Question about real battery capacity, charging to “100%” (notice the quotes)

[Its PJ Bia]

I charge to 90% during the week, the once every couple of months I will charge to 100% to rebalance the cells.

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[Adventureboy]

I literally went from 100% to 0% just a week and a half ago. Running out did not cause irreparable harm, there’s a reserve and a buffer but not to the tune of 148kW.

Charging to 100% or depleting to 0% won't kill your battery. Doing it regularly will age them faster.

Ford has thought this through and will not let you use the buffer. It would be too hard on the batteries. If you ran the cells truly down to 0% including buffer, you very likely would brick the truck if it sat there for any period. Sitting at true 100% for any period will also bake the batteries, hence why Ford won't let you do that.

Ford recommends something less than 100% because that keeps the cells within better health parameters for longevity. They don't bother with the low end since most folks won't run down to 0%. If you want your cells to last well past the 8 year, 100,000 mile warranty, the normal daily operating range of 90%-10% SOC should get you there with plenty to spare. That is about 85%-15% of the true battery capacity and well within the "Knees" for good battery health.

 

[Adventureboy]

I charge to 90% during the week, the once every couple of months I will charge to 100% to rebalance the cells.

Rebalancing the cells does not happen often even when you charge to 100%. It has happened once in my 18 months of ownership on my wife's MME and not yet on my 11-month-old Lightning. When the MME did a top balance, the next day I drove 50km before the SOC meter came off 100%. It was an interesting experience. That day I probably could have driven 500km on the 430km MME.

 

[SmoothJ]

I only charge to about 90%, however sometimes during a pre-con or remote start it hits 91% but that doesn't happen often. If I drive to work, I only use 12-15%, and then charge it back up again to 90%. I think I only charged it to 100% maybe 20 times, one of which was due to a OTA update and the other was short road trips to PA.

On my wifes Bolt, which we want to trade-in for a Mach-E, we keep it around 88 to 90%. I can't give you an exact number since its based on a slider vs a number. It fine for what it is, but we keep that low to avoid a "possible fire" related to those batteries packs. We still have yet to get a replacement battery, and GM offered $1400 to keep the current battery pack with strings attached.

 

[MickeyAO]

You have to charge over 80%.

Source?

 

[MickeyAO]

Rebalancing the cells does not happen often even when you charge to 100%. It has happened once in my 18 months of ownership on my wife's MME and not yet on my 11-month-old Lightning. When the MME did a top balance, the next day I drove 50km before the SOC meter came off 100%. It was an interesting experience. That day I probably could have driven 500km on the 430km MME.

Rebalancing happens any time the polarization curve dips below the average charge/discharge time constant learned by the BMS. This may mean spending more than 8-12 hours of just resting.

As an example, during our BOL (Beginning of Life) test, I use a standard or manufacturer recommended cycle, until the cells stop gaining capacity (yes, new cells will gain capacity when initially exercised) and then spend 24 hours at rest so we can find the actual discharge polarization time constant. Then charge the cell and spend 24 hours at rest to find the charge polarization time constant. discharge time constant is typically anywhere from 3 minutes (LTO) to 8 hours (LMO). Charge time constants are typical double of the discharge.

I should have a good idea of the SKE805A time constants next month (but I won't be able to directly tell you what they are)

 

[RonTCat]

Source?

BECM engineers.

 

[Jim Lewis]

Rebalancing happens any time the polarization curve dips below the average charge/discharge time constant learned by the BMS. This may mean spending more than 8-12 hours of just resting.

Am I likely to have any cell rebalancing problems if I never charge above 80% but often let my truck sit for days just plugged in, not charging, at 50% charge? And, since I've never charged to 90% or 100%, will I be missing some capacity achieved by cycling new cells? According to actually trip experience and to GOM estimates, I am achieving the Lariat EPA range estimates in spite of my above practices, so I'm a happy camper, mainly interested achieving the maximum battery lifespan with retained performance. Based on my experience so far and my ignorant interpretation of your post that I'm referencing, it seems like I should be doing OK.

