80% charge or 90% charge for daily use?

[astronut325]

Charge to 80% twice during the weekdays at work if I'm lucky enough to get a charging spot at work.

Charge to 85% on weekends only if needed.

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[mkhuffman]

I guess everyone’s lives are different.

I’ve just never had a situation I suddenly had to drive 300+ miles away and had to get there as fast as possible with no stops.

So I spend zero minutes of my life worrying about that unlikely situation.

Other people? May need to.

That’s why my first post on this thread said to “do what you think you’ll need.”

Interestingly, I am at the beach this week and using the NEMA 14-50 outlet I installed with my Grizzl-e travel charger. I hooked the outlet up to a spare 50 Amp GFCI breaker that was used for a hot tub that is no longer here. The Grizzl-e breaker goes an hour or two and then detects a ground fault and throws the breaker.

So this week I will be plugging in whenever the car is in the driveway, and keeping the car at 90%. When we are ready to leave, I will only need to do a 10% charge to 100%. If the breaker throws, no big deal. I will be charged enough.

Doing that relieves my stress and I can relax while here, not worrying about if I have enough charge to get home.

 

[EVPiper]

I'm an automotive engineer. I do not work for Ford but have worked worked with automotive batteries with a similar chemistry.
Rules of thumb to maximize battery life:

• Don't do daily charges to a high state of charge, I'm not sure I'd even go to 80% every day. My Mach E is on order but my plan is to try to charge to 70% unless I know I'm going somewhere out-of-town. 80% is probably okay, I don't like the idea of regularly going to 90 or 100%.
• Only go to full charge if you know you're going to go on a long trip.
• These type of batteries really like being at 50% SOC. Unless you need the range, I wouldn't charge around at 50%.
• Don't let the battery stay at really high (above 80-ish) or really low states (below 20-ish) of charge for long periods of time.
• Don't let the vehicle just sit for months on end at any state of charge, the battery likes use. Use helps balance the cells.
• If you baby it, I bet this battery will go over 300k miles but if you abuse it, probably half that.

 

[fpasta]

I don't need to charge daily. 85% when I do charge. Once a month or twice I go to 100%. I never got below 25% yet before charging.

 

[BigMach-E]

I think 85 percent is a good medium for me. I tend to drive locally a lot, I'm at almost 18k miles in just over a year and two months, and my car had about a month with no driving. I figure in the decade from now that I "might" need a new battery, it will be at a significantly less costly proposition to replace the HV Battery than it is now, maybe with a better chemistry. I think I've only been in the teens of SoC once.

 

[DevSecOps]

How often have you had a few hundred mile “emergency” to deal with?

Me? Never in my life.

But if it did happen……. Borrow a car, get a ride with a friend, rent a car, or Uber are all viable options.

People spend a lot of time, energy and money worrying about the “unlikely what ifs” in life.

I prefer not to have that kind of anxiety.

In a typical week, I often have situations where I have to respond to far locations for work. I have an ice vehicle but I also live in a rural area. To go from the office to home and back out to a freeway would easily be 45 minutes. Leaving from work, which is in town, is much more feasible.

For that reason I charge every day to 90%. That stress you talk about, is exactly why I charge to 90% daily. I don't want to wonder if I have the charge to get somewhere. I would rather have the assurance that I do.

Either way, people worry too much about changing percentages. Just charge the damn car and drive it. All this battery "babying" makes EV owners look like a bunch of pansies and feeds negativity towards EVs. In California we have a 10yr/150k mi warranty on the battery. I won't have this car for more than 3 years. Its degradation is someone else's problem.

 

[daemonic3]

I'm an automotive engineer. I do not work for Ford but have worked worked with automotive batteries with a similar chemistry.
Rules of thumb to maximize battery life:

• Don't do daily charges to a high state of charge, I'm not sure I'd even go to 80% every day. My Mach E is on order but my plan is to try to charge to 70% unless I know I'm going somewhere out-of-town. 80% is probably okay, I don't like the idea of regularly going to 90 or 100%.
• Only go to full charge if you know you're going to go on a long trip.
• These type of batteries really like being at 50% SOC. Unless you need the range, I wouldn't charge around at 50%.
• Don't let the battery stay at really high (above 80-ish) or really low states (below 20-ish) of charge for long periods of time.
• Don't let the vehicle just sit for months on end at any state of charge, the battery likes use. Use helps balance the cells.
• If you baby it, I bet this battery will go over 300k miles but if you abuse it, probably half that.

Since you are knowledgeable on these specific batteries, when you say 80% do you mean of the FULL rating of the battery or 80% of the USEABLE portion of the battery? On the ER the 100% mark is 91kWh of useable of a 98.7kWh battery. I have been figuring charging to 90% is already 0.9 * 91/98.7 which is roughly 83% already. But I'm wondering your opinion on it?

