Battery Life/ Preservation/Health

[ChuckA]

The 3 main reasons why I charge to 100% are:
1. I might need the range the next day. Never really know for certain what my needs are going to be

2. My car might not charge overnight. Happens every once in a while for reasons unknown.

3. I have to remain over 50% S.O.C. in order to cool my battery while parked on plug without also allowing the HVB to charge. Another apparent programming fault.

Everyone’s situation is different.

1) I don’t need the max range and can charge anytime I want at home.

2) I won’t go on extended trips until the fast charging locations in CT increase.

3) I plan on keeping the MME when the Options balloon becomes due.

3) The batteries in my cell phones and laptops degraded when kept at 100%.

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[ChuckA]

Our battery will fall out at 8 years? I better make sure I don't park over any cuddly animals on that date.

Yes….avoid at all costs.

 

[SnBGC]

Everyone’s situation is different.

1) I don’t need the max range and can charge anytime I want at home.

2) I won’t go on extended trips until the fast charging locations in CT increase.

3) I plan on keeping the MME when the Options balloon becomes due.

3) The batteries in my cell phones and laptops degraded when kept at 100%.

Laptop and cell phone batteries aren't managed like the battery in your car so the comparison isn't worthwhile. Very very different situations going on there. All have batteries, but the similarities end there.

 

[SpaceEVDriver]

Even if the 8-year myth were true, the degradation of the battery is not 100% loss of capacity. It's no more than about 20% permanent loss of capacity. And with Ford's method of reserving buffer, they could easily release an update (or by then tuners could) that would open up all the reserve and "refresh" the capacity.

But, keeping your Mustang's battery at 100% SOC (displayed) is not dangerous for the battery unless you're storing in very high temperatures—not Phoenix high, 55 Celsius (130 F) high—for very long periods of time without ever discharging it.

We have several elderly family who live road-trip distances away and we like to be prepared. So we keep the Mustang home-charged to 90% SOC (displayed) and know that if we need to leave immediately, we can get to the first DCFC without an issue.

I have zero concerns about the life of the battery keeping it charged to 90% for days at a time.

 

[timbop]

Charging at 90% may have a positive effect, but have no down side.

Yes, that was the point I was attempting to make.

The 3 main reasons why I charge to 100% are:
1. I might need the range the next day. Never really know for certain what my needs are going to be

2. My car might not charge overnight. Happens every once in a while for reasons unknown.

3. I have to remain over 50% S.O.C. in order to cool my battery while parked on plug without also allowing the HVB to charge. Another apparent programming fault.

For you it makes sense and there's no reason not to charge to 100% - in fact it is a good thing due to your mentioned software "glitch". I think you are the odd case; I suspect most people drive far shorter distances than you every day. My car generally sits during the week, and then gets driven on the weekends. The vast majority of time when I do drive on the weekend it's less than 30 miles. When I do drive far I know it ahead of time and top off the night before.

Even if the 8-year myth were true, the degradation of the battery is not 100% loss of capacity. It's no more than about 20% permanent loss of capacity. And with Ford's method of reserving buffer, they could easily release an update (or by then tuners could) that would open up all the reserve and "refresh" the capacity.

That's not how the buffer works. All of the cells are wired essentially in parallel, so they are all used all the time. When you charge the whole battery to x%, then each individual cell is charged to roughly that amount. Since each cell isn't absolutely identical (and for other reasons) some can be a little higher or lower, but for the sake of argument all of the cells are in use. There aren't cells "set aside for future use".

I have zero concerns about the life of the battery keeping it charged to 90% for days at a time.

Nor do I

 

[timbop]

That's not how the buffer works. All of the cells are wired essentially in parallel, so they are all used all the time. When you charge the whole battery to x%, then each individual cell is charged to roughly that amount. Since each cell isn't absolutely identical (and for other reasons) some can be a little higher or lower, but for the sake of argument all of the cells are in use. There aren't cells "set aside for future use".

