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Definitive pack rebalance technique?

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There has been much discussion about pack balancing, loss of range, etc, but I can't seem to find a definitive approach to rebalancing the battery pack. Can some of the experts on this forum please post a summary of the best approach to rebalance? Perhaps the mods can make it a sticky. Thanks in advance.
 
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We don't have official information from Tesla on balancing, so the best we can do is use experience from the Roadster, information from service techs (which is sometimes conflicting) and feedback on what has worked from other owners.

There are two factors at play:

1. Calibration of the algorithm that estimates battery pack capacity (CAC, or calculated amp hour capacity). On the Roadster the capacity is recalculated when by doing a single drive (single key turn) from >85% SOC to <20% SOC and then recharging in Standard mode. We don't know what triggers a capacity measurement in the Model S, but as a starting point we can assume it's the same as the Roadster (and this seems to agree with advice given by service techs).

2. Pack balancing. On the Roadster this done directly after a Standard or Range charge completes, but is faster and more effective after a Range charge. The length of time it takes depends on how far out of balance the pack is.

So the basic procedure for balancing and recalibration of your pack is:

1. Charge in Range mode and let sit for a few hours or overnight.

2. Drive to less than 20% SOC on a single key turn.

3. Charge back to 90%.

4. Repeat until the range estimate stops rising.

Note that letting your battery sit at 100% and doing deep cycles shortens long term battery life. It's best to combine balancing/recalibration with long road trips when you actually need the full range rather than doing unnecessary balancing just to get a higher number displayed on your screen.
 
Here's someone describing a successful balance on a Model S (firmware 4.4):
I gained 3 miles back on a standard charge! Yippie.

To battery balance my car, I did a full range charge last night on 110v and i got back a 3 mile increase on a subsequent standard charge of my 60kwh car. It has 9700 mi on the odo. I'm now at 185 mi instead of 182 mi on a standard charge using firmware 4.4

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'm absolutely thrilled that I now know how to rebalance my battery when std range starts declining over time.

Note that in order to more quickly do the full range charge I first did a standard charge on 40a 240v. Then, did a slow range charge using 110v plug

It does not require you to drive down to lower SOCs (that's only necessary to "re-calibrate" your pack, not necessary to balance it). However, unlike the Roadster, it does require you to charge to 100% and leave it there for a while.
 
We don't have official information from Tesla on balancing, so the best we can do is use experience from the Roadster, information from service techs (which is sometimes conflicting) and feedback on what has worked from other owners.

There are two factors at play:

1. Calibration of the algorithm that estimates battery pack capacity (CAC, or calculated amp hour capacity). On the Roadster the capacity is recalculated when by doing a single drive (single key turn) from >85% SOC to <20% SOC and then recharging in Standard mode. We don't know what triggers a capacity measurement in the Model S, but as a starting point we can assume it's the same as the Roadster (and this seems to agree with advice given by service techs).

2. Pack balancing. On the Roadster this done directly after a Standard or Range charge completes, but is faster and more effective after a Range charge. The length of time it takes depends on how far out of balance the pack is.

So the basic procedure for balancing and recalibration of your pack is:

1. Charge in Range mode and let sit for a few hours or overnight.

2. Drive to less than 20% SOC on a single key turn.

3. Charge back to 90%.

4. Repeat until the range estimate stops rising.

Note that letting your battery sit at 100% and doing deep cycles shortens long term battery life. It's best to combine balancing/recalibration with long road trips when you actually need the full range rather than doing unnecessary balancing just to get a higher number displayed on your screen.

As added tips:

- Don't do this if you will not be using up the 'range charge' energy relatively soon afterwards.
- Avoid doing this if the ambient temperature is super hot.

Tesla has the best underlying battery chemistry to protect against this relative to other EVs and excellent active cooling (not sure it fully negates the second point), but I imagine it still has a minor impact on longevity. Battery life degradation happens as a function of time spent near its upper charge voltage specs, with it being worse at higher temperatures.

Note: feel free to correct me if I'm wrong, this is all educated conjecture on my part based on
https://www.youtube.com/watch?v=pxP0Cu00sZs
 
Why would I want to restore the (displayed) range of the car, using range charging, if I don't plan to drive that range?
out of curiosity. Understandable, but I'll try to help myself with that.
want to sell the car. OK, but perhaps contact the buyer if it is OK with him to add degradation to the pack.
 
Why would I want to restore the (displayed) range of the car, using range charging, if I don't plan to drive that range?
out of curiosity. Understandable, but I'll try to help myself with that.
want to sell the car. OK, but perhaps contact the buyer if it is OK with him to add degradation to the pack.
If the pack is unbalanced, it's real loss, not displayed (fake) loss. Rebalancing will restore actual range.

But, yes, that should be weighed against the degradation you're causing. Short-term gains vs. potential long-term losses.

