Daily Charging Limit Percentage - what's yours set to?

[Adventureboy]

Day to day its 80% in the summer and 90% in the winter. 100% whenever I think i will be putting more miles on that day

Regardless of the safety buffer built into the battery a lower percentage increases pack lifespan. Quick chatgpt answer here for an ER that drives 15k per year.

Charge to 100% daily (≈1.88% annual loss)
• After 10 years: 82.7% remaining → ~17.3% degraded → ~108.4 kWh usable
• After 20 years: 68.4% remaining → ~31.6% degraded → ~89.6 kWh usable

Charge to 90% daily (≈1.63% annual loss)
• After 10 years: 84.8% remaining → ~15.2% degraded → ~111.1 kWh usable
• After 20 years: 72.0% remaining → ~28.0% degraded → ~94.3 kWh usable

Charge to 80% daily (≈1.36% annual loss)
• After 10 years: 87.2% remaining → ~12.8% degraded → ~114.2 kWh usable
• After 20 years: 76.0% remaining → ~24.0% degraded → ~99.6 kWh usable

As with many things ChatGPT, it doesn't tell the whole story. The Depth of Discharge (DOD) is a significant factor in determining the rate of degradation and is perhaps more impactful than the target SOC, given our top-protected packs. Draining your truck to 10% then charging it to 90% weekly, is harder on battery degradation than charging from 75%-90% daily. As the cells charge and discharge, they expand and contract, causing tiny microfractures in the cells that cause degradation. The deeper the discharge, the more microfractures are caused per kWh discharged (it's an exponential scale, not a linear scale). ChatGPT doesn't capture this significant detail in the numbers.

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[BluesClues]

do some people just not charge everyday? i started just charging weekly to 95% and running it down to 40-60%

 

[fhteagle]

70% summer.
90% winter.

Gets me to at least one (if not two) DCFCs in each direction I'm likely to go in case of an unplanned trip. No, we don't have that many DCFCs per road mile out here...

 

[Adventureboy]

Running to very low SOC: back in the days of NiCad batteries, there was a significance of "battery memory" where if one regularly ran down to say 50%, then after awhile, the battery would run out at that point instead of still having half its capacity remaining. I understand that lithium ion technologies have substantially, if not completely eliminated this effect, but I have a gut feeling that there may be a tiny effect still. I wouldn't recommend on planning to get that low, but occasionally breaking a personal rule like never running it down below 10% (or your personal minimum) shouldn't cause a problem, and may be beneficial.

Memory effect has been eliminated with NMC and LFP technologies. It does more harm than good to drain the batteries really low with the two most common Lithium technologies.

 

[Calvin H-C]

Memory effect has been eliminated with NMC and LFP technologies. It does more harm than good to drain the batteries really low with the two most common Lithium technologies.

I have heard that, but isn't this part of the reason for "0%" on the gauge to really be something like "5%" for the actual battery pack?

I'm just saying that running the battery over the entire range that it's management system is designed for isn't as bad as many seem to think.

 

[Brons2]

If you never charge above 85% you risk masking a module failure. I recommend charging to 100% occasionally for this reason.

I always charge the Lightning and the Mach-E to 100% once a month. I usually try to do it on the 1st of the month. I'm doing it today with my truck as noted earlier in the thread.

 

[chl]

80% works for me

If going on a vacation and it will sit idle, then 40%-50%

I keep the 12V on a trickle charger with an AGM mode when not is use as well to keep it topped off at 100%.

 

[Bigisland Guy]

This topic has been on the forum numerous times. If you care to review your more then welcome to, but I'll go with what our retired battery Guru says and stay the course at 85%.

 

[Adventureboy]

I have heard that, but isn't this part of the reason for "0%" on the gauge to really be something like "5%" for the actual battery pack?

I'm just saying that running the battery over the entire range that it's management system is designed for isn't as bad as many seem to think.

Taking an NMC battery below 20% true SOC starts exponential degradation. Below 10% and the degradation rate ramps up quickly. True, we are protected from the bottom 5% because in some cases, with cell-level discharges down to near 0% , the cells sometimes won't recover. Ford saves us from that (in most cases); however, anything below 15% displayed SOC starts a more aggressive degradation curve per kWh used.

There is little to be afraid of if you take it down to 5% displayed SOC once or twice, but just don't do it on a regular basis. Repeated deep discharges accumulate small amounts of degradation over time and eat away at SOH in little bites at a time. Keeping it above 15% displayed SOC most of the time takes much smaller bites per kWh from the SOH.

 

[Grumpy2]

what our retired battery Guru says

I agree, also remember temperature becomes important to this discussion if the battery becomes really hot. I wonder what he thinks of that EV9 ....

 

[flyin525]

60% Summer
70% Winter

I charge to 100% every 3 months or so for cell balancing if I havent needed 100% for a trip. I keep it plugged in, and try to avoid going below 20% unless absolutely necessary.

This may be a bit overkill but my daily needs dont require a lot of range so it works for me.

 

[telrod11]

85% Daily, or when I reach 60% or less.

Once a month, 100% whether I need it or not

 

[Adventureboy]

In this case i specifically asked it to consider 15k per year and charged daily.

I didnt put in any of the other factors because they get too varied across users to mean anything. DoD, environmental temp, fast charge frequency, etc all become highly specific

Good reference point. Given Ford's protection approach on the top and bottom, we might yield better results. Time will tell where we land.

 

[EV Engineer]

I have heard that, but isn't this part of the reason for "0%" on the gauge to really be something like "5%" for the actual battery pack?

I'm just saying that running the battery over the entire range that it's management system is designed for isn't as bad as many seem to think.

Agree here. This all seems so over-analyzed. We're approaching something like 2 million EV's sold a year in the USA. I trust that all the manufacturers have done extensive testing before offering 8 and 10 year 100k warranties on these things without putting these batteries through their paces.

I charge exactly like I gas my ICE. When I feel it's getting on the lower end I'll plug it in to 90% (as FoMoCo has recommended). Sometimes thats three times a week. Other times it's not for 10 days.
Every 6 weeks or so we take a road trip anways so I go to 100%.

 

[K6CCC]

Yep, this whole thread is mostly opinions, so here's what I'm doing...
At my house I have a one lane driveway and I have to be in the rear spot for the charge cable to reach. Our son takes my wife's car overnight normally on Tuesday and Friday nights so most of the time I take advantage of being the only vehicle in the driveway to charge those nights. This is southern California so keeping the battery or vehicle from freezing and pre-conditioning is not that much of a deal.
When I was working I would charge Tuesday and Friday nights at home (normally to 90%), and anytime I could get one of the free charging spots at work where I would charge to 100% (it was free). Each round trip to work and back used about 18%. If I had a weekend trip planned I would charge to 100% on Friday night. I did have a departure time set so the cabin would warm up automatically on work days.
Now that I'm retired I am still generally charging Tuesday and Friday nights to 90%, but without my 52 mile round trip commute to work every day my total consumption has dropped quite a bit. I deleted the scheduled departure time. As before, if I have a weekend trip planned, I will charge to 100% prior to the trip. So far the lowest I have had the truck was 13%.

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