015
djp Unfortunately there's no easy way without going into the service diagnostics menus.�
Jan 14, 2015
ecarfan IMO, you really don't need to concern yourself with that question. The car will take of itself. Just leave it plugged in, if possible, when you aren't driving it.�
Jan 14, 2015
Volta Thanks both, and understood. I shall do as you suggest - and shan't worry; but instead simply enjoy what must be THE most fantastic car in the world to drive ...
Thanks again.
Volta.�
Jan 19, 2015
wycolo > You can buy the pump online for $100 (Bosch PCA 12V Part number 0 392 022 002), but I wouldn't let anyone but a Roadster service tech do the swap because you have to bleed the air bubbles out of the coolant lines. It's not difficult to do, [tomsax]
You could series in an elevated hose loop maybe with a reservoir* at the top. Then do an overnight 120v charge. By next day all the air should be in the reservoir.
*reservoir from manual vacuum kit, used for brake bleeding etc - among several choices (no home should be without one):
Amazon.com: Brake Bleeder and Vacuum Pump Kit: Everything Else
--�
Jan 19, 2015
wiztecy How did Marco & Jerry do it? They've been there, done that�
Jan 19, 2015
spaceballs If you watch the How it's made on installing the ESS and Motor for the roadster, you see they use a cooling system vacuum purge to remove the air bubbles in coolant lines. It's a common tool used for removing air bubble in cars, most all mechanic shops should have this tool.
Amazon.com: ATD Tools 3306 Cooling System Vacuum Purge and Refill Kit: Automotive
If someone need to borrow one let me know.�
Jan 20, 2015
dhrivnak Please remember to add or update your data in the Roadster Owner Battery life study. It is our best chance to glean how batteries are holding up. Plug In America�
Feb 7, 2015
gregd So let me extend this thread a bit, and discuss an "inverted" battery management scheme. I think this is OK, but want to check.
The normal / recommended charge mangement scheme is to plug the car in when you get home, and leave it there until you drive off to work in the morning. Repeat each night. Simple.
My employer, however, gives us 4hrs of free Level 2 charging each day, and my 50 mile round trip can be replenished in about 3hrs. So for me, it's ideal (most cost effective) to plug the car in when I get to work, move it to a non-EV parking slot after the charge is complete (to give access to others), and NOT plug it in at home each night or on weekends unless I need the extra charge for weekend activities.
So the car will spend most of its time sitting in the garage at home, unplugged, at about 60% SOC. This includes sitting for several days, across weekends and days when I take the ICE to work (e.g. bad weather).
Is this ok? The car is a 2010 2.0 (#834). I'm the car's second owner, but from what I understand, the ESS is original to the car, and has about 29k miles on it. A standard mode charge shows about 170 miles ideal range; CAC is 142 according to the logs.�
Feb 7, 2015
ecarfan I see nothing wrong with your "inverted" battery management approach. Keeping the Roadster battery at around 60% SOC most of the time is fine.�
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