Why is charging to 100% a bad thing?

[ChasingCoral]

I have my car set to Fords recommended 90% max charge for daily use. I tend to let the battery drain until like 65-70% then charge it back up to 90%. I will charge it to 100% the night before I plan on doing a long distance drive so it is fully charged in the morning ready to go.
For example Friday I am driving from Austin to Fort Worth. I will be telling the car when I go to bed on Thursday to charge to 100%. Any hotel I stay out while in DFW I will let it charge to 100% as it should be again a 1-2 night only thing in preparing for my drive back home.
I did the same thing when I drove to Houston. 100% the battery the night before got to the hotel at a lower state of charge and 100% it there. I got back to my house in Austin with a 10% charge.

I do the same except I normally try to let the battery drop to around 40% before recharging at home.

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[dhoerl]

This article jumps into the technical side of lithium ion battery degradation. Figure 6 is relevant to this discussion, where they tested lithium ion battery capacity after using the same type of battery repeatedly with a 100-25% charge cycle, 100-40% charge cycle, 85-25% charge cycle, etc.

You can see how the battery will degrade with use no matter what, but that certain charge cycles are more damaging, and how it makes much less of a difference once you are avoiding the extremes (i.e. by not regularly charging to 100% if you don’t need it).

What I’m getting from this article (figure 6) is that for cars doing small daily trips, charge nightly and maintain a near-constant charge. The article tested a 75%-65% range. But elsewhere there are statements that 50% may be the best overall average charge level.

So I’m thinking, if I only drive 20 miles most days, with an occasional long trip, for the former keep the charge between say 55%-45% then the night before the long trip, go to 90%. But even for the long trip, best to recharge half way with a L2 charger - to again minimize the gap.

 

[agoldman]

Not sure about the long term, but I have been charging to 100% since recieving the car in Feb/March, and if anything, rage has increased noticeably. Of course, I expect a winter drop like a stone once temps plummet.

 

[dhoerl]

Not sure about the long term, but I have been charging to 100% since recieving the car in Feb/March, and if anything, rage has increased noticeably. Of course, I expect a winter drop like a stone once temps plummet.

If garaged droop might be less. When driving current flow heats the battery which should help. I haven’t seen posts here that imply winter range plummets but I haven’t read every post!

 

[RedDragon]

How long is too long to leave the MME charged at 100pct? I'm assuming a few hours is ok?

 

[RickMachE]

How long is too long to leave the MME charged at 100pct? I'm assuming a few hours is ok?

Days, weeks.

You really need to relax about the battery.

 

[Blue highway]

How long is too long to leave the MME charged at 100pct? I'm assuming a few hours is ok?

A few hours will be imperceptible. Its good to avoid leaving the battery at 100% any longer than you need to but don’t stress over it. I’ve seen academic articles that show in a worst case scenario if a lithium battery is left at 100% at 100F they will loose ~20% capacity in something like 6-12 months. If left at 80% at 72F its something like 3-4%.

It’s also good to know that there is a buffer at the top and bottom of the state of charge…. 100% on the dash isn’t quite 100% SOC…. Car makers do this to preserve the battery in case user charge to 100% or drive to zero%.

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