djp
Model 3 Performance
Depends on how hard you punch the accelerator. Resting pack voltage is 412V in Range mode and 403V in Standard mode.
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Depends on how hard you punch the accelerator. Resting pack voltage is 412V in Range mode and 403V in Standard mode.
dhrivnak
Active Member
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.
Voltage is not a good measure of the state of charge in Lithium batteries.
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.
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.
djp
Model 3 Performance
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.
JRP3
Hyperactive Member
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.
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.
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!
djp
Model 3 Performance
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.
spaceballs
Member
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.
wiztecy
Active Member
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.
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tomsax
Member
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:
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.
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:
- 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.
djp
Model 3 Performance
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).
wiztecy
Active Member
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.
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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
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
wiztecy
Active Member
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.
heychubs
Member
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.
tomsax
Member
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.
heychubs
Member
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.
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