You might consider charging slower

[dennis]

Yes, I believe that has always been the assumption. And that means a 'full' range charge which means going ON for a few minutes then OFF, over and over until finally all segments of the pack are equal.

1) What do you mean by a 'full' range charge? Is it as simple as setting the charge limit all the way to the right and then plugging in? Or does the last part of the charge need to be done at low amps in order to balance the pack?

2) Is a single 'full' range charge once per 30 or 60 days good enough to keep the pack balanced? Or do you need multiple range charges on successive days for a week or so to fully restore the pack to its maximum capacity as I read elsewhere on TMC?

 

[Puyallup Bill]

Is balancing only done when you range charge?

I doubt it. The following is a lift from a Tesla engineer(?) discussing the Roadster battery, and it would seem to me to be applicable to the MS as well.

Just remember that the car does benefit from being allowed to sit fully charged in Standard mode, and should be allowed to do so frequently, especially if being used on a daily basis. Leaving the car plugged in in Standard mode after it is done charging will initiate this balancing program automatically. This doesn’t take much time, 30 minutes or so should do. It may take several of these balancing cycles to bring the car back to a balanced state if it has become imbalanced, which is something that a lack of regular Standard mode top ups and subsequent balancing cycles can induce.

The full text is at: http://www.teslamotorsclub.com/showthread.php/3848-Tesla-Roadster-Battery-Care

 

[liuping]

I doubt it. The following is a lift from a Tesla engineer(?) discussing the Roadster battery, and it would seem to me to be applicable to the MS as well.

Just remember that the car does benefit from being allowed to sit fully charged in Standard mode, and should be allowed to do so frequently, especially if being used on a daily basis. Leaving the car plugged in in Standard mode after it is done charging will initiate this balancing program automatically. This doesn’t take much time, 30 minutes or so should do. It may take several of these balancing cycles to bring the car back to a balanced state if it has become imbalanced, which is something that a lack of regular Standard mode top ups and subsequent balancing cycles can induce.

The full text is at: http://www.teslamotorsclub.com/showthread.php/3848-Tesla-Roadster-Battery-Care

I'm not really sure what they mean by "a lack of regular Standard mode top ups and subsequent balancing cycles can induce."

Does that mean if I only charge to 70% daily it will not run the balancing program regularly?

 

[jerry33]

Does that mean if I only charge to 70% daily it will not run the balancing program regularly?

Hard to say. There is, unfortunately, no indication of when balancing is taking place.

Bear in mind that there is driving as well as charging. My understanding is that it's better for the battery to drive between 90% and 50%. So it's possible that charging to 50% and driving may be worse than charging to 90% and driving.

 

[montgom626]

The Chevy Volt has a "charge based on departure time" feature. I really like it, and it is near the top of my list for desired software upgrades for the Model S.

GSP

Chevy did some great work on the Volt.

 

[djp]

IMO, balancing is overrated. A properly balanced battery will give you a slightly higher range on a full charge, which might make people feel better by seeing a high number on their screen, but doing regular max charges for the sole purpose of balancing does real damage to the battery for a purely optical benefit.

For example, the 40kWh models never get top end balanced since they're limited to 66% of a 60kWh battery. The balancing doesn't matter since the top 33% never gets used.

A battery that is out of balance isn't permanently degraded, a couple of 90% or 100% charges will bring it back to its full potential. I'd avoid doing max charges just for the sake of balancing and let the battery balance on its own whenever you do a full charge for a longer trip.

 

[liuping]

Hard to say. There is, unfortunately, no indication of when balancing is taking place.

Bear in mind that there is driving as well as charging. My understanding is that it's better for the battery to drive between 90% and 50%. So it's possible that charging to 50% and driving may be worse than charging to 90% and driving.

I plan on charging to 70% during the week, which would put me just below 50% at the end of the day most days and rarely below 40% even if I have to run errands, etc.

There is a lot of conflicting info on what is really best for the batteries, but staying as close to middle as possible seems to be one of the consistent bits as far as I can tell.

 

[AmpedRealtor]

> Is balancing only done when you range charge? [liuping]

Yes, I believe that has always been the assumption. And that means a 'full' range charge which means going ON for a few minutes then OFF, over and over until finally all segments of the pack are equal. Quite a ruckus just before a long trip if the contactor is clunking away under your bedroom while you are still trying to sleep. :frown:

I don't think TM Ownership is going to sway R & MS owners *not* to range charge on some kind of regular basis; this would be for Engineering to do. Keeping a balanced battery is rather basic. My R gets charged only every few weeks and I finally did a full range charge. Might have been the only one it ever got (over 7k miles on clock). Result was 235 miles, whew, which is very good. I plan to do full range charges every 60 days on the MS if long trips don't require this beforehand. Staying around 50% SOC is fine, but doing balancing is a separate requirement.
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Your advice is dangerous and contrary to Tesla's recommendations. Max charging reduces the long term life of your battery. Tesla has never said that the battery requires "balancing" and that max charging accomplishes that. Can you please cite a source for this information?