 

[RonTCat]

I really don't want to, but I do have to refute the 90% AC vs DC is no different. There is a world of difference based on the current levels used.

@PreservedSwine if you want to know how to make the cells last virtually forever, find the guy that runs the Energy Storage Technology Center, read all his post of 12 years of hands on testing and data. Should take a couple of hours to get through them all.

BTW, I do not follow his advice on acceleration, but I do on SOC levels.

I do not disagree with your statements.

My point is if the poster has his truck 7 years from now, and charges to 100% once in a while, then the remaining battery "% of new capacity" might be 91%, instead of the 92% percent he would have had if he only went to 80% every time or only topped it at Level 2. Functionally, the poster will not see a tangible difference in the performance of the vehicle or battery.

 

[Jim Lewis]

Just happened to watch Tom Moloughney's State of Charge test of a 2019 Tesla Model 3 that has >100,000 miles on it in four years. In his 70 mph range test, he finds that the vehicle still has 90% of its usable battery capacity. The vehicle had been charged ~75% on DC fast chargers, 25% on AC, occasionally charged to 100% available capacity but then used right away and not allowed to sit at full charge. He found the vehicle consumed 66 kWh in his test vs. 73 kWh of usable capacity in a new Model 3.

At the following time points in his video, he discusses capacity and good battery care habits. Note: this website does not correctly handle the 2nd YouTube timepoint in Moloughney's video. I'll try putting the link in a 2nd independent post to see if that works better.

FIRST TIME POINT (about 14:08 in):

 

[TheWoo]

There is all kinds of miss information and myths about EV Batteries...

Talk to much on your phone and constantly using Apps your battery will go down fast.

One of the myths is that using your phone will have any appreciable impact on efficiency.

My 4400 mAh phone battery is about 16 watt hours, or 0.01% of my truck's usable capacity. Not 1%, 0.01%. Talking on your phone all day long won't have that much impact even taking running the speakers and microphone into account.

I just don't like giving people the impression that they should worry about things like charging their phone or running a laptop. I could run a TV off my pro-power all afternoon and not have much impact at all.

Cabin heater? Now that takes some serious power. Even the A/C isn't that big a power draw in the grand scheme.

 

[Jim Lewis]

Note: this website does not correctly handle the 2nd YouTube timepoint in Moloughney's video. I'll try putting the link in a 2nd independent post to see if that works better.

I couldn't get the second timepoint in Moloughney's YouTube video to play correctly by adding it to my previous post. So here it is by itself in hopes the video starts at the point intended. Perhaps some sort of caching issue I don't understand.

SECOND TIME POINT (about 21:03 in):


P.S. For anyone else with similar problems, pasting the link https: // www.youtube. com/watch?v=EnpKtyrPPKw&t=21m03s with minutes and seconds seems to work better in terms of this website storing the correct time in its database, even though both the above link and the following link https: // www.youtube. com/watch?v=EnpKtyrPPKw&t=1263s result in the text [ MEDIA=youtube]EnpKtyrPPKw:1263[/MEDIA ] being put in the posted text.

 

[Jseis]

Does anyone know for sure?

Once upon a time I had a ‘62 VW Bug. It had a 10 gallon tank. Would go forever on a fill up. One day I ran the needle below reserve. Pulled into the gas station. Put 10 gallons in it (to a couple of inches below the fill tube).

I sensed I’d entered a space-time portal where only String Theory and Schrödinger's Cat knew WTF was going on. The LT exhibits the same behavior.

 

[John Becker]

Is it true that 50% SOC is ideal?
If so, then keeping the SOC between, say, 60% - 40% is better than, say, 80% - 20%?
Or am I over-thinking this (again)?
Regardless, what are the ideal SOC high and low points?

 

[PreservedSwine]

I suspect the battery has, in reality, a substantially higher capacity than 98KW.
Keeping SOC in the middle is good- but the difference between 20-80 and 40-60 isn’t as great as it sounds because of this.
As someone once said, the truck should be working for you, not the other way around.
enjoy!

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