The problem, though is that there's no definitive way for owners to tell some kind of algorithmic shortcoming vs. the pack legitimately being imbalanced. If you're just training the algorithm by following this process, you are simply fixing the displayed (fake) loss AND causing long-term degradation. Obviously you don't want to be doing that.
 
We don't have official information from Tesla on balancing, so the best we can do is use experience from the Roadster, information from service techs (which is sometimes conflicting) and feedback on what has worked from other owners.

There are two factors at play:

1. Calibration of the algorithm that estimates battery pack capacity (CAC, or calculated amp hour capacity). On the Roadster the capacity is recalculated when by doing a single drive (single key turn) from >85% SOC to <20% SOC and then recharging in Standard mode. We don't know what triggers a capacity measurement in the Model S, but as a starting point we can assume it's the same as the Roadster (and this seems to agree with advice given by service techs).

2. Pack balancing. On the Roadster this done directly after a Standard or Range charge completes, but is faster and more effective after a Range charge. The length of time it takes depends on how far out of balance the pack is.

So the basic procedure for balancing and recalibration of your pack is:

1. Charge in Range mode and let sit for a few hours or overnight.

2. Drive to less than 20% SOC on a single key turn.

3. Charge back to 90%.

4. Repeat until the range estimate stops rising.

Note that letting your battery sit at 100% and doing deep cycles shortens long term battery life. It's best to combine balancing/recalibration with long road trips when you actually need the full range rather than doing unnecessary balancing just to get a higher number displayed on your screen.

I've also been told to change it to run it down to 0% then charge to 100% and keep it there for three days to make sure it goes through calibration and rebalancing.
 
Because balancing takes time. It took me 4 months to get back 33 rated miles, and I need every one of them on the weekends.

That sounds like you do a range charge and a long drive every weekend. Basically you do as recommended in this thread to balance it.
How can the pack become unbalanced at the first place, if operated like that? Perhaps did no letting it sit plugged in at a high SOC?

* confused *
 
That sounds like you do a range charge and a long drive every weekend. Basically you do as recommended in this thread to balance it.
How can the pack become unbalanced at the first place, if operated like that? Perhaps did no letting it sit plugged in at a high SOC?

* confused *
"A" packs have different cells and firmware.
 
I've also been told to change it to run it down to 0% then charge to 100% and keep it there for three days to make sure it goes through calibration and rebalancing.

Tesla tells you specifically to do neither of these two things, not 0%, and not 100%.

The S battery balances automatically. I can buy a balancing charger for $40.00 to charge and autobalance an RC toy battery pack, why wouldn't Tesla's charger have the same thing.

I also asked a Tesla tech and he told me that the S autobalances.
 
Tesla tells you specifically to do neither of these two things, not 0%, and not 100%.

The S battery balances automatically. I can buy a balancing charger for $40.00 to charge and autobalance an RC toy battery pack, why wouldn't Tesla's charger have the same thing.

I also asked a Tesla tech and he told me that the S autobalances.
Then how do explain the numerous people that still have out of balance packs (which a proper balance has been confirm to fix)?

Make no mistake, I'm not saying Tesla doesn't do a "maintenance" middle balance (which can be done at any SOC above ~50% assuming the car has an accurate voltage to SOC map), but such a balance is still less accurate than a true top balance (which charging to 100% will ensure). The reason why not to do this all the time is: 1) charging to 100% and keeping it there is not good for the battery 2) balancing wastes energy so if you don't need the extra range, no point in wasting the energy.

For an RC toy and other consumer devices though, most users always charge to 100%.
 
Tesla tells you specifically to do neither of these two things, not 0%, and not 100%.

The S battery balances automatically.


^^^ This.

I've said many times that I've experienced minimal apparent degradation in both my Roadster (over 3years) and Model S (over 18 months) and all I do is plug both cars in every night and let them standard charge. I range charge maybe 3-4 times a year when I'm going on a long trip. I know plenty of others who do the same and have no complaints.

In other words I follow Tesla's advice and I'm really happy. Personally I think Tesla made a mistake introducing the slider bar as that motivated folks to start guessing if a different charging pattern would work better. When anyone asks me I tell them to just plug in every night, doesn't matter if you drove 10 miles or 200 miles that day.
 
Then how do explain the numerous people that still have out of balance packs (which a proper balance has been confirm to fix)?

There is a great deal of speculation by owners as to whether their pack is "out of balance" or not. It is pure speculation. Owners do not have access to the data necessary to definitively determine whether or not that is actually the case. The range mileage number is not enough information to make that determination.
 
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As added tips:

- Don't do this if you will not be using up the 'range charge' energy relatively soon afterwards.
- Avoid doing this if the ambient temperature is super hot.

Tesla has the best underlying battery chemistry to protect against this relative to other EVs and excellent active cooling (not sure it fully negates the second point), but I imagine it still has a minor impact on longevity. Battery life degradation happens as a function of time spent near its upper charge voltage specs, with it being worse at higher temperatures.