Yes, I believe that has always been the assumption.

You just spent around $100,000 on a car with brand new technology. The most expensive item in your car is the battery. Why in heavens name would you base your charging habits on assumption rather than facts and recommendations provided by Tesla? Nothing that you say about "balancing" the battery is supported by facts or anything that was actually stated by Tesla.

When you make a recommendation to someone here, shouldn't it be based on facts rather than assumption?

 

[MarkR]

I am, perhaps, naïveté. I gotta think that the Tesla engineers want to do everything they can to extend the life of the battery and maximize the number of miles that we can drive on a charge. I REALLY like the idea of having a "charge by xx:00" option that enhances the functionality and life of the battery. I have faith that we'll get the software options we want in due time because its in everyone's best interests.

 

[ModelS1079]

Okay Jerry33, I have been relying on you for tech advice for over a year, and I give you the final word- what is the best way to charge our batteries. Full standard charge or mid range somewhere? Full speed at 40A etc, or more slowly? Rebalance yes no hogwash absolutely? Marianne, or Ginger?

 

[jerry33]

Okay Jerry33, I have been relying on you for tech advice for over a year, and I give you the final word- what is the best way to charge our batteries. Full standard charge or mid range somewhere? Full speed at 40A etc, or more slowly? Rebalance yes no hogwash absolutely? Marianne, or Ginger?

I don't pretend to be an expert on batteries. However, hcsharp is, and he's written the best explanation I've seen. Post #16.

I charge at 32 amps normally. This has more to do with being easy on the grid, UMC, and house wiring than it does with the car.

I don't believe rebalancing needs to be done very often. My opinion is that most of the variations seen to date are due to software changes, not battery degradation (other than perhaps a few outlier cases). Measuring SOC is not an exact science--there is a lot of estimation done. What's known about rebalancing and reduced amp charging comes from the Roadster. We're making assumptions that the Model S will work like the Roadster in this regard. It probably does, but we just don't know and won't know for awhile.

Marianne. I think Ginger would get on your nerves after a short time. However, as Bad Billy Pratt says, "I wouldn't mind eating a whole chocolate cake once in a while."

 

[stopcrazypp]

I doubt it. The following is a lift from a Tesla engineer(?) discussing the Roadster battery, and it would seem to me to be applicable to the MS as well.

The evidence so far seems to show that the MS does not do the same kind of balancing the Roadster does in Standard mode. The only way that reliably forces the Model S to do balancing is extremely slow charging in Range mode (or 100% equivalent). Here's how you know balancing is happening (adjust range number as appropriate to match you pack):

Interesting observations during the full range charge using 110v:

- the car topped off showing 199mi

- the car's charge port ring stopped blinking/pulsing when it reached 199mi but the car proceeded to continue to charge for over an hour. I presume the battery balancing was occurring during this time.

I agree with djp though. The battery does not have to be balanced regularly. The only benefit that carries is the psychological one of seeing slightly higher numbers on the screen. I have only recommended it when people are wringing their hands over "losing" a couple miles of range recently (it gives them the peace of mind they needed).

 

[Dreamin]

The Leaf also has a finish by X setting. An algorithm shouldn't be particularly hard.

1. The driver sets minimum start time (for TOU), stop time, ideal SOC, and ideal amps.

2. The car starts charging at the minimum start time and calculates when the finish will happen based on ideal amps and ideal SOC.

3. If the calculation in #2 is prior to the stop time, ideal amps are reduced (or increased if it appears that it won't finish in time).

4. At regular intervals the car checks the SOC and remaining time and adjusts the amps as required.

5. Car stops charging at the stop time.

FWIW, I've normally charged at less than the maximum--more to prevent overheating of the UMC than anything else. After the recent discussion about cell equalization, I reduced that to 16 amps. I'll see how it goes.

Jerry, what thread were you referring to here?

 

[yobigd20]

IMO, balancing is overrated. A properly balanced battery will give you a slightly higher range on a full charge, which might make people feel better by seeing a high number on their screen, but doing regular max charges for the sole purpose of balancing does real damage to the battery for a purely optical benefit.

THIS.