 

[EVPiper]

My guess is that it is usable. I'm not sure what Ford is doing but I've seen multiple vehicle manufactures and battery suppliers report usable. State of charge is just an estimate. It is based on several things but mainly a function of battery voltage.

My main point is to not fully charge very often. If you could use the battery from 60% to 40% it would be ideal and would maximize life. 70-30 would be great. 80-20 is likely starting to stress it on a regular basis. 90-10 or 100-0 will shorten life. I want to baby my battery and plan to charge to 70 unless I know I'm going out-of-town. I know that limits range but I am in a two car family with the second car being gas for the foreseeable future.

 

[ChuckA]

We keep SOC between 45% to 90%. We’ve owned the MME exactly 1 year. First 2 months of ownership we charged to 80% then switched to 90%. The car is plugged in only after we fall below 50%. I’ve charged to 100% twice, once by the dealer.

 

[ripperAZ]

Eh. No love for 85%. ?. Ridin the middle. Splitting the difference.
Jes sayin. How about 84. ? Or 86 ?
That’s me. Thinking out of the box ….you’re welcome.

 

[kennethjk]

One more thing... the many quotes of the manual telling users to "charge to 90%" are essentially missing the intent. it says Don't charge to more than 90% daily.

the on line manual says to charge less than 100% .

”You can increase the battery life by maintaining your state of charge below 100%.”

I thought at one point it said to normally charge to 90% but maybe the on line manual changed .

I also thought my car came with a paper manual but just went out to the car and there isn’t one.

 

[kennethjk]

I'm an automotive engineer. I do not work for Ford but have worked worked with automotive batteries with a similar chemistry.
Rules of thumb to maximize battery life:

• Don't do daily charges to a high state of charge, I'm not sure I'd even go to 80% every day. My Mach E is on order but my plan is to try to charge to 70% unless I know I'm going somewhere out-of-town. 80% is probably okay, I don't like the idea of regularly going to 90 or 100%.
• Only go to full charge if you know you're going to go on a long trip.
• These type of batteries really like being at 50% SOC. Unless you need the range, I wouldn't charge around at 50%.
• Don't let the battery stay at really high (above 80-ish) or really low states (below 20-ish) of charge for long periods of time.
• Don't let the vehicle just sit for months on end at any state of charge, the battery likes use. Use helps balance the cells.
• If you baby it, I bet this battery will go over 300k miles but if you abuse it, probably half that.

Considering that 90% charge is really 80% use of battery does that make a difference on first comment that 80% is ok?

 

[Vulnox]

I like 85%. I know I’ve seen some on YouTube like Kyle mention they keep theirs at 60% if not driving them daily and that probably is the ideal if you can swing it. I’ll probably aim for 80-85% because we have the F-150 for any emergency situation where we have an unexpected long trip. If we only had EVs I would probably keep them both at 90%.

With that in mind I think it’s the important distinction aside from the manuals recommendation. Keep it between 60% and 90% if charging daily. And where you land in that range is determined by your own needs. Do you have another vehicle as a back up in case of a sudden longer trip? Do you have a long commute and have a risk of getting stuck in a traffic jam that would turn your 70% charge into a liability compared to starting at 80%?

 

[Blue highway]

the on line manual says to charge less than 100% .

”You can increase the battery life by maintaining your state of charge below 100%.”

I thought at one point it said to normally charge to 90% but maybe the on line manual changed .

I also thought my car came with a paper manual but just went out to the car and there isn’t one.

The main point is to not charge to a higher level than you need to on a daily basis or there will be consequences in battery capacity over time. The battery chemistry in our cars does not like to be at a high state of charge especially at high temperatures...

In the short run (a year or two) nobody is going to notice any difference in range if they charge to 100% every day at home. In the longer run eventually there is a difference. This is not an open question. The open question is whether the degradation this causes is enough that it matters to you.

The manual dumbs this down to some number (90% last I looked) to not charge above on an every day basis.

Think of it like smoking. Smoke a cigarette now and then when you are young and say... no problem... Smoke a pack a day when you are young and say... no problem... The problems come after time often much later.

 

[kennethjk]

The main point is to not charge to a higher level than you need to on a daily basis or there will be consequences in battery capacity over time. The battery chemistry in our cars does not like to be at a high state of charge especially at high temperatures...

In the short run (a year or two) nobody is going to notice any difference in range if they charge to 100% every day at home. In the longer run eventually there is a difference. This is not an open question. The open question is whether the degradation this causes is enough that it matters to you.

The manual dumbs this down to some number (90% last I looked) to not charge above on an every day basis.

Think of it like smoking. Smoke a cigarette now and then when you are young and say... no problem... Smoke a pack a day when you are young and say... no problem... The problems come after time often much later.

I get all that but the person I was quoting said he is an automotive engineer and has worked with batteries in that field. He made specific comments and I wanted to know his thoughts as to how this relates to the MME Battery.

specifically he mentioned charging to 70% normally. That is really approx 60% of MME battery.

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