To elaborate on this a little further: you can think of the battery as a water bucket. When brand new you can fill it to the top and no water leaks out. However, over time the bucket develops a crack in it. If you fill the bucket beyond that then the water above the crack all leaks out, essentially limiting how much the bucket holds to the volume below the crack. Even if the crack doesn't extend to the top, you can't use the volume above the crack because there's no way to skip where the crack is.

 

[SpaceEVDriver]

That's not how the buffer works. All of the cells are wired essentially in parallel, so they are all used all the time. When you charge the whole battery to x%, then each individual cell is charged to roughly that amount. Since each cell isn't absolutely identical (and for other reasons) some can be a little higher or lower, but for the sake of argument all of the cells are in use. There aren't cells "set aside for future use".

I think I wasn't clear in how I stated it. Obviously the real "buffer" is in the software controlled number of kWh pushed into (or pulled from) the battery. The difference between actual and available kWh is software controlled. If Ford is using a specific value (say 88 kWh) as its available kWh regardless of the actual capacity, then degradation isn't really a factor until/unless the actual degrades to below that number (88 kWh). If, instead they're using a % of actual to determine available, then they can change available to be closer to actual as the battery degrades.

 

[SpaceEVDriver]

To elaborate on this a little further: you can think of the battery as a water bucket. When brand new you can fill it to the top and no water leaks out. However, over time the bucket develops a crack in it. If you fill the bucket beyond that then the water above the crack all leaks out, essentially limiting how much the bucket holds to the volume below the crack. Even if the crack doesn't extend to the top, you can't use the volume above the crack because there's no way to skip where the crack is.

When we reserve battery capacity on spacecraft, we do it via software as a % of actual capacity. After however many years of service, when the battery starts degrading, we release some of that capacity to the system through a software update to reduce the difference between actual capacity and usable capacity.

Eventually as the battery degrades, we have to make usable = actual or start shutting off systems to maintain reserve.

 

[timbop]

I think I wasn't clear in how I stated it. Obviously the real "buffer" is in the software controlled number of kWh pushed into (or pulled from) the battery. The difference between actual and available kWh is software controlled. If Ford is using a specific value (say 88 kWh) as its available kWh regardless of the actual capacity, then degradation isn't really a factor until/unless the actual degrades to below that number (88 kWh). If, instead they're using a % of actual to determine available, then they can change available to be closer to actual as the battery degrades.

Sure, but rather than using percentages let's use kwh - these numbers are made up by me but we need a point of discussion. My car has the updates so the ER battery is allowed to charge to 96kwh and then is marked "full". However, since the battery is not allowed to drop below 4kwh the usable is 92kwh. If the battery gets to the point that it only holds 94kwh, then my usable would be 90kwh. The only change Ford could make to the buffer is the bottom - making the minimum SOC 2kwh or 3kwh. Since allowing the battery to drop to a very low SOC is far worse for it than charging to 100%, that would accelerate the degradation for those that routinely let SOC get very low. I don't think ford will do that.

 

[timbop]

When we reserve battery capacity on spacecraft, we do it via software as a % of actual capacity. After however many years of service, when the battery starts degrading, we release some of that capacity to the system through a software update to reduce the difference between actual capacity and usable capacity.

Eventually as the battery degrades, we have to make usable = actual or start shutting off systems to maintain reserve.

OK, but you folks know what you're doing, understand the implications, and don't have to worry about warrantees. I don't think Ford will open up the bottom buffer, but I guess its possible.

 

[SpaceEVDriver]

OK, but you folks know what you're doing, understand the implications, and don't have to worry about warrantees. I don't think Ford will open up the bottom buffer, but I guess its possible.

We're both just speculating.

If Ford uses a constant value for available capacity (96 kWh or 88 kWh or whatever), then we won't see any degradation until the battery capacity falls below that constant value. And the degradation won't be as manageable because over time the SOC% displayed will creep closer to SOC% actual and we'll be storing our vehicles closer to 100% SOC (actual) for longer and longer periods of time.

If Ford uses a % of current maximum true capacity to determine available capacity, then we will see degradation as the battery degrades, but the degradation will be mitigated somewhat because we'll always be lower than 100% SOC (actual).