For example, the 40kWh models never get top end balanced since they're limited to 66% of a 60kWh battery. The balancing doesn't matter since the top 33% never gets used.

very good point.

A battery that is out of balance isn't permanently degraded, a couple of 90% or 100% charges will bring it back to its full potential. I'd avoid doing max charges just for the sake of balancing and let the battery balance on its own whenever you do a full charge for a longer trip.

I second this.

 

[bob_p]

Tesla's official position is that charging to 100% (maximum range) infrequently or other charging habits (as long the battery doesn't become discharged) should have little long-term impact on the battery life and capacity. Their recommendation continues to be to have the car plugged in, when possible.

They have yet to officially indicate why the variable charging feature was added - and how they recommend it should be used.

For the vast majority of Tesla owners, following Tesla's simple instructions is probably the best strategy - and if Tesla determines that a change in charging practice should be adopted for owners, they'll provide us something in writing and/or make a change to the car's onboard software to help owners implement a different charging practice.

That doesn't mean that the strategy recommended by some owners to charge to 50% or to use lower charging rates may not help - but only Tesla really knows the real impact of those practices on the battery pack - and hopefully by tracking how we are all charging our cars, they'll learn what practices work best.

I've already got 16K miles on my Model S - and if I continue driving at this rate - I'll have a much better idea in the next year of how charging to 90% and leaving the car plugged most of the time - impacts range.

 

[yobigd20]

They have yet to officially indicate why the variable charging feature was added - and how they recommend it should be used.

I believe they said that it was "because owners requested it", and that they recommended to "charge to only what you need". If I recall that was purely from statements by Elon and their other V.P., and I don't think its "officially" written on any documentation anywhere.

 

[Sacrament055]

IMO, balancing is overrated. A properly balanced battery will give you a slightly higher range on a full charge, which might make people feel better by seeing a high number on their screen, but doing regular max charges for the sole purpose of balancing does real damage to the battery for a purely optical benefit.

For example, the 40kWh models never get top end balanced since they're limited to 66% of a 60kWh battery. The balancing doesn't matter since the top 33% never gets used.

A battery that is out of balance isn't permanently degraded, a couple of 90% or 100% charges will bring it back to its full potential. I'd avoid doing max charges just for the sake of balancing and let the battery balance on its own whenever you do a full charge for a longer trip.

Actually the 40KWh pack is limited to 72% of 60KWh battery and although I expected to never see losses because I reasoned that I'd have to see 28% loss before I noticed any degradation, that has proven incorrect. Apparently the car is taking into account that the top end has reduced and there for 72% of that has also reduced. When I got the car (admittedly on older firmware) it used to show 145 rated miles on full charge. Lately I'm seeing 139 (it's been 4.5 months) I know how to drive for max range and feel like I could still go close to 150 miles on a single charge if needed but I'm a bit surprised to see the rated range drop so quickly. I'm taking it in next week to get the fog lights added and will ask about the range loss and see what they say.

 

[djp]

Actually the 40KWh pack is limited to 72% of 60KWh battery

I think the 72% accounts for the fact that some of the charge range at top and bottom is hidden, so the 40kWh uses 66% of the total 60kWh but 72% of the available capacity.

I'm surprised you're seeing a drop too. Let us know what the techs say, it could be changes in the firmware.

 

[bob_p]

I believe they said that it was "because owners requested it", and that they recommended to "charge to only what you need". If I recall that was purely from statements by Elon and their other V.P., and I don't think its "officially" written on any documentation anywhere.

I've only connected to a public (pay) charger several times - and using the slider to limit the charging would be a useful feature to limit the cost of charging the car only to the level needed.

 

[wycolo]

Re Battery Pack in MS:

1. If it balances it does so internally; it is the Roadster that balances by turning EVSE on & off repeatedly at the very end of charge cycle. My bad.

2. Why obsess over this issue? The battery you try so hard to 'save' may not be yours for long. Mine was replaced @8000 miles due to circuitry issues.

3. If you can plan a long max range trip, do it! Don't take the ICE due to fear of doing a range charge.

4. 'Regular Basis' - I read this as either monthly or every other month.

5. I've just recently gotten 4.5 and with 5.0 being released, things are in flux, at least the GUI. Actual battery management being in Firmware may continue unchanged(?).

6. I occasionally arrive home with 20 miles showing, at which point the 'battery limited' warning pops up. So this would border on stressing the battery. Thus my interest on being sure the battery is not out of balance or otherwise limited. Oddly, up at the Pass the miles is down to 16 but perhaps since the car doesn't stop, the warning does not appear.
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