Note: feel free to correct me if I'm wrong, this is all educated conjecture on my part based on
https://www.youtube.com/watch?v=pxP0Cu00sZs


I tried to watch the video but it was way too long, boring and technical, BUT that being said I did learn something from the bits and pieces I did understand. First that the battery can last a long time, if not forever if properly cared for. Second that charging SLOW does NOT improve anything. In fact from the stats presented charging slow is not good for the battery. Better to have it charge at the std 40 amp 240 volt, just dont leave it at a SOC without using it. So as Nigel has posted, we just basically charge the car at 240/40 each night to Std 85-90% and drive it each day. I do a range charge once in awhile, (maybe 1-2 times mo) when I am going to use the car a lot the next day (60-80% of capacity). So far in 20,000 miles I still have pretty much the same capacity 199 full and 174 std RR. Thinking about getting another Model S as my wife has pretty much taken the car during the week as she has a 50 mile daily commute and mine is only 8 miles unless I am out of the office on business when I am doing 100+ miles per day. Have never had an issue with the 60 so that will be the way to go for me. Also do 95% of my charging at home, but have used the PSL and PO Superchargers more than twice. Love the car and how it is holding up.
 
We're all making one very large assumption - that the estimated range displayed after charging accurately measures how much battery charge is present across all of the batteries.

What if that number is actually an estimate? Is the car actually able to measure the amount of charge in each of the 7000+ batteries?

Or could it be that the number is an educated guess, based on the measurements the car can take - and then gets more accurate after the battery starts discharging?

While there's been a lot of discussion on the potential range loss - can't recall seeing any discussion about how the range number is actually being calculated or how accurate it is.

What I do see - is that when I first drive the car after charging - that the measured energy usage on the trip display is extremely large - and that it takes a while for that large number to be averaged out as the car is driven.
 
We're all making one very large assumption - that the estimated range displayed after charging accurately measures how much battery charge is present across all of the batteries.

What if that number is actually an estimate? Is the car actually able to measure the amount of charge in each of the 7000+ batteries?

Or could it be that the number is an educated guess, based on the measurements the car can take - and then gets more accurate after the battery starts discharging?

While there's been a lot of discussion on the potential range loss - can't recall seeing any discussion about how the range number is actually being calculated or how accurate it is.

What I do see - is that when I first drive the car after charging - that the measured energy usage on the trip display is extremely large - and that it takes a while for that large number to be averaged out as the car is driven.

^^^Exactly. Also as stated by Nigel. There's been a frenzy about re-balancing, and fact is we really do not know. There are 5 possible things that could cause lower estimated (rated or ideal) range over time: 1) the estimating algorithm loses accuracy, 2) the estimating algorithm (or its inputs) change with software updates, 3) the estimating algorithm includes factors (such as outdoor temp averages), 4) the pack gets out of balance and therefore loses some charging capacity until rebalanced, and 5) the pack degrades (permanently loses capacity). Likewise, when you go through the recommended "rebalancing" exercises (i.e., range charge, running down to 20%) there are two things that could be happening: 1) rebalancing, and/or 2) estimating algorithm re-calibrates low and high capacity of pack.

I've been reading all of the related threads for months with great interest. I know someone's going to claim authoritative knowledge and shout me down, but IN MY OPINION, NOBODY KNOWS EXACTLY WHAT IS HAPPENING.

It would be nice if Tesla Motors would someday give us something authoritative, but I suspect that they view all of this as "within reasonable parameters", and have other more important fish to fry. PS, I do not view info passed from a Service Manager, Service Center technician, etc. as authoritative unless they can provide a Tesla letterhead TSB that shows it in writing. Bless those service guys, they're great, but they do not own the car, and therefore know less about day-to-day charging patterns than we do.
 
If the pack is unbalanced, it's real loss, not displayed (fake) loss. Rebalancing will restore actual range

To be fair, this is an assumption being made by owners. There has been no independent confirmation that this is the case. Just an assumption.

Then how do explain the numerous people that still have out of balance packs (which a proper balance has been confirm to fix)?

There could very easily be other factors at play, or a problem with the algorithm.

There is a great deal of speculation by owners as to whether their pack is "out of balance" or not. It is pure speculation. Owners do not have access to the data necessary to definitively determine whether or not that is actually the case. The range variety number is not enough information to make that determination.

Agreed. The "balancing regimen" posted earlier does nothing more than teach the algorithm the endpoints of your battery's charge. This enables the algorithm to more accurately calculate your range estimate, which appears as "recovered" range. This is just as valid of an interpretation of what is happening as those who speculate about unbalanced battery packs. However, it's not recommended to charge to 100% if you don't need the range. Please, be careful about charging to 100%, then leaving it there, then running to 0% (dangerous). While it may look like you have "recovered" some range by following this procedure, you are also reducing the long term life of your pack.

I do think Tesla needs to address this issue with some communication, but I would be surprised if it was real deterioration.