Which strategy Ford has decided to use is anyone's guess. I don't even know which one I would prefer.

In your bucket analogy:
The first strategy doesn't decrease how much we fill the bucket despite the crack growing until the crack reaches our fill level.
The second strategy keeps a constant distance between the fill level and the crack. As the crack grows, the fill level decreases.

In both strategies, the spout on the bucket stays where it is at 5% above the bottom of the bucket.

 

[SnBGC]

Yes, that was the point I was attempting to make.


For you it makes sense and there's no reason not to charge to 100% - in fact it is a good thing due to your mentioned software "glitch". I think you are the odd case; I suspect most people drive far shorter distances than you every day. My car generally sits during the week, and then gets driven on the weekends. The vast majority of time when I do drive on the weekend it's less than 30 miles. When I do drive far I know it ahead of time and top off the night before.


That's not how the buffer works. All of the cells are wired essentially in parallel, so they are all used all the time. When you charge the whole battery to x%, then each individual cell is charged to roughly that amount. Since each cell isn't absolutely identical (and for other reasons) some can be a little higher or lower, but for the sake of argument all of the cells are in use. There aren't cells "set aside for future use".


Nor do I

Agree. I am an odd case for sure. In more ways than one.

For the vast majority of users out there, charging to 90% displayed is a very reasonable practice.

 

[woody]

My MME still regenerates at 100% charge.
My Bolt does not regenerate at 100%.
Since you state that 100% charge in the MME is actually 100% (not 90%), where are the electrons from regen. going, if there is no place for them?
Why 88kWh and no 99kWh?
If the entire 99kWh battery is full at 100%, why am I able to regenerative brake at 100%?
Are those extra 10kWh locked in a safe with armed guards saying, "You can't touch this."? Or is there a magic button somewhere that allows access to full battery capacity? Or are we actually charging to 90% at 100%?
I thought when I purchased the MME I would have full battery access. Obviously I was mistaken.
My other EVs are not set up this way.
Just trying to figure out why.

 

[timbop]

My MME still regenerates at 100% charge.
My Bolt does not regenerate at 100%.
Since you state that 100% charge in the MME is actually 100% (not 90%), where are the electrons from regen. going, if there is no place for them?
Why 88kWh and no 99kWh?
If the entire 99kWh battery is full at 100%, why am I able to regenerative brake at 100%?
Are those extra 10kWh locked in a safe with armed guards saying, "You can't touch this."? Or is there a magic button somewhere that allows access to full battery capacity? Or are we actually charging to 90% at 100%?
I thought when I purchased the MME I would have full battery access. Obviously I was mistaken.
My other EVs are not set up this way.
Just trying to figure out why.

Every BEV manufacturer saves room at the top and bottom of the battery to prevent degradation. Ford tells you the actual size of the battery and the usable size. Tesla is cagy about the full battery size, and I have no idea about GM. The software controls charging, and the software cuts off charging when the battery hits the threshold deemed the "top" buffer. As @SpaceEVDriver says we're speculating about Ford's algorithms, but it is possible that the software controlling regen allows the battery to go above the "100%" charging mark.

 

[SnBGC]

My MME still regenerates at 100% charge.
My Bolt does not regenerate at 100%.
Since you state that 100% charge in the MME is actually 100% (not 90%), where are the electrons from regen. going, if there is no place for them?
Why 88kWh and no 99kWh?
If the entire 99kWh battery is full at 100%, why am I able to regenerative brake at 100%?
Are those extra 10kWh locked in a safe with armed guards saying, "You can't touch this."? Or is there a magic button somewhere that allows access to full battery capacity? Or are we actually charging to 90% at 100%?
I thought when I purchased the MME I would have full battery access. Obviously I was mistaken.
My other EVs are not set up this way.
Just trying to figure out why.

100% displayed is about 96% actual. (After 37,000 miles). I think that figure was just over 1% lower when the car was new. (Around 95.2% if I remember correctly....) That may indicate that my battery has degraded around 1.2% so far in 37,000 miles. Not sure though.....it actually is a much more complicated thing to determine.

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